2010 Title, Contents, and Minutes (78th Annual Western Snow Conference, 2010)
Content includes Table of Contents SNOW NOTES Minutes of the Western Snow Conference Executive Committee Meeting Minutes of the Western Snow Conference Business Meeting 78th Annual Meeting of the Western Snow Conference – Attendees

A Modeling Approach to Evaluating the Impacts of Climate Change and Mountain Pine Beetle Infestation on Water Resources in the Okanagan Basin, British Columbia - Borden, C.; Delaney, P.; Ying, Q.; Kobor, J.; Guy, Brian (78th Annual Western Snow Conference, 2010)
Rapid population growth coupled with increasing agricultural demands from a burgeoning viticulture industry has resulted in a significant increase in water demand in the Okanagan Basin over the past few decades. Global Climate Model (GCM) predictions of increases in temperatures will likely result in significant decreases in winter snow accumulations and shifts in the timing and magnitude of the spring freshet from the high elevations. The forested areas in the basin are currently experiencing a large-scale mountain pine beetle infestation. The Okanagan Basin Water Board and its partners began a basin-wide study of the supply and demand of water resources in the basin in 2004. One component of this study is the construction of a numerical model of the basin using the distributed hydrologic model MIKE SHE. The model was calibrated to naturalized streamflow hydrographs, snow accumulation data, and independent estimates of lake evaporation and baseflow. The calibrated model provides the framework for evaluating a series of water supply scenarios involving the impacts of climate change, loss of forest cover due to beetle kills, and the combined effects of these two phenomena. The climate change scenarios are based on a series of IPCC scenarios and utilize statistically-downscaled GCM data that is available for the basin at a 500-meter resolution.
Keywords: MIKE, Okanagan Basin, distributed hydrologic modeling, climate change, water management

Radiative Forcing by Dust in Snowmelt-dominated Hydrologic Systems Using Coupled Satellite and In Situ Measurements - Bryant, A.C.; T H Painter (78th Annual Western Snow Conference, 2010)
Snow is the primary source of fresh water in the western United States. With the highest albedo of any naturally occurring surface on earth, pure snow reflects roughly 90% of incident solar radiation. The addition of dust to snow decreases the albedo, increases the melt rate of snow, and spurs a decline in total snow extent, which in turn leads to increased heating of the troposphere (the snow-albedo feedback). Although dust has had an enduring presence in snow, land-use change in semi-arid regions around the world has increased dust deposition to mountain regions in the past 200 years. This paper describes the MOD-DRFS model, which leverages the MODIS surface reflectance for snow grain size and radiative forcing from dust in snow. The model has been initialized using the past 10 years of MODIS data nadir to the Colorado River Basin. MODIS data coupled with in situ data, provide insight into the relationship between dust concentration in the optically-relevant portion of the snowpack and a spatially comprehensive dataset of basin scale (and larger) dust-induced energy inputs to the snowpack. Further, this paper shows there is heterogeneity of dust deposition throughout the study region and that the 2008/2009-snow year had significantly more dust radiative forcing than other years in the record. The products of this research will inform hydrologic modeling in the western US and lay the foundation for understanding how radiative forcing by dust on snow and the snow-albedo feedback can affect the global hydrologic cycle and climate.
Keywords: MODIS, radiative forcing, dust deposition, snowmelt, albedo, Colorado River

Managing Water Resources for Climate Variability and Change Using SNOTEL Data - Casola, J.H. (78th Annual Western Snow Conference, 2010)
Seasonal snowpack throughout the West is vulnerable to year-to-year climate variability. SNOTEL observations of daily snow accumulation, snow loss, and air temperature can be exploited to create seasonal forecast products to estimate April 1 SWE and the rate of spring melt. The April 1 SWE forecasts are based on historical observations of late winter snowfall, while the spring melt forecasts are based on anticipated spring temperatures. These forecast products could be useful for managers since they are mathematically simple, provide lead-time for planning purposes, and are delivered in terms of hydrologically-useful variables (such as April 1 SWE) with easy-to-understand estimates of uncertainty. The transparency of the uncertainty information allows users to devise and examine climate-driven scenarios, which can incorporate their tolerance for risk. These forecast products can also be applied to longer timescales to consider the impact of warming on snow accumulation and melt. In this paper, forecast products for April 1 SWE and the rate of spring melt are presented for the Skagit watershed in the Washington Cascades. For the seasonal accumulation forecast, a skillful prediction range for April 1 SWE can be generated as early as February 1.
Keywords: SNOTEL, seasonal forecasting, Pacific Northwest, degree-day model, adaptation

Estimated Residence Time of Two Snowmelt Dominated Catchments, Boulder Creek Watershed, Colorado - Cowie, R; Williams, M.; Caine, N.; Michel, R. (78th Annual Western Snow Conference, 2010)
Delta-O-18 and 3-H (tritium) measurements of precipitation and stream waters from 2002 to 2009 were used as isotopic tracers to investigate residence times in two headwater catchments within the Boulder Creek Watershed in the Front Range of Colorado. The 225--ha Green Lake 4 alpine catchment and the adjacent 664--ha Como Creek subalpine catchment are established research sites for both the Niwot Ridge Long Term Ecological Research Network and Boulder Creek Critical Zone Observatory Network. The Green Lake 4 catchment had a mean residence time of 1.12 years while the Como Creek catchment had a mean residence time of 1.8 years. Tritium levels in Green Lake 4 were consistently similar to that of incoming precipitation indicating little exponential decay and indicative of shallow flowpaths and short residence times. Como Creek tritium levels were also close to incoming precipitation during spring and summer snowmelt with elevated levels appearing during baseflow indicating some contribution of bomb Spike waters likely being delivered from deeper flowpaths with longer residence times. These results indicate that headwater catchments within Boulder Creek Watershed have relatively short mean groundwater residence times with the potential for older groundwater contributions during low flow conditions in the sub-alpine.
Keywords: Boulder Creek, isotopic tracers, residence time, flowpaths, groundwater, Niwot Ridge

An Experimental and Modeling Investigation of the Impact of Silvicultural Manipulation on Snow Hydrology in the Cedar River Watershed, WA - Forsyth, J.; Lundquist, J.; Wayand, N. (78th Annual Western Snow Conference, 2010)
Over the past 80 years, forest harvesting throughout the western U.S. has resulted in a shift in the dominant forest structure to young, dense forests. Meanwhile, declining trends in mountain snow water equivalent (SWE), summer river flow, and earlier snowmelt have largely been attributed to climate with little consideration of the impact of the concurrent changes in vegetation from forestry practices. Silvicultural manipulation has the potential to increase snow water storage, change snowmelt timing and restore ecological processes that might normally be adversely affected by climate change. This study is primarily concerned with snowmelt timing, since it is crucial to watershed management in basins with limited reservoir storage. Any delay in snowmelt from silvicultural manipulation could reduce winter flood hazards and increase summer runoff when water demand for cities and agriculture is the highest. This study commenced in the 2009 water year and takes place in the Cedar River Watershed, WA, located in the climate-sensitive intermittent snow zone. Using a combination of distributed field measurements and point and distributed hydrologic models, we are investigating i) the heterogeneity of snow accumulation and melt in different forest structures, and ii) which forest changes are of comparable magnitude to climate change in their effects on snow hydrology.
Keywords: Snow water equivalent, seasonal runoff, runoff timing, timber harvest effects, Cedar River

Tracking the Impact of Climate Change on Central and Northern California's Spring Snowmelt Subbasin Runoff - Freeman, G.J. (78th Annual Western Snow Conference, 2010)
A simplified index system was set up at Pacific Gas & Electric Company (PG&E) to evaluate the current impact of climate change and produce a simplified trend forecast of spring snowmelt runoff for relatively small hydroelectric operational subbasins in central and northern California. The need for PG&E to classify and index these relatively small subbasin drainages in terms of runoff impact from climate change became apparent with the need to increase overall awareness of the relatively rapid change in water availability timing since about 1970 and to focus on identifying potential associated business risks. Spring runoff from snowmelt has historically been depended upon for filling the nearly one hundred seasonal reservoirs that PG&E manages. Within any given large watershed, there are considerable differences in the characteristics of contributing subbasin reaches, and those characteristics influence how the subbasin runoff will respond to climate change. Isohyetal maps can sometimes be utilized to identify these areas from averaged precipitation amounts that are often related to topography and elevation differences. During this review, it was found that orographically influenced subbasins were least impacted from the effects of climate change, while those areas that were either in a rain shadow or were behind topographic barriers revealed larger climate change impact in the form of reduced snowpack, spring runoff, and sometimes runoff for the water year.
Keywords: PG&E, California, subbasin runoff, snowmelt, climate change, topographic control

Relative Significance of Interception and Wind Redistribution in Subalpine Forest Differential Snow Accumulation - Leaf, C.F. (78th Annual Western Snow Conference, 2010)
In subalpine forests, the relative significance of interception and wind redistribution causing differential snow accumulation varies with species, evapo-sublimation, topography, wind, forest cover density, opening size, and seasonal snow accumulation. Wind induced differential snow accumulation increases with the intensity of selective or partial cutting. On average, wind redistribution accounts for less than 25 percent of the increased snowpack for lighter cuts to approximately 50 percent for complete removal of forest cover density. During a near-minimum snowpack year with lower wind energy, reduced interception losses accounted for 62 percent of the differential snow accumulation in a 6 tree height strip cut on Fool Creek at the Fraser Experimental Forest. Thirty-eight percent was attributable to wind redistribution. During a near-maximum snowpack year with higher wind energy, wind redistribution accounted for at least 58 percent of the differential snow accumulation and 42 percent from reduced interception. Simulated increased snow accumulation using the algorithms developed for reduced interception loss and wind induced redistribution correlate well with snowpack increases observed for various levels and patterns of basal area removal.
Keywords: Fool Creek, Fraser Experimental Forest, Colorado, differential snow accumulation, snow interception, wind redistribution, snowpack, subalpine forest

Modeling the Effect of Vegetation on the Accumulation and Melting of Snow - Mahat, V.; Tarboton, D.G. (78th Annual Western Snow Conference, 2010)
This work investigates the variability of snow accumulation and differences in the timing of melt and sublimation between open (grass/shrubs) and forest (conifer/deciduous) locations at a mountain study site in the Western US. Observations include continuous automated climate and snow depth measurements supported by periodic field measurements of snow water equivalent and temperature in four different vegetation classes (grass, shrubs, coniferous forest, deciduous forest) at the TW Daniel Experimental Forest located 30 miles N-E of Logan. The Utah Energy Balance physically based snowmelt model was enhanced by adding new parameterizations of: i) snow interception and unloading; ii) transmission of radiation through the canopy; and iii) atmospheric transport of heat and water vapor between the snow on the ground, intercepted snow in the canopy and the atmosphere above. The enhanced model was evaluated by comparing model simulations of meteorological conditions (temperature, wind, radiation) and snow properties (water equivalent, depth, temperature) in and beneath the canopy with observations. Observations showed approximately 10 to 20% more snow accumulation in open areas compared to forest areas. Ablation rates were also found to be higher in open areas than in forest areas. In comparison to coniferous forest, deciduous forest had high rates of accumulation and ablation. The model performed well in representing these effects based on inputs such as canopy height, canopy coverage, leaf area index and leaf orientation.
Keywords: Utah Energy Balance Model, snow accumulation, melt timing, sublimation, interception, snowmelt

Predicting Flow Volumes in the Upper Colorado River Basin during Three Climate Cycles of the 20th Century Using Sep-Mar Complementary Temperature and Precipitation Patterns - Matter, M. (78th Annual Western Snow Conference, 2010)
Efficient and effective use and management of available water resources depend on accurate and timely forecasts. Variability in climate and hydrology is a consequence of natural causes and human activities, including large-scale ocean/atmosphere interactions (Hegerl et al., 2007); variations in the solar cycle (Meehl and Arblaster, 2009), climate change (e.g., Pagano and Garen, 2005; Garfin et al., 2008), and modifications to land use and land cover (Milly et al., 2008). Hydroclimatic variability increased over the 20th Century, so it is therefore critical to understand the underpinnings of hydroclimatic variability. Climate cycles are a fundamental form of hydroclimatic variability, and are shaped by large-scale ocean/atmosphere interactions, or climate modes, that influence hydroclimate in a region, and are affected by natural and anthropogenic external forcings. Prevailing temperature and precipitation conditions (e.g., cool/wet or warm/dry) lasting approximately 25-30 years characterize climate cycles, and they change with variations in the climate modes (McCabe et al., 2008). In the Colorado River Basin (CRB), climate modes which influence hydroclimate and shape climate cycles include the Atlantic Multidecadal Oscillation (AMO), Pacific Decadal Oscillation (PDO), and El Niño/Southern Oscillation (ENSO). Three climate cycles occurred in the CRB during the 20th Century. Results of applying the methodology to the upper Yampa and Gunnison river basins demonstrate that complementary temperature and precipitation conditions accompany wetter or drier conditions on climate cycle and annual scales, and that complementary conditions may be utilized for purposes including improving accuracy and increasing lead time of water supply forecasts.
Keywords: Colorado River, hydroclimatic variability, snowmelt runoff, forecasting, climate change, climate cycles

Elevational Differences in Snowpack Variability: A Case for Increased Monitoring In the Olympic Mountains - McDonald, S.; Barry, D. (78th Annual Western Snow Conference, 2010)
Climate change projections indicate that snowpack could be most affected at mid-elevations due to an increase in rain-on-snow events. For the past three winters, we collected snow and meteorological data from eleven snow courses and six remote mini-meteorological stations in the Dungeness watershed of the Olympic Mountains in western Washington. We compared our mid-elevation snow and weather data with data collected from the Dungeness SNOTEL over the same period. Most of our snowpack data do not correlate well with SNOTEL data, and temperature and relative humidity readings from our stations suggest that there are additional site and elevational differences that suggest that the existing SNOTEL site does not capture the range of variability within the watershed. Our findings indicate that increased permanent monitoring (e.g., by new SNOTEL sites) of snowpack in the Dungeness watershed as well as throughout the rain-on-snow elevation areas of the Pacific Northwest would improve our understanding of potential climate change influences on snowpack at all elevations, improve spatially-explicit snowpack and streamflow modeling efforts, and support improvements in water resources forecasting and management.
Keywords: Dungeness Creek, snowpack variability, climate change, Olympic Mountains, rain on snow, streamflow modeling

Dust on Snow, Ice Column Formation, and Meltwater Flow Paths at Niwot Ridge - Petrzelka, J.; Williams, M.; Zukiewicz, L. (78th Annual Western Snow Conference, 2010)
The presence of dust on the snow's surface has been shown to decrease albedo by as much as 40% compared to a clean snow cover. Thus dust on snow affects snow surface radiative fluxes, generally resulting in earlier snowmelt compared to clean snowpacks. Less understood is how dust on snow events may affect infiltrating meltwater movement in the snowpack. An aeolian dust event with a distinctive red color that was deposited in February of 2006 at Niwot Ridge in the Colorado Front Range provides opportunity to investigate how dust on snow may change the surface characteristics of snow and meltwater movement through the snowpack. Ice columns found in clean snow had a mean depth of 60 cm, which was significantly longer (p=0.0001) compared to the mean depth of 16.7 cm in red snow. The shape also varied, with ice columns in clean snow having a uniform width along the entire length, whereas those found in red snow were widest at the snow surface and decreased in width with depth. The movement of liquid water through the snowpack in red snow appears to be more uniform, decreasing the size of preferential flowpaths that give rise to ice columns when compared to clean snow. Thus the variation in ice column morphology between red and clean snow gives insight into how dust deposition events may affect the energy balance, subsequent melt, and meltwater flowpaths in snow covered areas
Keywords: Niwot Ridge, meltwater, ice columns, dust on snow, flowpaths, surface roughness, albedo

Infrastructure Improvements for Snowmelt Runoff Assessments of Climate Change Impacts on Water Supplies in the Rio Grande - Rango, A.; Steele, C.; DeMouche, L. (78th Annual Western Snow Conference, 2010)
It has become apparent that the effects of climate change will be especially important for Southwestern US water users. The NSF-funded EPSCoR project Climate Change Impacts on New Mexico's Mountain Sources of Water focuses on improving hydrometeorological measurements, developing basin-wide and sub-basin snow cover mapping methods, generating snowmelt runoff simulations and long-term climate change assessments, and informing the public of the results through outreach and educational activities. Five new and 12 upgraded SNOTEL sites, four SCAN stations and about 30 new automated weather stations are being added to New Mexico measurement networks. 25 sub-basins of the Rio Grande have been identified as important snowmelt basins where development and testing of snow cover mapping methods will be conducted. High spatial resolution Landsat TM data (30 m) are being used to evaluate estimates of snow cover from Terra MODIS moderate spatial resolution data (250m and 500 m). We aim to identify the best snow-mapping algorithm for the Rio Grande basin using Snowmelt Runoff Model (SRM) simulations. For the snowmelt modeling, we are using an updated revision of SRM which can automatically assess the climate change effects on water supplies of future climate scenarios.
Keywords: New Mexico, climate change, snowmelt runoff, hydrometeorological instrumentation, snow cover mapping, water supply

Influence of Recent Major Atmospheric River Events on Snowpack in Western Washington - Schick, L.; Pattee, S. (78th Annual Western Snow Conference, 2010)
Mid-latitude, east Pacific cyclones, with attached atmospheric rivers (ARs), are important in producing extreme, basin-wide precipitation events along the west coast of the U.S. and Canada. ARs are narrow corridors, less than about 1,000 km wide, of concentrated low-level water vapor, extending more than about 2,000 km long (Bao et al., 2006). After making landfall, ARs often produce abundant orographic rainfall when intersecting mountainous terrain. They are a major component in linking weather with climate, as they can produce a relatively high amount of the annual winter precipitation in a few days. ARs play an important role in water management, flood control, and water supply, as well as public safety. Studies indicate ARs generally increase snowpack through California, but in western Washington their influence generally causes minor decreases in snow water equivalent due to generally lower terrain and relatively higher AR snow levels. This paper explains the nature of recent major AR weather events (WY 2004 - 2009) and examines their effect on the snowpack in western Washington.
Keywords: Canada, U.S., atmospheric rivers, orographic rainfall, precipitation, flood control, water management

Simulated Effects of Beetle Attacks and Salvage on Water Yield - Swanson, R.H. (78th Annual Western Snow Conference, 2010)
The purpose of this paper is to estimate plausible hydrologic effects of mountain pine beetle attacks and subsequent salvage efforts on annual water yield and peak flows from affected watersheds. I use the WinWrnsHyd program, based on the WRENNS (USEPA 1980) procedure to estimate annual water yield and peak flow changes. The WinWrnsHyd program is used to simulate attack by mountain pine beetles under four scenarios: a) No salvage, b) immediate salvage of all merchantable timber, and c) 1-5 year delay of salvage. In each case I impose two wind regimes, 1) winter wind speeds 15-20 km/h and 2) winter wind speeds less than 4-7 km/h. Salvage clear-cuts are 20 ha blocks. The 'no salvage' and 5-year delayed salvage scenarios produce the greatest increase in water yield and peak flows. Both results are attributed to the standing dead trees which form a barrier to wind penetration to the snow surface to minimize the effect of wind on winter snow loss. The 'immediate salvage' scenario produces varying results depending upon winter wind speeds and the size of salvaged areas. The snow in 20 ha clear-cuts is susceptible to wind-driven erosion and sublimation losses. With 20 km/h winds, the snow pack can be completely depleted until the height of regrowth (about 20 years after initial beetle attack in this case) is sufficiently high to protect the snow surface from erosion and sublimation
Keywords: WRENNS, WinWrnsHyd, annual water yield, mountain pine beetle, salvage

Relationship between Climatic Conditions and Soil Properties at SCAN and SNOTEL Sites in Utah - Vaughn, K.; Julander, Randall P. (78th Annual Western Snow Conference, 2010)
To improve our understanding of the influence of climatic conditions on soil properties, long-term in-situ monitoring is essential. The USDA's Natural Resources Conservation Service's National Water and Climate Center has established a nationwide network of climate monitoring stations known as the Soil Climate Analysis Network (SCAN) and Snowpack Telemetry (SNOTEL) Network. Both SCAN and SNOTEL provide real-time soil moisture and temperature data coupled with additional climate information for use in natural resource planning, drought assessment, water resource management, and resource inventory. Above and below ground climatic conditions are well documented in Utah with 35 SCAN and 97 SNOTEL stations. Research at high elevation sites (>2500 m) reveals that snow water equivalent and snow depth have profound effects on soil temperature patterns. Along an elevational gradient in the Uintah Mountains in northeastern Utah, soil temperature is not proportional to air temperature under snowpack due to differences in snow accumulation. Additional research at middle elevation sites (2000 m) explains how vegetation communities are impacted by differences in edaphic properties across short distances. Data collected at SCAN and SNOTEL stations are used primarily to forecast water supply in the west, improve irrigation efficiency, and indicate the presence of drought conditions, however, the collection of climatic data, such as these, is integral to managing the agricultural and environmental needs we face now and into the future.
Keywords: Soil, climate, snow water deficit, soil temperature, soil moisture, Utah

2009 Title, Contents, and Minutes (77th Annual Western Snow Conference, 2009)
Content includes Table of Contents SNOW NOTES Minutes of the Western Snow Conference Executive Committee Meeting Minutes of the Western Snow Conference Business Meeting 77th Annual Meeting of the Western Snow Conference – Attendees

An Analysis of Long-Term Precipitation and Snow Water Equivalent Records in the Lake Tahoe and Truckee River Watersheds - Boyle, D.P.; Schumer, R.; Ashby, J.; Klieforth, H.; Makowski, A.; Barth, C.; Garner, C. (77th Annual Western Snow Conference, 2009)
As part of the long-term Nevada Cloud Seeding Project, continuous manual measurements of storm precipitation and snow water equivalent (SWE) were made from 1966 through approximately 2001 at 29 sites throughout the Lake Tahoe and Truckee River watersheds in Nevada and California. Monthly values of precipitation for each of the sites have been estimated from the storm-based precipitation records from approximately 1968 through 1992. The processing of the remaining years of precipitation data and the entire period of record for the SWE measurements is underway and the entire data set will be available on the Nevada Water Resources Research Institute web site when completed. In this poster, we present an overview of this unique data set and its utility for: (1) improving the calibration of precipitation-runoff models to support river and reservoir operations in these watersheds; (2) testing and evaluating independent models (e.g., SNODAS, PRISM) designed to estimate the distribution of precipitation and SWE; and (3) estimating temporal and spatial statistics of precipitation and SWE in the watersheds. (Abstract only)
Keywords: Precipitation observations, cloud-seeding, SWE, long-term records, Lake Tahoe, Truckee River

Diminishing Snowfall in Central and Northern California's Mixed Rain and Snow Elevation Zone - Freeman, G.J. (77th Annual Western Snow Conference, 2009)
Snowfall over large areas of the low elevation snow zone in central and northern California below the 1,524 m (5,000 ft) elevation has significantly diminished since the mid-twentieth century and for some areas where it has historically snowed, precipitation now occurs only as rainfall. An analysis of snowfall measurements from several NOAA National Weather Service cooperative weather stations throughout central and northern California revealed a significant decrease in measured snowfall in recent years. Earlier studies have mostly focused on snow courses and automated snow sensors at elevations above 1,524 m (5,000 ft). This study analyzed snowfall measurements only between the 457 m (1,500 ft) and 1,524 m (5,000 ft) elevations. Snowfall is typically measured manually utilizing a snowboard that is measured daily, swept clean, and then reset for the following day's collection. Some of the NOAA cooperator climate stations offer usable data and are an excellent source for evaluating low elevation precipitation type utilizing measured snowfall. Several mountain communities in California exist in the rain-snow zone between the 457 m (1,500 ft) and 1,524 m (5,000 ft) elevations. Continuing reductions in snowfall for these mountain communities reduces the need for snow removal equipment, designing building structures for heavy snow loads, and is creating a changed winter lifestyle, one with less snowfall.
Keywords: Declining snowfall, California mountains, mid-elevation zone, cooperator stations

Changes to North American Snowpack from 1979-2004 Based on the Snow Water Equivalent Data of SMMR and SSM/I Passive Microwave Sensors and Related Climatic Factors - Gan, T.Y.; Rajagopalan, B.; Barry, R.; Gobena, A.K. (77th Annual Western Snow Conference, 2009)
Changes to the North American (NA) snowpack from 1979-2004 based on the snow water equivalent (SWE) values retrieved from the SMMR and SSM/I Passive Microwave data were analyzed using the non-parametric Kendall's test, given that significant decrease in snow cover has been observed in the Northern Hemisphere since the 1980s and drastic increase in the surface temperature of NA has been observed since the 1970s. About 30% of detected decreasing trends in SWE for 1979-2004 are statistically significant alpha/2 = 0.05, which is about 3 or more times more frequent than detected increasing trends in SWE. Significant decreasing trends in SWE are more extensive in Canada than in the US, where such decreasing trends are mainly found along the American Rockies. The overall mean trend magnitudes are about -0.4 to -0.5 mm/year which means an overall reduction of snow depth of about 10 to 13 cm (assuming a snowpack density of 0.1) which can have significant impact to regions relying on spring snowmelt for water supply. The PC1 of NA's SWE are found to be significantly correlated to the Pacific Decadal Oscillation (PDO) index, marginally correlated to the Pacific North American (PNA) pattern, but not much related to El Nino Southern Oscillation (ENSO).
Keywords: Snow water equivalent, passive microwave, SWE trends, decreasing snowpack, global warming

Comparison of Snow Water Equivalent Retrieved from SSM/I Passive Microwave Data Using Artificial Neural Network, Projection Pursuit, and Nonlinear Regressions - Gan, T.Y.; Kalinga, O.; Singh, P.R. (77th Annual Western Snow Conference, 2009)
The snow water equivalent (SWE) for the Red River basin of North Dakota and Minnesota was retrieved from data acquired by passive microwave SSM/I (Special Sensor Microwave Imager) sensors mounted on the US Defense Meteorological Satellite Program (DMSP) satellites, by an artificial neural network called Modified Counter Propagation Network (MCPN), a Projection Pursuit Regression (PPR) and a nonlinear regression. The airborne gamma-ray measurements of SWE for 1989 and 1997 were used as observed SWE, and SSM/I data of 19 and 37 GHz frequencies, in both horizontal and vertical polarization, were used for the calibration (1989 data from DMSP-F8) and validation (1997 data from DMSP-F10 and F13 of both ascending and descending overpass times were combined) of the models. The SSM/I data were screened for the presence of wet snow, large water bodies like lakes and rivers, and depth-hoar. The MCPN model produced encouraging results in both calibration and validation stages (R2 was about 0.9 for both calibration (C) and validation (V)), better than PPR (R2 was 0.86 for C and 0.62 for V), which in turn was better than the multivariate nonlinear regression at the calibration stage (R2 was 0.78 for C and 0.71 for V).
Keywords: Snow water equivalent, SSMI, passive microwave, neural network, Red River Basin

Declining Snowpack Depths and Snow Water Equivalent at Snowpack Monitoring Sites in the Rocky Mountain Region, USA, 1993-200 - Ingersoll, G. P.; Mast, M.A.; Campbell, D.H.; Clow, D.W.; Nanus, L. (77th Annual Western Snow Conference, 2009)
Recent studies indicate the widespread decline of snowpack depths and snow-water equivalent in the western USA. Since 1993, the US Geological Survey, National Park Service, and USDA Forest Service have operated a network of up to 62 snowpack-chemistry-monitoring sites at elevations above 1,500 meters in the Rocky Mountain region. Two 8-year periods before and during the 2001-2008 drought indicate significant decreases in both snowpack depth and SWE. Further comparisons of trends in the Northern, Central, and Southern Rockies subregions yielded moderate to highly significant declines in snowpack depth and SWE in only the Central Rockies. Regionally decreasing trends in SWE were more pronounced at lower-elevation sites than at higher-elevation sites, however, trends in both snowpack depths and SWE were decreasing with moderate significance at higher-elevation sites during the study.
Keywords: Declining snowpack, snow depth, Rocky Mountains, regional trends

Assessing the Sensitivity of Wasatch Mountain Snowfall to Temperature Variations - Jones, L.P.; Horel, J.D. (77th Annual Western Snow Conference, 2009)
Three methods are employed in this study to estimate the sensitivity of snow falling in the Wasatch Mountains of northern Utah to observed and projected changes in atmospheric temperature. Daily precipitation data from 1 October to 30 April 1979-2008 are examined from selected snowpack telemetry (SNOTEL) sites in northern Utah. Profiles of wet bulb temperature from near crest level (700 mb) to elevations along the mountain slopes of selected watersheds are estimated on days with precipitation soundings launched from the nearby Salt Lake City airport. The rain-snow line is assumed to correspond uniformly to the elevation of the wet bulb temperature equal to 1oC. Probability distribution functions of the fraction of precipitation falling as snow as a function of daily wet-bulb temperature are computed. The percentage of precipitation estimated to fall at wet-bulb temperatures in the range 0-1oC is assumed to switch from snow to rain if temperatures increase by 1oC. While the sensitivity to temperature depends strongly on elevation within the watershed, an increase in tropospheric temperatures of 1oC is estimated to lead to an 8-10% decrease in snow when averaged over the selected watersheds.
Keywords: Wasatch Mountains, climate change, snow sensitivity, SNOTEL

Advances in Spatial Snow Modeling in Mountain Terrain - Kienzle, S.W. (77th Annual Western Snow Conference, 2009)
Snow modeling is a demanding task in itself, but is even more demanding in complex terrain such as the Rocky Mountains. Snow modeling is carried out here with the ACRU agro-hydrological modeling system. A critical advancement was the development of a new method to separate snow and rain (Kienzle, 2008). As a further improvement, a new GIS based method that determines two daily minimum and maximum temperatures, based on incoming radiation calculations and leaf area index adjustments, is presented. This results in a daily, lapse rate dependent, air temperature to determine the precipitation type (snow or rain), and a near-ground air temperature to determine snow melt and evapotranspiration rates. A drawback in most distributed hydrological models is that area calculations are based on the horizontal plane rather than the sloped area. A method is presented to use two area calculations for each hydrological response unit: a horizontal area, which is used for precipitation input calculations, and a larger sloped area, which is used for all other hydrological processes, including interception, sublimation, snow melt, soil moisture, or groundwater recharge.
Keywords: Snow modeling, Rocky Mountains, precipitation type, lapse rate, air temperature, ACRU

Quality Assurance Procedures for Reclamation's AgriMET Weather Station Network - Palmer, P.L.; Hamel, J.L. (77th Annual Western Snow Conference, 2009)
Competition for limited water resources in the western United States continues to increase. To this end, the U.S. Bureau of Reclamation (Reclamation) and Bonneville Power Administration (BPA) partnered to create a network of automated agricultural weather stations - called AgriMet - in the Pacific Northwest. These stations collect and telemeter the meteorological parameters required to model crop evapotranspiration (ET). The information is used by irrigation districts, farmers, resource conservation agencies, and agricultural consultants for irrigation scheduling and related purposes. The network consists of over 70 weather stations in the Pacific Northwest that telemeter weather data each hour via the Geostationary Operational Environmental satellite (GOES). Each station measures air temperature, relative humidity, solar radiation, wind speed, wind direction, and precipitation. Other stations have additional sensors, such as soil temperature, crop canopy temperature, leaf wetness, and diffuse solar radiation. Accuracy of the weather data is critical to successful crop water use modeling and other applications. Quality assurance for the AgriMet program consists of five interdependent components: laboratory sensor calibration, an annual maintenance and calibration visit to each weather station, automated data quality control procedures, manual data quality control procedures, and an annual review of weather and associated evapotranspiration parameters.
Keywords: AgriMet, irrigation, evapotranspiration, water use efficiency, crop coefficients, Kimberly-Penman, NRCS

Modeling Alpine Snow Hydrology in the Canadian Rocky Mountains - Pomeroy, J.; MacDonald , M.; DeBeer, C.; Brown, T. (77th Annual Western Snow Conference, 2009)
Field and modeling studies at Marmot Creek Research Basin in the Canadian Rocky Mountain have been directed to advance the understanding of snow processes and to improve hydrometeorological models of snowpack, streamflow and related atmospheric variables. Modeling studies of blowing snow over alpine terrain are showing promise in the prediction of the spatial distributions of snow water equivalent in complex environments. It calculates snow accumulation as a residual of the snow redistribution and sublimation processes. An important new feature is the application of the model to aggregated landscape units (Hydrological Response Units or HRU). Comparisons of model outputs to snow surveys suggest that this level of spatial resolution and physically based simulation can produce reliable snow accumulation estimates in Canadian Rocky Mountain alpine catchments. Snow ablation studies have focussed on application of the energy balance to estimate snowmelt over landscape units with consideration of sub-unit depletion of snow covered area. The calculated melt rates agree well with observations snow surveys. Improved algorithms are being used to update a modular, object-oriented computer simulation of the cold regions hydrological cycle, the Cold Regions Hydrological Model, CRHM.
Keywords: Marmont Creek, blowing snow, snowmelt, snow covered area depletion, hydrological modeling, CHRM

Field Testing and Comparison of Four Snowmelt Model Approaches in the Quesnel Highlands, Interior British Columbia - Przeczek, K.; Déry, S.; Menounos, B.; Moore, D. (77th Annual Western Snow Conference, 2009)
In an attempt to improve the performance of the basic temperature-index (TI) snowmelt model, modifications, including the addition of energy balance terms, have been introduced. One of the more popular modifications has been the inclusion of a shortwave radiation term or proxy term. We compared the performance of a selection of temperature-index snowmelt models at a partly forested site in the interior of British Columbia, Canada. A basic TI model, a TI model with slope, aspect, and forest cover correction factors (HBV-EC, CHC 2006), a TI model with a modeled potential incoming shortwave radiation term (Hock, 1999), and a TI model with a measured shortwave radiation term (Pellicciotti et al., 2005) were compared against snow course measurements on north and south aspect open and forested sites, total season melt on east and west aspect open and forested sites, and against daily automatic snow pillow melt data. Including the effects of slope and aspect and forest cover in some form in TI models does appear to improve melt modeling. The HBV-EC model performed better than the basic TI model and about the same or better than the two models that included solar radiation explicitly. There was little difference observed between the slightly varying radiation index models from Hock (1999) and Pellicciotti et al. (2005).
Keywords: Temperature index, snowmelt model, shortwave radiation, snow pillow, HBV-EC model, British Columbia

Evaluating Snowmelt Modeling Methods of Different Complexities at a Watershed in the Canadian Rockies - Singh, P.R.; Gan, T.Y.; Gobena, A.K. (77th Annual Western Snow Conference, 2009)
Three snowmelt models of different degrees of model complexity and data requirement were used to simulate snow accumulation and ablation processes for a watershed in the Canadian Prairies. Results show that modifying the popular temperature index method by incorporating near-surface soil temperature as an additional predictor to air temperature could considerably improve the model performance. In addition, the modified method could achieve hourly simulation results that are comparable to a physically based energy balance method. Majority of the improvement in the modified temperature index method occurs when the melt rate is varied as a function of near-surface soil temperature.
Keywords: Canadian prairie, snowmelt, modeling, MacKenzie River, energy balance

The Relationship Between Monthly Precipitation and Elevation in the Canadian Rocky Mountain Foothills - Smith, C.D. (77th Annual Western Snow Conference, 2009)
Many areas of the Canadian Rocky Mountains foothills have very sparse or no instrumentation for climate monitoring. To better monitor and understand precipitation processes in the Alberta foothills, the Foothills Orographic Precipitation Experiment (FOPEX) was initiated. FOPEX consists of six meteorological sites installed in a 40 km east-west transect between Caroline and Limestone Mountain in west-central Alberta, Canada. The sites are strategically located at elevations between 1070 and 2120 metres above sea level and were operational between October-2001 and May-2007. Regression analysis showed strong linear relationships between monthly cold season (October through April) precipitation when accumulations are not lower than 70% of the long-term average. When these conditions are met, the rate of increase of monthly precipitation with elevation is shown to be dependent on the total monthly precipitation observed. This increase with elevation is 88% for each 1000 m increase in elevation. Spatial and topographical influences on precipitation during the warm season (May through September) weaken any linear relationship with elevation but it is shown that the average increase with elevation is 38 mm/1000 m when precipitation is not lower than 70% of the long term mean but decreases to 18 mm/1000 m in drier months. A linear relationship between snowpack snow water equivalent (SWE) and elevation is also shown and is found to vary with the amount of precipitation received at lower elevations. Monthly snowpack correlations with elevation are generally weaker than for accumulated precipitation.
Keywords: Orographic precipitation, Canadian Rocky Mountain Foothills, snowpack, FOPEX

The Relationships Between Snowfall Catch Efficiency and Wind Speed for the Geonor T-200B Precipitation Gauge Utilizing Various Wind Shield Configurations - Smith, C.D. (77th Annual Western Snow Conference, 2009)
Most precipitation gauges experience a significant systematic bias in the measurement of snowfall during windy conditions. This bias can be reduced by utilizing various wind shield configurations around the precipitation gauge, but the measurement error for snowfall during windy events often remains substantial and requires an adjustment. To adjust snowfall measurements made by the Geonor T-200B, the relationship between gauge (and wind shield) catch efficiency and wind speed at gauge height must be derived. The most accepted methodology is to compare the catch of the gauge to that of the World Meteorological Organization reference for solid precipitation, the Double Fence Intercomparison Reference (DFIR). Using the precipitation gauge intercomparison facility at Bratt's Lake SK, Catch Efficiency - Wind Speed relationships have been developed for the Geonor T-200B gauge utilizing single Alter, double Alter, and a large octagonal double fence (similar to the DFIR) wind shields. The Geonor T-200B catch efficiency for snowfall typically drops off exponentially with increasing wind speed at gauge height. Of the shielded gauges that were compared to the DFIR, the single Alter exhibits the lowest catch efficiency followed by the double Alter.
Keywords: Bratt's Lake, Saskatchewan, snowfall measurement, precipitation gauge, wind shield, wind effects

Managing Snowcovers in Grain Fields Harvested for Straw Fiber - Steppuhn, H.; Stumborg, M.; Lafond, G.; McConkey, B. (77th Annual Western Snow Conference, 2009)
Agriculture across the Northern Great Plains and Canadian Prairies depends on snowcover resources for dryland crop production in semi-arid environments. On average, between 15 to 35% of the mean annual precipitation within this region falls as snow. Selecting the harvest method and controlling the stubble height of grain crops are among the techniques available to farmers and ranchers for managing the snow that falls upon or blows across their fields. Considerable crop stubble is now harvested and converted to useful bio-products, and more straw for fiber will be utilized in the future. This creates a challenge to devise new equipment and improve techniques in order to harvest both crop grain and straw but also maintain enough standing stubble to retain snow for subsequent crop production. One technique uses a stripper rather than the standard sickle header on the combine to harvest the grain-filled seed-heads when ripe. The stripper leaves ample straw which can be harvested later in various ways to also trap snow and manage snowcovers. Preliminary field results with the stripper in harvesting wheat, flax, lentils, barley, and other crops encourage the continuation of field trials to evaluate snow retention with the implement.
Keywords: Snow management, stubble management, snow control, stripper header, dryland crop harvest, soil-water management

Effects of Mountain Pine Beetles and Timber Harvesting on Stand Attributes and Snow on the B.C. Interior Plateau - Teti, P. (77th Annual Western Snow Conference, 2009)
Considerable progress has been made in describing the effects of clearcut harvesting and reforestatation on snow accumulation and melt relative to mature healthy forests. However, in the aftermath of the recent mountain pine beetle infestation in B.C., the effects of harvesting beetle-killed pine stands need to be compared with what would have happened if the killed stands had been allowed to develop naturally. This paper reports on a project in which snow accumulation and ablation were compared in recent clearcuts, partially recovered plantations, and in natural pine stands at different stages of disturbance and recovery. SWE and ablation rates in treed plots were standardized by calculating ratios of SWE and ablation rates in treed plots to those in nearby clearcuts. SWE ratios were > 1 in only 3 of the 19 treed plots - a recently-defoliated stand and two plantations under 15 years old. Snow ablation ratios were > 1 only in a 15 year-old plantation. SWE ratios and ablation ratios in plantations and killed pine stands were analyzed as functions of time since disturbance. Results suggest that harvesting recently-killed pine stands could increase the rate of snowmelt for 15 to 25 years on the B.C. Interior Plateau.
Keywords: forest harvest; Pine beetle; snowpack reduction; timber harvesting

Perception of Winter in Canada through La Presse Newspaper (1959-2006) - Toupin, J.; Langevin, R. (77th Annual Western Snow Conference, 2009)
A classification has been developed in order to analyze how La Presse Newspaper (one of the largest French-speaking newspapers in Canada and published in Montreal, Quebec) introduces winter to its readers (about one million). A total of 10 winters (from November 1st to April 30th with focus on page 1 and 3) ranging from 1959 to 2006 were selected: 1959-1960, 1965-1966, 1970-1971, 1975-1976, 1980-1981, 1985-1986, 1990-1991, 1995-1996, 2000-2001 and 2005-2006. In all, 894 articles were classified into 7 categories: 1) Snowstorm/Accident/Death, 2) Sport/Tourism, 3) Debates/Ideas, 4) Crime, 5) International News, 6) Festivals, and 7) Environment. As years go by, one notices that the number of articles talking about winter is considerably less significant (for instance 355 articles for 1959-1960, and only 52 articles for 2005-2006), but is more targeted on the front page and on page 3, occupying a larger space and focusing more and more on negative aspects (including more pictures) of the cold season.
Keywords: La Presse Newspaper, classification, winter, snow, cold

A Summary of Research into the Effects of Mountain Pine Beetle Related Stand Mortality on Snow Accumulation and Ablation in British Columbia, Canada - Winkler, R.D.; Boon, S. (77th Annual Western Snow Conference, 2009)
Extensive mountain pine beetle related forest mortality throughout the Interior of British Columbia raises concern regarding the effects of stand deterioration on snow accumulation and ablation, and spring runoff. Studies quantifying post-pine beetle snow accumulation and ablation rates show that, on average, once 50% or more of the canopy in mature stands has been lost (defined here as grey attack), snow accumulation is only 13% lower than that in the open compared to a 25% reduction in mature green/red attack. Reductions in snow ablation rate were similar, on average, in the green/red and grey attack: 38% and 31%, respectively. The average snow duration in both attack classes is also similar (3-4 d longer than in the open). Differences in snow accumulation and melt are highly variable between study locations and years, with spatial differences often exceeding those related to stand condition. Development of best management practice guidance for broad geographic areas is dependent upon coordinated research efforts at the same scale, as well as consistency in project design, stand description, survey and data analysis methods.
Keywords: British Columbia, pine beetle, forest mortality, snowpack reduction

2008 Title, Contents, and Minutes (76th Annual Western Snow Conference, 2008)

Ultrasonic Snow Depth Sensor Accuracy, Reliability, and Performance - Anderson, J.; Wirt, J. (76th Annual Western Snow Conference, 2008)
The Natural Resources Conservation Service Snow Survey Data Collection Office (DCO) in Boise, Idaho began installing Judd Communications Snow Depth Sensors in the late-1990s. Since that time the number of SNOTEL sites in the DCO with snow depth sensors has increased to 76 out of a total of 117 sites. Over the years 348 depth sensor ground truth measurements have been made each time snow water equivalence was measured at a site. Telemetered SNOTEL snow depths compare very well with manually sampled depths with a high degree of accuracy (R2 = 0.98). To test the reliability of the sensor during the accumulation phase of winter, hourly data between 12/1/2007 - 3/20/2008 were analyzed to determine the number of missed measurements (full-scale readings). Results showed that out of 228,798 hourly readings, 14% were full-scale. No clear relationship was found between the age of the depth sensor and its reliability. In 1999 the Idaho DCO began editing daily snow depth data. This editing process has provided an opportunity to observe the performance of depth sensors. Performance related to damaged transducers, transducer obstruction, wind effects, sensor misalignment and storm effects are discussed.
Keywords: Snow depth sensor, SNOTEL, NRCS, Idaho, sensor reliability

Assessing the Impacts of Global Warming on Snowpack in the Washington Cascades - Casola, J.H.; Cuo, L.; Livneh, B.; Lettenmaier, B.P.; Stoelinga, M.; Mote, P.W.; Wallace, J.M. (76th Annual Western Snow Conference, 2008)
The decrease in mountain snowpack attributable to global warming is difficult to estimate in the presence of the large year-to-year natural variability in observations of snow water equivalent (SWE). A more robust approach for inferring the impacts of global warming is to estimate temperature sensitivity of spring snowpack and multiply it by putative past and future temperature rises attributable to global warming. Estimates of sensitivity can be obtained from (a) geometric considerations regarding the change in the climatological snow line resulting from warming, (b) regression of historical April 1 SWE measurements upon mean winter temperatures, (c) a hydrological model forced by daily temperature and precipitation observations, and (d) the distribution of precipitation versus temperature at SNOTEL stations. All four methods yield an estimated 20% loss of spring snowpack for 1deg C warming; considering warming-induced precipitation increases, the sensitivity would decrease to 16%. Using various rates of temperature rise over the Northern Hemisphere, it is estimated that spring snow water equivalent in the Cascades portion of the Puget Sound drainage basin should have declined by 8-16% over the past 30 years due to global warming and it can be expected to decline by another 11-21% by 2050.
Keywords: Snowpack decline, global warming, Washington Cascades, temperature

The North Olympic Peninsula Solutions Network: Extending NASA Tools Beyond the Research Community to Resource Management User Groups - Doherty, M.; Ward, J.; Barry, D.; Wigmosta, M.; McDonald, S.; DeSisto, C.; Sehlke, J.; Rome, C. (76th Annual Western Snow Conference, 2008)
The North Olympic Peninsula Solutions Network (NOPSN) is extending the tools, knowledge, and results of National Aeronautical and Space Administration's (NASA) Applied Sciences Program beyond the science and research communities to contribute to national priorities with societal benefits, such as in ecological forecasting, water management, and agricultural efficiency. NOPSN is interacting with local, state, regional, and national user groups to identify new opportunities to use NASA tools and technology; our overall approach will be to leverage these relationships and extend them to include the use of NASA tools and technologies. This paper explains our Solutions Network and its initial project developing improved streamflow forecasting in a rain-and-snow-dominated watershed in western Washington State. Many of the tools and concepts we are employing can be readily extended to regional and national scales, so there are opportunities for developing discussion partnerships with NOSPN to determine the best way to provide NASA tools and technologies to other user groups to improve existing or future decision-support systems or tools, to assess and manage ecological impacts across regional, national, and international borders.
Keywords: NASA, ecological forecasting, water management, Washington, Dungeness River

Untangling Climate and Wildfire Influences from Snow Water Equivalent Measurements on the Deer Park, Washington Snow Course - Drake, E.; DeSisto, C.; McDonald, S.; Evans, S.; Barry, D.; Baccus, B. (76th Annual Western Snow Conference, 2008)
In 1988, the Deer Park Fire burned 170 acres within Olympic National Park, WA. The wildfire burned up to the southern end of the NRCS/NPS Deer Park Snow Course. The burn eliminated a forest stand downwind and down-slope of the snow course; this study reports on a potential decline in snow water equivalent (SWE) measured by the course as a result of this adjacent change in forest cover. Regional climate trends based on Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) were incorporated into the evaluation, allowing the wildfire's impacts to be isolated from climatic variability. A comparison of mean SWE values before (1949-1988) and after (1989-2007) the wildfire for every reporting month in every climate cycle showed a clear trend of a decline after the wildfire; these differences are statistically significant in April and May for all climate cycles except for positive PDO+negative ENSO. Overall, estimates of effect size of the difference between means were uniformly negative and as low as 2.9 for February 1 snowpack in warm, dry climate cycles and as high as 17.1 for May 1 snowpack in cool, wet climate cycles.
Keywords: Deer Park fire, Olympic National Park, snow course, SWE, PDO, ENSO, snowpack decline

Snow Sinking Studies - Farnes, P.E. (76th Annual Western Snow Conference, 2008)
In snow covered regions, predator-prey relationships change with snow conditions. Some snow conditions are advantageous to the predators while other snow conditions favor the prey species. To understand the relationship between bearing pressure imposed by the various animals and how deep they sink into the snowpack, and different snow parameters, 193 measurements were taken over a 13 year period. Most of the sampling was done in Yellowstone National Park on the Northern range at four to six locations three to four times each winter. Curves were developed to predict how far an animal or object having a known bearing pressure will sink into a snowpack of a given depth and density. Equipment developed and procedures used will be described. Results have been combined into a graph to simplify use. Data is particularly important to evaluating animal's ability to move through snow and predator-prey relationships involving snow, but can also be used to evaluate how deep oversnow vehicles, helicopters with snow pads, skis or snow shoes sink into the snowpack.
Keywords: Predator-prey, snow condition, foot pressure, snow density

Climate Change and Flood Control Operations in the Sacramento Basin - Fissekis, A.; Lund, J.; Townsley, S.; Brekke, L.; Fickensher, P.; Faber, B. (76th Annual Western Snow Conference, 2008)
Shasta, Oroville and New Bullards Bar reservoirs are being studied to determine how Northern California's flood control projects respond to climate changed inflows. The goal of this project is to identify why flood control curves should be based on data-gathering and technological improvements that have occurred since the curves were created in the mid-1900s. In collaboration with the Institute for Water Resources, the Bureau of Reclamation, the California-Nevada River Forecast Center (CNRFC) and the Hydrologic Engineering Center, the U.S. Army Corps of Engineers is using climate projections for the year 2030 to test how flood control rule curves respond to changes in timing and magnitude. Preliminary research indicates that both temperature and precipitation changes will occur during that period and that they will alter historically observed flows. As California receives most precipitation between November and May, adapting to changes in peak flow timing and snowmelt runoff is not only crucial to reserve an adequate supply of water into the summer and fall, but also to ensure adequate flood storage.
Keywords: Climate change, flood control, rule curves, runoff timing, CNRFC

Runoff Impacts of Climate Change on Northern California's Watersheds as Influenced by Geology and Elevation - A Mountain Hydroelectric System Perspective - Freeman, G.J. (76th Annual Western Snow Conference, 2008)
Northern California's Pit, McCloud, Feather, Yuba, and American Rivers each have regional differences that set them apart from the higher elevation, less porous Sierra watersheds to the south. The watersheds from Lake Almanor north are primarily characterized by relatively porous volcanic basalt rock flows with several large springs that provide a large sustained base flow component. Relatively low overall elevation sets these northern watersheds apart as some of the first watersheds in California anticipated to be affected from climate-induced change to snowpack. During an average water year, for much of the Pit and McCloud Rivers, approximately 80-90 percent of river runoff is water from past years that emerge from springs as aquifer outflow. For those rivers that overlay large volcanic aquifers, the form of precipitation has much less significance on runoff timing than watersheds south of Lake Almanor. Climate change is not anticipated to significantly affect timing and quantity of runoff for the basalts, but it will likely have relatively large timing and quantity changes for the Yuba, American, and some reaches of the North Fork Feather River. The Yuba River Basin which has a relatively large proportion of exposed granite in its headwaters is revealing a significant timing shift in runoff into earlier months. This will have effects on hydrogeneration and reservoir operation.
Keywords: Sierran watersheds, basalt rock, spring flow, Pit River, Yuba River, runoff timing, runoff quantity

Characteristics of Snow Water Equivalent to Precipitation Ratios in Utah - Julander, Randall P.; Bricco, M. (76th Annual Western Snow Conference, 2008)
Snow water equivalent (SWE) to precipitation (PCP) ratios have recently been used as evidence to support climate change. The assumption is that when a site or region's SWE to PCP ratio declines, temperature is a driving mechanism. In fact, there is a reasonable linear statistical relation between these two variables, but there may be other influencing factors involved in both the site and regional SWE to PCP relations. There are distinctly different physical phenomena occurring at land surface relative to the location of the orifice of a precipitation gage some distance above that surface, such as vegetation and wind direction, run and general velocity. There also is a large 'scale' difference in exposed area of data collection between a 3.05 meter diameter snow pillow and a 30.5 cm diameter precipitation gage. SWE to PCP ratios change throughout the snow accumulation season and SWE, in general, outpaces precipitation accumulation. Therefore, a SWE to PCP ratio analysis on some arbitrary date such as April 1 may have strong systematic bias. The result is that the overall magnitude of SWE in any given year may be a strong indicator of the eventual SWE to PCP ratio.
Keywords: SWE, precipitation, climate change, ratio, systematic bias

Effect of Snowpack Changes in the Central Sierra Nevada on Water Supply Forecasts in the Truckee River Basin - Lea, J. (76th Annual Western Snow Conference, 2008)
Water supply forecasts rely on a historic record of precipitation, snow and streamflow. The snowpack in the central Sierra Nevada has been measured each year since the early 1900s. Currently the USDA Natural Resources Conservation Service and the California State Cooperative Snow Survey program measure snow in the Sierra Nevada and keep long term records of the snowpack. These long-term records are a good indicator of seasonal precipitation in the building of the snowpack in the region. A statistical analysis of the snowpack record at Donner Summit compared to Tahoe City precipitation reveals a shift in the relation that occurred in the late 1970s. This change in the relation of the April 1 snow and cumulative seasonal precipitation in the area is statistically significant at the 99.9% level. Since the late 1970s, there no trend has been observed in annual precipitation amounts and annual streamflow volume on the Truckee River. However a decrease in the amount of cumulative snowpack on April 1 in comparison to the seasonal precipitation of October through March between these two sites has been observed. This indicates that from 1980 to 2007 there has been more rain than snow compared to the previous 43 years.
Keywords: Runoff forecasting, snow accumulation timing, Donner Summit, declining snowpack, water supply

Modeling Spatial Differences in Snowmelt Runoff Timing - Lott, F.C.; Lundquist, J.D. (76th Annual Western Snow Conference, 2008)
Discharge in small, tributary streams affects water table heights, riparian vegetation, and habitat in subalpine meadows. This project investigates how topographic shading affects the advance of snowmelt onset and the date snow disappears as temperatures warm in Yosemite National Park, California. Observations show that in years where the temperature warms earlier in the season, south-facing sub-basins start melting over a week earlier than north-facing basins. Thus, meadow areas fed by sub-basins with southern aspects are expected to be much more sensitive to warming temperatures than areas fed by sub-basins with northern aspects. Traditionally, most future hydrologic simulations are run for large basins, and these effects would not be captured. The Distributed Hydrology Soil Vegetation Model (DHSVM) is used to test if high-resolution (150m) modeling containing a topographic shading component can represent these observed differences in various sub-basins and meadow regions. The findings help define the model complexity needed to properly represent the effects of shading in mountainous terrain.
Keywords: Subalpine meadows, Yosemite, Tuolumne River, DHSVM, runoff timing, topographic shading

Near-Term Global Warming Effect on Hetch Hetchy Inflow - McGurk, B.J.; Hannaford, M.A. (76th Annual Western Snow Conference, 2008)
Studies have shown that changes in winter air temperature have an effect on snow deposition and runoff patterns in the Sierra Nevada. Hetch Hetchy Reservoir, on the Tuolumne River at 3,806 feet, impounds 459 square miles of Yosemite National Park. Hetch Hetchy Water and Power (HHWP) uses a monthly runoff forecasting model that incorporates historical temperature, precipitation, and snowpack to predict monthly inflow. Given current conditions, the model estimates monthly runoff for the rest of the water year based on 48 years of historical climatology. An evaluation of an estimated 3 degrees F increase in temperature, assumed to occur by 2025, was performed. The historical daily maximum and minimum temperatures were increased by 3 degrees F, and the adjusted monthly runoff results were compared to the base run. On average, 7% of the annual runoff shifted from the April through June period to the November through March period. Less snowpack accumulated in the lower elevation zones due to the rise in the rain-snow line. The effect was proportionally larger for dry years than for wet years. Implications to water supply in the near term are minor, but long-term impacts that are coupled with increased demand are of concern.
Keywords: Climate change, runoff timing, temperature rise, statistical model, Tuolumne River

Changing Climate of Idaho: Future Prediction Maps - Moore, B.C.; Walden, V.P.; Humes, K.S. (76th Annual Western Snow Conference, 2008)
Scientific evidence of decreasing snow packs (Mote et. al., 2005; Mote, 2006) and changing streamflows (Gahn et. al., 2006; Gahn and Shippert, 2006) in the Pacific Northwest (PNW) have prompted water managers around the West to begin planning for the potential effects of climate change on water resources. Idaho is particularly sensitive to potential changes in both water supply and demand, because the state's economy depends heavily upon agriculture, forestry, and tourism, as well as hydroelectric power generation; all of which are at risk due to rapid shifts in climate. Because of this, numerous scenarios of possible meteorological and hydrological conditions are needed to allow for planning of the state's future. We outline a method to improve the downscaling of climate scenarios from the Intergovernmental Panel on Climate Change, as well as how to combine the downscaled climate scenarios with historic snow cover images to produce future snow related products.
Keywords: Climate change, Idaho, water supply, water management, downscaling

Assessing the Representativeness of the NRCS SNOTEL System at a Basin-Wide Scale - Nolin, A.W.; Brown, A. (76th Annual Western Snow Conference, 2008)
Information from the NRCS SNOTEL system is used throughout the West for streamflow forecasting, disaster preparedness and scientific research. Measurements taken from the network are often fed into climate models where they can be used to analyze patterns and illustrate changes. Within the Willamette Basin the majority of the network falls within mid range elevations of 1000-1500 meters. While there are few sites located below 1000 meters, there is no instrumentation above 1500 meters. The upper elevations make up a relatively small proportion of the entire basin, however, they do account for about 50 percent of the total snow covered area. Projected climate warming in the Pacific Northwest places an increased importance on accurate instrumentation and forecasting of snow covered areas. An analysis of the relationship between at-risk snow zones and the location of SNOTEL sites illustrates the need for the development of a methodology to insure the representativeness of the system.
Keywords: NRCS, SNOTEL, basin scale, Willamette Basin, climate change

Glacier Melt Makes a Significant Contribution to Summertime Streamflow in the Upper Middle Fork Hood River - Nolin, A.W.; Phillippe, J. (76th Annual Western Snow Conference, 2008)
Mount Hood is the tallest mountain in Oregon and six of its 11 glaciers feed into the five irrigation districts in Hood River Valley. Glacier meltwater reduces the interseasonal and interannual variability of streamflow. However, the volume of meltwater from Mount Hood glaciers is not known because the glacial-fed streams are not gaged. The objectives of this research are to: 1. Determine the interseasonal and interannual proportions of glacier meltwater to streamflow in the Upper Middle Fork Hood River; 2. Estimate changes in glacier meltwater production on timescales of 10- to 50-years and impacts on low flows in the Upper Middle Fork Hood River. Our approach uses a combination of direct streamflow measurements and a snowmelt-runoff model. During summer 2007, we installed water height recorders at the termini of Eliot and Coe glaciers and at locations several kilometers further downstream. Isotope tracers were also used to compute the relative contributions of water from glacier melt and groundwater. Our measurements indicate that during the lowest flow period of the summer, roughly 74% of the water in the Upper Middle Fork Hood River is derived from glacier melt. These data also served to calibrate a glacier melt-runoff model. Our projections indicate that in about fifty years, the glacier melt contributions to streamflow in the Upper Middle Fork Hood River will have declined by about 31%.
Keywords: Mt. Hood, glacier, glacier meltwater, Hood River, snowmelt, runoff fraction

Snow Measurement Using Ground-Based Tripod LIDAR - Osterhuber, R.; Howle, J.; Bawden, G. (76th Annual Western Snow Conference, 2008)
Using tripod mounted LiDAR, imagery scans of targeted areas of snow covered terrain were collected at various intervals during Winter 2008 both at the main study site of the Central Sierra Snow Laboratory and at a State of California snow course on Donner Summit, California. LiDAR's high measurement accuracy in both range and position facilitates the generation of very detailed three-dimensional data sets that were then analyzed for snow volume over the targeted area. Repeated scans of targeted areas were used to calculate changes in snow depth and volume. Snow depth values as measured by the LiDAR scanner correlated well (R2 = 0.96) with coincident hand measured values.
Keywords: LiDAR, Central Sierra Snow Lab, Donner Summer, snowpack, snow volume

AgriMet: Automated Weather Observations for Evapotranspiration Modeling - Palmer, P.L. (76th Annual Western Snow Conference, 2008)
Competition for limited water resources in the western United States continues to increase. To this end, the Bureau of Reclamation and Bonneville Power Administration partnered to create a network of automated agricultural weather stations - called AgriMet - in the Pacific Northwest in the 1980's. These stations collect and telemeter the meteorological parameters required to model crop evapotranspiration (ET). The network started with three stations in 1983, but has since grown to over 60 stations in Reclamation's Pacific Northwest region, 22 stations in the Great Plains Region in western Montana, and seven stations in the Mid Pacific region. These automated weather stations transmit their data hourly by the GOES satellite, and the information is used in the Kimberly-Penman 1982 evapotranspiration model to compute reference ET at each station. Crop coefficients are then applied to estimate water use for specific crops grown at each station for every day of the growing season. Use of AgriMet information in irrigation scheduling results in water and energy savings, reduced soil erosion, and protection of surface and ground water supplies. Near real time hourly weather data from AgriMet is also used for a variety of applications, including peak power load forecasting, agricultural frost protection, and short term weather forecast verification.
Keywords: AgriMet, irrigation, evapotranspiration, water use efficiency, crop coefficients, Kimberly-Penman, NRCS

Embedded Sensor Network Design for Spatial Snowcover - Rice, R.; Bales, R. (76th Annual Western Snow Conference, 2008)
Scaling point observations of snow water equivalent (SWE) to model grid-element scales is particularly challenging given the considerable sub-grid variability in snow accumulation over complex terrain. In an effort to capture this sub-grid variability and provide spatially explicit ground-truth snow data an embedded snow sensor network was designed and installed in Yosemite National Park. Extensive snow surveys were used to guide the installation of the network and to relate the observations to more detailed spatial SWE fields. Four years of continuous spatial and temporal data from both Yosemite National Park indicate that accumulation and ablation rates can vary as much as 50% based on variability in topography and vegetation. These snow distribution patterns are especially apparent in the open forests where vegetation structure largely controls variability in snow distribution. Comparisons with historical snow course data shows that a single point measurement is a poor estimator of snow depth over a homogenous area, but 4 or more measurement points can reduce the uncertainty by 50%. Further analyses indicated that an optimal snow depth network consists of 7 to 10 snow depth sensors.
Keywords: Sensor network, snow accumulation, Yosemite, snow deposition, SWE

Enhancing Stream Forecast Modeling in California Mountain Watersheds - Shupe, J.; Potter, C.; Klooster, S. (76th Annual Western Snow Conference, 2008)
This study describes research using the NASA Ames version of the Carnegie-Ames-Stanford Approach (CASA) ecosystem model coupled with a surface hydrologic routing scheme called the Hydrological Routing Algorithm (HYDRA) to model the system of California watersheds. To assess CASA-HYDRA's ability to estimate actual water flows in both extreme and non-extreme precipitation years, we have compared the gridded model results on a monthly time scale with gage station data throughout the state. Considering the importance of the snow pack to the state's water regime, we are particularly interested in CASA-HYDRA's performance in California's mountain watersheds. Consequently, we made additional comparisons between our model and results generated from the USDA Snowmelt Runoff Model (SRM) applied to the Merced River watershed in Yosemite, CA. The results of both comparisons highlighted the need to enhance CASA-HYDRA's snowmelt algorithm. The efficacy of the degree-day approach has been demonstrated by the consistently solid performance of the SRM, so we have integrated this algorithm into CASA-HYDRA.
Keywords: Ecosystem model, CASA, HYDRA, runoff prediction, snowmelt, Merced River

Forty Years of International Cooperation: Columbia River Treaty Hydrometeorological Committee 1968-2008 - Smith, S.; R Allerman (76th Annual Western Snow Conference, 2008)
The Columbia River Treaty was ratified in 1964 and established an agreement between the United States and Canada to build three storage projects on the Columbia River system in Canada (Mica, Arrow, Duncan) with the option to build Libby on the Kootenai River in the U.S. The goals of the Treaty were to provide better flood control for communities on the Columbia River, and to provide for the development of hydroelectric power generation in both countries. The Columbia River Treaty Hydrometeorological Committee (CRTHMC, or Committee) was formed in 1968 under the Treaty and was given the responsibility for planning and monitoring the operation of data collection facilities to support the Treaty. The Committee is comprised of members from B.C. Hydro in Canada and the U.S. Army Corps of Engineers Northwest Division and Bonneville Power Administration in the United States. A data exchange system, CROHMS, was developed by the Corps to manage the exchange of information across the Columbia basin to report on and support planning of the operation of Treaty projects on the Columbia River. The Committee has provided a forum for the exchange of ideas to advance the science of water supply forecasting in the Pacific Northwest
Keywords: Columbia River, hydrometeorological committee, flood control, treaty, CROHMS

Forecasting Coquitlam River Basin, British Columbia - Solano, C.V. (76th Annual Western Snow Conference, 2008)
Rain-on-snow events during warm periods with high precipitation amounts can produce high floods. Due to the complexity of the process, predicting run-off during these events is difficult and current conceptual hydrologic models are believed to simulate rain-on-snow events only very poorly. The inability of conceptual hydrologic models to simulate rain-on-snow events correctly may eventually translate into a greater risk adopted into BC Hydro's operations. For this purpose, hydrologic simulations and forecasts of several rain-on-snow events for the coastal Coquitlam watershed, British Columbia, Canada, were selected for analysis. In the first part of this study, the ability of the UBC Watershed Model to simulate Coquitlam Reservoir inflows during rain-on-snow events using observed precipitation and temperature data as model input was investigated using various performance measures. In the second part of this study, performance measures for hydrologic forecasts for the selected rain-on-snow events were calculated and the forecast skill determined.
Keywords: Runoff forecasting, rain on snow, BC Hydro, Coquitlam River, UBC watershed model

Too Much or Too Little: Sustaining Watershed and the People Who Need Them - Toch, S.L. (76th Annual Western Snow Conference, 2008)
Around the world, decreasing water availability and increasing costs of water purification serve as an indicator of our struggle between human demands and the maintenance of ecological functions and processes of natural resources. But while much has been written on the degradation of natural areas, and growing concerns for human health, little has been done to address their connections. While inherently we know that there is a connection between how we use our water resources and the resources available to us, the challenge has been to define this connection in terms that are considered valid, and to apply this knowledge in a strategy for action. This work outlines the similarities and interactions between ecological and human needs; serving as a basis for the identification and development of effective risk assessment and management alternatives that focus on an increased awareness of the tradeoffs inherent in every resource decision. By exploring the connections between water quantity and quantity in land use, water quality and human health, we can gain a better understanding of how human effects on ecological processes do, in fact, affect our quality of life.
Keywords: watershed management, hydrologic system, ecological processes, environmental health, environmental planning, land use, water quality

2007 Title, Contents, and Minutes (75th Annual Western Snow Conference, 2007)

Uses of Natural Resources Conservation Service Snow Survey Data and Products - Abramovich, R. (75th Annual Western Snow Conference, 2007)
In the Western U.S., the annual accumulation of the mountain snowpack and the resulting predictability of streamflow have created a wide range and diverse use of Natural Resources Conservation Service (NRCS) Snow Survey data and products. The key factor in the West is how much snow falls and where it falls for water users to speculate what may happen and plan accordingly. Historically, the NRCS inventoried the mountain snowpack to predict spring and summer streamflow for irrigated agriculture. The installation of the SNOTEL (SNOw TELemetry) Network in the early 1980s and a daily climatic data set has increased the use of this high elevation data. Many customers use this data to assist in their day-to-day decisions, for winter or summer recreation, to hedge financial decisions, or for wise management of water as a natural resource. This paper discusses the importance of snow in the West, how it accumulates, and melts to provide our water supply, and associated decisions made each season to manage and plan accordingly based on the winter snowfall. A seasonal timeline illustrates when customers need and use Snow Survey data and products. The obvious, but also unusual uses of snow survey data and water supply products are discussed.
Keywords: Snowpack, predictability, SNOTEL, snow accumulation, water supply

A Monte Carlo Model for Simulation of Rain-on-Snow Events in the Pacific Northwest - Brunengo, M.J. (75th Annual Western Snow Conference, 2007)
Northwestern North America experiences blasts of heavy winter rainfall, when rain plus melting snow can cause high streamflows and erosion. Geographic variability and sporadic occurrence of rain-on-snow complicate study, but some questions can be addressed through modeling. A computer program combines probabilistic and deterministic elements to perform Monte Carlo simulation of ROS events over many years, generating realizations of initial and weather conditions; within each event, snow accumulation/melt and percolation are tracked, and water avail-able for runoff is the output. Frequency distributions are based on data from the Washington Cascades, some as functions of elevation and date, so the model can be applied to specific sites or generalized zones. Validation focuses on Stampede Pass, a major weather station and snow measurement site. The model is evaluated by comparing statistics and frequency relations of the instrumental record and model realizations for precipitation, R+SM and WAR. In early model applications, the regional zone of greatest ROS enhancement to WAR seems to lie at about 750 m; future uses include assessment of ROS in forest clearings, and possible consequences of climatic change.
Keywords: Rain on snow, Washington Cascades, snow accumulation, snow melt

Estimating Forage Production and Winter Severity on the National Elk Refuge, Jackson, WY - Cole, E.K.; Farnes, P.E. (75th Annual Western Snow Conference, 2007)
Each October through November, elk and bison migrate to the National Elk Refuge (NER) near Jackson, WY to feed on native forage produced on the Refuge. Usually by late January, standing forage has been utilized or becomes unavailable because of snow and ice, and NER staff then supplies supplemental feed in the form of alfalfa pellets. For the past 34 years, NER staff has estimated total annual forage produced on the Refuge by clipping vegetation within different plant community types. Keetch Byram Drought Index (KBDI), and growing degree-days (GDD) based on daily average temperature threshold of 5 deg C have been calculated daily for Jackson and Moose climatological stations since 1949. Also, daily snow water equivalent (SWE) has been estimated for these stations using climatological records. Critical temperatures (-18 deg C for elk) have been summarized using departure from daily minimum temperatures. SWE, forage production, and critical temperatures are weighted and combined to determine Index of Winter Severity (IWS) for elk and bison. Methods for calculating the IWS for elk and bison and how the IWS is used for Refuge operations will be presented. Average KBDI for different accumulations of GDD and spring precipitation are compared to production of grass and forbs on 34 different plant community groups.
Keywords: National Elk Refuge, Jackson, elk, temperature, SWE, forage, Index of Winter Severity

Rapid Climate Change and the West: Snowpacks and Forests at Risk - Diaz, H.F. (75th Annual Western Snow Conference, 2007)
There is a growing recognition in the broader scientific community that rapid climate change from the enhanced greenhouse effect is affecting the western United States. The available data indicates rapid warming in the past 3 decades, with an amplification of the warming signal with elevation. Future climate change scenarios developed as part of the Fourth IPCC Assessment Report suggest that the recent warming trends in the West will continue and intensify. The warming alone will induce greater aridity in much of the West, with worst-case scenarios suggesting a significant reduction in stream flow in most western river basins coupled with much higher risks of forest fires. An ad-hoc interdisciplinary community of climate scientists-including climatologists, hydrologists, and forest ecologists (The Consortium for Climate Change Research in Western Mountains, CIRMOUNT)-has come into existence in the past three years, with the aim of communicating in plain language the environmental and potential socioeconomic threats facing western society from climate change. This paper will examine some of the evidence for rapid warming in the West in recent decades and describe some of our efforts to communicate key findings by the climate science community about ongoing and expected impacts to western society. (Abstract only)
Keywords: Climate change, IPCC, drought, streamflow reduction, CIRMOUNT

Estimating Average Annual Runoff from Montana Streams - Farnes, P.E. (75th Annual Western Snow Conference, 2007)
Procedures for estimating runoff from un-gaged streams will be presented. First and most important is to have an accurate average annual precipitation map for the current base period. The precipitation map needs to be based on a maximum elevation grid of 500 meters and preferably a 100 to 200 meter grid. It needs to be based on a procedure that looks at the nearest two or three neighbors and one that assigns measured values to measured points. The Montana SILC3 Land Cover Classification provides the cover types for most areas. Some of the 36 different cover types that have similar hydrologic responses can be combined for hydrologic analysis. Data from SNOTEL sites and climatological stations in the area was used to determine the relationship between average annual precipitation, average April 1 snow water equivalent, and average April through July precipitation for the current base period. Average annual precipitation and runoff from gaged streams in the area and percent forested area for each gaged watershed are used to determine a runoff vs. precipitation curve for drainages if all of the forest was removed. By applying factors from the cover type vs. forest species age curves, the runoff was determined for the area of each cover type in each precipitation zone. These were accumulated to determine runoff for each watershed or HUC of interest. Using fire history or logging by decades, usually available from land managing agencies, it was possible to determine changes in runoff by decade from any given watershed.
Keywords: Runoff prediction, Montana, SNOTEL, precipitation, cover type, fire history

Precipitation Phase Discrimination by Dew Point and Air Temperature - Feiccabrino, J.; Lundberg, A. (75th Annual Western Snow Conference, 2007)
Correctly reported precipitation phases are crucial for estimation of snow storage in hydrological, regional and global climate models. Precipitation phase is especially critical for models simulating processes in tree canopies, since the canopy storage capacity is about one order of magnitude larger for snow than rain. The number of manned meteorological stations is decreasing, making determination of precipitation phase more difficult. Most hydrological models use an air temperature threshold to separate rain from snow, but there are indications that a dew-point temperature threshold might work better. This study utilized forty-five years of three-hour man-made observations for nineteen Swedish station ranging from 55 deg N to 68 deg N consisting of precipitation mass and phase, air and dew point temperatures. Precipitation events were classed as snow or rain, excluding mixed precipitation, were used for the initial analysis. Air temperature was found to be a better indicator of precipitation phase then dew point temperature. On occasion 0 deg C is used as an air temperature threshold, but if the air temperature rain/snow threshold 0 deg C is replaced by 1.0 deg C, the misclassified precipitation would be reduced by almost half in Sweden.
Keywords: Precipitation phase, air temperature, Sweden, tree canopy

Seasonal Snow Extent and Snow Mass in South America Using SSM/I Passive Microwave Data (1988-2003) - Foster, J.L.; Hall, D.K.; Chiu, L.; Kelly, R./Powell, H. (75th Annual Western Snow Conference, 2007)
Seasonal snow cover in extra-tropical areas of South America was examined in this study using passive microwave satellite data from the Special Sensor Microwave Imagers (SSM/I) on board the Defense Meteorological Satellite Program (DMSP) satellites. For the period from 1988-2003, both snow cover extent and snow mass were estimated for the months of July, typically the coldest winter month. Most of the seasonal snow in South America is in the Patagonia region of Argentina. The average snow cover and snow mass for the 16-year period was 284,492 km2 and 0.763 x 1013 kg, respectively. The year with the greatest average snow extent and snow mass during the 16-year period of record was 1992 -- 551,875 km2 and 2.073 x 1013, respectively. If the strong El-Nino years of 1991-1992 and 1997-1998 are excluded, the July snow mass shows a linear trend of 28% over the 16 years period, with a p-value of 0.0098, which is significant at the 85% level.
Keywords: Seasonal snow cover, SSM/I, South America, satellite

A Cloudseeding Program to Increase Aquifer Outflow in Northern California's McCloud and Pit River Watersheds - Freeman, G.J. (75th Annual Western Snow Conference, 2007)
Northern California's Pit and McCloud River watersheds overlay a combination of highly fractured porous, volcanic High Cascade and flood basalts. Pacific Gas and Electric Company (PG&E) is completing a project that will place 15 ground based cloud seeders in the mountains on and around Mt. Shasta. These seeders will be remotely operated and disperse heated plumes of silver iodide crystals to enhance snowfall over several hundred square miles of forested watershed. A natural lag in runoff response is expected to provide increased outflow from the springs, even during dry years when there may be a scarcity of clouds to seed. Adding additional snow to the snowpack utilizing cloudseeding is anticipated to enhance aquifer pressure increasing naturally occurring groundwater outflow from springs by as much as 9%. The increased artesian outflow is anticipated to increase the McCloud and Pit River combined runoff by 308 cubic hectometers (250,000 acre feet) or by approximately 0.35% producing approximately 330 gigawatt hours per year (GWh/year) additional hydroelectric generation. The increased runoff delivered daily throughout the year from springs can provide additional opportunity for downstream residential, agricultural, and industrial use as it passes through Shasta Lake, the Sacramento River, and eventually entering the San Francisco Bay estuary.
Keywords: Pit River, McCloud River, cloudseeding, hydrogeneration, snowpack, PG&E

Laboratory Test of Snow Wetness Influence on Impulse Radar Amplitude Damping - Granlund, N.; Gustafsson, D.; Feiccabrino, J.; Lundberg, A. (75th Annual Western Snow Conference, 2007)
The two-way travel time of impulse (ground penetrating) radar operated from helicopters and snowmobiles is used to determine snow water equivalent for annual snowpacks, glaciers and polar ices. Presence of liquid water in a snowpack creates uncertainties, which for a typical snowpack with 5% (by volume) liquid water can lead to overestimation of the snow water equivalent by about 20%. It would therefore be helpful if the radar could also be used to determine snow wetness. Damping of wave amplitude varies with electric conductivity and the dielectric constant. The dielectric constant can be calculated using the radar pulse travel time and knowledge about the depth, hence studying amplitude damping should reveal how conductivity depends on snow wetness. A laboratory test was set up to study the relationship between conductivity and wetness. Three sets of measurements, two with old and one with new-fallen snow, were made on initially dry one-meter thick snowpacks contained in a plywood box with cross-section area about 0.5m2. Water was stepwise added to the box in between radar measurements. A tentative relationship between conductivity and wetness was found, but further tests including studies of the effect of variations in snow salt concentrations and in experiment design are needed to assess the generality of the relationship.
Keywords: Ground penetrating radar, SWE, liquid water, electric conductivity, dielectric constant, snow wetness

Evaluation of Streamflow Forecasts for Multiple Basins in the Pacific Northwest Using an Enhanced Version of the Snowmelt Runoff Model - Harshburger, B.J.; Moore, B.C.; Blandford, T.R.; Humes, K.S.; Walden, V.P. (75th Annual Western Snow Conference, 2007)
Runoff in mountainous areas of the Pacific Northwest is largely dominated by snowmelt. Thus accurate streamflow forecasts are critical for the management of water resource systems. The objective of this project is to develop a short to medium range streamflow prediction system (1 to 15 days) based on the Snowmelt Runoff Model (SRM) for mountainous basins in the Pacific Northwest. Enhancements were made to the model to optimize model efficiency and aid in its operational implementation. Results from retrospective forecast model runs, using statistically downscaled temperature and precipitation forecasts from the NCEP Global Forecasting System (GFS) model (2003-2006) will be examined.
Keywords: Snowmelt runoff, streamflow forecasts, SRM, Downscaled forecasts, GFS

The Vital Role of Snow in Protecting Yellow-Cedar from an Extensive Forest Decline in Alaska - Hennon, P.E. (75th Annual Western Snow Conference, 2007)
Yellow-cedar (Chamaecyparis nootkatensis) is a culturally and economically important tree in Alaska that has been suffering from a severe mortality problem. Recent research indicates that a number of site factors predispose yellow-cedar to freezing injury in spring. Aerial surveys identified nearly the entire broad distribution of decline, which covers about ½ million acres of forestland. This broad distribution of dead and dying forests aligns closely with the lowest snow accumulation zone in a regional snow model. At the mid-spatial scale, analysis of color infrared photographs revealed that cedar decline is limited to lower elevations, but extends somewhat higher on southerly aspects where snowmelt likely occurs earlier in spring. Measurements of forest trees, snow depth (by remote digital cameras), and hourly soil temperature at the finest spatial scale (small watershed) indicated that cedars remain healthy where snow persists through April. Snow apparently protects yellow-cedar in spring by either the delay of dehardening (loss of cold tolerance) by postponing the onset of soil warming, or by providing insulation from soil temperatures lethal to cedar roots (-5?C). Yellow-cedar decline serves as an early example of the damaging ecological consequences of climate warming and, particularly, the detrimental effects of reduced snow pack.
Keywords: Yellow cedar, tree mortality, spring freezing, snow depth, climate change

Development of Daily Cloud-Free MODIS Snow Cover Maps for Pacific Northwest - Hruska, R.C.; Lee, R.; Koudelka, J.; Rope, R.; Brizzee, J. (75th Annual Western Snow Conference, 2007)
Increasing demands for water resources in the West has given rise to many conflicts, increasing the need for more accurate and timely water management decisions. As a result there has been increased emphasis placed on the need to improve the numerous snowmelt run-off models that have been developed. Many of these models use snow cover extent maps derived from satellite imagery as an input variable. However, the utility of satellite derived snow-cover datasets have been limited due to the large number of scenes that are contaminated with cloud cover. In order to extend the utility of the MODIS Daily Snow Cover Products a method was developed to predict snow-cover in cloud-obscured areas using a snow occurrence mapping in the Big Lost River Basin in Idaho and was further applied to Pacific Northwest (PNW). Model results show that this method effectively increases the usefulness of the MODIS products in mapping how snow cover extent evolves over time across the entire PNW.
Keywords: Water management, runoff model accuracy, satellite, snow cover, MODIS, Pacific Northwest

Trends in Snowpack Chemistry and Comparison to National Atmospheric Deposition Program Results for the Rocky Mountains, U.S.A. 1993-2004 - Ingersoll, G. P.; Mast, M.A.; Campbell, D.H.; Clow, D.W.; Nanus, L.; Turk, J.T. (75th Annual Western Snow Conference, 2007)
Seasonal snowpack chemistry data from the Rocky Mountain region for 1993-2004 was examined to identify long-term trends in concentration and chemical deposition in snow, and in snow-water equivalent. Comparisons of trends were made between snowpack data and National Atmospheric Deposition Program wetfall data from nearby sites in the region. We used an innovative, non-parametric correlation method known as the Regional Kendall Test. This technique expressed the slope, direction, and probability of trend for several sites at once in each of the Northern, Central, and Southern Rockies subregions. Seasonal Kendall tests were used to evaluate trends at individual sites. Sulfate deposition decreased with moderate to high significance in all three subregions in both wetfall and snowpack. Precipitation trends consistently were downward for wetfall-, snowpack-, and SNOTEL data for the Central and Southern Rockies subregions (p<0.02), while no trends were noted for the Northern Rockies subregion.
Keywords: Snowpack chemistry, Rocky Mountains, NADP, Kendall test, sulfate

An Engineering Design Study of Electronic Snow Water Equivalent Sensor Performance - Johnson, G.B.; Gelvin, A.; Schaefer, G.L. (75th Annual Western Snow Conference, 2007)
The USA ERDC CRREL and the USDA NRCS developed an electronic SWE sensor based on the results of field and theoretical studies of SWE pressure sensor performance. The CRREL/NRCS sensor is about 3 m square and is modular consisting of nine perforated panels, a center panel and eight outer surrounding panels that allow water to percolate through the sensor. Water percolation minimizes thermal differences between the sensor and surrounding soil and the eight surrounding panels act to buffer the center panel, where SWE is measured, from stress concentrations that develop along the perimeter of the sensor. Two years of field-tests (winters of 2005-2006 and 2006-2007) at Hogg Pass, OR, demonstrate that the CRREL/NRCS sensor's center panel accurately measures SWE variations even when stress concentrations are observed on the sensor's outer panels. During the first winter, stress concentrations occurred on the outer panels during periods of rapid snow settlement following large snow accumulations and when the rate of snowmelt at the sensor/snow interface was significantly different from the snowmelt rate at the soil/snow interface of the surrounding ground. SWE measurement performance is optimal when the sensor has no freeboard.
Keywords: Snow sensor, SWE, CRREL, NRCS, Hogg Pass, freeboard

Soil Surface Temperature Difference Between Steel and Hypalon Pillows - Julander, Randall P. (75th Annual Western Snow Conference, 2007)
Systematic bias in data collection systems is often difficult to identify and moreover, on a site specific basis, hard to correct. Systematic bias in the SNOTEL record between steel and hypalon pillows has been identified and ranges between 0% and 25% (Julander and Bricco, 2006, Osterhuber, 1996). Observationally, the greater differences are typically at lower elevations and warmer temperatures while higher elevation, cooler sites typically have lower differences or none at all. Since originally the entire SNOTEL system was installed with steel pillow and since that time many steel pillows have been replaced with hypalon, it is essential to take a second look at these parameters to insure data consistency and accurate results. Hypalon pillows could become a heat sink, absorbing energy in the summer and slowly releasing it through later periods which could impact early season snow accumulation. The black pillows might possibly increase solar energy absorption during ablation, increasing melt rates in the spring. To test this hypothesis, temperature sensors were placed under co-located hypalon and steel pillows at Parleys Summit and Trial Lake SNOTEL sites in Utah. Results indicate that there is a substantial temperature difference and that it is possible that this difference could impact snow accumulation and ablation.
Keywords: SNOTEL, hypalon, stainless steel, snow accumulation, systematic bias

Trends in 20th Century U.S. Snowfall Using a Quality-Controlled Database - Kunkel, K.; Palecki, M.; Ensor, L.; Robinson, D.; Hubbard, K.G.; Easterling, D.; Redmond, K. (75th Annual Western Snow Conference, 2007)
A quality assessment has been undertaken of all U.S. long-term stations in which the authors have made an expert judgment on the quality of each station. Through this process, we have identified a set of stations we believe to be suitable for analysis of trends. We have analyzed snowfall variations back to 1900. Snowfall has generally decreased nationwide since peaks in the 1970s. At low snowfall stations, snowfall during the last 15 years has been lower than at any time since 1900. However, at moderate and high snowfall stations, snowfall was lower in the 1920s and 1930s. Since the late 1980s, extreme high snowfall years have been rather infrequent, while extreme low snowfalls have occurred at a near-average frequency. There are statistically significant relationships between temperature and the frequency of extreme snowfall years.
Keywords: Quality assessment, long-term US stations, climate data, declining snowfall

Differential Snowpack Accumulation and Soil Water Dynamics in Aspen and Conifer Communities: Implications for Water Yield - LaMalfa, E.M.; Leffler, A.J.; Ryel, R.J. (75th Annual Western Snow Conference, 2007)
Differences in snow water equivalent (SWE) in aspen and conifer stands in winters with low to high precipitation, sublimation rates of intercepted snow by conifer branches, and dynamics of soil moisture under aspen and conifer stands were in northern Utah. For low, average and high snowpack years, conifer stands averaged 33-44% lower SWE than paired aspen stands. Sublimation rates for sunlit simulated conifer branches were up to twice that of the ground snow surface; shaded branches had similar rates to the ground snow surface. When combined with the greater surface area of snow on conifer branches, sublimation could explain all or most of the differences in SWE between conifer and aspen stands. Soil column water content was generally higher in aspen throughout all periods of the year. For 2006, aspen stands were estimated to yield 400+ mm more water than the adjacent conifer stands and have saturated soil columns. In 2007, we predict that aspen soils will nearly reach saturation while conifer soils will be 100 mm below saturation.
Keywords: SWE, conifer, aspen, snow interception, sublimation, soil saturation

The NOHRSC SNODAS Snow Water Equivalent Determination on Mount St. Helens, Washington - Lea, J. (75th Annual Western Snow Conference, 2007)
Mount St. Helens in Washington State erupted in 1980 with devastating results due to pyroclastic debris flows entraining large amounts of the existing snowpack on the mountain. With the renewed volcanic activity that began in October 2004, close monitoring of the snowpack is required. The total snowpack snow water equivalent (SWE) volume determined by the Natural Resources Conservation Service (NRCS) is used by other federal agencies to determine the flood size that could be expected from a rapid snowmelt flooding event from possible eruptive activity on the mountain. In the 2006 and 2007 water year, the National Weather Service (NWS) National Operational Hydrologic Remote Sensing Center (NOHRSC) Snow Data Assimilation System (SNODAS) model was used to determine the total amount of SWE on the mountain. In early May 2006, a series of intensive snow surveys undertaken by 7 teams around the mountain. This additional data was then ingested into the SNODAS model and slight changes in the gridded data and SWE total resulted. The snow survey improved the modeled snowpack, especially in the high elevation environment.
Keywords: Mt. St. Helens, floods, eruption, Toutle River, SNODAS, SNOTEL, SWE

Distributed Temperatures in the Snow Zone: Spatial Patterns and Innovative Measurement Techniques - Lundquist, J.D.; Rochford, C. (75th Annual Western Snow Conference, 2007)
Mountains are spatially complex and sparsely sampled. Temperatures are usually interpolated from distant stations assuming a standard atmospheric lapse rate (decrease of 6.5°C per 1000 m elevation gain). However, examination of observed surface temperatures indicates that temperature patterns differ diurnally, synoptically, and seasonally and do not always increase linearly with elevation. Fortunately, new technology has become available to monitor temperature in remote locations, such as the Onset Hobo and the Maxim i-button. Approximately 200 of these self-recording sensors have been deployed in Yosemite National Park, California and Niwot Ridge and Rocky Mountain National Park, Colorado over the past several years. Empirical orthogonal functions (EOFs) are used to identify the dominant spatial temperature patterns within each study area and how they vary in time. Comparison between study sites allows for generalizations of temperature patterns across space (mapping spatial patterns using topography) and time (mapping temporal variations using large-scale weather parameters), which can be utilized in more sparsely sampled areas. Experimentation with such a large number of sensors also illuminates how to best deploy these small instruments to sample topographically-controlled, versus vegetation-controlled, versus radiation-controlled, temperatures.
Keywords: Yosemite National Park, temperature, lapse rate, EOF, spatial temperature patterns

The Implementation of the Snowmelt Runoff Model in ArcGIS - Moore, B.C.; Harshburger, B.J.; Blandford, T.R.; Humes, K.S.; Walden, V.P. (75th Annual Western Snow Conference, 2007)
To provide water resource managers and other end-users with operational forecast products and tools, we have implemented an enhanced version of the Snowmelt Runoff Model (SRM) that operates within ArcGIS 9.2. We have also implemented tools within ArcGIS that generate the necessary inputs to SRM. This ArcGIS-SRM system allows the user to easily: 1) delineate watersheds, 2) incorporate remote sensing images of snow cover, meteorological forecasts, and real-time streamflow values via the Internet, 3) compute several SRM model parameters, and 4) generate streamflow forecasts.
Keywords: Forecasting, SRM, ArcGIS, watershed, snow cover

Effects of Past and Future Climate Change on Ski Areas - Mote, P.W.; Casson, J.; Hamlet, A.F.; Reading, D. (75th Annual Western Snow Conference, 2007)
We examine USDA snow course data for ski areas during the ski season to determine the degree to which midwinter snow is statistically sensitive to temperature. For most of the 16 Northwest ski areas analyzed here, a reasonably strong negative partial correlation of mid-season snow depth with antecedent temperature indicates that further warming will have an impact on the quantity of snow. The effects of these physical changes on the profitability of a given ski area will depend in part on the adaptive capacity of the ski area.
Keywords: Snow course, ski areas, temperature, snow depth, climate change

Delaying Snowpack Ablation - Osterhuber, R.; Hogan, M.; Grismer, M.; Drake, K. (75th Annual Western Snow Conference, 2007)
Just north of Lake Tahoe in California's Sierra Nevada, three 9 m2 areas of the melting spring snowpack were covered with layers of wood chips, 2, 5, and 10 cm thick. This was an investigative exercise to determine if snowmelt rates could be significantly altered during soil restoration projects. Snowmelt under the wood chips was found to be exponentially slower than the surrounding snowpack, while melting at a highly linear rate. Melt rate corresponded to the thickness of the wood chip layer. The snow plot covered with 10 cm of chips was found to melt slowest, losing on average 0.87 cm of water equivalent per day. The snow under the thickest layer of wood chips persisted 23 days longer than the surrounding snow cover.
Keywords: Snowmelt, albedo, snowmelt rates, Lake Tahoe, wood chips

Applying Hydro-Climatological Research to Improve the Scientific Basis Of Local Watershed Decision-Making - Pattee, S.; Ingersoll, T.; Ward, J. (75th Annual Western Snow Conference, 2007)
The North Olympic Peninsula Resource Conservation & Development (NOP RC&D) Council proposes to evolve a Solutions Network of local, regional and national organizations to provide watershed management teams with decision support through NASA-funded earth-sun research results. The NOP RC&D Council built a team of eight other major partners for this Project, including the NASA-funded Pacific NorthWest Regional Collaboratory (PNWRC); USDA Natural Resources Conservation Service; Pacific Northwest National Laboratory (PNNL) Idaho National Laboratory (INL); Olympic National Park (ONP); Clallam County; the National Association of RC&D Councils (NARC&DC) in Washington, DC; and Peninsula College (PC). The science portion involves applying hydro-climatological research, through the Hybrid hydrology model, to improve the scientific basis of local watershed decision making. A Solutions Network of User Groups, Research Scientists, and an Operation Center will be developed in the Dungeness and Elwha River watersheds during the first two years of this project. The Elwha River watershed is also the site of the largest dam removal project ever undertaken in the Nation and therefore posed additional opportunities to collaborate with Peninsula College, Olympic National Park, and the Elwha Research Consortium.
Keywords: Watershed management, NASA, Dungeness River, Elwha

Global Warming Effects on Snowfields and Water Supply Evaluated Using Snowmelt Runoff Modeling and Normalized Annual Data - Rango, A.; Martinec, J.; Roberts, R. (75th Annual Western Snow Conference, 2007)
The effect of global warming on the snow cover and runoff in mountain basins can be evaluated by comparing present and future conditions modeled for a climate scenario. Rather than use a single historical year to represent today's climate, an improved method is presented which consists of deriving a so-called normalized year. In the Rio Grande basin near Del Norte, CO (3414 km2, 2432-4215 m a.s.l.) the effect of a hypothetical temperature increase of +4o C on the snow cover and runoff as experienced in hydrological year 1979 was evaluated. Because 1979 had relatively frequent temperatures below -4o C, snowmelt as well as conversion of snowfall to rainfall was limited during winter. The data set of 1979 was modified by applying the so-called normalized temperatures for the period 1957-1994. The predicted future snow conditions in the normalized year show a complete disappearance of snow in the lowest elevation zone (2432 - 2926 m a.s.l.) on April 1, due to an increased snowmelt in the winter. The resulting winter runoff which increased from 7.6% to 12.8% of the annual total, in 1979, now increases from 11.7% to 24.2% of the normalized annual total.
Keywords: Global warming, snow cover, runoff, normalized year, Rio Grande

Snowcover Along Elevation Gradients in the Upper Merced and Tuolumne River Basins of the Sierra Nevada of California from MODIS and Blended Ground Data - Rice, R.; Bales, R.; T H Painter; Dozier, J. (75th Annual Western Snow Conference, 2007)
Accurate, frequent satellite-derived snow covered area (SCA) products provide the opportunity to explore the spatial patterns of snow, as well as the impact of snow accumulation and ablation on snow distribution along elevation gradients. Blending a MODIS fractional snow cover product with interpolated point snow water equivalent (SWE) measurements and energy balance calculations yields composite maps of the spatial distribution of SWE. Results from the 2004 and 2005 water years show the utility of the MODIS fractional SCA product to estimate snow accumulation and melt along 300-meter elevation gradients in the Upper Merced and Tuolumne River Basins of the Sierra Nevada of California. The analysis considers the elevation bands from 1,500 to 3,900 m with 40% of the elevation between 2,100-2,700 m, while the 1,500 m elevation band is considered the transitional rain/snow zone. Spatial maps of SWE highlight elevational bands that contribute significantly to snowmelt across the basin, as well as those elevational bands that are susceptible to warming and thus rapid depletion of the snowcover. The results of the 2004 ablation season demonstrate the implications along the elevation gradients of an above normal mid-season snowcover of 120% impacted by an unseasonable warm and dry air mass that rapidly depleted the snowcover across all elevation gradients, leading to a below average snowpack of 84% by April 1.
Keywords: Snowcover, Merced, Tuolumne, satellite, MODIS, SWE, SCA

Experimental Study on the Bond Destruction Between Snow/Ice and Anti-Freezing Pavements, Depending on Properties of Snow/Ice and Number Of Wheel Load Passes - Takeichi, K. (75th Annual Western Snow Conference, 2007)
The bond destruction between snow/ice and anti-freezing pavements is mainly assessed quantitatively by the relationships between bare pavement ratio (using computer image processing), the degree of scatter or stripping of snow/ice, the friction coefficient (u), and the number of wheel load passes. Results are compared with test results from the dense-graded asphalt pavement used as a control pavement. As for the snowpack, the bond-destruction and the increase of u are evaluated on the gum-rolled pavement that has a flexible surface texture under 100 to 500 passes at -5 deg C and 5 kN wheel load (200 kPa tire pressure). As a result of tests, the anti-freezing effects of anti-freezing pavements are evaluated and confirmed at -5 deg C. For the same tests and pavement but at -10 deg C, increased friction effects were found to be insufficient under the passenger car wheel load. Therefore, it is necessary in the future to develop a more effective hybrid type anti-freezing pavement (such as gum-rolled pavement combined with a deicing chemical in the asphalt mixture) to cause bond-destruction to all of snow/ice surfaces at -10 deg C.
Keywords: Bond destruction, anti-freezing, pavement, snow, ice

A Distributed Modeling System for Short-Term to Seasonal Ensemble Streamflow Forecasting in Snowmelt-Dominated Basins - Wigmosta, M.S; Gill, M.K.; Coleman, A.M.; Prasad, R.; Vail, L.W. (75th Annual Western Snow Conference, 2007)
This paper describes a distributed modeling system for short-term to seasonal streamflow forecasts with the ability to utilize daily remotely-sensed snow cover products and real-time streamflow and meteorology measurements. Canopy interception, snow accumulation and melt, and simplified soil water movement are simulated in each computational unit. The model is run at a daily time-step with surface runoff and subsurface flow aggregated at the basin scale. This approach allows the model to be updated with spatial snow cover and measured streamflow using an Ensemble Kalman-based data assimilation strategy that accounts for uncertainty in weather forecasts, model parameters, and observations used for updating. Model inflow forecasts for the Dworshak Reservoir in north-central Idaho are compared to observations and to April-July volumetric forecasts issued by the Natural Resource Conservation Service (NRCS) for Water Years 2000 - 2006. October 1 and March 1 volumetric forecasts are superior to those issued by the NRCS. The ensemble spread brackets the observed April-July volumetric inflows in all years except for the October 1, 2006 forecast.
Keywords: Distributed modeling, streamflow forecasting, remote sensing, snow cover, Dworshak Reservoir

2006 Title, Contents, and Minutes (74th Annual Western Snow Conference, 2006)

Simulating Long-term Landcover Change and Water Yield Dynamics in Forested, Snow-dominated Rocky Mountain Watersheds - Ahl, R.S.; Woods, S.W. (74th Annual Western Snow Conference, 2006)
Changes in the extent, composition, and configuration of forest cover over time due to succession or disturbance processes can result in measurable changes in streamflow and water yield. Removal of forest cover generally increases streamflow due to reduced canopy interception and evapotranspiration. In watersheds where snow is the dominant source of water, yield increases and advanced peak discharge are attributed to increased snow accumulation, and enhanced melt rates in forest openings. Because knowledge of long-term watershed-level streamflow responses to landcover dynamics is limited by relatively short-term gage data, we present a modeling approach that combines existing vegetation and hydrologic simulation systems to evaluate these interactions. Our findings suggest that both vegetation and hydrologic characteristics of the research watershed are at the limits of their estimated natural ranges. Although species composition remained fairly stable over time, the size and connectivity of current landcover patches are at the upper end of the estimated temporal distribution. The large proportion and continuous nature of forest cover associated with current conditions coincide with water yield, peak discharge rates, and flow variability that are at the low end of their modeled distributions.
Keywords: Landcover change, water yield, forest snow cover, streamflow, forest management

How is the Earth's Snow Cover Responding to a Warming Climate? - Armstrong, R.L.; Brodzik, M.J.; Knowled, K.; Savoie, M. (74th Annual Western Snow Conference, 2006)
The extent and variability of seasonal snow cover are important parameters in climate and hydrologic systems due to effects on energy and moisture budgets. Northern Hemisphere snow cover extent, comprising about 98 percent of global seasonal snow cover, is the largest single spatial component of the cryosphere, with a mean maximum extent of 47 millions square kilometers (nearly 50 percent of the land surface area). During the past four decades much important information on Northern Hemisphere snow extent has been provided by the NOAS weekly snow extent charts derived from visible-bank polar orbiting and geo-stationary satellite imagery. This product is available from NSIDC as the Northern Hemisphere EASE=Grid Weekly Snow Cover and Sea Ice Extent Version 2. Because of the ability to penetrate clouds, provide data during darkness and the potential to provide an index of snow depth or water equivalent, passive microwave satellite remote sensing offers an additional source for hemispheric scale snow monitoring with the availability of a twenty-three year data record (Scanning Multichannel Microwave Radiometer (SMMR) 1978-1987 and Special Sensor Microwave/Imager (SSM/I) 1987-present). However, trend analysis on the passive microwave record is complicated by the change in sensors from the SMMR to SSM/I and by the short overlap period. We present analysis of land surface stable targets as detected by SMMR and SSM/I brightness temperatures during the overlap period to quantify possible discontinuities in sensor observations and derived snow extent and SWE. (Abstract only)
Keywords: Snow cover, climate change, northern hemisphere, NSIDC, satellite, SMMR, SSM/I

Spatial, Seasonal, and Synoptic Variations in Air Temperature Lapse Rates - Blandford, T.R.; Humes, K.S.; Harshburger, B.J.; Moore, B.C.; Walden, V.P. (74th Annual Western Snow Conference, 2006)
The average atmospheric lapse rate of -0.65 ºC/100m commonly applied in snowmelt/streamflow prediction models and other investigations of environmental processes is a spatially-global and temporally-climatic average (or standard). It should be applied with caution at other scales. The objective of this research is to evaluate daily surface (2 m) air temperature lapse rates at a spatial scale that has not been evaluated thoroughly in other literature. Specifically, seasonal and synoptic weather type variations in lapse rates will be evaluated for a basin less than 10,000 km2. The performance of long-term average versus seasonal lapse rates is evaluated using cross-validation. Application of the lapse rates to forecasted air temperature is discussed. (Abstract only)
Keywords: Lapse rate, snowmelt modeling, spatial scale, seasonal weather variation

NOAA's National Snow Analyses - Carroll, T.; Cline, D.; Olheiser, C.; Rost, A.; Nilsson, A.; Fall, G.; Bovitz, C.; Li, L. (74th Annual Western Snow Conference, 2006)
NOAA's National Operational Hydrologic Remote Sensing Center (NOHRSC) provides comprehensive, near real-time, snow observations, snow analyses, data sets, and map products in multiple formats at high spatial and temporal resolution for the Nation. The NOHRSC routinely ingests all of the electronically available, real-time, ground-based snow data, airborne snow water equivalent data, satellite areal extent of snow cover information, and numerical weather prediction (NWP) model forcings for the coterminous U.S. The NWP model forcings are physically downscaled from their native 13 km2 spatial resolution to a 1 km2 resolution for the CONUS. The downscaled NWP forcings drive the NOHRSC Snow Model (NSM) that includes an energy-and-mass-balance snow accumulation and ablation model run at a 1 km2 spatial resolution and at an hourly temporal resolution for the country. The ground-based, airborne, and satellite snow observations are assimilated into the model state variables simulated by the NSM using a Newtonian nudging technique. The principal advantages of the assimilation technique are (1) approximate thermal balance of the snowpack is maintained by the NSM, (2) physical processes are easily accommodated in the model, and (3) asynoptic data are incorporated at the appropriate times. The NSM is updated with assimilated snow observations and is used to generate a variety of snow products that combine to form NOAA's NOHRSC National Snow Analyses (NSA). The NOHRSC NSA incorporate all of the information necessary and available to produce a best estimate of real-time snow cover conditions at 1 km2 spatial resolution and hourly temporal resolution for the country.
Keywords: NOHRSC, numerical weather prediction, snow model, airborne SWE, snow cover, snowpack

Regional Patterns of Snow Water Equivalent in the Colorado River Basin Using Snowpack Telemetry (SNOTEL) Data - Derry, J.E.; Fassnacht, S.R. (74th Annual Western Snow Conference, 2006)
Previous clustering of data has typically grouped stations based on spatial proximity or been restricted due to the temporal resolution of snow-course data. This investigation utilizes daily data from 216 snowpack telemetry (SNOTEL) stations located in and around the Colorado River Basin over a 15-year period (1991-2005) to cluster stations - identify regions of homogeneity - based on their patterns and variability. To achieve this, data were submitted to a self-organizing map (SOM), a particular application of artificial neural networks. The number of clusters can be specified to the SOM based on the level of generalization desired. A SOM consisting of a four, six, nine, and sixteen-cluster were constructed as well as a six-cluster derived from physical variables (elevation, aspect, distance to moisture source, etc.) for each station. For each cluster, a linear multivariate regression was used between physiographic variables and SWE to determine a regression equation that best explained the variability in SWE. Results show an unbiased clustering of stations defined not by geographic location, but by each station's particular SWE variability. The established snow climatologies show some general homogenous course-scale clusters, particularly in Wyoming and Arizona, but overall there are no definite spatial patterns to the climatologies, indicating that local topographic variables dominate SWE processes. Regression results indicate southwest barrier height, aspect, elevation, and southwest shield height are the key variables in predicting SWE within each cluster.
Keywords: Regional SWE patterns, Colorado River, SNOTEL, neural network, clustering, SWE variability

Change in the Date of Snow Disappearance in the High Arctic - Foster, J.L.; Robinson, D.A.; Hall, D.K.; Estilow, T. (74th Annual Western Snow Conference, 2006)
In this paper, we show changes in the dates of snow disappearance in the high Arctic (70° north latitude) between the late 1960s and the early 2000s. NOAA satellite data were employed to make these snow observations (from snow cover to snow free conditions), using arbitrary but consistent boundaries. Continuing the study presented by Foster et al, (1992) on springtime snow disappearance in the high Arctic, the date the snowline retreats during the spring (when it first moves north of the 70 degree parallel), for many Arctic locations, has occurred approximately a week earlier in recent years compared to the late 1960s. The tendency toward earlier snowmelt previously observed during the past several decades has apparently neither been a local phenomenon nor a short-term fluctuation. However, unlike other markers of climate warming in the Arctic, since 1990, the date of snow disappearance has not occurred noticeably earlier. It is possible that the date of snow disappearance is not an adequate benchmark for detecting warming signal.
Keywords: Arctic snow cover, satellite, snowline retreat, climate change

Evaluation of Model Enhancements and Probabilistic Forecasting Techniques for The Snowmelt Runoff Model - Harshburger, B.J.; Moore, B.C.; Blandford, T.R.; Humes, K.S.; Walden, V.P.; Hruska, R. (74th Annual Western Snow Conference, 2006)
Accurate streamflow forecasts are critical for the responsive management of water resource systems, which are designed and operated for the purposes of irrigation, flood control, and hydroelectric power generation. In the Western United States, water supplies are often derived form runoff due to snowmelt. The objective of this project is to develop an ensemble (probabilistic) prediction system for short to medium range streamflow forecasts (1 to 15 days). The hydrologic model used in this study is the Snowmelt Runoff Model (SRM), which is a conceptually-based model designed to simulate and forecast daily streamflow in mountain basins where snowmelt is a major contributor to runoff (Martinec et al., 1994). To optimize model efficiency and aid in its operational implementation, three enhancements have been made to the model. These enhancements are: 1) the use of an antecedent temperature index method to track snowpack cold-content and account for the delay in melt associated with diurnal refreezing, 2) the use of both maximum and minimum critical temperatures to partition precipitation into rain, snow, or rain/snow mixed, and 3) the stochastic modeling of forecast errors to generate streamflow ensembles, from which exceedence probabilities can be obtained. Results from retrospective model runs, using temperature and precipitation forecasts from NCEP GFS model (2000-2004) will be examined and used to identify the error in the streamflow forecasts. (Abstract only)
Keywords: Streamflow forecasts, ESP, SRM, Big Wood River Basin, antecedent temperature, forecast errors

Correlation of Temperature and Snow Water Equivalency in the Sierra Nevada - Hassen, C.; McManigal, K. (74th Annual Western Snow Conference, 2006)
Much of the world's resources, such as fresh water in the form of snow are decreasing, as is evident in the Sierra Nevada. This can be attributed to many factors but, most importantly, the continual rise of global temperatures. Nine NRCS (Natural Resources Conservation Service) snow telemetry (SNOTEL) sites were studied in a geographic range from Lake Tahoe to Mono Lake in order to identify a correlation between temperature and snow water equivalency (SWE). GIS results suggest a direct relationship of temperature to SWE. Mountain communities are the stewards of these vital areas and combined with support from the state of California, have an obligation to preserve and protect these areas from anthropogenic abuses. If nothing is done to reduce the human causes of global warming trends, what once was known as the Snowy Mountain range, may soon be exhausted of its valuable snowpack. (Abstract only)
Keywords: Sierra Nevada, global warming, SWE, SNOTEL, snowpack decline

Annual Hydrochemical Fluxes from Alpine Subalpine Catchments in the Snowy Range, Wyoming - Hicks, D.L.; Stednick, J.D.; Fassnacht, S.R.; Musselman, R.C. (74th Annual Western Snow Conference, 2006)
Annual hydrochemical fluxes were calculated from 1989 to 2004 for two alpine-subalpine catchments, West and East Glacier Lake Outlets in the Snowy Range, Wyoming. Mean annual atmospheric deposition inputs within Glacier Lake Ecosystem Experiments Sites (GLEES) were 3.50 kg ha-1 yr-1 and 2.27 kg ha-1 yr-1 for inorganic nitrogen (NO3-N, HNO3-N and NH4-N) and sulfur (S), respectively. Dry deposition, as measured by CASTNET, accounts for less than 20% of total deposition for inorganic N and S. Lakes at GLEES are oligotrophic with a water quality specific conductance range of 5-15uS cm-1. During the 1989 sampling period at West Glacier Lake, cations were in decreasing order of Ca2+, Mg2+, Na+, K+, NH4-N and anion were in decreasing order of Cl-, SO4-S, and NO3-N. Chloride inputs were approximately equal to outputs suggesting proper accounting of precipitation and streamflow volumes. Hydrochemical outputs for major cations were greater than inputs and differences attributed to parent material and soil weathering. Inorganic N inputs are greater than outputs for annual hydrochemical fluxes from 1989-2004 suggest that GLEES catchments are accumulating N.
Keywords: Chemical fluxes, alpine catchment, Snow Range, dry deposition, Glacier Lake, hydrochemical output

Soil Storage of Snow Water: Linking Sediment Source Control to Water Supply - Hogan, M.; Grismer, M. (74th Annual Western Snow Conference, 2006)
Water supply and quality in the arid west is becoming an increasingly problematic issue. This is nowhere more important than in mountain resort areas where an increased pressure on surrounding real estate can have significant impacts on the water supply, often through building and other construction activities. Further, global climate change is expected to have significant effects on both the amount and type of precipitation received in mountainous areas as well as the storage period of frozen water. These elements of western water supply suggest distressing trends in timing, quality and amounts of downstream delivery of water resources. Ski resorts offer the potential for both a focused study of changing watershed dynamics as well as the opportunity to develop a host of mitigation measures. Some of these measures offer the potential to both store additional water and to attenuate the runoff hydrograph. This paper describes two related processes and outcomes. The first is a soils restoration process that has been implemented and shown to increase water infiltration into the soil, in some cases by over an order of magnitude. The second is a proposed experimental project that uses wood chips as a snow surface cover to reduce snowmelt rate, thus extending and attenuating the runoff hydrograph. Further, when snow finally melts, the wood chips provide a highly effective soil surface mulch, thus reducing erosion potential. (Abstract only)
Keywords: Water supply, ski resorts, water shortages, climate change, soils restoration, bark chips

Temperature Extremes and the Snow Scale - Howe, H. (74th Annual Western Snow Conference, 2006)
The purpose of this investigation is to determine the effect of temperature extremes on the standard snow scale reading and to quantify these effects. An additional benefit will be to determine the optimum temperature for snow scale calibration checking.
Keywords: Temparture effect, snow survey, snow scale, scale calibration

Geostatistical Methods for Estimating Snowmelt Contribution to an Alpine Water Balance - Hultstrand, D.M.; Fassnacht, S.R.; Stednick, J.D. (74th Annual Western Snow Conference, 2006)
The performance of nine spatial interpolation models was evaluated to estimate snowmelt contributions to streamflow in the West Glacier Lake watershed. In April 2005, peak accumulation snow depth and snow density measurements were collected within West Glacier Lake watershed. The distribution of snow water equivalent (SWE) was calculated as the product of snow depth, snow density, and snow-covered area (SCA). Snow depths were spatially distributed throughout the watershed through spatial interpolation methods. Snow densities were spatially distributed through multiple linear regression analysis. The nine spatial snow depth models explained 18% to 94% of the observed variance in the measured snow depths. Co-kriging with solar radiation produced the best results explaining 94% of the observed variance in snow depth measurements. Estimated SWE from the field survey data was 67% greater than winter precipitation gauge estimates. The annual water balance, expressed as equivalent water depths was total precipitation (1,481 mm), snow sublimation (251 mm), and streamflow (1,000 mm), resulting in an estimate of evapotranspiration (230 mm). Winter precipitation as snow accounted for 85% of the annual precipitation.
Keywords: Spatial interpolation , snowmelt runoff, streamflow, West Glacier Lake, SWE, co-kriging, water balance

Web-based Flood Chronology of the Carson River basin, California and Nevada, from 1852 to the Present - Jeton, A.E. (74th Annual Western Snow Conference, 2006)
As new areas are developed to accommodate growth, communities are increasingly faced with the need to develop in flood-prone areas. Current efforts by the State of Nevada Floodplain Management Program, Nevada Division of Water Resources (NDWR), to support the Federal Emergency Management Agency's (FEMA) Map Modernization program, have been to act as a point of contact at the State level in communicating mapping needs for Nevada communities. In conjunction with floodplain mapping, NDWR has identified the task of compiling flood-hazard information in a format accessible and understandable to the general public and Federal, State, regional, and local agencies. The Nevada Floodplain Management Program considers it essential to make historical flood information publicly available, particularly for river basins with significant current and future population growth. The U.S. Geological Survey with the support of FEMA through NDWR's Floodplain Management Program has developed a web site to make historic flood information for the Carson River Basin publicly available. The web site contains information to help the general public in understanding the extent and frequency of flood hazards and risks in the Carson River Basin. Available information on specific flood events may include photographs, video clips, and links to related web sites, flood-frequency analyses, meteorological data, narratives, and streamflow data. USGS Fact Sheet 2006-3102 provides additional information, and the URL for this web site is http://nevada.usgs.gov/crfld/.
Keywords: Floods, Nevada, floodplain mapping, FEMA, USGS, Carson River

An Examination of External Influences Embedded in the Historical Snow Course Data of Utah - Julander, Randall P.; Bricco, M. (74th Annual Western Snow Conference, 2006)
Snowpack data collection has a long and storied history in Utah as well as the western United States. In Utah, records extend back to at least 1912. Systematic measurements began in the mid 1920's with many long-term snow courses established at that time. Each site was meticulously mapped, described and most important, photographed from several angles. Comparisons are made between the 1936 photographs, maps and descriptions and current conditions, specifically with regard to vegetation. General conclusions are made regarding the impact that vegetation change has had on snow accumulation at each course. With the advent of weather modification programs, changes in snow accumulation could reasonably be expected. Utah began a relatively small test weather modification program in the 1950's in central Utah. The Utah cloud seeding act was passed in 1973 and the seeding program has continued since that time. Snow Courses affected by this program are identified and the potential impact on historical data. The impact of sensor change from steel pillows to hypalon is discussed. Physical changes at data collection sites are estimated. Finally, recommendations for individual snow course suitability for long-term study based on consistency are made for each of the courses examined. SNOTEL sites, the automated version of the snow courses began to be installed in the late 1970's and early 1980's. These sites to a lesser degree due to the shorter historical time of data collection, have been impacted by vegetation change as well.

Floods, Droughts, and Extremes in Utah Snowpacks - Julander, Randall P. (74th Annual Western Snow Conference, 2006)
Utah has seen hydrometeorological extremes over the past decade. Last year saw snowpack records not just exceeded but shattered at some sites. In one case, snowpack was 50.8 centimeters higher than the previous record long term maximum snow water equivalent. This single year erased the total deficit of the six previous drought years at this site. Other sites had record snowpack in southern and northeastern Utah. Previously, six consecutive years of drought had decimated reservoir storage, caused huge forest and range mortality in even the hardy Atemesia species. Tree ring records indicate that this was one of the more significant droughts over the past 480 years in the Colorado River Basin (Woodhouse, 2003). The drought has caused significant agricultural damages as well as to other sectors of the economy such as power and tourism. The ever present concern over global warming and its impact on western snowpacks has been mentioned in numerous studies as well as through public discourse. Historical analysis has shown that at 15 carefully chosen, long term snow courses snowpacks have been on a gradual decline although none were statistically significant. This study quantifies the impacts of these extremes on snowpack averages at these 15 sites. Are these times really different than those of historical past and are they really more extreme?
Keywords: Extremes, drought, tree rings, Colorado River, global warming, declining snowpack

Snow Density Observations in the Washington Cascades - Kay, J.E. (74th Annual Western Snow Conference, 2006)
Density is a fundamental physical property of snow. Both the meteorological conditions during snowfall and snow pack processes affect snow density. As a result, field observations of snow density vary from 10 to 500 kgm-3. Yet, conversion between snow water equivalence (SWE) and snow depth and modeling of snow processes is often accomplished using a fixed snow density of 100 kgm-3. I use snow telemetry (SNOTEL) snow depth and snow water equivalent measurements to estimate snow density in the Washington Cascades, a maritime, temperature-driven snow pack. Spot field measurements are used to validate the seasonal evolution of densities estimated from SNOTEL observations and to understand the vertical profile of snow density. Then, using visual inspection and principal components analysis (PCA), I document and compare the seasonal evolution and regional coherency of SWE and snow density. Specifically, I address: Can SNOTEL observations reveal seasonal and spatial patterns in snow density?, What is the regional coherency of SWE and snow density on seasonal timescales?, and How is snow density influenced by elevation and location in a cross barrier flow?
Keywords: Snow density, Washington Cascades, SWE, snow modeling, SNOTEL, density profile, elevation

Issues with Identification of Trends in the 20th Century U.S. Snowfall - Kunkel, K.; Palecki, M.; Hubbard, K.G.; Robinson, D.; Redmond, K.; Easterling, D.; Ensor, L. (74th Annual Western Snow Conference, 2006)
Daily data from the National Weather Service cooperative observer network taken prior to 1948 was recently put into digital form, opening the door to analyses spanning the entire 20th Century. An examination of the U.S. daily snowfall records for the 20th Century revealed numerous apparent inconsistencies. For example, in many cases long-term snowfall variations and trends among neighboring stations differ greatly. Given the close proximity, such differences most likely are not the result of atmospheric processes, but instead probably reflect inhomogeneities in the snowfall records. Internal inconsistencies in the snow records of some of these stations also point to inhomogeneities. For example, the frequency of daily observations with a 10:1 snowfall to liquid equivalent ratio declined nationwide from 30% in the 1930s to a current value of around 10%, a change that is clearly due to observational practice. Since the change in the ratio of snowfall to liquid equivalent is due to observational practices, there must be biases in cold season liquid equivalent precipitation, or snowfall, or both. An empirical adjustment of snow-event, liquid-equivalent precipitation indicates that the potential biases can be statistically significant.
Keywords: Cooperative observer, US daily snowfall, snow density change,

Difference in Water Balance Between Aspen and Conifer Communities: The Fate of Spring Snow Melt in a Northern Rocky Mountain Watershed - LaMalfa, E.M.; Ryel, R. (74th Annual Western Snow Conference, 2006)
Differences in water balance between mature deciduous quaking aspen (Populus tremuloides) and evergreen conifer (e.g. Abies concolor, Abies lasiocarpa, Picea engelmannii and Pseudotsuga menziesii) forest communities occur as a result of complex physical and biological interactions. To better understand the potential effects of aspen conversion to evergreen conifer on watershed water yield in the northern Intermountain West, USA, we assessed several water balance transfer mechanisms, including snow accumulation, ablation, evaporation/ sublimation, soil moisture recharge, and transpiration, to determine how major differences in water balance occur in adjacent mature aspen and conifer forests during spring snowmelt. Measurements of fall sap flux were indexed to determine the annual transpiration activity period for aspen and conifer communities. Soil moisture was monitored to determine the timing of soil moisture recharge during winter snow accumulation, and field observations of snow water equivalent (SWE) and snowpack sublimation were obtained. We found SWE was the factor most different between aspen and conifer stands, with conifer stands averaging 34% less SWE at peak snowpack than adjacent aspen stands. We conclude peak SWE is likely the most important factor affecting watershed water yield between aspen and conifer stands, but that differences in soil moisture accumulation could further enhance this difference.
Keywords: Water balance, spring snowmelt, Rocky Mountains, sap flux, water yield, runoff timing, peak SWE, aspen, conifer, type conversion

Estimating the Quantity and Quality of Snow at the Aspen Ski Area for the Years 2030 and 2100 - Lazar, B.; Smith, J.; Williams, M. (74th Annual Western Snow Conference, 2006)
We evaluated how climate change resulting from increased greenhouse gas (GHG) emissions may affect the quantity of snow at Aspen Mountain ski area in 2030 and 2100. We modeled climate change using MAGICC/SCENGEN, and ran combinations of five general circulation models (GCMs) and three GHG emission scenarios. Snow quantity was evaluated using the Snowmelt Runoff Model (SRM), and a module developed to estimate snow quantity during the accumulation season, before snowmelt initiation. We used the five GCMs that best simulate current conditions, and three emission scenarios representing low, mid, and high emissions conditions. The date when snow starts to accumulate at the base area is delayed by six to seven days by 2030 and anywhere from 1.5 to 4.5 weeks by 2100. For mid-winter snows, a 15% increase in snowfall compensates for a 1.5°C increase in air temperature such that there was little change in snow depth. Snow depth goes to almost zero for the base area in 2100 under the medium GHG emission A1B scenario. In the high GHG emission A1F1 scenario, snow depth goes to near zero for the entire lower two-thirds of the mountain. The effect is substantially reduced under the low GHG emissions B1 scenario.
Keywords: Climate change, Aspen Ski Area, decreased snowpack, emission scenarios, GCM, SRM

An Evaluation of SNODAS for Determining Snow Water Equivalent on Mount St. Helens - Lea, J.; Reid, I. (74th Annual Western Snow Conference, 2006)
When Mount St. Helens erupted on May 18, 1980 melting snow and ice on the mountain enhanced a large debris flood wave from all sides of the mountain, creating exceptional flooding along the Toutle River in southwest Washington. Mount St. Helens became active again in September 2004. During both of these episodes there was considerable concern that another eruption would entrain the existing snowpack resulting in a devastating flood. The US Department of Agriculture (USDA), Natural Resources Conservation Service (NRCS), National Water and Climate Center (NWCC) was requested to provide weekly snow water equivalent (SWE) on Mount St. Helens to the National Weather Service Northwest River Forecast Center (NWRFC) and North Pacific Division of the US Army Corps of Engineers for determining potential flood magnitude in the event of an eruption. In the 1980s the snowpack was determined from the NRCS SNOTEL station network located around the mountain. SNODAS uses a physically based, spatially-distributed energy and mass-balance snow model in conjunction with assimilated satellite, airborne and ground-based observations of snow covered area and SWE to determine several snowpack parameters and modeled SWE at a 1 km grid scale national coverage. The SNODAS system is compared to the traditional SNOTEL method of determining the snowpack at three elevation bands and four quadrants on Mount St. Helens. SNODAS provides an improved model of the snowpack SWE around Mount St. Helens.
Keywords: Mt. St. Helens, floods, eruption, Toutle River, SNODAS, SNOTEL

Recent Improvements in Statistical Water Supply Forecasting in the Klamath Basin, Oregon - Lea, J.; Kennedy, A.; Garen, D. (74th Annual Western Snow Conference, 2006)
The Klamath Basin has had recent national focus for water supply issues in the West. This focus began in 2001, the 5th driest year since the early 1900s, which provided the backdrop of water supply shortages, pitting irrigation, fish, tribal needs and wildlife against each other in an effort to procure enough water for their competing needs. Since that time, efforts by the US Geological Survey and Natural Resources Conservation Service, supported by the Bureau of Reclamation, have improved the statistical forecasting techniques to increase water supply forecast accuracy. Recent changes have included using spring temperature, groundwater measurements and climate indices. The Trans-Niño Index is a new climate index that has improved the forecasts early in the season, where other climate indices are not well correlated. Spring temperatures provide a measure of snowpack conditions that drive runoff in the basin. The two groundwater parameters provide long term basin baseflow characteristics and recent climate effects on the groundwater resources that support surface water runoff in the spring and summer. These improvements have increased the accuracy of the water supply forecasting by 5 to 10 percent for the Upper Klamath Basin.
Keywords: Klamath Basin, water supply, drought, forecasting techniques, spring temperature

Integration of SNODAS Data Products and the PRMS Model - An Evaluation Of Streamflow Simulation and Forecasting Capabilities - Leavesley, G.H.; Cline, D.; Carroll, T.; Hay, L.E.; Viger, R.J. (74th Annual Western Snow Conference, 2006)
The U.S. Geological Survey (USGS) hydrologic model PRMS is being used to simulate and predict daily snowmelt runoff for a number of basins in the western United States. PRMS is a distributed-parameter model that uses the concept of polygon or gridded hydrologic response units (HRUs) to account for the spatial and temporal distribution of snow accumulations and melt. It was developed for application to a wide range of basins where available meteorological data are typically limited to daily precipitation and maximum and minimum air temperature. An energy balance and water balance are computed daily for each HRU. The sum of the water balances of each HRU, weighted on a HRU-area basis, produces the daily basin response. The Snow Data Assimilation System (SNODAS) is a modeling and data assimilation system developed by the National Weather Service's National Operational Hydrologic Remote Sensing Center (NOHRSC) to provide estimates of snow cover, snow water equivalent, snowmelt, and associated snowpack variables at a 1-km spatial resolution to support hydrologic modeling and analysis. SNODAS includes procedures to ingest and downscale output from Numerical Weather Prediction (NWP) models; a physically based, spatially-distributed energy-and-mass-balance snow model; and procedures to assimilate satellite-derived, airborne and ground-based observations of snow covered area (SCA) and snow water equivalent. These gridded products can be used for comparing and/or updating spatially distributed state variables in PRMS. Comparison of PRMS and SNODAS SCA on selected basins show comparable results. (Abstract only)
Keywords: PRMS, HRU, energy balance model, SNODAS, NOHRSC, satellite

An Evaluation of the Spectral Mixture Analysis Applied to MODIS Data - Mazurkiewicz, A.B.; Callery, D.G.; Nolin, A.W. (74th Annual Western Snow Conference, 2006)
Satellite images of snow-covered area (SCA) have become increasingly useful tools in hydrologic and climatological studies. SCA images are used to help estimate snow water equivalence, a critical input variable for modeling in these fields. Two techniques have been used to map SCA from satellite data: 1) binary, which applies a snow/no-snow threshold to a normalized difference snow index and 2) fractional, which uses spectral mixture modeling. The objective of this work is to assess the differences between the MODIS SCA product and fractional SCA images computed using MODIS surface reflectance data, and identify the importance of vegetation correction. We compared SCA images at peak and mid-melt snowpack in two meso-scale watersheds with mixed land cover in the Pacific Northwest. The spectral mixture model estimated a much lower percent SCA at peak snowpack in comparison to the MODIS SCA images. During mid-melt, snow cover existed only in the forested upper portions of the basin. In this case, the mixture model and the standard MODIS image predicted similar amounts of SCA. At peak snowpack, the spectral mixture model calculated low SCA in forested areas above the snowline in both study basins. These results suggest that the spectral mixture modeling method, as applied here, is inadequate for identifying snow cover beneath a forest canopy where adjoining open areas are also snow-covered. For areas with a more homogeneous snow reflectance conditions, the current MODIS algorithm may estimate SCA as accurately as the spectral mixture method.
Keywords: Snow covered area, SCA, satellite, MODIS, SWE, binary, fractional, mixture modeling,

Physical Controls of Snowmelt in the HJ Andrews Experimental Forest - Mazurkiewicz, A.B.; Callery, D.G. (74th Annual Western Snow Conference, 2006)
The relative importance of snow energy balance (EB) components in rain-on-snow environments is poorly understood. We investigated the snow EB over eight snow seasons (1996-2003) at three meteorological sites in the H.J. Andrews Experimental Forest. We used a physically based snowmelt model (SNOBAL) to quantify EB components at annual, bi-weekly and event timescales. The study period included 20 measurable ROS events. Net radiation flux dominated the EB over the annual timescale. Even during ROS events, net radiation dominated snow EB-turbulent exchanges of sensible and latent heat dominated melt only during periods of high winds. During the largest ROS event in 1996, latent and sensible heat fluxes amounted to 32 % of total flux. In general, ground heat fluxes were high when there was a shallow transient snowpack. Energy balance components during several ROS events varied among three sites, however, net radiation was the dominant driver of melt at each of the sites, even during ROS events.
Keywords: Energy balance, rain on snow, HJ Andrews, SNOBAL, radiation flux, net radiation

Statistical Analysis of Spatial and Temporal Variations of Snowpack Density Using SNOTEL Data - Mizukami, N.; Perica, S.; Hatch, D. (74th Annual Western Snow Conference, 2006)
In this study, we examined the spatial and temporal characteristics of snowpack density, and developed climatological maps of average monthly snow density for the contiguous western United States. Monthly averages were computed from SNOTEL daily measurements of snow depth and snow water equivalent available from 1999 through 2004. Our analysis indicated significant evolution of average snowpack densities from November to April, but only small inter-annual variability, regardless of the geographic location. The inverse-distance technique was used to create gridded maps of average monthly snow depth estimates, showing modest large-scale variability of monthly snowpack density.
Keywords: Spatial characteristics, snowpack density, monthly density, SNOTEL, inverse-distance

Integration of the MODIS Snow Cover Products into Snowmelt Runoff Modeling - Rice, R.; T H Painter; Bales, R. (74th Annual Western Snow Conference, 2006)
Use of recently developed satellite snow covered area (SCA) products as quantitative inputs to hydrologic models require resolution of temporal noise, introduced owing to varying satellite viewing angles. For MODIS , a NASA space-borne scanning radiometer, which receives the electromagnetic radiation reflected or emitted by the earth and atmosphere, requires a multiple endmember spectral mixture analysis model, inverting MODIS surface reflectance products (MOD09) for enhanced fractional snow cover, plus the grain size and albedo of the fractional snow cover. However, to accurately incorporate SCA into snowmelt runoff models requires the resolution of a temporal inconsistent fractional snowcover product. Inconsistencies in the MODIS fractional SCA product results from daily differences in the local sensor view angle which ranges between 0-65 degrees. These daily differences in the radiometer scan angle can result in a 30% occlusion of snowcover over forest covered areas, and a proportional variation in SCA estimates. Results are presented that resolve the temporal inconsistencies from the forest occlusion of snowcover by using empirical corrections based on forest canopy densities. The empirical corrections result in a temporal consistent fractional SCA product for development of a composite spatial map that blends the MODIS fractional SCA product with interpolated snow water equivalence (SWE). This tool, the MODIS Snow Covered Area and Grain Size/Albedo (MODSCAG) model, specifically provides an accurate estimate of snowcover and albedo for regional studies in mountainous areas. (Abstract only)
Keywords: Satellite, snow covered area, SCA, MODIS, scanning radiometer, fractional snow cover, MODSCAG

Estimation of Snowmelt Runoff in the Poqueira River Basin (Province of Granada, Spain) Using SRM and MODIS Images - Rigueiro, G.V; Giraldez, J.V; Gonzalez-Dugo, M.P.; Gomez-Landesa, E.; Mateos-Iniguez, L. (74th Annual Western Snow Conference, 2006)
In mountain basins, where part of the precipitation is snowfall, snowmelt runoff can be a significant contribution to the total river discharge. This is the case of the Poqueira River, in Southern Spain, a tributary of the Guadalfeo river in the southwestern slope Sierra Nevada, where snowmelt is the main water supply of an ancient irrigation system. The Mediterranean climate of the Poqueira basin is influenced by the relief, elevation, and proximity to the sea. The relief affects the entry of the western winds, the main cyclone track, inducing a great variability in the precipitation. The elevation is responsible for the snow fall that occurs even in middle of the Spring when temperatures at the sea coast are very mild. The snow usually accumulates during late Fall, Winter and early Spring. Snowmelt starts in Spring lasting until early Summer. In this paper we present a snow water resources evaluation which applies to Poqueira River basin in order to quantify the water availability for irrigation. The evaluation is based on the simulation of the snow fusion using the snowmelt runoff model (SRM) and satellite data that provide the snow cover distribution (Rango, 2003).
Keywords: Snowmelt runoff, Poqueira River, Spain, water supply, irrigation

Monitoring Monthly Snowmelt Runoff in the Sierra Nevada to Detect Climate Change - Roos, M. (75th Annual Western Snow Conference, 2006)
Substantial changes in temperate zone mountain snowmelt water supply are projected to occur as a result of global warming. Water resources managers already collect extensive data to use in forecasting and in operations of water projects. If they are interested in climate change, they should look carefully at their long term records of operating projects to see if signs of change are apparent and what the rates of change are. The author will present a couple of samples from northern California of the long term history of the fraction of mountain water year runoff occurring during the April through July period of snowmelt. The charts show a small declining trend during the past 50 years, but a decrease in the rate of change during the last 15 years. Reconstruction of natural flows will be briefly discussed as well as why the change in runoff patterns is so important to the large water projects in California. A related potential effect is an increase in the size of flood events because of more watershed area contributing rain runoff during winter storms, possibly augmented by higher storm rainfall intensity. A 100-year sample of the flood record on a major Sierra river will be used to illustrate this problem.
Keywords: Climate change, monthly snowmelt, Sierra Nevada, flood size, rainfall intensity

New Snow Density Across an Elevational Gradient in the Park Range of Northwestern Colorado - Simeral, D.B.; Borys, R.D.; Wetzel, M.A. (74th Annual Western Snow Conference, 2006)
A study was conducted to examine the spatial variability of new snow density across an elevational gradient on the windward side of a mountain. The field campaign took place in February, 2005 at the Storm Peak Laboratory in northwestern Colorado. Snow sampling and in-situ meteorological measurements were conducted along an elevational gradient at five sites ranging in elevation from 2200 m to 3244 m above MSL. Snow was intermittently sampled during snow events from snow boards. Meteorological measurements of air temperature, relative humidity, wind speed, and direction were continuously logged at five minute intervals throughout the month. In addition, supplemental observations of snow crystal habit, size, and degree of riming were noted at each sampling visitation. Results showed observed mean new snow densities ranged from 83 kg m-³ to 101 kg m-³ with the lowest mean densities found at 2200 m and 2771 m. Individual densities measurements ranged from 26 kg m-³ to 188 kg m-³. The results of correlation analysis indicated a direct relationship between new snow density and several explanatory meteorological variables, such as, approximated 700 millibar temperature (0.74), lifted condensation level air temperature (0.59), wind speed (0.55), and surface air temperature (0.55). Linear regression analysis utilizing the best single predictor variable (~700 millibar level air temperature) resulted in an R² = 0.54.
Keywords: New snow density, spatial variability, Colorado, snow crystal, riming, 700 millibar temperature

Perception of Winter in Canada: A Comparison Between Edmonton (Alberta) and Montreal (Quebec) - Toupin, J. (74th Annual Western Snow Conference, 2006)
Canada, the second largest country in the world, is known namely for its large amount of snowfall, as well as the roughness of its cold winters. From coast to coast, more than 100 cm of snow (close to 1000 cm in certain areas of the Canadian Rockies) is expected to fall every winter. Southern parts of the country may easily see winter stretching over five months. Such a scenario raises the question on how Canadians really feel about winter, snow and cold; this is precisely what this paper examines. Although physical aspects of winter have been studied at length, very little has been done in the field of social climatology, particularly in Canada. In order to verify two major hypotheses: does age, and local winter climate influence how Canadians feel towards winter? Overall, 300 residents (about half of this total in Edmonton, Alberta and the rest in Montreal, Quebec) were interviewed about their perception of winter. This study reveals that there is indeed an urban perception of winter (rather quite negative) that is, to a degree, a function of age (winter is perceived to be worse as people get older) and minor differences according to local winter climates.
Keywords: Canada, winter, Canadian Rockies, negative perception of winter, urban, age

Snow and Ice Crystals: Observations With Low Temperature Scanning Electron Microscopy (Review) - Wergin, W.P.; Rango, A.; Foster, J.; Josberger, E.G.; Erbe, E.F.; Pooley, C. (74th Annual Western Snow Conference, 2006)
This review summarizes the advantages of LTSEM for observations of samples of snow and ice by illustrating the type of surface information that is obtainable, the resolution that can be attained and how the depth of field allows one to observe crystals with significant topography. In addition, we illustrate samples collected from remote locations, samples from time sequences during a storm and finally show examples of snow and ice biota as well as, artificial and Martian snow.
Keywords: LTEM, electron microscopy, snow, crystals, Mars

2005 Title, Contents, and Minutes (73th Annual Western Snow Conference, 2005)

Satellite Remote Sensing of Snow: Opportunities and Challenges for Operational Hydrology and for the Research Community - Bales, R.C.; Hartmanh, R.; Pagano, T.; Roos, M. (73rd Annual Western Snow Conference, 2005)
A set of papers highlighting some of the recent advances in using information from satellites to improve estimates of basin-scale snowpack and snowmelt runoff was followed by comments from four individuals whose organizations continue to evaluate how to best make use of satellite information for operational hydrologic forecasting. The following paragraphs are a synthesis of their remarks.
Keywords: Satellite snowcover, remote sensing, runoff forecasting, basin-scale SWE

The Documentation of Extreme Events: Two Case Studies in Utah, Water Year 2005 - Bardsley, T.; Julander, R. (73rd Annual Western Snow Conference, 2005)
The Natural Resources Conservation Service (NRCS), formerly the Soil Conservation Service, has monitored mountain snowpack and precipitation in the Western United States since 1934. The automation of measurement sites began in the late 1970s and now over 700 SNOw TELemetry (SNOTEL) sites are installed, most reporting hourly. The established length of record and hourly records now make it possible to evaluate and document extreme hydrometeorlogical events. Two recent events in Utah brought attention to the current lack of protocol for documenting extreme events. During October 20 - 22, 2004 the twenty four hour precipitation intensities for six Utah sites exceeded the National Weather Service estimated 100-year average return interval, and eleven of seventy seven Utah sites with 15 years or longer record, measured the maximum twenty four hour precipitation intensity of record. A second event Jan 8th to 12th hit SW Utah with high intensity rains and snow leading to the flooding of the Santa Clara River and the destruction of over twenty homes.
Keywords: NRCS, SNOTEL, extreme precipitation, Santa Clara River, flooding

Interpolating Surface Air Temperature for Use in a Semi-distributed Snowmelt Runoff Models - Blandford, T.R.; Harshburger, B.J.; Humes, K.S.; Moore, B.C.; Walden, V.P. (73rd Annual Western Snow Conference, 2005)
Surface air temperature is an important meteorological input variable for snowmelt runoff models, as well as for models of other hydrologic processes. Methods for incorporating this variable into models range in complexity from simply calculating average values from available weather station measurements and then applying a constant lapse rate, to more spatially-explicit methods, such as ordinary kriging. In complex terrain, such as that found throughout much of Idaho, it is necessary for the method of spatial interpolation to specifically account for orographic effects. Apart from most other past studies that compare spatial interpolation, this research examines techniques at a relatively fine spatial scale (basin size of ~1600 km2) and at a daily temporal scale. This research compares the performance of various temperature spatial interpolation techniques, including the lapse rate method, ordinary kriging of elevationally-detrended data, and the use of climate interpolation models (PRISM).
Keywords: Air temperature, snowmelt, runoff models, spatial interpolation, PRISM

A Simple GIS-Based Snow Accumulation and Melt Model - Brooks, E.S.; Boll, J. (73rd Annual Western Snow Conference, 2005)
A simple distributed snow accumulation and melt (SAM) model was developed for use in GIS-based hydrologic models. Snow drifting is simulated using observed wind speed and distributed snow drift factors, which are generated as a pre-processing step using the SnowTran-3d model. Snowmelt is simulated through a mass and energy balance applied to a single layered snow pack. Snow surface temperatures are simulated without the requirement of an iterative solution using a simple damping depth approach. The SAM model was applied to a 2 ha watershed in Troy, ID having three years of detailed snow water equivalent (SWE) measurements. Snow surface temperatures predicted by the SAM model using a fixed snow damping depth of 0.05 m showed good agreement with SHAW model predictions. The root mean square error (ERMS) between simulated and observed SWE across the site (10-46 mm) was consistent with and in some cases smaller than the ERMS at points where the maximum predicted SWE was fit to field observations (21-26 mm).
Keywords: Snow accumulation, melt, Snow-Tran, Troy, ID, SWE,

Evaluation of Gridded Snow Water Equivalent and Satellite Snowcover Products For Mountain Basins in a Hydrologic Model - Dressler, K.A.; Leavesley, G.H.; Bales, R.C.; Fassnacht, S.R. (73rd Annual Western Snow Conference, 2005)
The USGS Precipitation Runoff Modeling System (PRMS) hydrologic model was used to evaluate experimental, gridded, 1-sq km snow covered area (SCA) and snow water equivalent (SWE) products for two headwater basins within the Rio Grande (i.e. upper Rio Grande River basin) and Salt River (i.e. Black River basin) drainages in the Southwestern United States. The SCA product was the fraction of each 1-sq km pixel covered by snow and was derived from NOAA Advanced Very High Resolution Radiometer imagery. The SWE product was developed by multiplying the SCA product by SWE estimates interpolated from National Resources Conservation Service Snow Telemetry (SNOTEL) point measurements for a six-year period (1995-2000). Measured SCA and SWE estimates were consistently lower than values estimated from temperature and precipitation within PRMS. Greatest differences occurred in the relatively complex terrain of the Rio Grande basin, as opposed to the relatively homogeneous terrain of the Black River basin where differences were small. Differences between modeled and measured snow were different for the accumulation period vs. the ablation period and had an elevational trend. (Abstract only)
Keywords: PRMS, satellite snow cover, modeling, Rio Grande, Salt River, SNOTEL,

Climate change in Montana - Farnes, P.E. (73rd Annual Western Snow Conference, 2005)
Records from climatological stations having approximately 100 years of record and snow courses with approximately 75 years of record were analyzed to determine how temperatures, precipitation, and snowpack have changed over the past 100 years. There were 24 snow courses in Montana with about 70 years of record that were analyzed. Trend analysis indicates an average of about 15 percent decrease in April 1 snow water equivalent. However, three snow courses in Glacier National Park that have been measured for over 80 years show an upward trend of about 4 percent over the 70 year period and a 13 percent increase for the 83 year record. Part of the explanation of decreasing snow packs might be related to increasing tree canopy cover. Those that are located in more open areas show less of a decrease than those located in more timbered stands. Trend analysis for these 17 stations showed the average annual temperature has increased about 1.40 C over the past 100 years. None of the stations show any acceleration of temperature increases in the more recent years suggesting that increases may be more natural than man caused. The trend of annual precipitation at 20 stations (four in Northwest Wyoming) showed an increase of about two percent over the last 100 years. However, some stations showed increases while others showed decreases. Again, there does not appear to be different rates of change in recent years compared to earlier years.
Keywords: Climate change, Montana, snow courses, Glacier National Park, temperature increases, tree canopy

Evaluation of Enhancements to the Snowmelt Runoff Model - Harshburger, B.J.; Blandford, T.R.; Humes, K.S.; Walden, V.P.; Moore, B.C. (73rd Annual Western Snow Conference, 2005)
As part of a larger effort to develop tools for improved short-term (1-2 week) streamflow forecasting in snowmelt-dominated basins, the Snowmelt Runoff Model (SRM) is used to simulate and forecast streamflow in the Big Wood River basin, Idaho. Several enhancements to SRM will be evaluated: a) a new method to estimate degree-days; b) new techniques used to assign and temporally update model parameters (degree-day factor and runoff coefficients) that make use of data from SNOTEL sites located within the basin and; c) the incorporation of relative humidity and wind speed data into a new (optional) model module designed to improve model performance during rain-on-snow events. Model results will be evaluated to determine the usefulness of these enhancements.
Keywords: SRM, Big Wood River, degree days, SNOTEL, rain-on-snow

An Analysis of the Timing of Snow Course Measurement and the Potential Error Compared to April 1 Measurement in Utah - Julaner, R.P. (73rd Annual Western Snow Conference, 2005)
Snowpack data collection began in an organized fashion in Utah during the late 1920's. The April 1 measurement soon proved to be one of the most important surveys with regard to water supply forecasting. These snow survey data, used historically as April 1 data were seldom actual April 1 measurements rather they were normally sampled at some time prior to April 1, in the latter part of March. In the way that Snow Survey Data were being used, principally in linear regression applications versus accumulated streamflow, this presented little error in the forecasting scheme. However, with the advent of telemetered snowpack information, there exist now two sets of data - those manual sites still measured during the end of March and the SNOTEL or electronic data which are actual April 1 values. The snow course data would underestimate the actual April 1 snowpack compared to the SNOTEL data set, however the magnitude of the error has not been determined. Climate change is being characterized by impacts seen in snowpack. For this type of analysis, the longer the data set, typically the better and more substantial and conclusive the findings. SNOTEL has a relatively short record being installed in the late 70's and early 80's but the snow course data reach back into the 20's, making the analysis far more long term. SNOTEL replaced many of the long term snow courses, thus reducing the pool of available long term data for analysis. This analysis compares the potential error associated with actual measurement timing to April 1 and provides an average correction factor for adjusting long term snow course data to observed SNOTEL data in Utah.
Keywords: Utah, snowpack, snow survey, runoff forecasting, SNOTEL, climate change, SWE prediction, April 1

Soil Type and Site Location Impacts on Soil Moisture Data Collection at High-Elevation SNOTEL Sites - Julaner, R.P.; Holcombe, J. (73rd Annual Western Snow Conference, 2005)
The Natural Resources Conservation Service has recently begun the installation of soil moisture sensors at SNOTEL sites in the western United States in an effort to better characterize watershed hydrology pertaining to snowmelt runoff. Most research in the movement of water through a soil profile has been done in agricultural settings where topography is relatively flat, vegetation is relatively homogenous, and soils are typically fine textured and deep. This paper attempts to document some of the anomalies encountered in soil moisture data from mountainous sites and link them to potential site physical characteristics such as topographic convergence or divergence, distance to bedrock, and elevation, as well as soil type and texture.
Keywords: NRCS, SNOTEL, soil moisture sensors, soil profile, topographic convergence, elevation

SNOTEL Representativeness in the Rio Grande Headwaters using Remotely Sensed Snow Covered Area Data and Energy Balance Modeling - Molotch, N.; Bales, R.C. (73rd Annual Western Snow Conference, 2005)
Snowpack telemetry (SNOTEL) sites in and around the Rio Grande headwaters basin are located at the middle elevations of the watershed, in relatively dense vegetation, and toward the western boundary of the watershed. Based on 8 years of Advanced Very High Resolution Radiometer data (1995 - 2002), the snow cover persistence index value at the six SNOTEL sites ranged from 3.9 to 4.4 with an average 12% greater than the mean persistence of the watershed. Therefore, information from the sites does not capture the variability in snowpack accumulation and ablation processes across the watershed. Using elevation, western barrier distance, and vegetation density, a 32-node binary regression tree model explained 75% of the variability in average snow-cover persistence. Terrain classes encompassing the Lily Pond, Middle Creek, and Slumgullion SNOTEL sites represented 4.1, 6.4, and 4.0% of the watershed area, respectively. SNOTEL stations do not exist in the spatially extensive (e.g. 11% of the watershed) terrain classes located in the upper elevations above timberline. The results and techniques presented here will be useful for spatially distributed hydrologic analyses in that we have identified the physiographic conditions currently represented by SNOTEL stations (i.e. the snowpack regimes at which SWE estimation uncertainty can be determined).
Keywords: SNOTEL, Rio Grande, AVHRR, remote sensing, snowpack variability, regression tree, spatially distributed

Operational Simulation Modeling at the NRCS National Water and Climate Center - Pagano, T.C.; Erxleben, J.; Perkins, T. (73rd Annual Western Snow Conference, 2005)
The Water and Climate Services (WCS) division of the Natural Resources Conservation Service National Water and Climate Center produces seasonal water supply outlooks monthly, January through June, in partnership with the National Weather Service (NWS) and local cooperating agencies, such as the Salt River Project in central Arizona. Although forecasts have historically been regression based, simulation modeling is an emerging forecasting technology and an experimental prototype system for 16 basins was established in 2004. This system requires a high level of automation and objectivity because of the limited resources available to WCS and the time-critical demands of realtime forecasting. This paper describes the current status of the prototype and anticipated near-term future directions of WCS with respect to the use of simulation models. It begins with a description of the water supply forecasting operations, and continues with a review of past attempts to adopt operational simulation models. Next, the modeling environment is described, with emphasis on one model, the Precipitation Runoff Modeling System (PRMS) and its environment, the Modular Modeling System (MMS). Automatic calibration is used to derive parameter values and spatially-based quality control is applied to the historical data. Case studies of two basins are provided, the role of soil moisture on the Santa Clara Basin, Utah and quick hydrograph response and flooding on the Little Wood Basin, Idaho.
Keywords: NRCS, water supply forecasting, PRMS, MMS, simulation modeling

AgriMet: Modeling Evapotranspiration for Irrigation Water Management - Palmer, P.L. (73rd Annual Western Snow Conference, 2005)
In 1983, the U.S. Bureau of Reclamation and Bonneville Power Administration entered into a formal agreement to promote irrigation water use efficiency. This agreement resulted in the installation of a network of automated agricultural weather stations called AgriMet (for Agricultural Meteorology) in the Pacific Northwest. These stations collect and telemeter the meteorological parameters required to model crop evapotranspiration (ET). The information is used by irrigation districts, farmers, resource conservation agencies, and agricultural consultants for irrigation scheduling and related purposes. Since the initial installation of 3 stations in 1983, the network has grown to over 60 stations in Reclamation's Pacific Northwest region, 21 stations in the Great Plains Region in Montana, and seven stations in the Mid Pacific region. These automated weather stations transmit their data by the GOES satellite, and the information is used in the Kimberly-Penman 1982 evapotranspiration model to compute reference ET at each station. Crop coefficients are then applied to estimate water use for specific crops grown at each station for every day of the growing season. This information is available on the Internet, and is integrated into various on farm technical assistance programs by local agricultural consultants, the Cooperative Extension Service, and the USDA Natural Resources Conservation Service. Use of AgriMet information in irrigation scheduling results in water and energy savings, reduced soil erosion, and protection of surface and ground water supplies. Various agricultural consultants have reported water and power savings ranging from 15 to 50 percent (Dockter, 1996). Some irrigators have reported real savings of as much as $25 per acre in pumping costs when using AgriMet ET data to schedule their irrigations (Palmer, 2004).
Keywords: AgriMet, irrigation, evapotranspiration, water use efficiency, crop coefficients, Kimberly-Penman, NRCS

Weather, Water and Climate of the Lewis and Clark Expedition (1803-1806) - Preston, V.L. (73rd Annual Western Snow Conference, 2005)
The first scientific records of weather, water and climate in the western United States were collected during the Lewis and Clark Expedition of 1803 to 1806 as the Corp of Discovery traversed the vast uncharted region between St. Louis, Missouri and the Pacific Ocean. In addition to general daily weather comments and events, journal writers recorded climatic regimes through detailed descriptions of flora and fauna in what are known today as the Narrative Journals. Lewis and Clark kept a separate Weather Diary that documented systematic daily observations of temperature, wind, weather conditions, and river levels. It would be nearly 60 years before systematic daily observations of weather, water and climate would begin in the region explored by this Expedition. The written observations contained in the Narrative Journals by expedition members as well as Lewis and Clark's Weather Diary have been collated and organized into one document and an overview will be presented.
Keywords: Lewis and Clark, western weather, climatic regimes, flora, fauna, weather diary

Physically-Based Point Snowmelt Model Application and its Spatial Distribution with Radiation Index Method in Turkey - Sensoy, A.; Sorman, A.A.; Tekeli, A.E.; Sorman, A.U; Garen, D.C. (73rd Annual Western Snow Conference, 2005)
The Euphrates Basin is largely fed from snow precipitation over the uplands of northern and eastern Turkey. For the improved management of sustained periods of high flows during the spring resulting from melting of the snowpack, a two-layer point model is applied to calculate snow ablation and melting in the Upper Karasu Basin, a tributary to the Euphrates in the eastern part of Turkey, during the 2002-2004 snow seasons. Metamorphism within the snowpack during accumulation and ablation are controlled by the energy of the snowpack; thus, for simulating the processes at the land-snow-atmosphere interface, the only strictly correct way is using an energy budget approach. All energy terms (radiation, turbulent and ground fluxes) are evaluated to understand the key processes that have a major impact on the snow simulation at a two-hourly time step. The model performance is evaluated comparing the results with observed snow water equivalent, snow depth and snow lysimeter yield.
Keywords: Snowmelt runoff, Euphrates, Turkey, energy budget, SWE, lysimeter

Testing the Crocus Snowpack Model in a High-Latitude Maritime Snow Climate Using Remote Data Collection Methods - Shallies, W.; Hood, E.; Knuth, E. (73rd Annual Western Snow Conference, 2005)
The city of Juneau is located in southeastern Alaska has a high level of urban avalanche danger, with several large slide paths located above residential areas. In addition, the nearby Eaglecrest ski area has high in- and out-of-bounds avalanche danger, which is mitigated by a rigorous control program. We are currently collecting a suite of meteorological and snowpack data from a remote automated weather station located in the ski area at 670 m.a.s.l. Parameters being collected include: net and incoming solar radiation, wind speed and direction, snow depth, precipitation, relative humidity, and temperature. All data are transmitted to our lab at the University of Alaska Southeast via wireless modems and are available in real time. In addition, weekly snowpits at the study site provide information about snow temperature, density and stratigraphy. The aim of this study is to test the Crocus snowpack model in this high-latitude maritime snow climate. We present information on: snow-temperature profiles, snow depth, average density, snow water equivalent (SWE), and snow grain metamorphism. Qualitative analysis of the model's simulations and comparison to simultaneous snowpit observations at the study site allowed for an analysis of the model's effectiveness in the snow climate of southeastern Alaska. Results showed the Crocus model is a good predictor of snowpack hydrological parameters such as height of snowpack, SWE, and average density. In comparing the modeled temperature profiles with actual profiles taken at the study site, the model seemed to consistently under-predict the snow temperature. (Abstract only)
Keywords: Avalanche, Juneau, Eaglecrest, Crocus model, snow temperature, snowpit, maritime

Salinity, Snow, and Salvation - Steppuhn, H. (73rd Annual Western Snow Conference, 2005)
The reclamation of salinized soil involves lowering ground water levels, draining the vadose zone, and leaching the salts from the root zone. Plastic drain tubing placed 1.5 to 1.8 m below the land surface can lower watertables and drain phreatic water, but irrigation is usually required to leach the offending salts. The leaching process in non-irrigated drylands depends on natural precipitation. Rows of tall wheatgrass, Thinopyrum ponticum (Podp.) Lui & Wang, (1.2 m mean height) spaced on 15.2-m centers across saline fields can retain blowing snow, augment water for leaching salts, and moderate evapotranspiration when grown in conjunction with subsurface drainage. The mean salinity of saturated soil paste extracts from sets of soil samples taken every fall from such a site in southwestern Saskatchewan averaged 14.1 dS/m during 1985-90 before the drainage was installed, 13.0 dS/m for 1991-92 after drainage but before the grass windbreaks became established, and 9.6 dS/m for 1993-99 with both drainage and windbreaks in place.
Keywords: Saline soil, ground water level, wheatgrass, blowing snow, salt leaching

IRIS: An Informational River and Reservoir Simulation Display - Swank, L.; Abramovich, R. (73rd Annual Western Snow Conference, 2005)
Water District #1 has developed computer software displaying statewide water supply conditions for all major river basins in Idaho. This scaleable software visually simulates reservoir contents, river discharges, major diversions, and snow water equivalents. USBR Hydromet data and NRCS SNOTEL data are transmitted through an automated FTP transfer process to Water District #1's server and database, and linked to the R*TIME near real-time software created by SCIENTECH INC. This software allows water managers to quickly display current water supply conditions and graphically compare the data to previous historical years. The computer simulation is a time-scaled replay feature that has pause, rewind, and fast forward buttons; enabling users to animate reservoir, river and snow displays at variable speeds. It is a valuable tool that can be used for water management purposes and will increase understanding of both professionals and the general public concerning water supply and water distribution.
Keywords: NRCS, SNOTEL, water supply, condition display, software

Using the WINWRNSHYD program as a didactic tool - Swanson, R.H. (73rd Annual Western Snow Conference, 2005)
The WinWrnsHyd computer program is a complete implementation of the hydrology section of the USEPA WRENSS procedure plus some additional routines related to forest growth. As such its principal use has been to estimate the changes in water yield associated with forest management activities. However, it is not limited to this use. Forest harvest affects water yield by altering evapotranspiration, the differential accumulation and retention of snow, the timing of snow melt, the intensity of harvest, and the speed of vegetative regrowth. The WinWrnsHyd model simulates the magnitude of each of these factors and integrates the net result to give an estimate of annual water yield. Hydrologists often examine each of these factors in isolation and it is not always clear what magnitude of the effect that each one has on the integrated whole.
Keywords: WRENSS, WRNSHYD, WinWrnsHyd, snow accumulation, forest management, peak flow changes

Perception of winter from children and teenagers in Alberta, Canada: a case study of Edmonton and Plamondon - Toupin, J. (73rd Annual Western Snow Conference, 2005)
A major characteristic of Canada, second largest country in the world, remains its winters. Its population (about 32 million) has to endure one of the toughest cold season on Earth. Canadian Prairies' coldest month (January) averages about -15oC (5º F) and over 100 cm (more than 3 feet) of snow is expected to fall every year. This paper investigates the hypothesis that there is an urban perception of winter that tends to be rather negative among children (8 to12-year-old) and teenagers (13 to17-year-old) that live in the city of Edmonton, Alberta, a city with a population of about 1 million. However, children and teenagers in the rural village of Plamondon, population less than 1,000, have a winter perception that is relatively better. More than 100 participants were interviewed on six major aspects of their perception on winter. Although the winter season is perceived as the worst (namely because of the cold) by participants in both locations, children and teenagers in the rural area tend to spend more time outside (snowboarding, skiing, playing hockey), describe this season in better terms (beautiful, white, nice), prefer to spend it in a rural area, and find winter shorter than their urban counterparts. To a degree, age is also a factor in explaining how they look at winter.
Keywords: Canada, winter, negative perception, urban, Edmonton, Plamandon,

2004 Title, Contents, and Minutes (72th Annual Western Snow Conference, 2004)

Evaluating the stuffblock and tilt board snowpack stability tests as snow avalanche forecasting tools - Carter, P.; Heavner, M.; Hood, E. (72nd Annual Western Snow Conference, 2004)
Snow avalanche forecasting relies on, among other factors, an assessment of snowpack stability derived from careful observation of snow cover stratigraphy. Snowpack profiles and stability tests provide quantifiable information about the location and strength of weak layers in the snowpack. This study found: 1) good comparative results between the stuffblock and compression tests and, 2) a relationship between tilt board test results in level study sites and skier-triggered avalanches.
Keywords: Avalanche, avalanche forecasting, snowpack stability, stuffblock, tilt board

The Effect of Basin Scale on Diurnal Streamflow Timing - Lundquist, J.D.; Dettinger, M. (72nd Annual Western Snow Conference, 2004)
Hourly streamflow timing, as revealed by diurnal fluctuations in discharge in snowfed watersheds, provides a new tool for understanding transport times and processes in river basins. Travel time delays at different basin scales were measured in nested subbasins (6 to 775 km2) of the Tuolumne River in Yosemite National Park throughout the spring 2002 and 2003 melt seasons. The travel time increases with longer percolation times through deeper snowpacks, increases with longer travel times overland and along longer stream channels, and increases with slower in-stream flow velocities. In basins smaller than 30 km2, snow properties that determine the travel times through the snowpack dominate streamflow timing. In particular, daily peak flows shift to earlier in the day as the snowpack thins and mean discharge increases. In basins larger than 150 km2, snowpack heterogeneity and mixing cause the hour of peak flow to be remarkably consistent, with little or no variation due to snowpack properties. Basins with areas in between 30 and 150 km2 exhibit different characteristics in different years, illustrating the transition between small and large-scale basin characteristics. Increasing channel travel times as the snowline retreats to higher elevations are not enough to offset the observed decrease in mean snowpack travel times.
Keywords: Streamflow timing, Tuolumne River, travel time, basin scale, diurnal flow

Variability and trends in mountain snowpacks in western North America - Mote, P.W.; Hamlet, A.F.; Lettenmaier, D.P. (72nd Annual Western Snow Conference, 2004)
Snow course and SNOTEL measurements of spring snowpack, corroborated by a physically-based hydrologic model, are examined here for climate-driven fluctuations and trends during the period 1916-2002. Much of the mountain West has experienced declines in spring snowpack, especially since mid-century, and despite increases in winter precipitation in many places. Analysis and modeling shows that climatic trends are the dominant factor, not changes in land use, forest canopy, or other factors. The largest decreases have occurred where winter temperatures are mild, especially in the Cascade Mountains and Northern California. In most mountain ranges, relative declines grow from minimal at ridgetop to substantial at snowline. Taken together, these results emphasize that although the Pacific Decadal Oscillation has played some role in fluctuations in the region's SWE, the West's snow resources are already declining as Earth's climate warms.
Keywords: Snow course, SNOTEL, snowpack trends, PDO, climate change

A history of the Skagit River basin snow surveys and hydroelectric project - Pattee, S. (72nd Annual Western Snow Conference, 2004)
Follow the trials and tribulations of snowpack data collection through a historic timeline within the Skagit River Basin in the North Cascade Mountains of Washington State. From past to present, snow survey data was collected in support of the major hydroelectric project that provides electricity primarily to the City of Seattle. The first recorded snow surveys were conducted by the United States Geological Survey (USGS) in 1944 at 8 manual snow courses. Canadians began collecting data in support of the project in 1946. Throughout the years, numerous snow courses and Aerial markers were started and some later discontinued. The Natural Resources Conservation Service, in cooperation with Seattle City Light, took over data collection responsibility in 1979 and began converting select manual sites to automated SNOTEL stations. The network now consists of 6 SNOTEL sites and 11 manual snow courses with support of 7 aerial markers.
Keywords: Snow course, SNOTEL, Skagit River, hydroelectric, Seattle City Light

Trip report of Lightning Creek Trail snow survey accident: Skagit River, February 3, 1947 - Pattee, S. (72nd Annual Western Snow Conference, 2004)
Two snow surveryors attemted to do a snow survey in the upper Skagit River basin, and found bad conditions and had trouble getting to the survey cabins over a 6-day period. They completed the snow course at Freezeout Meadows and returned to the cabin that had a malfunctioning stove and little dry wood. They measured the Lightning Creek stream gage site on the third day, and finished another snow course on day 5. On the return trip, one of them lost footing on an icy slope and slid over a rock cliff and broke an arm and hurt his hips. The other continued on the return trip to get help, and the injured surveyor waited for hours until he got so cold he had to start crawling along the trail to stay warm. Well after dark, the rescue team returned and carried him out on a strecher. He spent a week in the hospital, but recovered.
Keywords: Lightning Creek, snow survey, British Columbia, snow survey, accident, rescue

The relationship between synoptic weather patterns and snowpack stability in a high-latitude maritime snow climate - Scheler, K.; Carter, P.; Hood, E. (72nd Annual Western Snow Conference, 2004)
Weather is considered to be the architect of avalanche formation. Understanding its effects on snowpack properties is an important tool in avalanche forecasting. This study investigated regional synoptic weather patterns and their correlation to near-surface faceted crystal formation and snowpack stability in a high-latitude maritime snow climate. Regional synoptic variables were classified from charts published by the National Weather Service into three types 1) on-shore, 2) off-shore, and 3) split flow. Synoptic patterns were compared to plot scale meteorology and snowpack measurements collected at two study plots located at 700 m and 720m above sea level near Juneau, Alaska. Here we report on three episodes in January and February of 2004 in which vapor pressure gradients measured in the upper 25 cm of the snowpack were in excess of 45 mb m-1. During all three periods, faceted crystals 1-2 mm in diameter formed near the surface of the snowpack. In one case, wet grains comprising a low density crust at the surface of the snowpack metamorphosed into a weak layer of faceted crystals. Snowpack stability measurements following all three episodes revealed near-surface instabilities and avalanche cycles were observed after each of the events.
Keywords: Avalanche, weather, snowpack, Juneau, synoptic variables, faceted crystals, weak layers

Snowmelt in a forest and clearcut - Spittlehouse, D.L.; Winkler, R.D. (72nd Annual Western Snow Conference, 2004)
Methods for obtaining daily snowmelt rates in forest and clearcut environments were evaluated at high elevation sites in the southern interior of British Columbia, Canada (Upper Penticton Creek Watershed Experiment). Snowmelt was measured during spring 1998 to 2002 in a clearcut with snowmelt lysimeters and calculated for the clearcut and a forest from the daily snow pack depth and snow density. Daily melt rate was calculated in the forest and clearcut from weather station data using an air temperature index method and with the energy balance. Measurements were used to calibrate clearcut and forest snow albedo models, to determine solar radiation transmission through the forest canopy and to calculate the canopy view factor for longwave radiation in the forest. Snow temperature measurements were used to define the beginning and end of the melt season when modelling snowmelt. Lysimeter and snow depth and density based measurements of snowmelt agreed quite well. The air temperature index method gave acceptable estimates of melt but tended to overestimate melt in the forest. The energy balance calculations slightly overestimated melt in the clearcut and slightly underestimated melt in the forest. Net radiation provides almost all the energy for melt in the forest and about 75% of the energy in the clearcut. Snowmelt rates of over 40 mm d-1 were measured in the clearcut and up to two thirds of this in the forest under the same weather condition.
Keywords: Snowmelt rates, Penticton Creek, lysimeter, snow albedo, canopy view factor, air temperature index

The complete WRENSS hydrologic model - Swanson, R.H. (72nd Annual Western Snow Conference, 2004)
In 1980, the USEPA published a set of graphical procedures to estimate the hydrologic effects of various forest silvicultural practices on water yield and quality. The results from the hydrologic procedures (which I abbreviate as Wrns to distinguish the hydrologic procedure from the entire WRENSS handbook) were the basis for most of the subsequent analyses. Most of the parameters needed to operate Wrns were available from sets of regionalized curves for all forested regions in the United States. Forestry Canada produced an MSDOS version, WRNSHYD, for the hydrologic procedures, with the regionalized curves extended into Canada based on climate and forest similarities, WRNSHYD has received wide use in both Canada and the United States. A new program developed jointly with the US Forest Service, WinWrnsHyd, that overcomes most of these drawbacks is now available. It incorporates the latest research on snow accumulation from the USDA Rocky Mountain Research Station. It is programmed in Microsoft Access and uses database tables as input so that harvesting scenarios can be created with a GIS or other forest planning tool. Silvicultural input data can consist of a series of “snapshots” of forested land units at various times and the subsequent impact on water yield simulated as a batch calculation.
Keywords: WRENSS, WRNSHYD, WinWrnsHyd, snow accumulation, forest management, peak flow changes

Effects of small logged openings on snow ablation during a high snow year - Teti, P. (72nd Annual Western Snow Conference, 2004)
The effects of small logged openings on snow ablation rate were studied from 1994 through 1998 at a sub-alpine silvicultural systems research site in the Quesnel Highland of B.C. Six snow plots were in north-facing treatment units from which 21 to 34 percent of the forest had been previously harvested and one was installed in an unharvested control. One purpose was to determine the potential effects of group selection on peak streamflows in the event that this silvicultural system is applied over large areas. Average ablation rates in openings increased from 1.6 to 2.2 cm per day as opening diameters increased from 1 to 5 tree heights (1H to 5H). There was no significant effect of small openings on ablation rates in the adjacent trees. The net effect of harvesting 30 percent of the area in the form of 3H and 5H openings was that ablation rates increased by 5 and 13 percent respectively in a year with above-average snowmelt-generated peak streamflows.
Keywords: Logging effect, snow ablation, Quesnel Highland, harvest treatments, ablation , peak streamflow

Identifying snow indices for forest planning in southern British Columbia - Winkler, R.D.; Gluns, D.; Golding, D. (72nd Annual Western Snow Conference, 2004)
Snow accumulation and ablation rates vary significantly across the forested landscapes of British Columbia. Changes in snow accumulation and ablation through logging and forest re-growth are assumed to have a direct effect on the quantity and timing of streamflow. To minimise the risk of increased spring peak flows, tree height is used as an operational index to changes in snow accumulation and melt in planning forest development. However, detailed measurements at two research sites in the southern interior have shown that inventory variables such as crown closure account for a larger proportion of the variability among stands, and may be more suitable indices to potential changes in runoff, than tree height. In this study, data from a broad range of sites have been analysed to evaluate which inventory variable provides the best local snow-index. Crown closure explained 68% and 57% of the variability in average standardised peak snow water equivalent and melt rate, respectively.
Keywords: Snow accumulation, ablation, British Columbia, streamflow timing, crown closure, SWE

Effect of alternative silvicultural treatments on snow accumulation in lodgepole pine stands, Montana, U.S.A. - Woods, S.W.; McCaughey, W.; Ahl, R.; Sappington, J. (72nd Annual Western Snow Conference, 2004)
Alternative silvicultural treatments such as thinning can restore the productivity and diversity of forested watersheds and reduce wildfire hazards, but the hydrologic effects of these treatments are not well defined. We evaluated the effect of even thinning (SE) and group-retention thinning (SG), both with ~ 60 % basal area removal, on snow accumulation in lodgepole pine stands at the Tenderfoot Creek experimental forest, west-central Montana. In 2003 and 2004, the snow water equivalent (SWE) close to the seasonal peak was measured at >250 locations in the SE and SG treatments, and a control. In both years, the mean SWE in the SE treatment was significantly higher than in the control and the SG treatment (P<0.0001). In contrast, the mean SWE in the SG treatment was not significantly different from the control. Spatial variability of SWE was up to 3 times higher in the SG treatment than in the SE treatment or the control. The increased snow accumulation in SE treatments is attributed to reduced interception. In the SG treatment, losses due to wind scour and evaporation offset gains due to reduced interception. These results demonstrate that thinning can have substantially different effects on snow accumulation depending on the spatial arrangement of the treatments.
Keywords: Forest thinning, snow accumulation, Tenderfoot Creek, SWE, interception

Computer-assisted avalanche forecasting: skier triggered avalanches - Zeidler, A.; Jamieson, B. (72nd Annual Western Snow Conference, 2004)
Computer-assisted avalanche forecasting has become a valuable tool in some forecasting operations in Canada. Avalanche forecasting models are based on statistical, numerical and/or rule-based methods, but usually predict natural rather than skier-triggered avalanches. A nearest neighbour forecasting model for skier-triggered avalanches on post storm weak layers was improved by adding snowpack properties including a stability index to meteorological variables. However, a skier stability index did not improve the forecasting success on storm snow instabilities. The best forecast could be achieved by using meteorological parameters.
Keywords: Avalanche, avalanche forecasting, nearest-neighbor, skier-triggered avalanches

2003 Title, Contents, and Minutes (71th Annual Western Snow Conference, 2003)

Satellite Snowcover Perspective on the Drought: Colorado and Rio Grande Basins - Bales, R.C.; Imam, B.; Brice, R. (71st Annual Western Snow Conference, 2003)
Estimating snowcover properties at a basin scale, particularly snow water equivalent (SWE), remains a challenge. We have used a combination of remote sensing and ground-based data to estimate snow covered area (SCA) and SWE for portions of the Southwestern U.S. for an eight-year period, 1995-2002. Two immediate applications for this product were to: i) evaluate the seasonal and interannual variability in snowcover patterns, and ii) provide snowpack information for evaluating hydrologic models of snowmelt runoff and other components of the water balance. Fractional snow covered area (SCA) maps with a 1-km2 grid were developed from AVHRR scenes using a three-part cloud masking procedure and spectral unmixing algorithm. A 1-km2 SWE product was developed for the same area using interpolation of ground-based SNOTEL data, followed by masking with the SCA scenes. The fractional SCA product showed areas with persistent snowcover to be relatively reproducible from year to year, corresponding to higher elevations. However, there were different January through June patterns of snowcover persistence during recent drought years as compared to previous years. The annual maximum snow extent, or area with any snowcover during the year, exhibited significant interannual variability, and was not well correlated with maximum SWE. The current products are available on a set of CD's (see http://resac.hwr.arizona.edu). Abstract only.
Keywords: Satellite snowcover, Colorado River, Rio Grande River, AVHRR, SCA

Temporal and Spatial SWE Predictions for Hydrologic Model Input - Carroll, R.W.; Dana, G.L., (71st Annual Western Snow Conference, 2003)
A multiple regression equation was developed to describe temporal and spatial variability of daily snow water equivalent (SWE) in Lake Tahoe's Incline Basin. SWE maps of the basin are needed for the parameterization of the physically-based Alpine Hydrochemical Model (AHM) to simulate basin hydrology and solute transport. SWE data collected during 2002's peak snow accumulation were used in conjunction with data from three local SNOTEL stations to calibrate the regression equation. Calibration was conducted during a dry and average water year using the sum of least squares. The multiple-regression was dependent on elevation, aspect, slope, vegetation density and solar radiation and was normalized by the average SWE measured at the three SNOTEL sites. Basin-wide computations were done at 30 m resolution in ArcView to generate daily SWE maps. Verification was performed at the three SNOTEL sites for a wet year and another average year. While errors in prediction were relatively low (approximately 0.3%), the regression over predicted peak accumulations for upper elevations, under predicted SWE at lower elevations and allowed greater attenuation of SWE into the summer months for lower elevations. In contrast, the mid-elevations were extremely well predicted in both timing of peak accumulation and overall SWE volume.
Keywords: SWE, multiple regression, Lake Tahoe, alpine hydrochemical model, SNOTEL, peak snow accumulation

Early forecasts of snowmelt runoff using SNOTEL data in the Upper Rio Grande Basin - DeWalle, D.R.; Eismeier, J.A.; Rango, A. (71st Annual Western Snow Conference, 2003)
Forecasts using SNOTEL data on November 1 and December 1 gave the best estimates of spring snowmelt runoff volumes almost as frequently as forecasts on March 1 and April 1 for the Upper Rio Grande basin in Colorado during 1983-2001. Forecasts for 2002, a record drought year, greatly overestimated flow volumes regardless of prediction month. Attempts at improving predictions using the El Nino/La Nina Southern Oscillation Index were not successful.
Keywords: Runoff forecasting, SNOTEL, Rio Grande, early season forecasts

Arizona Chapter of Soil and Water Conservation Society Responds to Recovery Efforts of Arizona's Largest Wildfire - Dye, H. (71st Annual Western Snow Conference, 2003)
The Arizona Chapter of the Soil and Water Conservation Society (SWCS) coordinated a special field demonstration of practices used to prevent soil erosion following the 2002 Rodeo-Chediski wildfire. The Rodeo-Chediski wildfire in east central Arizona, fueled by severe drought conditions, consumed approximately 1,890 square kilometers (467,000 acres) of timber on National Forest, White Mountain Apache Nation, and private lands becoming the largest wildfire in Arizona's history. About 33 square kilometers (8,192 acres) of private land, including 491 homes and businesses were burned. The U.S. Department of Agriculture's Natural Resources Conservation Service (NRCS) approved a $2.9 million Emergency Watershed Protection (EWP) project initiating a large-scale fire recovery assistance program for private landowners affected by the wildfire. Arizona SWCS Chapter members, NRCS EWP detailees, and NRCS Earth Team volunteers joined forces to provide technical assistance and to demonstrate conservation practices, designed to protect lives and property from the effects of flooding and erosion resulting from the wildfire. Practices constructed during the demonstration included seeding, straw mulching, straw bale diversions and check dams, and contour wattles. As a result of the demonstration, a severely burned sub-watershed was completely treated and residents were provided with technical information to assist them with the recovery of their fire-damage property.
Keywords: Rodeo-Chediski wildfire, emergency watershed protection, check dams, erosion, Arizona

Contributions of Snow Research to Forest Watershed Management in the Southwestern United States - Ffolliott, P.F.; Gottfried, G.J. (71st Annual Western Snow Conference, 2003)
Snowpacks that accumulate on high-elevation forested watersheds are an important source of water in much of the southwestern United States. However, snowpacks in this region differ from those in more northern regions because of the variability in annual snowfall accumulations and the intermittent melting throughout the winter season. Snow research over the past 50 years has indicated that there are possibilities of increasing snowmelt-runoff through the implementation of forest management practices. The effects of these forest management practices can often be predicted from inventory-prediction relationships. Other research has resulted in development of snow-runoff forecasting procedures and simulation models of forest snowpack dynamics leading to increased knowledge of snow hydrology.
Keywords: Snowpack, research, southwest US, watershed management

Climate Change and California's Diminishing Low-Elevation Snowpack - A Hydroelectric Scheduling Perspective - Freeman, G.J. (71st Annual Western Snow Conference, 2003)
Pacific Gas and Electric Company's (PG&E) Water Management Team did a review to identify possible effects on PG&E's hydro generation production of an increase in winter runoff from rainfall and a decrease in spring runoff from snowmelt. There are many indications that the reduced snowpack in the low-elevation Sierra snow zone, which has been observed in recent years, is a likely consequence of climate change. Climate change appears to be affecting runoff timing and flow quantities most significantly for those relatively low-elevation watersheds, which are situated from the Yuba River north. For PG&E, both the Feather River and the Yuba River Basins have large portions of their drainages at relatively low elevation and appear most sensitive in terms of potential to affect future hydro generation schedules. The November-through-February winter runoff quantities, which are mostly rainfall-produced, appear to have increased both in intensity and monthly quantity; and the spring snowmelt in the low elevations, from a somewhat diminished snowpack, appears to be taking place almost a month early for some portions of the Feather River. Full reservoirs near the end of the snowmelt period are a desirable outcome for meeting critical summer and fall electric load demands.
Keywords: Climate change, Feather River, hydrogeneration, runoff timing, decreased snowpack, reservoir carryover

Snowpack-Runoff Relationships for Forested Mid-Elevation Watersheds and a High-Elevation Watershed in Arizona - Gottfried, G.J.; Neary, D.G.; Ffolliott, P.F. (71st Annual Western Snow Conference, 2003)
Snowmelt from higher elevation forested watersheds is a major source of runoff for most of the rivers in the southwestern United States. Snowpacks in the Southwest melt intermittently throughout the winter. At some mid-elevation locations, between 2,135 and 2,285 m (7,000 and 7,500 ft), snowpacks appear and disappear, depending on the distribution of storms and temperature fluctuations during the winter. Snowpacks at higher elevations may experience periods of melting but generally accumulate snow throughout the winter with most snowmelt occurring during the spring. The USDA Natural Resources Conservation Service (NRCS) maintains a system of measuring stations to index snow conditions and predict snowmelt runoff. Peak snow water equivalent data from NRCS stations have been related to snowmelt runoff volumes and mean daily peak flows for the three mid-elevation Workman Creek watersheds north of Globe, Arizona and for the high-elevation East Fork of Willow Creek in the White Mountains of eastern Arizona. The statistically significant relationships for Workman Creek are being used as a basis to measure the effects of the Coon Creek Wildfire on watershed hydrology and to estimate winter streamflows for the years when the installations were closed. The comparisons between mid and high-elevation watersheds will increase our knowledge of snowmelt dynamics in the Southwest.
Keywords: Snowmelt, Arizona, Workman Creek, NRCS, peak snow water equivalent, Coon Creek wildfie

Climate Effects of Pacific Decadal Oscillation on Streamflow of the Feather River, California - Koczot, K.; Dettinger, M. (71st Annual Western Snow Conference, 2003)
The timing of maximum monthly-mean streamflow for the Feather River in northern California has come earlier in the year in recent decades (since the 1950s), as have timings in most rivers throughout California and the western United States. Much of the timing shift in the Feather River basin appears to coincide with interdecadal changes in the North Pacific climate regime. The coincident timing changes are seen as a shift in the month of maximum streamflow from April-May during the cooler Pacific Decadal Oscillation (PDO) phase to March-April during the warmer phase. The change in streamflow timing in the Feather River basin became an issue during the testing of a new set of watershed models of inflow to Lake Oroville, because model performance degraded in simulations of recent years (1998-2001). The model calibration period (1971-97) was dominated by the warmer (1977-98) PDO phase. However, the 1998-2001 period mostly corresponds to a newly reestablished cool PDO (beginning late 1998). Simulations during 1998-2001 failed to reproduce streamflow as well as simulations of the calibration period, probably because some model parameters, like those associated with rain-snow mixes or temperature and precipitation distributions, are not calibrated for climatic conditions that occur during a cool PDO.
Keywords: PDO, Feather River, streamflow timing, monthly streamflow, Lake Oroville

Pitfalls of Forecasting Water-Year Type Classification in New Hydropower Licenses - McGurk, B.J. (71st Annual Western Snow Conference, 2003)
Hydropower facilities typically operate under 30-year licenses from the Federal Energy Regulatory Commission. In the recent licenses that have been obtained by Pacific Gas and Electric Company (Company), a key part of the license is the setting of the minimum streamflow regime in the river reaches that are affected by project facilities such as dams and diversions. Current ecological concepts value inter- and intra-annual variation in streamflow that reflects the large year-to-year variation in water-year magnitude. Runoff forecasting based on snow resources allows the definition of water-year types as the winter progresses, and streamflows are implemented accordingly. Monthly forecasts are sensitive to a variety of error sources during the 4-5 month forecast period. Errors in water-year type designation can disrupt plans for biological studies, construction schedules, and adversely affect reproduction success of amphibian and other aquatic species. Errors in forecasting and license inflexibility can also result in implementation of streamflows that are higher than necessary and cost the Company millions of dollars. Collection of accurate data from well-designed snow course, snow sensor, and climate stations is essential to minimize forecast error.
Keywords: Hydropower, water-year type, FERC, PG&E, runoff forecasting, minimum streamflow

Modeling of Snow Water Equivalent Distribution in a Meso-Scale Mountainous Watershed with GIS - Mizukami, N.; Decker, R.; Julander, R. (71st Annual Western Snow Conference, 2003)
In rugged mountainous regions where snow is a major water resource, physical measurements of snow water equivalent (SWE) are necessary to estimate its spatial distribution, which is then used to predict the volume and timing of snow melt. This paper presents a methodology for construction of Iso-Snow-Climate-Polygons (ISCP) - areas where snow properties are relatively homogeneous - in order to establish optimal and efficient physical measurement strategies for SWE. A medium sized watershed, Parrish Creek (about 5.5 km2) in the Wasatch Mountains was used as a study site. The factors that control SWE distribution that are implemented in this process are elevation effect on snow accumulation, ablation due to solar radiation, wind redistribution (curvature, wind aspect), vegetation effect, and slope angle effects on avalanching and snow sloughing. For each effect, separate digital terrain maps are created using topographical variables including elevation, slope angle, aspect, solar angle and curvature, and vegetation. Finally, all maps are combined in an effort to determine that optimal set of ISCPs that cover the watershed. Also the total volume of SWE estimated using ISCPs compares well with that calculated using all the grid sampling points. In order to fully verify accuracy of the GIS based ISCP method, additional SWE field verification studies are needed.
Keywords: Modeling, SWE, Parrish Creek, Wasatch Mountains, SWE distribution

Optimization of binary regression tree models for estimating the spatial distribution of snow water equivalent in an alpine basin - Molotch, N.; Bales, R.; Colee, M.; Dozier, J. (71st Annual Western Snow Conference, 2003)
Regression tree models have been shown to provide the most accurate estimates of distributed SWE when intensive field observations are available. This work presents an approach that improves regression tree model performance by optimizing the use of independent variables and by comparing different residual interpolation techniques. The analysis was performed in the 19.1 km2 Tokopah basin, located in the southern Sierra Nevada of California. Snow depth, the dependent variable of the statistical models, was derived from three snow surveys (April, May and June, 1997), with an average of 990 depth measurements per survey. Estimates of distributed SWE were derived from the product of the snow depth surfaces, the average snow density (54 measurements on average), and the fractional snow covered area (obtained from the Landsat Thematic Mapper and the Airborne Visible/Infrared Imaging Spectrometer). Inclusion of the independent variable northness improved regression tree model fit. Co-kriging with solar radiation proved to be the best method for distributing residuals for April and June, with inverse distance weighting providing the best result for May.
Keywords: Regression trees, SWE, Tokopah, distributed SWE

Declines in Snow Water Equivalent in the Pacific Northwest and Their Climatic Causes - Mote, P.W. (71st Annual Western Snow Conference, 2003)
Observations of snow water equivalent (SWE) in the Pacific Northwest are examined and compared with variability and trends in temperature and precipitation at nearby climate stations. At most locations, substantial de-clines in SWE have occurred over the past 50 years. Largest percentage losses have occurred at lower elevations (below 1000m), a pattern that is consistent with observed increases in temperature during winter and early spring. In many locations the reductions in SWE occurred in spite of likely increases in precipitation.
Keywords: Pacific Northwest, declining SWE, precipitation, temperature, snow course

A Poor Man's ESP: Statistical Hydrograph Trace Adjustment - Pagano, T.C.; Garen, D.C. (71st Annual Western Snow Conference, 2003)
Water managers increasingly demand forecasts of hydrograph characteristics beyond seasonal volumes. Currently, most volumetric forecasts of seasonal streamflow are produced using statistical regression techniques. One way to provide additional long-lead information about peak flows, low flows, and number of days to a particular threshold is to apply the Ensemble Prediction System, first developed by the National Weather Service. This Ensemble Prediction System involves the calibration of a hydrologic simulation model, model initialization using current watershed states, and forcing based on a number of observed historical meteorological traces. The output is a series of possible future daily hydrographs, from which the above mentioned characteristics can be derived. As a low-cost alternative, an ensemble hydrograph forecast can be obtained by rescaling historical flow traces by the existing statistical seasonal streamflow volume forecast. The volume of streamflow from past years is mapped into the distribution of the statistical error bound of the official seasonal volumetric forecast to obtain a multiplier factor for each year. This multiplier is then applied to each daily flow value of the historical year. While this simple system has many shortcomings and limitations, it still provides useful information and may serve as a credible naïve forecaster baseline against which to compare the performance of other ensemble forecast systems.
Keywords: ESP, volumetric forecast, statistical rescaling, runoff forecasting

Development of a Remote Sensing-Snowmelt Runoff Forecasting System in the Rio Grande Basin - Rango, A.; Gomez-Landeza, E.; Havstad, K.; Bleiweiss, M.; Tanksley, K.; DeWalle, D.; Martinec, J.; Kite, G. (71st Annual Western Snow Conference, 2003)
Large river basins in arid and semi-arid regions, such as the Rio Grande, need forecasting systems that make use of data obtained from new technologies. For the Rio Grande basin, we are developing a forecasting system comprised of two linked models designed to use remote sensing data, namely, SRM and SLURP. SLURP requires MODIS satellite data for land use and evapotranspiration determination, and SRM requires MODIS snow covered area data plus snow water equivalent data from the meteor-burst data relay of SNOTEL. Working on some tributary basins, we have produced streamflow forecasts for 2001-2003. We are in the process of expanding the forecasting to all the snowmelt sub-basins as well as basins where rainfall dominates. The final product should assist local, state, and federal agencies in making improved water management decisions in the complex and water limited Rio Grande basin.
Keywords: Remote sensing, runoff forecasting, snowmelt, SRM, SLURP, MODIS, Rio Grande, water management

Near-Surface Faceted Crystal Growth and Snow Stability in a High-Latitude Maritime Snow Climate - Scheler, K.; Hood, E.; Carter, P.; Glude, B (71st Annual Western Snow Conference, 2003)
The City and Borough of Juneau, Alaska has several major avalanche paths located in close proximity to population centers and is routinely affected by avalanche activity. However, due to a lack of funding and research, Juneau is largely unprepared for potentially catastrophic avalanche events. This study investigates temperature and vapor pressure gradients associated with near-surface faceted crystal formation in the high-latitude maritime snow climate of southeast Alaska. Here we report on two episodes in March and April 2003 in which temperature gradients measured in the upper 25 cm of the snowpack were in excess of 70?C m-1. During both of these periods, faceted crystals 1-2 mm in diameter were observed to form near the surface of the snowpack. Field tests performed simultaneously at our study site demonstrated pronounced instabilities associated with the newly formed faceted crystals. Furthermore, avalanche activity was observed following both periods. Investigations of proximate avalanches showed that wind-loaded dry slabs were running on layers of near-surface faceted crystals.
Keywords: Juneau, Alaska, avalanche, temperature, vapor pressure, faceted crystal growth

Using Ensemble Streamflow Prediction for Water Supply Forecasting in British Columbia - Practicalities and Pitfalls - Smith, S.; Weber, F. (71st Annual Western Snow Conference, 2003)
BC Hydro has just completed new watershed model calibrations for 20 of its reservoirs, which would enable the use of Ensemble Streamflow Prediction (ESP) techniques for preparing water supply forecasts. ESP methods have been used to forecast the seasonal water supply for BC Hydro's large interior snow-driven basins for a number of years with much success. But using the technique for smaller coastal rain- and rain/snow-driven basins has proven to be much more challenging. This paper will focus on two known issues: snowpack simulation in the model and month-to-month model calibration bias. This study showed that in coastal and interior basins, snowpack adjustments improved the forecast accuracy and slightly decreased the dispersion. The bias correction technique computed daily bias correction offsets as differences between simulated and observed flows during the calibration period. The offsets were then applied to the ensembles of the forecast. The technique produced mixed results.
Keywords: ESP, forecasting, water supply, British Columbia, BC Hydro, UBC

Are Snow Resources on the Northern Plains and Prairies Dwindling? - Steppuhn, H.; Cutforth, H.W.; Judiesch, D.; Wall, K.G (71st Annual Western Snow Conference, 2003)
Snow across the Northern Great Plains and Canadian Prairies constitutes a very essential natural resource. A study to determine if northern snow resources have changed in magnitude over the last forty years was initiated. Snow-course data measured in non-irrigated agricultural fields, near Swift Current, Saskatchewan, reflect the large year-to-year and within-year variability typical of wind-swept plains. This variability rendered direct measurement and detection of snow-resource change difficult. However, analyses of a combined set of daily climatological data (Nipher-shielded snowfall water-equivalent and depth of snow-on-the-ground) at Swift Current show a significant reduction within the last twenty years in the frequency of the number of days with snowcover depths exceeding 10 cm. This reduction was accompanied by a 3.6% increase in winter rainfall, a 17.2% decrease in snowfall, and a 48% decrease in the theoretical snowpack water equivalent. Average daily maximum temperature increased by almost 2 oC between the same early and recent decades. If the change in temperature increased snowpack losses by -34.4% and the conversion of snowfall to rainfall by 13.6%, then snow resources on the northern plains and prairies have diminished by 48%. Extrapolating these data throughout the region, one may conclude that snowcovers on the northern plains and prairies are indeed dwindling.
Keywords: Swift Current, Saskatchewan, snowfall, temperature, prairie, declining water supply

2002 Title, Contents, and Minutes (70th Annual Western Snow Conference, 2002)

Investigations toward understanding the spatial representativeness of SNOTEL measurements of snow water equivalence - Bardsley, T.; McConnell, J. (70th Annual Western Snow Conference, 2002)
The spatial distribution of snow water equivalence (SWE) is important for accurately predicting water availability, particularly in semi-arid, high elevation regions typical of the Western United States where as much as 75 of stream flow originates as snowmelt. The Natural Resource Conservation Service (NRCS), formerly the Soil Conservation Service, provides much of the data currently available for operational snow hydrology in the Western United States through its Snow Telemetry (SNOTEL) and snow course network. While this network provides a valuable index to seasonal runoff, little is known about how well these stations represent the local snow distribution. This is of utmost importance as snow hydrologists look for data sources for ground truth of remote sensing applications and move towards physically based snowmelt models. Intensive field campaigns in the Colorado Rockies and the Sierra Nevada have been conducted to address these issues on the scales of 30m x 30m and 1km2. Both grid sizes are commonly used in Digital Elevation Models (DEM) and satellite remote sensing.Our results indicate that the measured SNOTEL sites tend to over represent SWE in their local areas.
Keywords: SWE, Topography, Snow distribution, Temperature profile

An assessment of the differences between three satellite snow cover mapping techniques - Bitner, D.; Carroll, T.; Cline, D.; Romanov, P. (70th Annual Western Snow Conference, 2002)
The National Operational Hydrologic Remote Sensing Center (NOHRSC), National Weather Service(NWS), National Oceanic and Atmospheric Administration (NOAA) provides daily satellite-derived snow cover maps to support the NWS Hydrologic Services Program covering the coterminous U.S. and Alaska. This study compared the NOHRSC snow cover maps with new automated snow cover maps produced by the National Environmental Satellite, Data, and Information Service (NESDIS) and the snow cover maps created from the Moderate Resolution Imaging Spectroradiometer (MODIS) imagery. The purpose of this paper is to demonstrate and account for the differences that occur between the three different snow cover mapping techniques. Because each of these snow cover products uses data from different sensors at different resolutions, the data were degradd to the coarsest relevant resolution. In both comparisons, forest canopy density was examined as a possible explanatory factor to account for those differences. NOHRSC snow cover maps were compared to NESDIS snow cover maps for 32 different dates from November 2000 to February 2001. NOHRSC snow cover maps were also compared to MODIS snow cover maps in the Pacific Northwest and the Great Plains for 18 and 21 days, respectively, between March 2001 and June 2001. In the first comparison, where the NOHRSC product (approx. 1 km) was degraded to match the resolution of the NESDIS data (aprox. 5 km), the two products showed an average agreement of 96%. Forest canopy density data provided only weak explanation for the differences between the NOHRSC andthe NESDIS snow cover maps. In the second comparison, where the MODIS product (500 m) was degraded to match the resolution of the NOHRSC product for two sample areas, the agreement was 94% in the sample area in the Pacific Northwest, and 95% in the sample area in the Great Plains.
Keywords: NOHRSC, Satellite snow cover, MODIS, NESDIS, Mapping comparison

GCM upper air winter synoptic links to winter precipitation in the western United States - Byme, J.; Townshend, I; Lapp, S.; Kienzle, S. (70th Annual Western Snow Conference, 2002)
Previous downscaling work based on the 1992 Canadian Climate Centre GCM (Byme et al 1999) derived future precipitation and runoff scenarios for two key locales in western North America. GCM downscaling techniqueshave proven to better replicate historical precipitation regimes for winter periods than direct GCM precipitation simulations. Here we have applied the downscaling analysis using the new runs from the CGCM1 model releasedin 2000 to develop future winter precipitation scenarios for the western United States. The downscaling methodology is described elsewhere (Lapp et al, 2001; Byme et al., 1999). The CGCM1 (3) run is a transient C02 model that accounts for the effects of greenhouse gases and the direct effect of sulphate aerosols (CCCMA, 2000). Historical synoptic frequencies and the approximate lxC02 (1962-85) upper airflow conditions are quite similar, but there are substantive variations in the approximate 2xC02 (2021-50) upper airflows. Relative occurrence (dominance) of historical synoptic patterns are statistically linked to historical winter precipitation for the study region. These linkages are used to forecast changes in future winter precipitation based on variations in synoptic pattern statistics for the 2xC02GCM upper airflow patterns. The changes in the spatial patterns of winter precipitation for the western US is presented.
Keywords: Canadian Climate Center, GCM, CGCM1, Winter precipitation

Geographic variation in snow temperature gradients in a mountain snowpack - Deems, J.S.; Kirkeland, K.W.; Hansen, K.J. (70th Annual Western Snow Conference, 2002)
The objective of this study was to investigate the relative importance of topography in controlling the geographic patterns of snow temperature gradients within a seasonal snowpack. Regression models quantified relationships between topographic parameters and temperature gradient statistics for our spatially distributed dataset. Demonstration of the relative importance of topography in influencing spatial snowpack temperature gradients could aid future modeling of snow layer development and behavior, with benefits for avalanche and snowmelt modeling. This spatial, or geographic, analysis of the relationship of snow temperature gradient patterns to topography, utilizes landscape-scale modeling in an attempt to identify responses in complex, mountainous terrain.During the snow season of 2001-2002, 30 temperature profiles were sampled on nine sample days. Profileswere collected through the use of a portable snow temperature profile probe (Deems, 2001). These data were used to calculate temperature gradients for each profile. Topographic attributes were derived using a GeographicInformation System (GIS) and a Digital Elevation Model (DEM). Linear regression assessed the relationshipbetween the topographic variables and snow temperature gradient patterns, and demonstrates the relative importance of the terrain variables in determining spatial patterns of temperature gradients. Analysis of the regression models shows a complex pattern of relationships between average temperature gradients and topographic variables. A qualitative assessment of weather variables suggests the utility of weather data in future modeling efforts.
Keywords: Topography, Temperature gradient pattern, Temperature profile, DEM

Spatial and temporal variations in snowmelt degree-day factors computed from SNOTEL data in the upper Rio Grande Basin - DeWalle, D.R.; Henderson, Z.; Rango, A. (70th Annual Western Snow Conference, 2002)
The spatial and temporal variation of degree-day melt factors (DDF's) computed from SNOTEL data wereevaluated for the Upper Rio Grande Basin to improve modeling and forecasting ofsnowmelt runoff. Data fromseven SNOTEL sites in the Upper Rio Grande Basin were analyzed for the 1996-2000 melt seasons. Average degree-day factors varied among sites with varying density of forest cover. DDF's also varied among years due to incidence of cloudy weather and timing of melt during the season. Degree-day factors for each year at each site generally increased linearly with Julian Date during the melt season, but the rate of change increased with site exposure. Best predictions of daily melt using SNOTEL data were obtained using daily degree days, Julian Date, and an indicator variable for presence/absence of precipitation. Overall, SNOTEL data produced estimates of daily DDF's that were in good agreement with data from previous studies.
Keywords: Degree-day, Melt factor, Rio Grande, SNOTEL, Snowmelt runoff, Forecasting

Relational databases as a tool to manage environmental data at the research plot scale - Erickson, T.; Donahue, D. (70th Annual Western Snow Conference, 2002)
Relational databases management systems (RDBMS) can be used as highly effective storage systemsenvironmental data. RDBMS are most suited to storing large volumes of repetitive data. RDBMS offer significantadvantages over data storage methods (such as ASCII text files or spreadsheet programs) by offering flexibility in the types of information stored, speed of retrieval, and the ability to share data with other computer programs. Information contained in RDBMS can be accessed through desktop programs or may be distributed over the Internet. However, RDBMS may not be appropriate for all types of collected data, especially when the format ofthe data changes frequently. Snow hydrology data can be efficiently stored in a RDBMS, particularly if many repetitive measurements aremade in time or in space, such as automated meteorological measurements obtained from data loggers. Intelligently designed RDBMS link metadata to the collected data and allow scientists to analyze and store comments on the quality of the data. Design issues encountered during the processes of data modeling, database design, and data distribution are described. Examples are taken from the currently operational Mammoth Mountain Energy Balance Monitoring Site database and a sample data model created to store information on Western Snow Conference(WSC) members and papers.
Keywords: Relational database, Environmental data, Mammoth Mountain, Meteorological data

Comparison of spatial interpolation methods for estimating snow distribution in the Colorado Rocky Mountains - Erxleben, J.; Elder, K.; Davis, R.E. (70th Annual Western Snow Conference, 2002)
In this study, the relative performances of four spatial interpolation methods were evaluated to estimate snow water equivalent (SWE) for three 1 km2 study sites in the Colorado Rocky Mountains. Each study site is representative of different topographic and vegetative characteristics. From 1-11 April 2001, 550 snow depth measurements and approximately 16 snow density profiles were obtained within each study site. The analytical methods used to estimate snow depth over the 1 km2 areas were 1) inverse distance weighting, 2) ordinary kriging,3) modified residual kriging and co-kriging, and 4) a combined method using binary regression trees and geostatistical methods. The independent variables used were elevation, slope, aspect, net solar radiation, and vegetation. Using cross-validation procedures, each method was assessed for accuracy. The tree-based models provided the most accurate estimates for all study sites, explaining 18-30 of the observed variability in snowdepth. Binary regression trees may have generated the most accurate estimates out of all methods evaluated, however, substantial portions of the variability in observed snow depth were left unexplained by the models. While the data may have simply lacked spatial structure, it is recommended that the characteristics of the study sites, sampling strategy, and independent variables be explored further to evaluate the causes for the relatively poor model results.
Keywords: SWE, Spatial interpolation, Colorado, Kriging, Binary regression tree

Diurnal and seasonal soil moisture variation along a forested and tegenerating clearcut hillslope in Colorado - Goodbody, A.; Elder, K.; Davis, R.E. (70th Annual Western Snow Conference, 2002)
Soils in midlatitude subalpine catchments play an important role in regulating the movement of melt water from seasonal snowpacks to drainage networks. Removal of forest canopy and undergrowth can change the soil moisture regime by decreasing evapotranspiration and eliminating interception of precipitation and radiation. Seasonal and diurnal soil moisture variation are examined along a clearcut and forested hillslope within a high-elevation mixed conifer forest in the Fraser Experimental Forest near Fraser, Colorado, USA. Volumetric soil moisture content was measured on both hillslopes during 53 separate neutron probe surveys starting on April 16, 2001 and ending on June 20, 2001. Prior to complete snow ablation, which occurred on May 14 on both hillslopes, intensive sampling schemes were used to characterize the diurnal variability during early, middle and late melt periods. Followingmelt out, soil moisture was sampled biweekly with the exception of one diurnal sampling period. Volumetric soilmoisture content was generally greater on the clearcut hillslope during the period of observation. Differences inaverage maximum diurnal soil moisture content change between hillslopes were not significant. Both hillslopesshowed a decrease in maximum diurnal soil moisture content change as the melt season progressed and soilmoisture content increased.
Keywords: Soil, Melt water, Vegetation removal effect, Fraser Experimental Forest

Spatial relationships between snow and ecosystem properties in a Wyoming alpine treeline ecotone: linking simulations and observations - Hiemstra, C.A.; Reiners, W.A.; Listen, G,E. (70th Annual Western Snow Conference, 2002)
Interactions among wind, topography, vegetation, and snow create a heterogeneous snow distribution in uppertreeline ecotones. These repeating patterns affect vegetation and biotic processes by determining the localabundance of water and growing season length. Spatial patterns of environmental variables determine aspects ofecosystem structure and function. These ecosystem components feed back and modify physical environmentalcharacteristics. Understanding spatial patterns of ecosystem properties requires simulation of physical processes ina spatially distributed manner, validation of these simulations, and exploration of how changes in driving variablesalter spatial patterns on this landscape. Simulation of snow redistribution by wind, subsequent melting of thesnowpack, and meltwater flow was performed for a 6.25 km2 area during the 1999-2000 water year. Ecosystemproperties'(e.g., snow depth and density, soil moisture, soil temperature, vegetation cover) were measured along aseries oftransects during spring and summer 2000. These properties were used to estimate model error andevaluate the possibility of accounting for the importance of moisture movement (snow and liquid) and growingseason length in this landscape.
Keywords: Snow distribution, Ecosystem structure, Redistribution, Growing season

The influence of thermal, hydrologic, and snow deformation mechanisms on snow water equivalent pressure sensor accuracy - Johnson, J.B.; Schaefer, G.L. (70th Annual Western Snow Conference, 2002)
A five-year field study was conducted to determine the mechanisms that cause snow water equivalent (SWE) pressure sensor measurement errors. We monitored a 3-m snow pillow and installed three prototype electronic SWE sensors to examine how SWE errors occur. We measured heat flux in the sensors and the soil, snow temperature, soil moisture content, and soil thermal conductivity. The SWE of snow cores were used to assess the accuracy of the sensors. Results indicate that SWE measurement errors occur when the snow/SWE sensor and/or the snow/soil interfaces are at the melting temperature of snow. SWE over measurement errors occur when the sensor heat flux is less than the surrounding soil. SWE under measurement errors occur when the heat flux through the sensor is greater than through the soil. The most severe errors occur during the transition from winter to spring when the snow cover first reaches an isothermal condition producing a maximum difference in snowmelt rate between the snow/SWE sensor and snow/soil interfaces. SWE measurement errors are minimized when the sensor is designed to match the thermal properties of the surrounding soil, allow water to flow through the sensor, or to diffuse heat into the adjacent soil.
Keywords: SWE, Pressure transducer error, Heat budget, Snow core

A historical comparison of snowpack averages in Utah. - Julander, Randall P.; Perkins, T. (70th Annual Western Snow Conference, 2002)
Snowpack data collection began in an organized fashion in Utah during the late 1920's and the first 30-yearaverage was calculated in the late 1950's. Individual sites are used to calculate moving 30-year averages each yearin this continuous record up to current data. Snowpacks are analyzed over this time period by site, region andelevation to determine any significant changes. Snowpacks in southern areas are compared to those in northernUtah as well as low elevation sites to the higher elevations to ascertain potential trends or differences. SNOTEL isa telemetering system providing daily snow water equivalent, precipitation and temperature data. Installed in thelate 1970's and early 1980's, it provides accurate data on site specific melt out dates. SNOTEL provides far greaterdata than the manual snow course system does, but has a much shorter period of record, limiting it's statisticalrelevance. Given the statistical limitations of a 25 year period of record, snowpack melt-out dates are examinedstatewide to determine if there are definable trends.
Keywords: SNOTEL, Utah snowpack, Telemetering, Snow courses

Soil moisture data collection and water supply forecasting: the sequel - Julander, Randall P. (70th Annual Western Snow Conference, 2002)
The strong relationship between snow water equivalent and seasonal water supply has long since been demonstrated. Theses statistical relationships vary in strength depending on a host of factors such as latitude, elevation, and others. Part of the error associated with these relationships is due to unknown future meteorological conditions that impact the timing and volume of the runoff.  Another part of the error associated with statistical relationships is due to the variable state of soil moisture.  Soil moisture conditions across a watershed are generally presumed to influence seasonal water supplies from snowpack (Wetzel and Woodward, 1987).  If extremely dry conditions are prevalent in the fall prior to the seasonal snowpack, then it is presumed that these soils have additional capacity to absorb and retain some greater than normal amount of snowmelt, leaving a reduced amount to generate seasonal streamflow. Conversely, if the soils are saturated prior to the onset of snowmelt, it is presumed that, since the soils have less capacity for infiltration and certainly less storage, that the majority of snowmelt should contribute directly to seasonal streamflow.  The total potential snowmelt loss to soil moisture recharge can be significant, assuming a 24 inch soil depth, 8 to 10 inches of snowmelt or more, could be infiltrated depending on soil type and condition.  Some portion of this would eventually contribute to runoff and some portion would be lost from the immediate contributing system through either evapotranspiration or to deeper groundwater.  The Natural Resources Conservation Service now has soil moisture sensors at five sites in Utah (Julander and Cleary, 2001) with plans to install many more.  Preliminary data indicate great potential value from these data in reducing water supply forecast error. Interesting relationships between summer/fall precipitation and soil moisture are analyzed.  Snowpack, soil moisture and runoff are compared.
Keywords: SWE, Spatial interpolation, Snow depth, Binary regression tree

Snow,hydrology or the Bear Creek Basin, Sierra Nevada - Kattelmann, R.C. (70th Annual Western Snow Conference, 2002)
Bear Creek is one of a few gauged streams on the west slope of the Sierra Nevada with a natural flow regime. The watershed above the gauging station is free of water management activities, roads, construction, forest harvesting, and most human influences. The streamflow record covers almost 80 years, and a few snow courses have been measured for more than 50 years. These characteristics allow Bear Creek to serve as an indicator of natural hydrologic processes in the mid- to upper-elevation portions of the Sierra Nevada snow zone. The cursory examination of the snowpack and streamflow records provide some general descriptive information that may be applicable to ungaged Sierra Nevada watersheds and suggests that there has been a slight increase in precipitation, snowpack, and streamflow in the past couple of decades.
Keywords: Bear Creek, Natural flow regime, Hydrologic process

Application of XTOP_PRMS model in Green Lakes Valley, Colorado front rabge: Runoff simulation and flowpath identification - Liu, F.; Williams, M.W.; Webb, R.; Ackerman, T. (70th Annual Western Snow Conference, 2002)
Stream runoff was simulated from 1996 to 2000 using XTOP_PRMS (coupling of TOPMODEL andPrecipitation Runoff Modeling System) model under Modular Modeling System at Martinelli and Green Lake 4catchments in Green Lakes Valley, Colorado Front Range. Two flowpaths determined by XTOP_PRMS model, surface flow (infiltration-excess overland flow) and subsurface flow, were compared against the flowpaths determined by mixing model using isotopic and chemical tracers. Three tracers (DOC, K/Si, and o^O) were used in mixing model to identify four flowpaths, i.e., overland, upper soil horizon, lower soil horizon, and base flow. Theresults showed that the runoff simulation using XTOP_PRMS model is reasonably successful for Martinellicatchment (8 ha in drainage area). The Nash-Sutcliffe efficiency is 0.76. The t-test of two means for paired sample showed that the difference between the observed and modeled runoff was not significantly different at a=0.05 at Martinelli catchment (n = 1611, p = 0.6). The flowpaths identified by XTOP_PRMS model matched the flowpaths determined by the tracer-mixing model reasonably well in magnitude, but poorly in pattern. The surface flow primarily occurred in the beginning of snowmelt at Martinelli as illustrated by the tracer-mixing model. Both runoff simulation and flowpath identification using XTOP_PRMS model were relatively poor at Green Lake 4 catchment, which has a drainage area of 220 ha. The runoff peaks observed in May and June were not captured in runoff simulation. The problem may be caused by poor understanding of behaviors of flowpath parameters and insensitivity of snowmelt to daily mean air temperature.
Keywords: Stream runoff, Simulation modeling, PRMS, Flowpaths, Tracers

Snow, topography, and the diurnal cycle in streamflow - Lundquist, J.D.; Knowles, N.; Dettinger, M.; Cayan, D. (70th Annual Western Snow Conference, 2002)
Because snowmelt processes are spatially complex, point measurements, particularly in mountainous regions, are often inadequate to resolve basin-scale characteristics. Satellite measurements provide good spatial sampling but are often infrequent in time, particularly during cloudy weather. Fortunately, hourly measurements of river discharge provide another widely available, but as yet underutilized, source of information, providing direct information on basin output at a fine temporal scale. The hour of maximum discharge recorded each day reflects the travel time between peak melt and the time most water reaches the gauge. Traditional theories, based on numerical models of melt-water percolation through a snowpack and localized, small-basin observations, report that the hour of daily maximum flow becomes earlier as the snowpack thins and matures, reflecting shorter travel times for surface melt to reach the base of the snowpack. However, an examination of hourly discharge from 100 basins in the Western United States, ranging in size from 1.3 km2 to 10,813 km2, reveals a more complex situation. The sequences of seasonal evolution of the hour of maximum discharge are unique to each basin, but within a given basin are remarkably consistent between years, regardless of the size of the snowpack. This seems to imply that basin topography strongly influences the timing of peak flow. In most of the basins examined, at the end of the melt season, the hour of maximum discharge shifts to later in the day, reflecting increased travel times as the snowline retreats to higher elevations.
Keywords: Snowmelt, Satellite, Maximum annual discharge, Seasonal discharge shift

Measurement of the bidirectional reflectance of snow at fine spectral and angular resolutions - T H Painter; Dozier, J. (70th Annual Western Snow Conference, 2002)
This paper presents measurements of the bidirectional reflectance factor (BRF) of snow made at finespectral and angular resolution with the Automated Spectro-Goniometer (ASG) for a range of solar zenith angles(0o = 40-50deg) and snow textures (surface grain size = 80 - 240 /an) on two days. Measurements of the stratigraphyof snow texture and density accompanied each day's suite of measurements. The BRF for fine grain, faceted snowexhibited a local backscattering peak at the view zenith near the solar zenith angle, whereas those for mediumgrain, clustered snow did not have a local backscattering peak. The BRF decreased at all wavelengths for anincrease in measured grain radius from 80 /mi to 240 /mi. However, the decrease in BRF in the visible wavelengthswas strongest at Or = 80deg in the forward direction and strongest for A > 1.8 /mi near Or = 30deg in the backwarddirection. As solar zenith angle decreased from 47deg to 41deg the BRF increased near nadir for A < 1.03 /mi but decreased with coherent angular structure for A > 1.03 /mi.
Keywords: Bidirectional reflectance factor, Solar zenith angle, Snow texture, Backscattering

Is peak snowpack in the North Cascade Mountains decreasing over time? - Pattee, S. (70th Annual Western Snow Conference, 2002)
Snowpack records have been kept within the North Cascade Mountains for the past 60 years or more. Analysis of long-term records at selected stations show a dramatic downward trend in peak snowpack accumulations. Data analysis, potential causes and probable effects will be addressed.
Keywords: Cascade Range, Snowpack records, Snowpack accumulation

Comparative satellite capabilities for remote sensing of snow cover in the Rio Grande Basin - Rango, A.; Gomez-Landesa, E.; Bleiweiss, M. (70th Annual Western Snow Conference, 2002)
From 1972 until near the end of the 20th century, the use of satellite data for snow cover mapping was a viableapproach under certain conditions. The spatial resolution of Landsat and the temporal frequency of NOAA-AVHRR (National Oceanic and Atmospheric Administration - Advanced Very High Resolution Radiometer) wereoptimum or possibly better than required individually, but seldom could they be exploited together. Now, with thelaunch of Terra, the forthcoming launch of Aqua, and numerous private satellites, both adequate spatial resolutionand temporal frequency is available for mapping most size basins. When these data are used in sub-pixel mappingalgorithms, detailed snow cover representations in basins smaller than 10 km2 are possible. Probably the best snowcover mapping sensor for combining reasonably high resolution (250 m) and frequent coverage (daily) is MODIS(Moderate Resolution Imaging Spectroradiometer), on board both Terra and Aqua platforms, but the choices ofsensors or satellites are numerous with most of the data being readily available to users. Comparison of the spatialresolution, observational frequency, feature detection, suitability for snowmelt runoff models, and cost will beillustrated using different size sub-basins of the Rio Grande.
Keywords: Satellite data, AVHRR, Aqua, Terra, Snow cover mapping, Rio Grande basin

Spatial and temporal snowpack variation in the crown of the contintent ecosystem - Selkowitz, D.J.; Fagre, D.B.; Reardon, B.A. (70th Annual Western Snow Conference, 2002)
Snowpack related ecosystem changes such as glacier recession and alpine treeline advance have been documented in the Crown of the Continent Ecosystem (CCE) over the course of the previous 150 years. Using data from the Natural Resource Conservation Service's SNOTEL sites and snow course surveys, we examined the spatial and temporal variation in snowpack in the region. SNOTEL data suggest CCE snowpacks are larger and more persistent than in most regions of the Western U.S., and that water year precipitation, rather than mean temperature, is the primary control on April 1 snow water equivalent (SWE). Snow course data indicate a statistically significant downward trend in mean April 1 SWE for the period 1950-2001 but no statistically significant trend m mean May 1 SWE for the longer period 1922-2001. Further analysis reveals that variations in both Apnl 1 and May 1 mean SWE are closely tied to the Pacific Decadal Oscillation, an ENSO-like interdecadal pattern of Pacific Ocean climate variability. Despite no significant trend in mean May 1 SWE between 1922-2001, glaciers m Glacier National Park receded steadily during this period, implying changing climatic conditions crossed a threshold for glacier mass balance maintenace sometime between the Little Ice Age glacial maxima and 1922.
Keywords: Snowpack, Crown of the Continent Ecosystem, SNOTEL, PDO

Measuring material properties of a wet and draining snowpack using crosshole radar tomography - Williams, M.W.; Knoll, M. (70th Annual Western Snow Conference, 2002)
Movement of liquid water through snow is one of the least understood aspects of snow hydrology. Most methods of investigating melt water flow through snow involve sparse or invasive sampling. This makes it difficultto study scale and time-dependent processes such as the evolution of preferential flowpaths. Imaging of internalsnow pack properties using radar wavelengths shows promise as a non-invasive technique. Here we report on aproof-of-concept experiment conducted to evaluate the potential of crosshole radar tomography to image and characterize the material properties of a wet and draining snow pack. The experiment was conducted using a pulseradar system with 250 MHz borehole antennas, each placed in 3 PVC pipe, 5 m in length. One pipe was located atthe bottom of the snow pack and the second at the top of the snow pack; both pipes were placed perpendicular tothe fall line of the snow field. Travel velocities ranged by more than a factor of two, from about 125 m u,s'' to 300m u,s'1, showing that material properties of the snow pack were influencing the propagation of radar waves throughthe snow pack. We then inverted the traveltime data to estimate the dielectric constant for each grid cell using acurved ray traveltime tomography algorithm. The estimated dielectric constants ranged from 1 to 4, similar to the 2.3 to 3.1 measured in a nearby snow pit using a Denoth Wetness Sensor. Conversion of the dielectric constants toliquid water content yield values of 1-3, slightly less than the 1.5 to 4.5 estimated by the Denoth WetnessSensor.
Keywords: Liquid water, Meltwater, Flow paths, Pulse radar, Dielectric constant

2001 Title, Contents, and Minutes (69th Annual Western Snow Conference, 2001)

SEASONAL STREAMFLOW FORECASTING USING CLIMATE INFORMATION - Baldwin, C.K. (69th Annual Western Snow Conference, 2001)
Note:This paper is a companion to “INCORPORATING SEASONAL STREAMFLOW FORECASTS INTO OPERATIONAL DECISIONMAKING” (Waage et al, this volume). It represents the text of a forecast provided to Denver Water in early November 2000.We present forecasts for 2001 April-July streamflow volume at four gages: Dillon Reservoir (DL), Williams Fork (WF), Fraser River at Winter Park (FR), and the South Platte at South Platte (SP). The first three gages are aggregated since they are highly correlated. We include recent information on the PDO and NIN03 indices to provide tercile probabilistic forecast and associated analog years. We rely on the nearest-neighbor analog (NNA) methodology. There is increased chance of upper tercile volume at DL, WF, FR and increased chance of lower tercile volume at PL.
Keywords: Seasonal forecasting

PRELIMINARY EVALUATION OF SNOW ACCUMULATION PATTERNS BASED ON STORM TYPE, MAMMOTH MOUNTAIN, CALIFORNIA 1996 - 2001 - Burak, S.A.; Davis, R.E. (69th Annual Western Snow Conference, 2001)
This study examined snow accumulation at 8 sites in the subalpine zone on Mammoth Mountain, California, over the course of 67 storms during the winters 1996-1997 through 1990-2001. Locations of the field sites resulted from considering the tradeoffs between avoiding areas subject to snow erosion or wind deposition and selecting sites that exhibited little mass loss due to interception by forest canopy. The sites ranged over 500m in elevation and occurred on aspects from the east to the north-northwest side of Mammoth Mountain. Observations of snow accumulation consisted of snow depth and density measurements from snow boards, representing storm total accumulations. Measurements from the snow boards were taken at the end of each storm cycle. Synoptic variables from standard charts published by the National Weather Service formed the basis of classif~,ing storms into four types: 1) mid-latitude front, 2) zonal, 3) cutoff or continental low and; 4) split flow. Measurements from the snow boards were related to similar observations made at a reference site by the Mammoth Mountain Ski Patrol. The analyses used regression analyses assuming linear models to evaluate trends in the accumulation measurements due to different storm types. The analyses showed that for most storms, snowfall exhibits strong correlation for specific storm types over scales of hundreds to thousands of meters, the range of distance between the sites. Storm-wise correlation among sites showed that different storm types exhibited different loading patterns. Results suggest that consideration of storm category could affect the type of interpolation one could use when dealing with operational station data.
Keywords: Snow accumulation patterns, Snow covered area

NOHRSC OPERATIONS AND THE SIMULATION OF SNOW COVER PROPERTIES FOR THE COTERMINOUS U.S. - Carroll, T.; Cline, D.; Fall, G.; Nilsson, A.; Li, L.; Rost, A. (69th Annual Western Snow Conference, 2001)
The National Operational Hydrologic Remote Sensing Center (NOHRSC), National Weather Service (NWS), National Oceanic and Atmospheric Administration (NOAA), generates satellite-derived areal extent of snow cover observations and makes airborne snow water equivalent measurements over large regions of the country. Additionally, the NOHRSC ingests a wide variety of real-time, ground-based hydrometeorological data sets along with real-time, numerical weather prediction (NWP) model data sets for the country. NWP model output data sets are used to force a physically-based, snow-modeling, and snow-data-assimilation system. The ground-based, airborne, and satellite snow cover observations will soon be assimilated, in near real-time, into the gridded fields generated by the snow accumulation and ablation model. Products include a variety of alphanumeric and gridded representations of the snow pack state variables.A distributed, energy-and-mass-balance snow model and data assimilation system has been developed and implemented at the NOHRSC to augment basic hydrologic analysis. The purpose of the Snow Data Assimilation System (SNODAS) is to provide a physically consistent framework for integrating the wide variety of snow data that is available at various times. SNODAS includes: (1) data ingest and downscaling procedures, (2) a spatially distributed energy-and-mass-balance snow model that is run once each day, for the previous 24-hour period and for a 12-hour forecast period, at high spatial (1 kin) and temporal (1 hr) resolutions, and (3) data assimilation and updating procedures. The snow model is driven by downscaled analysis and forecast fields from a mesoscale, NWP model, surface weather observations, satellite-derived solar radiation data, and radar-derived precipitation data. The snow model states can be updated using satellite, airborne, and ground-based snow observations. The model is cast in an assimilation framework and serves to organize various snow observations and to track the evolution of the snow pack between observations. SNODAS permits more frequent and timely product generation—near real-time model analyses and forecasts—and provides several new products, including maps of modeled snow characteristics such as snow ripeness, melt rates, and sublimation losses. Preliminary simulations for test periods during the 2001 snow season give encouraging results.
Keywords: Satellite, Simulation models, Snow Cover

TOPOGRAPHIC CONTROLS ON SPATIAL AND TEMPORAL VARIATION IN SNOW TEMPERATURES IN A MOUNTAIN SNOWPACK - Deems, J.S. (69th Annual Western Snow Conference, 2001)
The objective of this project is to analyze and model the geographic patterns of snow temperature profile characteristics as functions of topographic variables. The results of a pilot study are presented here. Snow temperature is a dominant variable in many physical processes in the seasonal snowpack. This spatial, or geographic, analysis of the relationship of snow temperature patterns to topography, utilizing landscape-scale modeling, attempts to identify temperature responses to effects of complex terrain. Data from the pilot study is used to create regression models predicting temperature profile characteristics throughout a basin, based on a combination of slope and slope aspect parameters at similar elevation. Prediction maps demonstrate the potential of this modeling technique. Future plans include collection and use of a larger dataset, inclusion of more topographic variables, and incorporation of a change-over-time component. Knowledge of the patterns of snow temperature profile characteristics over space and time could aid in avalanche prediction and snowmelt modeling.
Keywords: Modeling, Snow temperatures, Topographic control

THE 1994-1995 SNOW ACCUMULATION AND RUNOFF EVENT IN NORTHERN COLORADO, SOUTHEASTERN WYOMING AND THE NEBRASKA PANHANDLE - Dietrich, T.; Rieman, R. (69th Annual Western Snow Conference, 2001)
After a number of years of below normal snowpack in northern Colorado and southern Wyoming the weather took a dramatic change. Beginning in mid-April of 1995 the snow become coming down in a big way. Outside of the mountains, the valleys and plains received abundant rainfall to the point of causing flooding along the Laramie and North Platte Rivers in eastern Wyoming and the Nebraska Panhandle. In the upper part of the basin, at Saratoga, WY the North Platte River ran bankfull for several weeks resulting in some sandbagging to protect homes. Through the use the flood control pool at Glendo Reservoir and controlled releases flooding was held to a minimum.
Keywords: Controlled releases, Flooding, Snowmelt runoff

WATER RESOURCES FORECASTING IN THE NORTH PLATTE BASIN - Dietrich, T.; Rieman, R. (69th Annual Western Snow Conference, 2001)
Water needs have increased dramatically in many areas of the west. The North Platte and Platte River basins are no exception. Over the years water has become extremely valuable in the North Platte River basin. Downstream uses on the North Platte and Platte Rivers in Nebraska necessitate the need for both flood and water supply forecasts. In times of drought the water in the North Platte River is not enough to meet the needs of the users. As such, they are dependent on water that is stored in reservoirs such as Lake McConaughy in the Nebraska panhandle, near Ogallala.
Keywords: Forecasting, Storage needs

LANDSCAPE CONTROLS ON SNOW ACCUMULATION IN AN ALPINE CATCHMENT - Erickson, T.; Williams, M.W.; Tomaszewski, M. (69th Annual Western Snow Conference, 2001)
The central question addressed by this poster is relationship between landscape types and snow accumulation. Of particular interest is the relative amount of snow accumulation in talus areas. Talus areas play an important role in alpine hydrology because these areas have been shown to provide water late into the summer growing season. One reason that talus areas may provide important sources of water late into the growing season is because they accumulate more snow than other landscape types in alpine basins. The roughness of talus areas reduces the redistribution of snow by wind, which may cause an increase in accumulation. Furthermore, talus areas are often located beneath steep rock faces, and these areas may accumulate relatively high amounts of snow due to sluffs and avalanches.Snow surveys were conducted at maximum accumulation in the Green Lakes Basin in the Colorado Front Range during the years 1997 through 2000. This basin has been extensively studied in the past, and the major landscape types have been mapped and digitized onto a GIS. Using a combination of field measurements and geostatistical techniques we have estimated the distribution of snow water equivalent throughout the basin and compared it to the mapped landscape types.
Keywords: Roughness, Snow distribution, Topographic control

SNOWPACK MODELLING OF THE SALT BASIN WITH WATER MANAGEMENT IMPLICATIONS - Fassnacht, S.R.; Helfrich, S.R.; Lampkin, D.J.; Dressier, K.A.; Bales, R.C.; Halper, E.B.; Reigle, D.; Inman, B. (69th Annual Western Snow Conference, 2001)
The NOAA/NWS National Operational Hydrologic Remote Sensing Center produces maps of the areal extent of snow-cover over the Western US to assess the state of the snowpack. The binary product represents snow-no snow, but cannot estimate the snow-covered extent within an individual pixel (1 kin2). For the Colorado River Basin, fractional snow-covered area (SCA) has been derived from Advanced Very High Resolution Radiometer (AVHRR) data by the NASA Southwest Regional Earth Science Applications Center. The SCA maps are combined with snow water equivalent maps to develop snowpack water volume estimates. The uncertainty of using the binary product instead of the fractional SCA product for total SCA and snowpack water volume estimates were compared for the Salt-Verde watershed in central Arizona. The basin volume estimates derived from a combined binary SCA product and SWE estimates were evaluated assuming uniform 1%, 50%, 100% SCA and a linear and quadratic relationship between SCA and elevation. Inherent errors in the AVHRR fractional SCA and SWE product propagate into the snowpack water volume estimates. Snowpack estimates derived from AVHRR sub-pixel products are more accurate than the binary estimates.
Keywords: Colorado River, SCA, AVHRR, Snowpack estimates

EFFECTS OF STORM TRAJECTORIES ON SNOWFALL CHEMISTRY IN ROCKY MOUNTAIN NATIONAL PARK, COLORADO - Ingersoll, G. P.; Tonnessen, K. A.; Campbell, D.H.; Glass, B.R.; Torizzo, A.O. (69th Annual Western Snow Conference, 2001)
Snowfall samples from snowstorms lasting 1 to 4 days were collected near the Bear Lake snow telemetry (SnoTel) site in Rocky Mountain National Park, Colorado (ROMO), during the 1998-99 snowfall season to determine if storms moving in from different directions affect the chemistry of precipitation in the park. Storm pathways to Bear Lake during snowfall events were estimated using the HYSPLIT4 backward-trajectory model developed by the National Oceanic and Atmospheric Administration. Deposition of acidic ions of nitrate and sulfate in snowfall during the study varied substantially (two- to threefold) depending on storm trajectory because air masses traversing the park originated from different surrounding areas, including some having large sources of emissions of nitrate and sulfate. Concentrations of nitrate and sulfate in samples were lowest when storms reached ROMO from north and east of the park and were elevated when air masses traveled from the west where a number of power plants are located. Concentrations were highest in storms reaching ROMO from the south, a region with urban areas including Metropolitan Denver.
Keywords: Simulation model, SNOTEL, Snow chemistry

STREAMFLOW FORECASTING USING THE MODULAR MODELING SYSTEM AND AN OBJECT-USER INTERFACE - Jeton, A.E. (69th Annual Western Snow Conference, 2001)
The U.S. Geological Survey (USGS), in cooperation with the Bureau of Reclamation (BOR), developed a computer program to provide a general framework needed to couple disparate environmental resource models and to manage the necessary data. The Object-User Interface (OUI) is a map-based interface for models and modeling data. It provides a common interface to run hydrologic models and acquire, browse, organize, and select spatial and temporal data. One application is to assist river managers in utilizing streamflow forecasts generated with the Precipitation-Runoff Modeling System running in the Modular Modeling System (MMS), a distributed-parameter watershed model, and the National Weather Service Extended Streamflow Prediction (ESP) methodology.
Keywords: Data management, Simulation model

STREAMFLOW FORECASTING USING THE MODULAR MODELING SYSTEM AND AN OBJECT-USER INTERFACE - Julander, Randall P.; Cleary, S. (69th Annual Western Snow Conference, 2001)
Extreme deviations in hydroclimatic conditions are a source of considerable error in statistical water supply forecast models. Much attention has been given over the past years to the relationship between snowpack, precipitation and streamflow (Martinec, 1975, Hawley, et al. 1980, McCuen, 1993). These relationships tend to vary in strength, but in large part are satisfactory for water supply forecasting purposes. Many other hydroclimatic variables such as soil moisture are implicit in these statistical relationships. As long as these variables (soil moisture) remain proportional to the independent variables (snowpack, precipitation) in the forecasting relationship, then the model will be stable. If there is some amount of disproportion, then the model will most likely produce significant error. Such a case in northern Utah is presented along with an explanation of a small- scale implementation of soil moisture monitoring of two small watersheds in the Wasatch Mountains near Salt Lake City.
Keywords: Forecasting, Snowpack, Soil moisture