Remote sensing by event and satellite hydrology stations: present and anticipated utilization in water supply and snow melt forecasting - Baird, G.H. (53rd Annual Western Snow Conference, 1985)
The state of California Snow Surveys Office collects data for the California Cooperative Snow Surveys program from 93 remote telemetered sensors located in the Sierra Nevada and northern California mountains. The Mid-Pacific Region, USBR, provides funding and support for 24 of these stations. Sensing at each of the stations includes precipitation, snow, and temperature. The California standard, four 1.2 X 1.5 meter stainless steel tanks containing 190 liters glycometh, is the snow water equivalent measuring devise. Comparisons of the telemetered and snow tube measurements are described and illustrated. Real time reporting from the 'event' type stations provide valuable information on watersheds during storms. Reports are used to evaluate and arrive at inflow predictions for USBR reservoirs. Both 'event' and 'satellite' type station data provide information during the snow accumulations and depletions to update water supply forecasts and adjust the reservoir operations to meet demands of the Central Valley Project.
Keywords: Hydromet station, Remote sensing, Snow, Water supply

Acidic deposits and snowpack chemistry at a Sierra Nevada site - Berg, N.H.; Woo, S. (53rd Annual Western Snow Conference, 1985)
Snowpack chemistry studies evaluated the fractionation model of rapid release of acidic pollutants from the snowpack near Donner Summit, California. Event samples of precipitation and snowpack basal outflow, and weekly samples of snowpit layers and stream water were analyzed for pH, alkalinity, and sulfate and nitrate solute concentrations. Chemical signatures from specific precipitation events identified subsequent changes in the chemistry of the snowpack and outflow waters. Acidification was not apparent in either stream or snowpack basal outflow waters during the main spring melt period. The lowest seasonal pH's for stream and basal outflow waters were, however, recorded synchronously with rain or mixed rain and snowfall precipitation events during early- and mid-winter when both basal outflows and stream discharges rose. Fractionation may bave caused these pH minima. Snowfall was slightly acidic at the test site, and mean pH for rainfall, hail, and graupel was below 5.0. Snowpack layer pH remained generally constant through time.
Keywords: Acid snow, Acidification, Snowpack chemistry

A simulation model of Boulder's alpine water supply - Brendecke, C.M.; Sweeten, J.G. (53rd Annual Western Snow Conference, 1985)
A continuous water balance distributed parameter simultion model has been applied to the Boulder Watershed, an alpine basin operated for water supply purposes. The Precipitation Runoff Modeling System was modified to better represent the operation of the seven reservoirs in the basin. The modifications permit both simulation of given operating scenarios and determination of releases required to meet a given demand hydrograph. The model has been successfully calibrated and verified for several flow recording stations in the Watershed for water years 1982 through 1984.
Keywords: Hydrology, Reservoirs, Simulation, Snowmelt

Determining variability of snow accumulation and ablation on western rangelands - Cooley, K.R.; Robertson, D.C. (53rd Annual Western Snow Conference, 1985)
Snow accumulation and melt on western rangelands, where wind often plays a dominant role on snow distribution, can be extremely variable over even relatively small areas. This variability causes problems in 1) application and verification of snowmelt models, 2) determining flood and water supply relationships, 3) roadway design and maintenance, and 4) livestock and wildlife management and operations.This study was designed to determine variability in snow distribution and melt on a 26 ha site called Upper Sheep creek, which is part of the Reynolds creek Experimental Watershed located in southwestern Idaho. Instruments designed to continously monitor precipitation, incoming solar radiation, wind direction and speed, air temperature, relative humidity, snowmelt, and four layers of soil moisture and temperature have been in operation for one season. In addition snow depth and density measurements at 30 and/or 60 meter grid spacings, and aerial photos were obtained at approximately two week intervals during the snow accumulation and melt period.
Keywords: Ablation, Rangeland, Snow accumulation

Accuracy of hydrologic forecasts - Dracup, J.A.; Haynes, D.L.; Abramson, S.D. (53rd Annual Western Snow Conference, 1985)
The analysis in this paper concentrates on the Colorado River Basin. Analyses of the correlations between forecasted and observed runoffs were made using Spearman rank-order coefficients, Product-Moment correlation coefficients, average forecast errors, and a derived statistical measure referred to as the Coefficient of Prediction. In addition, further statistical measures including the t-test were used. The analysis showed that even as early as January of each year worthwhile forecasts are being developed. The Coefficient of Prediction and the correlation coefficients compare favourably when used to judge which forecast stations had relatively higher forecast accuracy. The two statistical tests of correlation coefficients and Coefficients of Prediction are in agreement when analyzing the average forecast errors. These coefficients increase when the average forecast error decreases. The t-test proved to not be as good a measure to use when comparing different data sets.
Keywords: Accuracy, Forecasts

Windy gap project streamflow forecasting - Eckhardt, J.R.; Leaf, C.F.; Baker, D. (53rd Annual Western Snow Conference, 1985)
The recently constructed Windy Gap Project is operated by the Municipal Subdistrict of the Northern Colorado Water Conservancy District. Key elements of the project include: (a) a diversion dam on the Colorado River, and (b) a pumping plant and pipeline which transports diverted water to the Colorado-Big Thompson System for subsequent storage and distribution to the Platte River Power Authority and the cities of Boulder, Estes Park, Greeley, Longmont, and Loveland. The basis for timely residual volume streamflow forecasts is a remote hydrologic data collection network which utilizes the GOES Satellite for data transmission to project headquarters in Loveland, Colorado. Snowpack, soil moisture, streamflow, precipitation, temperature, and wind data collected at 16 remote sites in the Fraser River Basin are used to update a computerized hydrologic simulation model. This process-oriented model, developed from Forest Service research and pilot-tested in NASA's Colorado ASVT on Satellite Snow Cover Observations, is being used for making forecasts of residual streamflow available to the Windy Gap Project.
Keywords: Snowmelt runoff, Streamflow forecasting

pH of mountain snowfall in Montana 1981-1984 - Farnes, P.E. (53rd Annual Western Snow Conference, 1985)
For the past four winters, the pH of surface snow has been measured at many snow courses in western Montana in conjunction with regularly scheduled snow surveys. This paper describes the field procedures used to obtain pH values and it summarizes year to year variation in pH and the possible sources for the acidic snow.
Keywords: Acid rain, Acid snow, pH

A comparison of melt rate methods used in forecasting runoff from an Alberta mountain environment - Ferner, S.; Wigham, J. (53rd Annual Western Snow Conference, 1985)
A split watershed version of the Streamflow Synthesis and Reservoir Regulation (SSARR) model was calibrated and verified for a small forested research watershed located in the Rocky Mountains west of Calgary. Five different techniques used to estimate melt rate were applied to the model to determine which provides the best forecasting result. The melt rate in mm/degree day C was the only input parameter changed in the model, which was run for the months of April, May and June over an eight year period, 1973-1980. Model performance was best using melt rates calculated from snow pillow data. An average melt rate from the snow covered area, as determined by five snow pillows at sites of different elevation and exposure provided the best forecasting result. Measured melt rates from just one snow pillow located at the middle elevation of the basin (2155 m) in a heavily forested area provide a comparable result. Snow pillows located at lower elevations in either open or closed areas, and snow pillows located at higher elevations in open areas provide a poor result.
Keywords: Melt rate, Snow pillow, Snowmelt, SSARR

Stochastic models for forecasting snowmelt runoff - Haltiner, J.P.; Salas, J.D. (53rd Annual Western Snow Conference, 1985)
Time series models of the ARMAX class were investigated for use in forecasting daily riverflow resulting from combined snowmelt/rainfall. The Snowmelt Runoff Model (Martinec-Rango Model) is shown to be a special case of the general ARMAX model. The advantage of the ARMAX approach is that analytical model identification and parameter estimation techniques are available. In addition, previous forecast errors can be included to improve forecasts and confidence limits can be estimated for the forecasts. Diagnostic checks are available to determine if the model is performing properly. Finally, Kalman filtering can be used to allow the model parameters to vary continuously to reflect changing basin soil moisture conditions. The above advantages result in improved flow forecasts with fewer model parameters.
Keywords: Snowmelt runoff, Streamflow forecasting, Time series modeling

Model studies of snowdrifts formed by livestock shelters and pond embankments - Jairell, R.L.; Tabler, R.D. (53rd Annual Western Snow Conference, 1985)
Although artificial barriers are commonly used to protect livestock from winter winds, the optimum design has yet to be determined for locations with blowing snow. This paper reports results from small-scale models studied outdoors under natural blowing snow conditions. Little snow accumulates initially on the lee side of solid shelters because blowing snow is entrained in the accelerated flow at the outer boundaries of the wake, and carried over or around the sheltered area. V-shaped and semicircular shelters form similar drifts and provide adequate protection if they are tall (3.7-5m), and have a diameter, or width, less than 15 times their height. A snow fence placed too close to the shelter increases deposition. Embankments should be confined to the downwind half of excavated stockwater ponds. A snow fence placed on top of an existing windward embankment will increase snow deposition within the pond.
Keywords: Blowing snow, Livestock shelters, Models, Snow fences, Snowdrifts

The redistribution and sublimation loss of the snowpack in the alpine watershed - James, E.D.; Brendecke, C.M. (53rd Annual Western Snow Conference, 1985)
A computer program was developed to estimate the redistribution and sublimation loss of the snowpack in the upper Green Lake Valley of the Boulder Watershed. The computer program is based on the the math models developed by R.A. Schmidt and Ronald Tabler on sublimation rate and redistribution of blowing snow. The program modifies the models to read daily weather data. The basin is broken into hydrologic response units (HRU), which are consistent to the segmentation of the Precipitation Runoff Modeling System (PRMS) used to model the runoff in the Boulder Watershed. The program computes how the snow is moved down the basin by the prevailing winds from one HRU to another and then computes average snow depth in each HRU for the winter months. The results are fed into the PRMS model prior to the start of the spring runoff.
Keywords: Modelling, Redistribution, Sublimation

Temperature indices of snowmelt during rainfall - Kattelmann, R. (53rd Annual Western Snow Conference, 1985)
Most of the snowmelt runoff models currently in operation use a special set of equations to estimate snowmelt during rainfall. The performance of eight rain-on-snow melt estimation equations was assessed using data from two Sierra Nevada locations. Daily snowpack water equivalent measurements during rain storms were used as the basis for comparison with calculated melt.The most commonly used equations, which require only air temperature, precipitation, and windspeed, estimated point snowmelt within a few centimeters of observed change in snowpack water equivalent. A simple temperature-only index equation performed almost as well as a more sophisticated equation. This temperature index method, where daily snowmelt = 0.46 cm per degree Celcius + 0.25 cm/day, may be of use where wind and precipitation data are unavailable or judged too difficult to extrapolate.
Keywords: Snowmelt, Snow-on-rain, Temperature index

Snowpack chemistry in south central British Columbia - Kotturi, M.S.; Richards, R.P. (53rd Annual Western Snow Conference, 1985)
This paper summarizes snowpack chemistry data collected at sixteen snowpack sampling sites in South Central British Columbia during the winter of 1980/81 to 1983/84. The samples were analyzed for pH, total acidity and strong acidity, sulphate, nitrate, chloride, flouride, phosphate, sodium, potassium, calcium, magnesium, ammonia and aluminum. Preliminary analysis of data suggests pH of samples ranging from 5 to 5.5 with the exception of a few samples. The mean sulphate to nitrate equivalent ratio of the samples collected in the winter of 1982/83 and 1983/84 was 0.88, suggesting the nitrate loading in snowmelt water was more than sulphate loading. Furthermore, an attempt has been made to discuss: (a) the relationship between upper air temperatures and higher elevation snowpack chemistry(b) the relation between cationic ratios in snowpack samples and sea water and (c) observed spacial variation of pH.
Keywords: Acid precipitation, pH, Snowpack chemistry

Five snowmelt models: a comparison of prediction accuracy - McGurk, B.J. (53rd Annual Western Snow Conference, 1985)
Snow melt forecasts may be made using models that range from simple temperature indices to complex heat and mass flux budgets. The process-based models offer improved predictive capability but require extensive and expensive data collection equipment. Depending on the use of the results, the improved prediction accuracy may not warrant the extra expense and the greater chance of equipment failure.The extensive hydrometeorologic data base at the USDA Forest Service's Central Sierra Snow Laboratiory was used to estimate the energy fluxes that produce melt. Estimates of hourly and daily melt were made using five melt models of varying complexity. Predicted melt during April and May was compared to outflow data from meltpans sited both in a forest and in a forest opening. Predicted melt was also compared to hourly snow pillow and daily isotopic profiling snow gauge snow water equivalents. The most complex long- and shortwave model overpredicted melt by 30% compared to the observed melt. The net radiation model produced better results than the simple temperature index model.
Keywords: Melt models, Snowmelt prediction

Basin division and snowmelt discharge in an alpine basin - Michaels, P.S. (53rd Annual Western Snow Conference, 1985)
An alpine basin in the Colorado Front Range was divided into topographically different grid squares in an attempt to define areas within the basin with similar snow and energy environments. The 188 grids were separated into 10 groups. A t-test between groups, of snowcover present June 23, indicates no significant difference in snowcover for that date. However, the same topographic characteristics (elevation, slope, aspect and angle) were more successful predicting ablation. Modifications in grid size and further statistical analysis are suggested. Three expansion rates for the isothermal snowpack (exponential, linear, and a growth curve) from the beginning of snowmelt to peak snowmelt runoff were tested. The exponential and linear models underestimated discharge by 33% and 14%, respectively, while the growth curve overestimated discharge by 10.5%. The 10.55% overestimate (89.5% basin efficiency) agrees well with Carroll's (1976) estimated basin efficiency of 90% for the same basin.
Keywords: Basin division, Isothermal snowpack, Models, Snowcover

Rainfall and snowmelt frequency in an alpine watershed - Payton, E.A.; Brendecke, C.M. (53rd Annual Western Snow Conference, 1985)
A frequency analysis of rainfall and snowmelt was conducted for two high elevation climate stations in the Boulder, Colorado Municipal Watershed. Snowmelt values for analysis were generated using a degree-day model. A diurnal distribution model was used to provide percentages of total daily snowmelt for durations less than 24 hours. Four theoretical probability distributions were evaluated for fit to the empirical rainfall and snowmelt distributions. Intensity duration frequency curves were constructed using a best fit exponential probability distribution. It was found that rainfall and snowmelt intensities decreased with increasing elevation. For a particular return period, snowmelt intensities were significantly lower than rainfall intensities at all durations but six hours.
Keywords: Colorado, Dam safety, Rainfall frequency, Snowmelt frequency

Results of the snowmelt-runoff model in an international test - Rango, A. (53rd Annual Western Snow Conference, 1985)
The World Meteorological Organization (WMO) recently conducted an international project on the Intercomparison of Models of Snowmelt Runoff. Eleven different snowmelt-runoff models were tested on six snowmelt-basin data sets. The data required for testing the snowmelt-runoff model (SRM) were obtained for four basins-the Dischma basin in Switzerland (43.3 sq km), the Dunajec River in Poland (680 sq km), the Durance River in France (2170 sq km), and the W-3 basin in the U.S.A. (8.42 sq km). Snow cover input data were obtained from aircraft orthophotographs (Dischma), satellite images (Dunajec and Durance), and snow course readings (W-3). SRM performance was evaluated by examination of hydrograph plots, the coefficient of determination of daily discharges (NTD), and the difference in observed and computed runoff volumes (PD). The performance of SRM during the snowmelt season can be summarized as follows: Dischma, n = 10, NTD = 0.84, PD = 3.3%; Dunajec, n =1, NTD = 0.76, PD = 5.1%; Durance, n = 5, NTD = 0.85, PD = 7.3%; and W-3, n =10, NTD = 0.80, PD = 8.2%.
Keywords: Intercomparison project, Model performance, Snowmelt runoff, World Meteorological Organization

Methodology for establishing ground snow loads - Sack, R.L.; Sheikh-Taheri, A. (53rd Annual Western Snow Conference, 1985)
Economical structural design is dependent upon accurate prediction of roof snow loads, which are obtained using ground snow loads. Various national, state and regional ground snow load studies are surveyed. Typical data bases consist of Soil Conservation Service (SCS) snow course records, and snow-load and snow-depth data from the National Weather Service (NWS) sites. Probabilistic models include Gumbel, lognormal and Log-Pearson Type III. A 50-year mean recurrence interval (mri) is generally used, but multipliers are adopted to shift to other mri's. Specific gravities of the snow must be estimated for converting NWS depths to loads. This is done using: a) a single value throughout the region; b) values dictated by forest type; c) conversion factor established from extreme depths and weights; or d) a depth-specific gravity relation given by seasonal maxima. Snow loads are spatially extrapolated plotting contours of either isolines, or normalized snow loads or by establishing snow load elevation relationships. The current study for the State of Idaho is described and a sample map created by computer plotting is shown.
Keywords: Extreme snow loads, Ground snow loads, Idaho snow loads, Snow densities, Structural snow loads

Stochastic transfer function time-series modeling of suspended sediment concentrations as a function of streamflow - Salway, A.A. (53rd Annual Western Snow Conference, 1985)
The conventional sediment rating curve approach results in simple linear regression models of log-transformed suspended sediment values, expressed as a function of log-transformed stream discharge. Such data, however, are frequently stochastic in nature and a time-series approach may be more appropriate. Box/Jenkins time-series analysis is applied to two sets of 1982 data for Duck and Arrow creeks near Creston, British Columbia, to illustrate this alternative approach. First order transfer function time-series models are generated that represent significant improvements over the simple regression models. The Box/Jenkins procedure is also applied to a 1981 data set for Arrow Creek to produce a first order model with a coefficient of determination of 0.722 comared to 0.418 for the simple regression model.
Keywords: Box/Jenkins, Regression models, Sediment rating curve, Stochastic transfer function, Stream discharge, Suspended sediment

Temporal variations in runoff from an alpine snowfield - Sarantitis, B.C. (53rd Annual Western Snow Conference, 1985)
Temporal variations in snowmelt were investigated on an alpine snowfield in the Colorado Front Range. An area of approximately 8 ha collected snow in two large drifts, the upper reaching 12m in depth, the lower, 6m. Losses averaged 8m over the entire pack. Runoff was measured continously with a stage recorder. Total stream discharge was 3.9 x 10(8) m(3). The discharge hydrograph is examined at two sampling intervals, daily and hourly discharge totals. Flow is well described by low order autoregressive equations. There is a trend towards earlier peak flows and decreased lag times through the melt season.
Keywords: Alpine, Autoregressive models, Snowmelt variation

Analysis of water supply forecast accuracy - Schaake, J.C. Jr.; Peck, E.L. (53rd Annual Western Snow Conference, 1985)
As part of a Federal interagency study to consider placing hydrometeorologic stations in wilderness areas of the Colorado River Basin, an analysis is being made of the factors contributing to errors in the forecasts. These factors include errors because of uncertainty in future climate (i.e. uncertainty in long-range weather events), limitations of data networks and limitations of forecast models. A statistical rationale is being developed to estimate these errors and to predict how these errors might be reduced by various improvements in data networks, models, and climate forecasts. This paper presents the early stages of development of the rationale and discusses the current status of the analytical methods being used.
Keywords: Accuracy, Error analysis, Forecasts

Ablation rates of snow fence drifts at 2300-meters elevation in Wyoming - Tabler, R. (53rd Annual Western Snow Conference, 1985)
From April 10 to June 14, ablation rates of lee drifts behind 3.8-m-tall snow fences, having moderate bottom-gaps on level terrain, averaged about 1.0 cm/deg/day. Mean ablation rate was 11% greater for a fence having a 90-cm bottom-gap. Ablation rate averaged aboaut 5% more over the windward half of the lee drift as compared to the downwind half. This uniformity allows drift length, cross-sectional area, and potential melt rate to be predicted over the melt season.The Federal snow sampler overmeasured the density of melting drifts by about 10%. Although desity of drifted snow before melt varies with depth, melting snowdrifts have a uniform desity of about 600 kg/m3.
Keywords: Snow ablation, Snow density, Snow fences, Snowdrifts, Snowmelt

Probability distributions of rain on snow for northcentral Oregon - Zuzel, J.F.; Greenwalt, R.N. (53rd Annual Western Snow Conference, 1985)
Rain-on-snow events can be a major factor in flood damage and can significantly increase water yield in some watersheds of the Pacific Northwest. Winter runoff that occurs on steeply sloping croplands and rangelands can result in serious soil erosion and sediment production. Although the literature documents this type of winter storm event, frequency and magnitude of these events are lacking. We developed algorithms for extracting rain on snow events from daily weather station records and then used them to analyze a 30-year November-through-March record from a weather station in northcentral Oregon. A rain-on-snow event occurs nearly every year, but the probability of a rain greater than 5 mm per day is only about 25%. Rain-on-snow events explainded 57% of yearly peak discharges at a nearby crest gage. Daily precipitation associated with runoff ranged from 5 to 32 mm. Daily precipitation amount and snow depth jointly accounted for 73% of the variance in runoff peaks for rain on snow events.
Keywords: Floods, Frequency analysis, Rain on snow

1984 Title, Contents, and Minutes (52nd Annual Western Snow Conference, 1984)

A snow capacitance instrument for the in-situ measurement of snow wetness - Bergman, J.S. (52nd Annual Western Snow Conference, 1984)
Under most conditions snow is a combination of air, ice, and liquid water. Although the ratio of liquid water to ice is small, detecting the magnitude of change and movement of the liquid portion during rain on snow and melt should lead to more precise estimates of the quantity and occurrence of snowpack outflow. Improved estimates would be and aid in streamflow forecasting and reservoir operation. This paper documents the development of a multi-sensor instrument that provides a precise in-situ vertical profile of snowpack liquid water (snow wetness) by measuring changes in snow capacitance caused by variations in snow wetness. The instrument consists of opposing pairs of discs mounted every 61 cm on a 5 m vertical mast. A slightly overlapping butterfly-shaped electrical field effectively detects changes in snow wetness, around each sensor pair, within 46 cm of the mast.
Keywords: Snow quality equipment, Snow quality measurement, Water supply forecasting

Making observations and models agree in spring snowmelt forecasting - Bissell, V.C.; Orwig, C.E. (52nd Annual Western Snow Conference, 1984)
No matter how well a hydrologic simulation model performs, results will inevitably differ from observed values in all but a few instances. In using the SSAARR model for snowmelt runoff forecasting, several 'knobs' are tweaked to keep the model in tune with observed conditions. Items for which close tracking is maintained are observed precipatation and temperature, discharge, snow covered area, melt rate, basin responsiveness to melt (and rain), and accumulated and residual seasonal runoff. Accessible model state variables and parameters are adjusted on a daily basis for individual basins within the Columbia basin. Forecasted downstream flows are summed to keep a close check on accumulated and residual flow at major flow points. Forecasts on the Boise River system during the spring of 1983 are discussed as examples.
Keywords: Daily adjustment of models, Flood warning, Forecasts, Reservoir operation, Simulation model, Snow melt, Water management, Water supply

The impact of automated hydrometeorological instrumentation upon data quality for the Feather River basin, California - Buer, S.M.; Spence, J.D.; Marchant, J.W. (52nd Annual Western Snow Conference, 1984)
Automation of instrumentation for measuring precipitation and snow water equivalent has made it possible to monitor the Feather River Basin, California in real time, significantly improving flood forecasting performance. However, the technology which makes the data useful in real time may introduce serious problems for long-term data use. These problems include data gaps due to equipment failure, data errors due to loss of calibration or instrument errors, and loss of data quality due to instrumentation constraints. As a result, the data may be of limited usefulness and may require extensive processing before it can be incorporated into a long-term data base for water supply forecasting. These problems must be considered, and an adequate strategy of equipment and data base management must be developed in order to fully realize the potential benefits of automated hydrometeorological instrumentation.
Keywords: Automation, Feather River Basin, Gauge, Instrumentation, Pillow, Precipitation, Sensor, Snow, Telemetry

The transition from manual to automated systems for acquiring snow data - Crook, A.G.; McCuen, R.H. (52nd Annual Western Snow Conference, 1984)
Manually observed snow course data have been used extensively in streamflow forecasting in the Western United States for decades. Telemetry of snowpack data from unattended sensors began in the late 1960's. In 1977, the SCS began operation of its SNOTEL telemetry system. There are currently nearly 500 active sites in the system, each of which telemeters snow water equivalent, precipitation, and air temperature to a central computer. As a history of automated data accumulates, the transition from use of manually collected to automated data becomes possible. The SCS is currently in this transition period and plans to rely primarily on its SNOWTEL data in the future. The paper discusses the reasons for this transition and presents the criteria used to judge the adequacy of automated data sites as replacements for their manual equivalents. Expected results and impacts of the transition are also discussed.
Keywords: Data, Meteor burst, Snowpack, Telemetry, Water supply forecasting

The use of data logging systems in snow hydrology - Cundy, T.W. (52nd Annual Western Snow Conference, 1984)
Meteorological data were collected in an open and forested site for one month. Air temperature, relative humidity, windspeed and the solar radiation were recorded over 30 minute, 30 minute, 10 minute and 10 minute intervals, respectively. Daily averages were calculated by averaging the data recorded over these shorter time intervals. Regression analyses indicated that the relationships between the open and forested sites for these variables were independent of the averaging intervals used here. The implications of this result are discussed.
Keywords: Forested versus open, Meteorological data, Snowmelt modeling

Influences of snow persistence on subalpine forest regeneration in small gaps, Colorado front range - Daly, C. (52nd Annual Western Snow Conference, 1984)
The potential impacts of snow persistence on the regeneration of Engelmann spruce and subalpine fir are assessed at two sites on the eastern slope of the Colorado Front Range. Study is focused on small gaps within the contiguous subalpine forest; snow drifting by wind is negligible, but variations in direct solar radiation exposure produce distinct patterns of snow persistence. Seedling density is considered to be an indicator of germination and establishment success. Neither spruce nor fir seedling densities vary significantly with snow persistence. At these sites, a difference in snow persistence of one to three weeks does not affect seedling establishment, even when snow persists into July. The time required for annual growth appears to be sufficiently short, and the growing season sufficiently long., to allow delays in growth initiation of several weeks without negative effects.
Keywords: Picea engelmannii, Regeneration, Seedling establishment, Snow persistence, Solar radiation

Micrometeorological measurements and instrumentation to support remote sensing observations of an alpine snowcover - Davis, R.E.; Dozier, J.; Marks, D. (52nd Annual Western Snow Conference, 1984)
Remote sensing measurements from satellites and aircraft provide radiometric information that can be used to calculate spatial distribution of snow properties over large areas. This information can then be combined with physical models of snowpack thermodynamics to estimate distribution of melt rates over a region or basin. However, this application of remote sensing has been severely limited because data from which to determine relationships between the physical and radiometric properties of snow have not been available. To calibrate remote sensing data we must first determine the energy and mass balance of the snow at an experimental site, measure those properties that affect snow's radiometric properties, and compare these to reflection and emission data. To satisfy these needs we have maintained a snow research and experiment site at Mammoth Mountain, California. We describe instrumentation and techniques to continuously monitor the energy and mass balance, and to measure critical snow properties, such as liquid water content, temperature and density profiles, crystal shape, and effective grain size under a variety of conditions during the snow season.
Keywords: Micrometeorological measurements, Remote sensing, Snowpack monitoring

Does Your Snow Sampler Overmeasure? - Farnes, Phillip E.; Richards, R.P. (52nd Annual Western Snow Conference, 1984)
If you are using the Standard Federal or Mt. Rose snow tubes and weighing scales to measure snow water equivalent, you are not alone. A large volume of snow data is still obtained by this method, and will continue well into the foreseeable future. As more people begin to rely on automatic sensors for their snow data, it is important to realize that such sensors do not measure the same as the manual core sampler. This discrepancy was the subject of several years of research that went into the Western Snow Conference's Report on Metrication of Manual Snow Sampling Equipment.

Predicting time of peak snowmelt runoff from snow pillow data - Farnes, P.E. (52nd Annual Western Snow Conference, 1984)
The first snow pillow was installed in Montana in 1963. Since then nearly 70 remote snow sensors have been installed and automated. These snow sensors accurately assess the effect of warming spring temperatures by measuring the daily snow water equivalent of the mountain snowpack. Simple time-sequence relationships between snowmelt and day of peak streamflow add another dimension to the hydrologist's ability to predict significant hydrologic events. To determine a relationship requires a few years of snow pillow records and streamgage data. To project dates of peak streamflow requires frequent measurements of snowmelt progress, usually from a real-time data collection system such as SNOTEL. This method provides a simple, realistic estimate of peak flow dates on streams where daily runoff forecast models have not yet been developed, where existing models cannot accurately predict date of peak flow, or as a check for peak flow dates projected with existing models.
Keywords: Peak flow, Snow pillows, Snowmelt

An inexpensive remote snow-depth gauge: an assessment - Goodison, B.; Wilson, B.; Wu, K.; Metcalfe, J. (52nd Annual Western Snow Conference, 1984)
In Canada the need exists for a reliable, low cost automatic snow depth sensor. Ultrasonic wave reflection was examined as one potential method for measuring snow depth. A prototype snow-depth gauge based on a commercially available Polaroid Ultrasonic Ranging unit which provided an economical means of accurately measuring target distance in terms of time to target was constructed. Comparisons of manual ruler measurements and sensor measurements were made. The snow-depth gauge consistenly undermeasured the actual snow depth. Incorporation of a microprocessor along with further refinement of the sensor should provide a viable method of automatically measuring snow depth at a remote station.
Keywords: Automatic, Polaroid, Remote, Snow depth, Ultrasonic

Portable ten-meter instrument mast - Jairell, R.L.; Tabler, R.D.; Schmidt, R.A. (52nd Annual Western Snow Conference, 1984)
This paper describes a portable 10-m mast for supporting vertical arrays of meteorological instruments. Constructed of aluminum and weighing 85 kg, the assembled mast with instruments attached can be moved by one person, and is easily adjusted to be verical over uneven or sloping surfaces. Complete fabrication drawings are provided.
Keywords: Instrument masts, Meteorological instruments, Wind profiles

Snowmelt lysimeters: design and use - Kattelmann, R.C. (52nd Annual Western Snow Conference, 1984)
Snowmelt lysimeters have become a widely used tool in snow hydrology. They have been used to develop and evaluate procedures for estimating snowmelt volume and timing, evaporation, water transmission and storage, and the mass balance of snowpacks. While their basic objective of collecting and measuring the liquid water outflow at some depth within the snowpack seems simple enough, many practical difficulties exist. The hydraulic characteristics of water flow through snow and its collection determine the effectiveness of lysimeter installations. The presence of an impermeable collection pan within the snowpack generates an 'end effect' analogous to a perched water table above the lysimeter interface. This end effect largely determines collection efficiency, dead storage, start-up time, and response of the snowmelt lysimeter. Over three dozen snowmelt lysimeter designs are summarized, tabulated, and compared. Some basic guidelines for lysimeter installation and operation are presented.
Keywords: Lysimeter design, Snowmelt lysimeter

Measurements of frost depth - McCool, D.K.; Molnau, M. (52nd Annual Western Snow Conference, 1984)
Knowledge of the extent and depth of soil frost is necessary for flood forecasting and for assessing the extent and severity of erosion on farmlands. Frost depth can be accurately determined by digging pits, a laborious process under the best of conditions. Determining frost depths at many sites is more easily done using tube-type frost gages. devices filled with colored water. When the water freezes, the dye is forced from the solution and clear ice results. Experiments have been underway for some years in the Pacific Northwest to find the best design for a tube-type frost gage. These experiments are described along with a description of the construction and use of the gages. A comparison of frost depths determined by the frost gages and by soil moisture blocks is presented. The frost gages have been used for numerous experiments. Several of those most applicable to hydrologic practice are described.
Keywords: Climate, Frost depth, Frost gage, Frozen soil, Weather

Dilution method for measuring liquid water in snow - Perla, R.; LaChapelle, E.R. (52nd Annual Western Snow Conference, 1984)
The dilution method for measuring liquid water in snow samples was proposed by Bader (1948) as an alternative to calorimetry. The method involves adding an aqeous stock solution containing a small (<1%) concentration of dissolved impurity into a wet snow sample at 0 degrees C, mixing thoroughly, decanting some of the mixture, and computing how much liquid water was in the sample from the concentration ratio (mixture/stock). Experiments on 172 samples indicate that the method is applicable to a wide range of sample mass (100 g to 2000 g), is quick and simple, and produces mean errors of about 2 g of water per 100 g of sample mass.
Keywords: Snowmelt, Water in snow

Snow accumulation, melt and soil moisure recharge under various lodgepole pine stand densities in western Montana - Potts, D.F. (52nd Annual Western Snow Conference, 1984)
A systematic grid snowcourse (262 measuring stakes at 12m x 12m spacing) was established across a low elevation (1200 m), 50 year-old lodgepole pine stand in western Montana. The 3.85 ha stand was divided into 5 equal-size treatment sub-units - a clearcut, a control (1750 stems/ha) and thinnings at 3m x 3m, 4.5m x 4.5m, and 6m x 6m spacing. A total of 45 soil moisture access tubes were systematically place through the stand. Through the recharge period, snow accumulation was inversely proportional to basal area. The presence of canopy accelerated snowmelt timing. Nevertheless, soil moisture recharge was uniform in all treatments.
Keywords: Lodgepole pine, Snow accumulation, Snow melt, Soil moisture recharge, Western Montana

Snow pillow overloading by slope induced creep - Richards, R.P. (52nd Annual Western Snow Conference, 1984)
A snow pillow in southeastern British Columbia has been subject to overloading since it was installed in the summer of 1979. It had been installed in a sheltered meadow below a resource road where the ground slope was about 17 to 23%. Other pillows are installed in sloping sites, where overloading has not been observed, so creep loading was not anticipated. After a number of other possibilities had been rejected, the pillow was subjected to field testing when the snowpack was near its seasonal maximum. The test program involved trenching to isolate the pillow from the uphill slope and monitoring the pillow response. Extensive core sampling on and around the pillow, prior to the tests, were conducted to check snowpack uniformity and ice layers. By the time the uphill trench was completed, the pillow overload had all but disappeared. The results were sufficiently impressive to induce a relocation to a new site in August, 1983. The site and test results are described and illustrated.
Keywords: Creep, Cut-off trenching, Overloading, Snow pillow

Swiss improvements of the FMCW radar for snow measurements - Schmidt, R.A.; Gubler, H.; Hiller, M. (52nd Annual Western Snow Conference, 1984)
Low-power electronic circuits that produce greater sweep stability, improve signal-to-noise ratio, and permit remote operation from batteries have enhanced snow measurements with a swept-frequency, X-band radar. If snow depth is determined with 1% accuracy, the system predicts water equivalent of a dry snowpack within 5% of gravimetric measurements. Snow depths up to 6 m, determined by radar, compared well with probed depths. When density was estimated from an empirical depth-density relationship.
Keywords: FMCW radar, Snow measurements, Snow water equivalent, Snowpack

Analysis of 1983 snowmelt runoff production in the Upper Colorado river basin - Shafer, B.A.; Jensen, D.T.; Jones, K.C. (52nd Annual Western Snow Conference, 1984)
Spring and summer streamflow for 1983 was extraordinarily high in the Colorado River Basin as well as many others in the Western United States. Streamflow forecasts in these areas were low by from 30 to 100 percent. An investigation was undertaken to examine the hydrometeorological interactions that produced the unusually high runoff and caused such large errors. The synergistic interaction of snow water equivalent, snow areal extent, temperature, precipitation, and soil moisture were evaluated. SNOTEL data combined with satellite imagery were shown to be highly valuable in interpreting the sequence of events during the runoff period. Major causes for the extreme runoff are summarized and recommendations are made for improving forecast models to better predict future events of a similar nature.
Keywords: Colorado flooding, SNOTEL, Snow cover, Snowmelt runoff, Streamflow forecasting

Laser discrimination between rain and snow - Strachan, J.W.; McGurk, B.J.; Berg, N.H. (52nd Annual Western Snow Conference, 1984)
In mountainous environments where rainfall or mixed rain and snow comprise significant portions of the winter precipitation, warm-storm and rain-induced peak streamflow discharges can cause flooding and reduce the efficiency of reservoir operations. Most snow accumulation and melt and streamflow forecasting models use air temperature-based procedures to differentiate between rain and snowfall. The precipitation type-air temperature relationship is not completely deterministic and the scarcity of meteorological stations in mountainous areas often necessitates assumptions on temperature change with elevation. A prototype rain-snowfall discriminator is described. The laser/photo-detector unit monitors the fall velocity and indexes the shape of particles passing vertically through a 3-meter horizontal beam. In a laboratory environment the device discriminates between drop former 'rainfall'' and two types of small paper punches. Future research needs include the development and evaluation of a probabalistic algorithm for distinguishing between the three precipitate types, a low power light-emitting diode laser, precipitates more closely resembling snow, and a field prototype gauge.
Keywords: Laser, Precipitation gage, Remote sensing

The development of an automatic weather station for cold regions - Strangeways, I. (52nd Annual Western Snow Conference, 1984)
The Institute of Hydrology developed its first automatic weather station (AWS) in the 1960's using conventional sensors. In 1976 a project was started to develop an AWS able to operate in cold regions where severe icing normally prevents the collection of data. These developments are now well advanced. The AWS measure solar radiation, albedo, temperature, humidity, wind speed, wind direction and precipitation. Using a test site in the Scottish Highlands, techniques were developed, based on pneumatic shock-induction, flexing and the use of hydrophobic materials, to keep the station ice-free, without the use of power. New sensors and new ways of deploying sensors were developed to suit these techniques and their perfomance compared with that of conventional sensors. The ice prevention techniques, the new sensors, their performance and the path of future developments, are described.
Keywords: Arctic, Automatic weather station, Cold regions, Mountainous

Hydrometeorological instrumentation and automation-past performance, present utilization, and future directions - Strauss, F.A. (52nd Annual Western Snow Conference, 1984)
Snow hydrology is primarily an empirical science. Today's forecaster of snow melt runoff is highly dependent upon intimate knowledge of changes in the site and equipment used to obtain data forming the base for subsequent evaluations. The transactions of the Western Snow Conference detail the transitions that have occurred particularly with respect to equipment and to a lesser degree methods for detailing transitional changes at measurement sites. Todays data base, properly adjusted for transitional changes, is invaluable for refining, with increased statistical significance, many of the forecast methods of the past. Suggestions are made by which todays utilization of the data can be updated, and suggestions are given for the directions to be taken for the future.
Keywords: Automation, Instrumentation

Comparison of precipitation as measured in gages protected by a modified alter shield, Wyoming shield, and stand of trees - Sturges, D.L. (52nd Annual Western Snow Conference, 1984)
Monthly precipitation recorded at gages exposed to wind, but protected by a Wyoming shield and a modified Alter shield, was compared with precipitation mesasured in small forest openings. During months with snowfall (October-May), the gage protected by a Wyoming shield recorded 42% less precipitation than in the forest stand. Monthly undercatch was statistically significant from September through May; gages measured similar quantities of rainfall in summer. There was 32% undercatch of precipitation in months with snowfall at the gage protected by a modified Alter shield; but this gage also received additional protection from wind by scattered trees at the gage site. Undercatch was statistically significant from August through May. A regression relationship to predict precipitation undercatch in relation to storm windspeed at the gage protected by the Wyoming shield was developed for winter months.
Keywords: Alter shield, Precipitation gages, Precipitation measurement, Wyoming shield

Options for harvesting timber to control snowpack accumulation - Troendle, C.A.; Meiman, J.R. (52nd Annual Western Snow Conference, 1984)
Past research in the subalpine forest indicates that the effect of timber harvest on snowpack accumulation patterns and subsequently on streamflow can be optimized when 30-40 percent of the area is clearcut using 5-8 tree height openings. This paper will present the results of several recent studies looking at the effects of other harvesting practices on snowpack. Two years of post-harvest data indicate that large openings (26-tree height) can be created and a 25-30 percent increase in peak water equivalent (relative to undisturbed control) can be obtained through the use of residual stems and slash to create roughness and prevent scour. In another study five years of data on replicated plots of varying growing stock levels indicate that peak water equivalent in the pack can be increased up to 13 percent following thinning. Observations on a 40 ha subwatershed of the Fraser Experimental Forest where 35 percent of the basal area was removed by individual tree selection and 3 years of postharvest data is available, indicate peak water equivalent increased 10-15 percent over the entire area.
Keywords: Snow deposition, Snow redistribution, Snowpack accumulation, Timber harvest

Evaluation of the isotopic snow measurement gage - Wheeler, P.A.; Huffman, D.J. (52nd Annual Western Snow Conference, 1984)
Isotopic snow measurement gages have been in use in the Western states for monitoring snow water equivalent for the last nine years. They have demonstrated several advantages over mechanical snow gages, but have also presented some problems. This paper will review the status of the Isotopic Gage in monitoring snow. It will briefly describe the principles by which it works, evaluate its past experience, discuss its advantages and problems, present current technologic advances by use with micro processors, and suggest future research which will improve reliability. One area of research discussed is the use of solid state detectors, such as cadmium telluride, to eliminate the need for high voltage circuits.
Keywords: Isotopic gage, Snow measurement

A large, adjustable tipping bucket gauge for measuring snowmelt - Wilford, D.J. (52nd Annual Western Snow Conference, 1984)
Snowmelt research in the Queen Charlotte Islands of British Columbia is focusing on the influence of clearcutting on peak flows from rain-on-snow events. The use of large (10 square meter) snowmelt lysimeters necessitated large tipping bucket gauges. No large commercial tipping buckets could be found and experience with existing construction plans was not satisfactory. A large tipping bucket was designed and constructed in the fall of 1982. This paper describes construction details and field performance of the 'Smithers Magnum Adjustable Tipping Bucket'. The unit is robust, economical to construct, and adjustable, with a range of 200 ml to 1.5 l. This is a versatile, sensitive instrument for use in snowmelt or rainfall studies.
Keywords: Snow gauge, Snowmelt, Tipping bucket

1983 Title, Contents, and Minutes (51st Annual Western Snow Conference, 1983)

Record rain-on-snow flooding in North Dakota - Barnicle, R.G.; Carroll, T.R. (51st Annual Western Snow Conference, 1983)
The Des Lacs River basin (2400 sq km), located in northwest North Dakota, experienced record rain-on-snow flooding on April 19, 1979. Preceeding the flood event, the area experienced: (1) 150 percent of normal precipitation during September, (2) 150 mm of snow accumulation by the end of November, (3) peak snow water equivalent ranging from 50 to 130 mm, (4) 25 mm of new snow water equivalent during the first half of April, (5) air temperatures in excess of 15 degrees C with 60 mm of snow water equivalent on the ground on April 18, and (6) 15 mm of rain on the morning of April 19. A record stage of 6.47 mm was reached at approximately 8 am with a flow of 120.63 sq m/s. The record stage was 0.16 mm above the precious April 1970 record stage and 1.59 mm above flood stage. The return period is estimated to be one in 50 years.
Keywords: Flooding, Rain-on-snow

Reorganization of the USDA - Soil Conservation Service - snow survey and water supply forecast activity - Barton, M. (51st Annual Western Snow Conference, 1983)
In October 1981, the SCS initiated a study to determine whether its Snow Survey and Water Supply Forecast activity could be restructured for greater efficiencies. Study goals were to maximize SNOTEL system benefits, reduce the manual surveys system, improve forecasts and related services to water users without significantly increasing costs or personnel. A plan to meet these goals was issued in July 1982 by Chief Peter C. Myers. Reorganization is being implemented over the next several years. Data collection activities in Arizona, Nevada, Washington, and Wyoming are being assigned to the adjacent states of Colorado, Idaho, Montana, Oregon, and Utah. Forecasting, model development, data analysis, and data base management and water supply outlook reports will be the responsibility of a sizeably enlarged (from 8 to 16 persons) staff located at the Service's West National Technical Center in Portland, Oregon. Present plans call for Alaska to continue operations as in the past.
Keywords: Actions, Data collection changes, Implementation, Reorganization

Snowmelt during rain-on-snow in coastal British Columbia - Beaudry, P.; Golding, D.L. (51st Annual Western Snow Conference, 1983)
A study was conducted in Jamieson Creek Experimental watershed near Vancouver, B. C. to determine differences in melt rates during rain-on-snow events between a cutover and a Coastal Western Hemlock old-growth forest. An evergy balance approach was used to quantify the energy fluxes involved in the snowmelting process. Each site was equipped with two independent lysimeters; a pair of small (0.3 sq m) barrel lysimeters and a large (28 sq m) plastic sheet lysimeter recording through tipping bucket arrangements. Wind speed, relative humidity and air temperatures were measured at .6 meters and 1.5 meters above the snow pack to evaluate turbulent fluxes. Snowpack and ground heat exchange was measured with a profile of 6 thermocouples at 0, 0.3, 0.6, and 1.0 meter above ground surface and 0.05 and 0.1 meter below the ground surface. Radiation was monitored with net all-wave radiometers (1 in cutover, 3 in forest). Lysimeter results are compared to U.S. Corps of Engineers equations and theoretical calculations.
Keywords: Energy balance, Rain on snow, Snowmelt, Snowmelt lysimeters

Application of a snow water-equivalent prediction model to rain-on-snow events in the central Sierra Nevada - Berg, N.H.; Hannaford, M.A. (51st Annual Western Snow Conference, 1983)
Knowledge of snowpack water-equivalent is critical in evaluating the reaction of the snowpack to rainfall. Deep, high water-equivalent packs may retain some portion of the rainfall, while flood flows are more likely to result from rainfall on shallow, low water-equivalent packs. A regression model, involving 19 equations, has been developed for estimating real-time snowpack water-equivalent for locations within the American, Yuba and Mokelumne River basins of the central Sierra Nevada of California. The model yields multiple correlation coefficient values reaching 0.94. The equations use snowpack data from two manned hydrometeorological index stations and include information on site elevation, geographical coordinates, date and snowpack conditions at the index stations. Evaluation of the model during rain-on-snow conditions shows close agreement between predicted values and actual observations.
Keywords: Multiple regression, Prediction model, Snow water equivalent

Hydrologic response of central Sierra Nevada snowpacks to rainfall - Bergman, J.A. (51st Annual Western Snow Conference, 1983)
Seven natural rain-on-snow events of more than 4.5 cm were studied at the Forest Service's Central Sierra Snow Laboratory near Soda Springs, in the Sierra Nevada of California, to determine if a pattern of snowpack response exists. All or part of the snowpack was below freezing beforehand but warmed to almost 0 degrees C by the time rain ceased. The typical response was a decrease in overall snow depth, and increase in average density, no change or a slight decrease in snow water equivalent, and only a small increase in runoff due to rain-caused melt. High density layers that increased substantially in density during a storm may have delayed downward flow and directed water laterally into existing drainage channels; this would refute the theory that rain water may percolate evenly through the snowpack with drainage occurring only after its storage potential is satisfied.
Keywords: Rain-on-snow, Sierra Nevada snow zone, Snow hydrology

A comparison of US and Canadian airborne gamma radiation snow water equivalent measurements - Carroll, T.R.; Glynn, J.E.; Goodison, B.E. (51st Annual Western Snow Conference, 1983)
During the week of February 15, 1982, the National Weather Service and the Geological Survey of Canada made airborne gamma radiation snow water equivalent measurements on a network of 43 flight lines in central Saskatchewan. Seventeen flight lines were flown by both the National Weather Service and Geological Survey of Canada aircraft and provide data for a system comparison. The results indicate that the two systems can make independent snow water equivalent measurements with an RMS error of 4.5 mm between systems. In excess of 2500 ground-based snow depth and water equivalent samples were collected on three flight lines and indicate that airborne snow water equivalent measurements can be made with an RMS error of 6.2 mm and a bias of 4.3 mm (6.4 percent).
Keywords: Airborne gamma radiation, Snow water equivalent

Local flood warning to support emergency maintenance of forest roads: a do it yourself method - Christner, J. (51st Annual Western Snow Conference, 1983)
SNOTEL data, weather forecasts, and antecedent stream flow are used to predict the severity of flooding in the rain-on-snow zone of the westside of the Cascades in Central Oregon. Simple nomographs developed from historical records allow a rapid prediction of flood hazard. During periods of heavy runoff, the prediction is used to alert road maintenance crews so that measures can be taken to prevent or minimize damage to forest roads and drainage structures.
Keywords: Flood hazard, Flood warning, Snowmelt runoff

Monitoring a rain-on-snow event - Cooley, K.R.; Robertson, D.C. (51st Annual Western Snow Conference, 1983)
Most of the flooding and considerable erosion damage in the northwestern United States results from snowmelt during rain on snow events in the transient snow zone. Yet efforts to model snow accumulation and melt have concentrated on the deep or continuous snowpack regions. Equipment and procedures for measuring snow depth, snow water equivalent, and snowpack conditions in shallow and often drifted snowpacks, have not yet been adequately developed. This report describes an attempt to determine the water balance on small plots within a watershed during several snow accumulation and rain on snow melt periods. New equipment provides a means of obtaining estimates of evaporation from the snow cover. infiltration through frozen and unfrozen soils, and a photographic record of snowpack depth and coverage during the study periods. Results indicate that the equipment did provide good data for determining the water balance components involved. Evaporation rates compared favorably with previous studies and were generally ten percent or less of precipitation. Infiltration on the other hand varied from 0 to 100 percent of precipitaion depending on temperature, soil moisture, and snow cover conditions.
Keywords: Evaporation, Frozen soil, Infiltration, Rain-on-snow, Snowmelt, Water balance

Rain-on-snow flood event in central Arizona - Ffolliott, P.F.; Brooks, K.N. (51st Annual Western Snow Conference, 1983)
To better understand the effects of rain-on-snow precipitation events and to improve streamflow forecasting, events surrounding a flood which occurred on the Salt-Verde River Basins (Arizona) in February 1980 were examined. Precipitation, temperature, lysimeter runoff, and streamflow data from the upper and lower elevational zones were analyzed. A description of the study site and the type of precipitation (rain, snow, or mixed rain and snow) which the various elevations received are given. Also, a sequence of events can be seen by the comparison of precipitation, temperature, lysimeter runoff, and streamflow, which are graphically illustrated. It was concluded that, although snowmelt augmented streamflow, rainfall was the primary cause of the flood.
Keywords: Arizona, Flooding, Rain-on-snow, Streamflow forecasting

Analysis of three rain on snow floods in the Sierra Nevada, California - Hall, R.L.; Hannaford, J.F. (51st Annual Western Snow Conference, 1983)
Historic rain on snow flood conditions were investigated during the design flood study for a project in the American River basin of California. Basins analyzed range in elevation from under 300 m to nearly 3000 m and have average annual precipitation between 1000 and 2000 mm. Proximity to the Central Sierra Snow Laboratory operated by the U.S. Forest Service and a first order National weather Service station provided temperature, dewpoint, radiation and wind data that allowed use of relatively detailed procedures for calculation of snow accumulation and melt. Watersheds were subdivided into contributing areas and snow condition was calculated for each area on an hourly basis. Rainfall and snowmelt runoff values from each area were routed through the stream channels.
Keywords: American River, Flood-hydrograph, Floods, Rain-on-snow, Sierra Nevada, Snow accumulation, Snowmelt

Snow accumulation and subsequent melt during rainfall in forested and clearcut plots in western Oregon - Harr, R.D.; Berris, S.N. (51st Annual Western Snow Conference, 1983)
In 16 snowfalls, there were large differences in the accumulation and melting of snow between forested and clearcut plots. Prior to a 36-h melt period examined in detail, snow in the forest had already melted; snow reached the forest floor mainly as meltwater from canopy interception. Total water input (rainfall plus snowmelt and condensate) in the 36-h period was 57 mm in the clearcut plot compared to only 12 mm in the forested plot. Combined sensible and latent heat transfer accounted for nearly two thirds of total melt in the clearcut plot. Melt estimated by United States Army Corps of Engineers indices agreed well with measured melt.
Keywords: Clearcut logging, Energy balance, Interception, Snow, Snowmelt

A comparison of several snow accumulation and ablation algorithms used in watershed modeling - Huber, A.L. (51st Annual Western Snow Conference, 1983)
The snow water contribution to the water supply during the forage growing season is the major component of the water supply available on much of the rangeland in the Western United States. In such situations the behavior of the snowpack both during its accumulation and melt period constitutes the major determinant of the surface runoff, both in the amount and timing. The algorithms employed within several models developed to simultate the hydrologic response of such watersheds were tested and compared. The climatic driving variables for the models included minimum, maximum and average air temperature, precipitation and potential solar insolation. The algorithm employed in the NWSRFS model developed by Eric A. Anderson most closely matched the measured snow course values used for the testing.
Keywords: Simulation, Snow accumulation, Snowmelt, Watershed modeling

The isotope profiling snow gage: twenty years of experience - Kattelmann, R.C.; McGurk, B.J.; Berg, N.H.; Bergman, J.A.; Baldwin, J.A.; Hannaford, M.A. (51st Annual Western Snow Conference, 1983)
The gamma transmission profiling snow gage has been in use for about two decades. Sufficient experience has now been gained to evaluate its general utility in snow hydrology research and operational forecasting. The gage produces an incremental depth-density profile with minimal disturbance of the snowpack. Its principal value lies in its ability to repeatedly measure the same vertical section of snow and thus record density changes through time. The snow gage has been an essental part of many studies in the mid-elevation snowpacks of the Sierra Nevada. Data obtained with the instrument have been subject to errors resulting from source decay, electronic variations, and physical influences of the access tubes on the measured snowpack. Overall complexity and expense of the snow gage limit its use in routine monitoring and forecasting applications. The profiling snow gage continues to have great potential in various snowpack investigations.
Keywords: Snow density gage, Snow hydrology, Snow instrumentation, Snow profiles

Snow temperature profiles in the Central Sierra Nevada - McGurk, B.J. (51st Annual Western Snow Conference, 1983)
The temperature profile and cold content of a Sierra Nevada snowpack are significant indicators of it's potential response to environmental stimuli. An analysis of more than 2200 daily snow temperature profiles recorded at the U.S. Forest Service's Central Sierra Snow Laboratory in northern California identified those with marked subzero deviations and calculated temperature deviation frequencies. An anisothermal snow profile was defined and 31 cases were identified. January and February showed the highest proportion of anisothermal events and the largest temperature deviations while April and May showed the lowest proportion of events and the smallest deviations. Deep snowfalls produced most of the anisothermal profiles, but cold air and negative net radiation also created anisothermal profiles. Six significant rain-on-snow storms were identified and characterized. The rain reduced the snowpack's cold content and warmed interior snow temperatures to near 0 degrees C. The reduction in cold content was not uniform or proportional to rainfall depth.
Keywords: Snow temperature, Snowpack Temperature, Thermal gradient

A continuous frozen ground index for flood forecasting - Molnau, M.; Bissell, V. (51st Annual Western Snow Conference, 1983)
Floods occurring on frozen ground are a serious problem in the Pacific Northwest. These floods cause much damage and are costly to control. Timely warning of potential runoff amounts from frozen ground events can prevent some losses by allowing time for raising of levees or other property protection methods and evacuation of people. A frost index that will reflect the effect of frost on potential runoff from the basin was developed. This Index included the effect of snow depth, the current days temperature, and the previous days Index. The Index was applied to both frozen and unfrozen ground runoff events for Missouri Flat Creek near Pullman, WA and McKay Creek near Pilot Rock, OR. The Index proved useful for determining the runoff enhancement potential of these events. The Northwest River Forecast Center is currently using the Index as a guide in running the forecast models.
Keywords: Floods, Frozen ground, River forecast

Application of a simple snowmelt-runoff model to large river basins - Rango, A. (51st Annual Western Snow Conference, 1983)
The snowmelt-runoff model (SRM) developed by Martinec (1975) for use on small mountain basins (<50 sq km) has recently been extended to large river basins (200 -4000 sq km) using remotely-sensed snow-cover data. In addition to the snow-cover data obtained from satellites, the model only requires the input of daily temperature and precipitation data. For model operation, the following parameters must be determined: degree-day factor, runoff coefficient, recession coefficient, temperature lapse rate, and discharge time lag. Simple procedures allow use of SRM in a variety of conditions including rain on snow situations. The average absolute error between actual and simulted runoff volume for the snowmelt season for nine large basins was 3 percent. The average Nash-Sutcliffe R square value, which measures the daily flow fit, for the large basins was .85. In general, the simulation results tend to degrade as the quality of input data decreases which in most cases occurs as basin size increases. Techniques are currently being developed for using SRM in the forecast mode. To aid in application of SRM to a basin, a user manual is now available along with a sample data set for computer implementation.
Keywords: Remote sensing, Snow cover, Snowmelt-runoff, User manual

Structural snow loads - Sack, R.L.; Inverso, G. (51st Annual Western Snow Conference, 1983)
Snow loads on flat roofs are affected by local conditions, as well as the roof geometry, wind exposure and thermal environments. The dimensionless thermal factor Ct proposed by American National Standards Institute is examined in this study. Continuously monitored heat flux and temperature data for a structure with four distinct thermal environments were combined with National Weather Service data and snow core samples from the roof and ground during the winter of 1982-83. Models were developed based on these data and a standard energy balance to predict snow load for the four roof enviromnents and the ground. Ground-to-roof thermal conversion factors (Ct), both predicted and observed, were found to be a function of roof heat flux and substantially higher than those recommended by the American National Standards Institute.
Keywords: Building codes, Roof snow loads, Snow load codes, Snow loads, Structural snow loads, Thermal effects

Snow and ice in Caribou-Poker creeks research watershed, central Alaska. (Abstract only) - Slaughter, C.W. (51st Annual Western Snow Conference, 1983)
Seasonal snow and ice study has been conducted in the 104-sq km Caribou-Poker Creeks Research Watershed, (Latitude 65 10 N) since 1969. Three standard snow courses and one snow pillow installed in 1969 are operated by the Institute of Northern Forestry, USDA Forest Service (in cooperation with Soil Conservation Service). Snow accumulation was measured annually on 1000-M 'transects' at four locations on north- and south-facing slopes from 1970-75. A special study of snowpack drifting at Caribou Peak (773 M elevation) was conducted in 1975-76. The research basin provides good examples of both 'taiga' snow (extensive depth hoar development, density <0.20 g/cu cm) and of 'tundra' snow (extensive drifting, reworking, and wind-packing, density up to 0.45 g/cu cm). Extensive seasonal ice (aufeis) forms in the valleys of this research basin during most winters. Aufeis can impound up to 40% of total winter streamflow as solid-state storage, with local accumulations up to 3+ m thich and occupying an entire valley floodplain.
Keywords: Alaska, Aufeis, Snow cover

The influence of snowmelt in evaluating small hydropower generation potential - Tangborn, W.; Lettenmaier, D. (51st Annual Western Snow Conference, 1983)
The amount and time of runoff from mountain watersheds is a critical factor in the small hydro development that is currently underway in the Cascade Mountains of the Pacific Northwest. The main source of runoff in this region is the mountain snowpack, therefore, the total snowpack volume and its rate of melt are important considerations in hydroelectric plant design. A model is proposed that is designed to predict the discharge of small ungauged, mountain watersheds for the purpose of assessing small hydro feasility. Both watershed yield (total annual runoff) and timing (the daily distribution of flows throughout the year) are determined by this technique. The two main inputs to the model are the observed runoff for several adjacent watersheds, plus the area-altitude distributions for these watersheds. The model is designed to explain the observed runoff at the gauged sites on the basis of each watershed's area-altitude distribution. The resulting rational runoff-altitude distribution is applied to the area-altitude distribution of the ungauged sites.
Keywords: Hydrograph simulation, Hydropower development, Snowmelt runoff

Snowfencing for mined-land rehabilitation - Van Haveren, B.P. (51st Annual Western Snow Conference, 1983)
Snowfences twenty-four inches in height were installed at a coal mine reclamation site in northern Colorado. Snow depth and water content, soil water by volume, and vegetation response have been measured for four years on both fenced and unfenced reclamation plots. After fall seeding of the plots in 1979, the average peak snow depth during the 1979-80 winter on the fenced plots was 13 inches compared to 3 inches on the unfenced plots. For the 1981-82 winter season the peak snow depth averaged 11 and 8 inches for fenced and unfenced plots, respectively. The difference in snow accumulation between fenced and unfenced decreased in 1982 due to the vegetation establishment on all plots. Results of soil water and vegetation response are in the process of being analyzed.
Keywords: Snow fence, Vegetation response

Rain on snow: shallow, transient snowpacks with frozen soils - Zuzel, J.F.; Greenwalt, R.N.; Allmaras, R.R. (51st Annual Western Snow Conference, 1983)
Rain-on-snow events may contribute significantly to annual water yield and flood damage in some Pacific Northwest basins, but the soil and weather conditions required to trigger such events are not documented. Major upland runoff events were observed during the 1980 winter in north central Oregon. While soils were still frozen, high dew point temperatures and high windspeeds associated with the rapid intrusion of a warm, moist Pacific air mass liberated large quantities of heat (of vaporization) at the snow=air interface. This heat source accelerated the snowmelt rate beyond that expected from radiation, sensible heat, and heat content of the rain. Condensation melt accounted for up to 36% of the total hourly melt and averaged 31% for the entire event. Melt rate for the event was as great as 4.00 mm/h (.16 in/h) and averaged 2.1 mm/h (.08 in/h). A combination of snow water-equivalent, air-temperature regime and frozen soil similar to that in 1980 was present during the 1982 winter, but no rain-on-snow or surface runoff occurred.
Keywords: Frozen soils, Models, Rain on snow, Snowmelt

1982 Title, Contents, and Minutes (50th Annual Western Snow Conference, 1982)

Lake ice growth and conductivity - Adams, W.P.; Lasenby, D.C. (50th Annual Western Snow Conference, 1982)
The vertical variation in the conductivity of water obtained from subsampling ice blocks from Elizabeth Lake, Labrador and Lake St. George in southern Ontario was determined. For the Elizabeth Lake block, conductivity ranged form 72 micromhos/cm in the white ice to undetectable in the black ice. The variations in conductivity are related to the mechanism of ice formation and the structure of the ice blocks.
Keywords: Conductivity, Ice growth, Labrador, Lake ice, Slush, Snowcover, Southern Ontario, White ice

Spatial variability of snow and ice on lakes and a strategy for measurement based on three years' data from Elizabeth Lake, Labrador - Adams, W.P. (50th Annual Western Snow Conference, 1982)
Three sets of data, representing the late February snow, white ice and black ice cover of Elizabeth Lake, Labrador, are analysed and compared. Similar spatial patterns are found to exist between years with central and marginal Locations tending to exhibit consistently above or below average thicknesses. It is suggested that the data sets provide a useful basis for designing ice and snow surveys on all medium sized lakes in snowy environments.
Keywords: Black ice, Ice survey, Labrador, Lake ice, Lake snow, White ice, Winter limnology

Influence of clearing ponderosa pine on timing of snowmelt runoff - Baker, M.B. Jr. (50th Annual Western Snow Conference, 1982)
A 184-ha ponderosa pine forest basin in north-central Arizona was cleared and nonmerchantable material was piled into windrows. Analyses reveal that concentrated runoff during snowmelt periods is extended over a longer period of time following the clearing treatment. There is also a shift in streamflow so that the concentrated snowmelt runoff occurs earlier in the season. These results indicate that the average rate of concentrated runoff during snowmelt is more rapid under forested stands than under open conditions, because the runoff from forested areas, although reduced in quantity, is more concentrated in time. The desynchronization of runoff between forested and open areas could possibly be used to reduce potential spring flood hazard from these headland watersheds.
Keywords: Cutting effects, Snowmelt runoff, Timber harvesting, Timing snowmelt

Layer and crust development in a Central Sierra Nevada snowpack: some preliminary observations - Berg, N.H. (50th Annual Western Snow Conference, 1982)
Snow surface crusts and subsurface 'ice' layers densify exponentially. Crust thicknesses range form 4 to 10 cm; layer thicknesses are greater, ranging from 6 to 28 cm. Crusts exist on the majority of non-snowfall days and individually persist from 2 to 20 days. Layers may persist up to 50 days. All layers formed from burial of surface crusts under new snowfall. Pit studies show that layers can be discontinuous and that it is inappropriate to extrapolate point estimates of internal layer properties to wider areas.
Keywords: Crusts, Ice layers, Snow hydrology, Snow stratigraphy

Error assessment of airborne snow water equivalent measurements - Carroll, T.R.; Jones, W.K. (50th Annual Western Snow Conference, 1982)
The National Weather Service maintains an operational Airborne Gamma Radiation Snow Survey Program in the upper Midwest. A network of 300 flight lines, each approximately 15 to 20 km long and 300 m wide, has been established in the region. Natural terrestrial gamma radiation data are collected over the flight lines by a low-flying aircraft and used to infer mean areal snow water equivalent and soil moisture values over the 4.5 to 6.0 km sq area. Errors in the airborne snow water equivalent and soil moisture measurements are due primarily to: (1) uncertainties in the ground soil moisture calibration, (2) errors in the instrumentation used to measure air mass, and (3) limited radiation counting statistics. Nonetheless, the airborne gamma radiation attenuation technique is capable of making a snow water equivalent with an error of less than 1.0 cm and a soil moisture measurement with an error of approximately 3.9 percent soil moisture. Sources of error are discussed using ground and airborne data collected during the 1982 snow season.
Keywords: Airborne snow water equivalent, Airborne soil moisture, Gamma radiation, Nuclear techniques

Remote sensing applications in snow hydrology-past, present and future - Chang, A.T.C.; Rango, A. (50th Annual Western Snow Conference, 1982)
Recent advancement of spaceborne remote sensor systems provides much needed information to retrieve important parameters of snow hydrology. Considerable effort, accompanied by significant results, has been reported. These activities take advantage of certain characteristics of remote sensing data such as synoptic viewing, repetitive coverage, relative low cost and real time data acquisition. The Landsat and NOAA environmental satellite systems have provided many observations that are proving to have utility in monitoring snow coverage area. Research being carried out now also suggests that micowave observations may be able to monitor more fundamental variables needed by the water resources managers. Snowcovered area and snow water equivalent retrieved from microwave data obtained by Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) compare favorably with ground observations.
Keywords: Remote sensing, Snow hydrology

Peak streamflows from the transient snow zone, western Cascades, Oregon - Christner, J.; Harr, R.D. (50th Annual Western Snow Conference, 1982)
Streamflow records for six watersheds in Oregon's Willamette National Forest indicate hydrologic conditions of the watersheds have changed over the past 4-5 decades. Increased size of the peak flows appears related to cumulative effects of timber harvest activities, primarily clearcut logging in the transient snow zone. There is a strong possibility that higher windspeed and turbulence following clearcutting has increased the rate of melt of warm snowpacks during rainfall. More rapid delivery of water to soil and to streams increases the probability of landslides and stream channel erosion in headwater areas as well as channel erosion processes downstream. Timber harvesting scheduling should take into account both the possibility for changes in snow accumulation and melt resulting from logging in the transient snow zone and the time required for hydrologic recovery.
Keywords: Clearcutting, Runoff, Snowmelt

Snow cover distribution in forested and deforested landscapes in New Brunswick, Canada - Daugharty, D.A.; Dickison, R.B.B. (50th Annual Western Snow Conference, 1982)
Snow cover distribution in two small (391 ha and 660 ha) forested watersheds in central New Brunswick, Canada was measured for an eight-year period prior to removal of 94% of the forest cover from the smaller watershed in 1978-79. Three years of subsequent measurements are analysed to determine comparisons between the forested and de-forested condition. Basin-wide snow cover was not significantly altered prior to the time of maximum snowpack, but became significantly less in the clearcut area late in the season.The most significant mid-winter effect was a reversal of the usual increase of snow depth with elevation, resulting in gradients of -5.6 to -9.9 cm/100 m at the time of maximum snow depth. This is attributed partly to the removal of interception losses from the softwood cover which predominated at lower elevatons, and partly to increased drifting which tends to favour redistribution toward lower elevations.
Keywords: Snow cover, Snow cover/harvesting effects, Snow distribution, Snow elevation gradients

A new data base: a digital archive of northern hemisphere snow cover - Dewey, K.F.; Heim, R. Jr. (50th Annual Western Snow Conference, 1982)
The purpose of this paper is to acquaint the research and user community with a new data base, a digitized archive of Northern Hemisphere snow cover. Weekly snow and ice charts have been prepared by the Synoptic Analysis Branch of the National Earth Satellite Service (NESS) on a continuous basis since November 1966. Based upon photo interpretation of 6 or 7 consecutive days of satellite imagery, the snow and ice boundaries are drawn on a 1:50,0000,000 polar stereographic projection of the Northern Hemisphere. Each of these charts for the period November 1966 through December 1980 were digitized at the University of Nebraska utilizing an 89 by 89 element box grid overlayed on the polar stereographic map. The grid which was utilized was compatible with the satellite-based Earth radiation budget atlas of Winston et al (1979). The true geographic area of each grid box varies with latitude as a result of the polar projection. However, this was taken into account mathematically, so that a true areal coverage of snow could be determined for a chart or for a region on a chart.
Keywords: Digital archive, Satellite snow cover, Snow cover

Eastern snowpack conditions - characteristics and significance - Eschner, A.R. (50th Annual Western Snow Conference, 1982)
Eastern snowpack conditions are sharply different from those in the west; but not necessarily in the ways we might imagine. In New York, the seasonal snowfall approaches the average seasonal snowfall in many western areas, and is well correlated with melt season streamflow volumes. In spite of a substantial annual precipitation uniformly delivered over the year, the seasons when snow is present on the ground or in the process of melting provide the bulk of streamflow for many areas in the East. Although approximately as much precipitation falls in the growing season as the dormant season, its contribution to streamflow is small, and the snowpack is a significant parameter for predicting even total annual runoff.
Keywords: Eastern U.S., Runoff, Snow accumulation, Snowpack

Metrication of manual snow sampling equipment by western snow conference metrication committee - Farnes, P.E.; Peterson, N.R.; Goodison, B.E.; Richards, R.P. (50th Annual Western Snow Conference, 1982)
After four years of field testing, the Western Snow Conference Metrication Committee is presenting its proposal and design of two metric snow samplers.The WSC snow sampler for the deeper western snowpacks has 10.6 cm sq cutter area while the ESC-30 sampler for shallow snowpacks (up to 1 m depth) has 30 cm sq cutter area.The proposal is based on extensive field tests to compare ground truth with the standard Federal Snow Sampler, the proposed metric snow samplers, and other snow samplers. The committee developed drawings and specifications for the new metric snow samplers. The commmittee also proposes a method for converting the present standard Federal sampler into a metric sampler.
Keywords: Equipment - snow surveying, Equipment - Testing, Metrication, Snow sampler, Snow surveys

Northern hemisphere snow cover conditions during the winter of 1982 - Foster, J.; Ormsby, J.; Rango, A. (50th Annual Western Snow Conference, 1982)
During the winter of 1982 (December - February) the mean snow covered area in North America was the third greatest in the 16 year record (1966 - 1982). In Eurasia the snow covered area was near normal. But the snow covered area in both North America and Eurasia increased significantly over that of the previous year. Assessment of any long term climatic trends must wait extension of the snow cover data base.
Keywords: Eurasia, North America, Satellite, Snow cover

Canadian snow gauge experiment: recent results - Goodison, B.E.; Metcalfe, J.R. (50th Annual Western Snow Conference, 1982)
For several years the Hydrometeorology Division of the Atmospheric Environment Service has been conducting field tests on the accuracy and performance of various types of snow gauge installations used throughout Canada. This paper reviews results on the performance of two types of shielding for recording gauges - the Wyoming shield and a large Nipher-type shield now under test by the AES. The advantages and disadvantages of each type of shield are reviewed. Seasonal totals show that on the average the large Nipher-type shield undercatches the standard MSC Nipher snow gauge by less than 10%, while the Wyoming shieldied gauge undercatches it by about 25%. Alter-shielded recording gauges generally measure about 60% of the snowfall measured using the MSC Nipher shielded snow gauge. Inconsistencies in the daily measurements from some recording gauges were observed and these must be understood before the gauges can be operated successfully at automatic stations in Canada.
Keywords: Nipher shield, Snow gauge measurement, Wyoming shield

Western Snow Conference - the first fifty years - Henderson, T.J. (50th Annual Western Snow Conference, 1982)
The Western Snow conference is celebratinag its 50th anniversary this year in Reno, Nevada. The WSC finds its origin here in 1933, under the initial guidance of Dr. James E. Church, at that time a Professor of Classics at the University of Nevada. Following those early formative years, many individuals have been important to the growth of the Conference. The scientific and technological papers presented at the annual meetings have influenced the investigations of snow hydrology throughout the world. The WSC bibliography indicates the total number of papers which have been published in the Proceedings now exceeds 700. This historic organization continues to serve many important functions at the national and international levels within the fields of snow hydrology and meteorololgy.
Keywords: History, Western Snow Conference

Regression models in water supply forecasting - Huber, A.L.; Robertson, D.C. (50th Annual Western Snow Conference, 1982)
This paper presents a review of some of the most common index or regression methods for making seasonal water supply forecasts. It outlines a strategy for adapting the multiple regression technique to the problem of real or near real-time forecasting and concludes that the regression technique will remain a viable tool of the water supply forecaster because: 1. It is conceptually simple and widely accepted; 2. Confidence intervals about the estimate may be easily calculated; 3. It requires a minimum of computational facilities; 4. The forecast estimates are available instantaneously; 5. The forecast errors are acceptably small.
Keywords: Forecasting, Regression Models, Snowmelt, Water supply

Development of small-scale snowdrift simulation - Iversen, J.D. (50th Annual Western Snow Conference, 1982)
This history and development of snowdrift simulation is outlined, starting with work done by A. E. Finney nearly 50 years ago. Few attempts at small-scale simulation have been made through the years because of the difficulty of satisfying similitude requirements for two-phase flow. The modeling experiments that have been done are about equally divided between air and water as the modeling fluid. For this reason, and because of the problem complexity, controversies exist concerning the appropriate modeling parameters which must be satisfied. Also, because of the complexity of the similitude problem, many simulation attempts have been primarily qualitative. Since all important parameters cannot be satisfied, the appropriate parameters to be modeled depend on whether visibility, gross drift features, or other features of the depositional-erosional patterns are to be modeled. These similude requirements are discussed, and the efforts of the various investigators are compared and summarized.
Keywords: Deposition rate, Drift geometry, Modeling, Wind tunnel

Water yield improvement in the Sierra Nevada snow zone: 1912-1982 - Kattelmann, R.C. (50th Annual Western Snow Conference, 1982)
Forest management as a means of improving the yield and timing of runoff originating in the Sierra Nevada snow zone has been investigated for more than 70 years. This paper reviews published and unpublished research from the work of Dr. Church to the present. The principles developed in dozens of studies have been tested with large-scale timber harvests at two sites in northern California. Narrow cut strips oriented either east-west or north-south have been found to retain significantly more snow water equivalent than nearby uncut forest. Streamflow records near the Yuba Pass study indicate a substantial increase in runoff due to harvesting.Operational limitations on the application of watershed management practices are examined. Research needs are highlighted, and general guidelines for increasing and delaying streamflow are provided.
Keywords: Snowpack management, Water yield improvement

Remote data acquisition using random mode sub-telemetry systems - Kleppe, J.A.; Yori, L.G. (50th Annual Western Snow Conference, 1982)
There is increasing interest in automated wide-area data collection systems from various government agencies and private research groups. Applications for such automated networks are growing rapidly as budget constraints and manpower limitations prevent data collection from many remote sites by traditional manual methods. Current automated networks such as the U.S.G.S. GOES Satellite System and the Soil Conservation Service SNOTEL Meteorbust Network are restrictive, in that they are primarily limited to use by government agencies and users with hydrologic or meteorological missions. This paper describes a low-cost, random mode, sub-telemetry data acquisition system 'POPCORN' which can be used to significantly expand existing GOES and Meteorburst Networks. The availability of low-cost sub-telemetry equipment enhances the feasibility of a commercially operated wide area data collection system, known as 'DATANET'. This commercial network concept provides resources and services to a large group of users with diverse data collection requirements.
Keywords: Data acquisition, DATANET, GOES satellite, Meteor Burst Communication, POPCORN, SNOTEL, Telemetry

Reminiscences of Eastern Snow Conferences, 1950-1981 - Lansing, L. (50th Annual Western Snow Conference, 1982)
The author, with the able assistance of several long-time members and former members of the Eastern Snow Conference, has prepared an historical note on the development and history of that organization. We are seeking to bring back memories of people and events unknown to many of today's membership, but still very much alive in the minds of many others of us. We particularly wish to highlight cooperative efforts of the Eastern Snow Conference with government agencies, federal, provincial and state, on both sides of the border, as well as the numerous corporations that have contributed generously to our endeavors.
Keywords: Eastern Snow Conference, History, Snow surveying

Event reporting on Mount Saint Helens SNOTEL, flexibility for the future - Marron, J.K.; Davis, R.T. (50th Annual Western Snow Conference, 1982)
The eruption of Mount Saint Helens on May 18, 1980 demonstrated the need for an event identification system to monitor changes in the snowpack caused by either meteorological or volcanic contributions. An event system was developed and installed on Mount Saint Helens that demonstrated both the flexibility and expandability of the Soil Conservation Services' Snow Telemetry System (SNOTEL). With minor modifications, as demonstrated by the Mount Saint Helens event system, there is a potential for an addition to the SNOTEL system. The flexibility of the system shows different data needs can be solved by use of the SNOTEL system.
Keywords: Automated, Event, Probe, Remote site, SNOTEL, Subsystem

A history of snow research at the University of Idaho - Molnau, M.; Warnick, C.C. (50th Annual Western Snow Conference, 1982)
Water stored in the snow reservoir is very important to the economy of Idaho. The operation and management of irrigation projects, power, fisheries resources and recreation all depend upon the water stored in the snow and released during the spring melt. The Engineering Experiment Station conducted studies on precipitation gages from 1948 to 1959. Projects were then started to develop reliable radio transmitting and receiving equipment that could function in the hostile winter mountain climate. At the same time, parallel development of hydrologic sensors was being carried out. These sensors, for precipitation, temperature, snow water equivalent, etc., had to not only be rugged but had to accurately measure the variable in question.One of the best of these sensors, the snow pillow, was first installed in 1961. This was the first pillow installed anywhere.Snow hydrology studies have concentrated on snowmelt modelling on agricultural lands, frozen ground simulation and infiltration and uses of snow data in building design.
Keywords: Equipment, History, Idaho, Snow, Snow hydrology

Streamflow regionalization in western Montana - Potts, D.F. (50th Annual Western Snow Conference, 1982)
The improvement in our ability to estimate streamflow in Western Montana watersheds has paralleled the expansion and refinements of the co-operative snow survey. We have urgent and growing needs for the accurate inventory of our State's water resource.Existing methodologies are reviewed and their limitations discussed. Two additional methodologies have been adapted for our use. The first identifies 'homogeneous' regions of hydrologic character, the second employs the intuitive relationships between discharge and channel geometry. Model sensitivities and sources of error are discussed.
Keywords: Montana channel geometry, Streamflow regionalization

Climatic applications of a satellite snow/cloud discrimination sensor - Scharfen, G.R.; Anderson, M.R. (50th Annual Western Snow Conference, 1982)
As part of a larger project studying the relationships between cloud climatology and the hemispheric boundaries of snow cover (and sea ice), a new technique from satellites was tested. Snow and cloud signatures differ significantly in the 1.61 micro m spectral region. Data from an experimental 1.6 micro m sensor system of the Defense Meteorological Satellite Program are compared with DMSP visual and infrared imagery and operational snow indices for eastern North America. Promising results suggest that application of sensors in this bandwidth can aid operational discrimination between satellite observed snow and clouds.
Keywords: Cloud cover discrimination, Satellite imagery, Snow cover

A new device for sampling mass flux of blowing snow - Schmidt, R.A.; Tabler, R.D.; Jairell, R.L. (50th Annual Western Snow Conference, 1982)
Snow blown through a sharp-edged frame, 5 cm wide and extending 50 cm above the ice on a frozen lake, is trapped by a porous fabric bag. Wind shakes the snow from the bag into a 100-liter container in a steel casement beneath the surface, where it is weighed by an electronic balance. Connection to a remote computer allows 15 second readings of drift flux. The device provided excellent measurements during 236 runs of 5-min duration, in blizzards with transport rates as high as 300 g/m-s.
Keywords: Blowing snow, Hydrologic measurements, Instruments, Snow, Snowdrift

Development of a surface water supply index (SWSI) to assess the severity of drought conditions in snowpack runoff areas - Shafer, B.A.; Dezman, L.E. (50th Annual Western Snow Conference, 1982)
Colorado has experienced recent periods of drought in the winters of 1976-77 and 1980-81 which were detrimental to the state's economy. To deal with these conditions, Colorado has developed a drought response plan which relies upon a water availability assessment. A Surface Water Supply Index (SWSI) has been developed which when combined with the Palmer Drought Index, acts as both a triggering mechanism to activate the state's drought response plan as well as a yardstick to determine when a drought has effectively terminated. A single SWSI number is generated for each major basin on a monthly basis throughout the year. The index is derived from the cumulative probability distributions of snow course, precipitation, reservoir, and streamflow data. Each of the constituent variables in the index is weighted in proportion to its probable impact on total surface water resource of the basin. A SWSI map of Colorado is developed to display the information. The development of SWSI has been a joint endeavor of the Colorado State Engineer's Office and the U.S. Soil Conservation Service.
Keywords: Drought, Drought Index, Frequency analysis, Water supply

Runoff forecasting for reservoir operations - the past and the future - Speers, D.D.; Versteeg, J.D. (50th Annual Western Snow Conference, 1982)
Two techniques of long range water supply forecasting are compared for the Detroit Dam watershed, a 'rain-on-snow' basin in Western Oregon. A traditional multiple regression procedure has been employed to forecast spring runoff, which is of operational interest for refill of the reservoir. The second approach involves the use of a continuous, conceptual hydrologic model, the SSARR model. Comparing an 11 year test period, a similar degree of accuracy was achieved with each type of forecast. The paper illustrates, however, that the use of a hydrologic model can provide advantages over the statistical forcast, namely: (1) improved accuracy in a real-time setting through continuous adjustments of model parameters to observed conditions; (2) a greater variety of forecast products, including short term flood forecasts and probabalistic estimates incorporating a reservoir model.
Keywords: Models - snowmelt, Water Supply Forecasting

Factors affecting temperate variations in the albedo of snowcover - Strickland, N. (50th Annual Western Snow Conference, 1982)
A study of relationships between snowcover albedo, snow characteristics, air temperature and precipitation in Southern Ontario. USACE equations were found to predict albedo relatively poorly in this warm, moist, snow environment.
Keywords: Air temperature, Rainfall, Snow albedo, Snow properties, Snowfall, Snowmelt, Southern Ontario

Snowpack management on Marmot watershed to increase late season streamflow - Swanson, R.H.; Golding, D.L. (50th Annual Western Snow Conference, 1982)
The forested portion of Twin subbasin of the Marmot Creek Experimental Watershed in Alberta, Canada, was harvested in a honeycomb pattern of 1-tree height diameter circular clearings during 1977-79. Our goal for this treatment was to alter hydrograph shape in favour of late season streamflow. Our research on plot studies elsewhere indicated that at peak snowpack, this size clearing would contain 38 percent more snow than under uncut forest and that it would ablate 24 percent slower than either that under uncut forest or that accumulated in clearcuts larger than 3 to 5 tree heights across. These snow research findings suggested that the water yield from a catchment harvested in such tiny clearings might occur later in the water year -- a quite different time distribution than has been reported from harvests consisting of larger size clearcuts. For the first three years since treatment, 28 percent (50 mm) more snow water equivalent accumulated in the clearings than under adjacent treed patches. There has been no increase in total snowpack on the treated catchment. Annual water yield increased by 36 mm in 1980, 16 mm in 1981. There are insufficient data at this time to evaluate the effect on recession flow.
Keywords: Marmot Creek, Alberta, Snow management

Frequency distribution of annual peak water-equivalent on Wyoming snow courses - Tabler, R.D. (50th Annual Western Snow Conference, 1982)
An empirical sample frequency distribution of annual peak water equivalent, W, expressed relative to the station mean, W(bar), was determined for all Wyoming snow courses having 30 or more years of records. Because tests supported the hypothesis of homogeneous variance amoung location and elevation cases, a composite distribution was derived that provides a reasonable approximation for all snow courses in the State. The modular co-efficient, W/W(bar), is approximately normally distributed, with mean 1.0 and variance 0.088. A table of exceedance probabilities is provided to facilitate application.
Keywords: Frequency analysis, Snow courses, Snow surveys, Snowpack water equivalent, Wyoming

The effects of small clearcuts on water yield from the Deadhorse watershed; Fraser, Colorado - Troendle, C.A. (50th Annual Western Snow Conference, 1982)
Thirty-six percent of a small, 41-ha, subalpine watershed on the Fraser Experimental Forest was harvested using a system of small 5-Ha circular clearcuts. Annual water yield has increassed an average of 4.6 cm during the first 4 years after treatment with no detectable effect on peak flow rates. Significantly more snow was found in the openings than in the forest, but mean peak water equivalent for the watershed was not significantly altered.
Keywords: Clearcuts, Peak flows, Snowmelt, Vegetation manipulation, Water yield

Snow hydrology of the High Arctic - Woo, Ming-ko (50th Annual Western Snow Conference, 1982)
In the Canadian Arctic Islands, snowfall is the major form of precipitation. At the end of winter, snow distribution is highly eneven, reflecting the strong influence of local terrain upon snow drift. The snowpack is denser and harder than that of the subarctic and stratigraphically, it comprises a number of wind-slabs and hoar layers. During spring, snow accumulated over many months are released within a short spell. The magnitude and timing of floods are controlled by the amount of winter snowfall, the intensity of spring melt and the variable source of meltwater due to fragmentation of the basin snow cover. When meltwater reaches the snow-choked valleys, numerous snow jams further modify the flow.In view of the preponderant influence of snow on arctic hydrology, advancement in snow research will have significant applications to northern development.
Keywords: Arctic hydrology, Arctic snow, Snow distribution, Snowmelt, Snowmelt runoff

1981 Title, Contents, and Minutes (49th Annual Western Snow Conference, 1981)

A quantitative analysis of avalanche hazard on U.S. highway 550, southwestern Colorado - Armstrong, B.R. (49th Annual Western Snow Conference, 1981)
Avalanches have long been a hazard on U.S. Highway 550 in the San Juan Mountains of southwestern Colorado. Historical records document numerous avalanches involving people from the 1970's to the present. Today, highway traffic is increasing due to expanding mineral exploration and developing mining, milling, and energy-related activities in and surrounding the San Juan Mountains. This paper uses avalanche event data on U.S. Highway 550, which has been documented since 1951, to calculated expected encounters between vehicles and avalanches, and to develop a hazard index for the highway. Two statistical methods are used: Poisson distribution and a method devised by Schaerer in British Columbia, Canada. Results indicate that U.S. Highway 550 can be classified as a high hazard route. These calculated expected encounters and probabilities should be considered as index values in assessing future avalanche control policies for the highway.
Keywords: Avalanche, Hazard, Mountain highways

Application of airborne gamma radiation snow survey measurements and snow cover modeling in river and flood forecasting - Carroll, T.R.; Larson, L.W. (49th Annual Western Snow Conference, 1981)
The National Weather Service (NWS) has hydrologic forecasting reponsibilities for the United States. Two major technical procedures have recently been developed and implemented by the NWS to facilitate river and flood forecasting in large areas of the upper Midwest subject to extensive winter snow accumulation. First, a temperature based snow model is used to represent the physical processes associated with the accumulation and ablation of a snowpack and to simulate snow cover characteristics over much of the upper Midwest. Second, the implementation of an operational Airborne Gamma Radiation Snow Survey Program provides observed snow water equivalent data for large areas of the upper Midwest. A discussion of the snow accumulation and ablation model and its application to the NWS River Forecasting Procedure is given. In addition, the theory, application, capability, and limitation of the airborne gamma radiation attenuation technique are discussed.
Keywords: Airborne snow survey, Flood forecasting, Gamma radiation, River forecasting, Snow melt modeling

Effects of snowdrift management on rangeland runoff - Cooley, K.R.; Huber, A.L.; Robertson, D.C.; Zuzel, J.F. (49th Annual Western Snow Conference, 1981)
The installation of snow fences for increasing the size of snowdrifts, and thus increasing available water supplies, was investigated. Analysis of runoff from a 0.51 sq km watershed, and the size and shape of a drift induced by intallation of a 100 m long, 3 m high snow fence indicated that changes in runoff and size were insignificant, but the snow was distributed differently within the drift, possibly delaying snowmelt. Other studies have indicated increases, no change, and decreases in these parameters. Therefore, although increased drifts could provide important additions to local water supplies, it is very important to consider local conditions, which influence success before making any such installations. A more practical and reliable approach would be to locate natural drift sites and to install water harvesting systems in these areas.
Keywords: Runoff, Snow fence, Snowdrift, Water supply

Snow surveys and Mount Saint Helens - Crook, A.G.; Davis, R.T.; Moreland, R.E. (49th Annual Western Snow Conference, 1981)
On March 27, 1980, the first tephra eruption in approximately 123 years dusted the snowpack of Mount St. Helens, Washington. Within two weeks, special snow surveys were being conducted to assess the effects of tephra deposits on the snow. Preliminary evidence indicated there were substantial changes in snowmelt characteristics as a result of varying tephra thichnesses. On May 18, 1980, a catastrophic explosive eruption destroyed much of the residual spring snowpack. The snowpack outside the devastated area, and at higher elevations, was blanketed by a thick layer of tephra. The effect was a substantial reduction in snowmelt rates. Automated snow measuring equipment recorded preblast melt rates, the accumulation of tephra on the pack, and the subsequent rate of melt. During the fall of 1980, one destroyed data site was reestablished and three new sites installed. Now a total of seven snow monitoring sites automatically monitor snowpack conditions on the watersheds around the volcano. The data from these snowpack measuring sites are used in forecasting snowmelt volumes and streamflow rates for agricultural and power generation use, as well as flood warning.
Keywords: Snow survey, Snowpack, Telemetry, Tephra, Volcanic eruption

Application of a snowmelt model to two drainage basins in Colorado - Jones, E.B.; Shafer, B.A.; Rango, A.; Frick, D.M. (49th Annual Western Snow Conference, 1981)
The Martinec-Rango Snowmelt Model has evolved over a period of years from one that was developed for a relatively small drainage to its current application on much larger areas. The input requirements for the model include the remotely sensed percentage of snow-covered areas within the limits of the watershed, daily temperature, and precipitation. All of these data can be input on a multi-zonal basis.The current project analyzed the use of this model on the South Fork of the Rio Grande River (559 km sq) and on the Conejos River above Magote (730 km sq). Both of these watersheds are larger than had previously been considered for use with this model. The simulated volume of runoff versus the actual runoff were within 1 to 12 percent for the 6-month snowmelt period. Nash-Sutcliffe `R squared' values for daily runoff simulations exceeded 0.88 in all years except the very dry year of 1977.
Keywords: Landsat imagery, Runoff, Snowcovered area, Snowmelt runoff

A precipitation-runoff modeling system for evaluating the hydrologic impacts of energy resouces development - Leavesley, G.H.; Lichty, R.W.; Troutman, B.M.; Saindon, L.G. (49th Annual Western Snow Conference, 1981)
A modular design precipitation-runoff modeling system is being developed for evaluating the impacts of various combinations of precipitation, climate, and land use on runoff, sediment yields, and general basin hydrology. Normal and extreme rainfall and snowmelt events will be simulted for various combinations of land use to evaluate changes in water-balance relationships, soil-water relationships, flow regimes, flood peaks and volumes, sediment yields and groundwater recharge. A major component of the modeling system is snowmelt runoff. Initial development, testing, and verification of the snowmelt components are being conducted in the major coal and oil-shale regions of the western United States. A number of representative study basins have been instrumented in each region to provide data on basin hydrology before, during, and after energy resource extraction. An overview of the modeling system is presented and the snowmelt components are described in detail.
Keywords: Modeling, Precipitation, Runoff, Snowmelt

Snow wetness measurements and runoff forecasting - Linlor, W.I.; Clapp, F.D.; Angelakos, D.J.; Smith, J.L.; Berg, N.; Bergman, J. (49th Annual Western Snow Conference, 1981)
This paper presents results of our research in recent years, directed toward the development of snow-wetness measuring systems. During the 1979-80 season, microwave attenuation data were abtained twice daily for horns within the snowpack, from which the snow wetness was calculated using calibration equations. These tests were made at the Central Sierra Snow Laboratory; concurrent data were obtained on snow water equivalent and other meteorological quantities.The beginning of the pack-snowmelt was clearly evident in the microwave data; its timing agrees well with the changes in snow water equivalent. The increase in wetness during a day, and the decrease in wetness produced by drainage overnight were also readily measured. Results are given for water retention capability of the snow in volume and in weight percent.A brief discussion is given of the application of snow wetness data to runoff forecasting.
Keywords: Forecasting, Meteorological, Microwave, Snow wetness, Water retention

SNOTEL: a management tool for the future - McMillan, G.D. (49th Annual Western Snow Conference, 1981)
SNOTEL (for Snow Telemetry) is the automated portion of the Soil Conservation Service's snow survey and water supply forecasting activity. The 480 SNOTEL sites and two master stations make-up the largest known application of 'meteor burst' technology. Each site reports the water equivalent of snowpack, accumulated precipitation, and air temperature. Data from SNOTEL are used with snow course measurements to forecast snowmelt runoff. Those who benefit from SNOTEL include farmers and many individuals and agencies responsible for flood control, municipal water supply, reservoir management, power generation, recreation, industry, and fish and wildlife management. In the 1980's, SCS will focus its snow survey efforts on: (1) Further refining the SNOTEL system; (2) analyzing water user's real-time data needs; (3) strengthening cooperative relationships with others involved in the surveys or in managing water resources in the West; and (4) integrating the snow survey program into overall inventorying and monitoring efforts of SCS.
Keywords: Snow sensor, Snow survey, Water supply forecasting, Watershed Management

Evaluation of SNOTEL data during January 9-16, 1980 storm in the Tahoe-Truckee basins - Moreland, R.E. (49th Annual Western Snow Conference, 1981)
This paper covers the operation of SNOTEL data sites during the severe storm period January 9 to 16, 1980, in the Tahoe-Truckee Basins of California and Nevada. These sites are part of the Soil Conservation Service's SNOTEL data collection system. Precipitation over the basins was almost continuous from the 9th through the 16th of January. The nine SNOTEL sites in the Tahoe-Truckee Basins and four sites in the adjacent Carson-Walker Basins were the only near real time data collection sites functioning in these basins during the January 9-16 event. Four SNOTEL sites--Ward Creek No. 3, Independence Lake, Fallen Leaf, and Marlette Lake--all with different average annual precipitation patterns, provided snowpack snow water, precipitation, and temperature information to help interpret what was happening during the entire January 9-16 event. Snow water equivalents and precipitation amounts of the Central Sierra Snow Lab and the Blue Canyon gage are also presented. Data collected at SNOTEL sites during this storm period appears to be quite accurate.
Keywords: Precipitation data, Rain on snow event, SNOTEL data site, Snow pillow data, Snowpack profiles chart, Temperature data

Predicting deposition of blowing snow in trenches from particle trajectories - Schmidt, R.A.; Randolph, K.L. (49th Annual Western Snow Conference, 1981)
The paper presents a computational procedure that estimates the location of deposition behind backward-facing steps, assuming blowing snow particles have streamwise velocities equal to the wind speed and vertical velocities equal to partical fall velocities. Results suggest that the efficiency with which snow is trapped in contour trenches is independent of height, for the range 1 to 2 m. Predicted efficiency is much smaller if the windward slope is uphill approaching the trench.
Keywords: Blowing snow, Contour trenches, Snow drifts, Snow trapping efficiency

Snow pillow behavior under controlled laboratory conditions - Smith, F.W.; Boyne, H.S. (49th Annual Western Snow Conference, 1981)
This paper describes a series of experiments which have been conducted on metal snow pillows of the type used in the SNOTEL (for SNOwpack TELemetry) data acquisition system. The tests were conducted in specially designed pressure chambers so that the conditions to which the pillows were subjected could be controlled. The test results reported in this paper include response to uniform pressure, the effect of varying tubing size and type, the effect of the stiffness of the metal pillow skin and the response of the pillow to the application of nonuniformly distributed load.A theoretical model is also presented which is intended to describe the behaviour of snow pillows under uniform loading conditions. The model includes the effect of skin stiffness and the effects of differing temperatures on different parts of a snow pillow/manometer installation.It was found that the theoretical model accurately predicts the snow pillow behaviour for uniform loading conditions and that the effects of skin stiffness are negligible for that case.
Keywords: Snow pillow, Snow sensor, Snowpack

Seven years of weather modification in central and southern Utah - Summers, P.C.; Griffith, D.; Ogden, V.C. (49th Annual Western Snow Conference, 1981)
A post-hoc statistical evaluation of an operational cloud seeding project, designed to enhance winter snowfall in the mountainous sections of central and southern Utah, was based on comparison between several control areas and multiple target areas. Linear regression equations were developed for each control-target area combination based on average January-March precipitation, 1956-1973; from 1974 through 1980 the target was seeded consistently during these months. Ratios of observed to calculated precipitation are presented for the target areas and several sub-target areas based on the predictions using the control area precipitation as predictor for the seeded years. Significance of the results was determined using a one-tailed Wilcoxon-Mann-Whitney ranking test. On the basis of this evaluation it is concluded that seeding has been successful in increasing the January-March precipitation within the intended target areas over the seven years seeded period.
Keywords: Cloud seeding, Target areas, Weather modification

The impact of Mount St. Helens ash deposition on snowmelt - Tangborn, W.V.; Lettenmaier, D.P. (49th Annual Western Snow Conference, 1981)
The effect of Mt. St. Helens ash deposition on snowmelt was evaluated by comparing runoff from four affected (target) drainage basins and three unaffected (control) basins. The target basins (Nisqually, Cowlitz, Cispus, and American Rivers) received from 5 to over 25 mm of ash, primarily from the major May 18 eruption, while the control basins (Cedar and Stehekin Rivers and Thunder Creek) received insignificant ashfall. Five day mean runoff ratios for target versus control basins were computed for the base period 1951-79 and compared with the same ratios for March-August, 1980. Temperature range was used as a surrogate for cloud cover. The results showed an identifiable increase in runoff from the Nisqually drainage following the May 18 eruption and less apparent but perceptible increases following the minor, initial March 27 eruption from all four target basins. Runoff from the Cispus, Cowlitz, and American basins showed a decrease in runoff following the May 18 eruption, possibly due to the insulating effect of heavy ashfall.
Keywords: Mt. St. Helens, Snowmelt runoff, Volcanic ash

Wagon Wheel Gap watershed experiment revisited - Van Haveren, B.P. (49th Annual Western Snow Conference, 1981)
The Wagon Wheel Gap watershed study is indeed a unique event in the history of snow hydrology. It was the grandfather of watershed management studies in this country. Fortunately, the authors of the final report on the Wagon Wheel Gap experiment included all the daily climatic and hydrologic data collected over the experiment's fifteen years' duration. Recently, these data were keypunched and stored for computer access. The final report of Bates and Henry stated conclusions that were not based on any vigorous statistical tests. A reanalysis and statistical treatment of the original data have brought to light some discrepancies with the findings of Bates and Henry. Over forty hydrograph parameters were currenly investigated. The important snow hydorlogy parameters and their response to watershed deforestation are discussed.
Keywords: Deforestation, Hydrograph analysis, Water yield increase, Watershed management

1980 Title, Contents, and Minutes (48th Annual Western Snow Conference, 1980)

Snowmelt observations in Alberta - Barnaby, I.E. (48th Annual Western Snow Conference, 1980)
Since 1970 there have been several snowpillows in operation in Alberta. Some are located in the plains area (shallow snowpacks) and others in the east slopes of the Rockies (deeper snowpacks). These pillows have provided suitable data during the active snowmelt seasons. This paper analyses that data. It was found that the measured snowmelt quantities from the snowpillow data compared favourably with that computed from the theoretical snowmelt equation developed by the U.S. Army Corps of Engineers (1960).
Keywords: Pressure pillow, Snow measurements, Snow pressure pillow, Snowmelt

Operational airborne measurement of snow water equivalent using natural terrestrial gamma radiation - Carroll, T.R.; Vadnais, K.G. (48th Annual Western Snow Conference, 1980)
The National Weather Service has recently implemented an operational airborne snow survey program in North Dakota, South Dakota, western Minnesote and a portion of Saskatchewan. The airborne technique is capable of measuring mean areal snow water equivalent over 6-10 Square Km flight lines in the upper Midwest. Additionally, it is possible to measure areal snow water equivalent at 250 m intervals along a flight line.
Keywords: Airborne snow surveys, Areal snow water equivalent, Nuclear Techniques

Snow drifting on phosphate mine dumps in southeastern Idaho - Chacho, E.; Molnau, M. (48th Annual Western Snow Conference, 1980)
The snowdrift model developed by Tabler (1975) was applied to 12 sites located on four mine waste dumps and two natural areas in southeast Idaho where windward ground slopes ranged from 18-48%. The model predicts snow drift slopes as a function of catchment area topography. Those sites with steep positive, leeward ground slopes showed good agreement with the snow slopes predicted by the model. The predicted snow slopes from sites with slightly negative or nearly flat leeward ground slopes matched the measured slopes but underpredicted the depth of the drift. For the sites with steep negative leeward ground slopes the model predicted negative snow slopes while the actual slopes were measured positive. It was concluded that Tabler's model requires some modification before it can be used in the phosphate mining area.
Keywords: Mining, Snowdrifts, Wind

Snowmelt modeling of upper Missouri river watersheds with SSAR - Cundy, T.W.; Brooks, K.N.; Sveum, D. (48th Annual Western Snow Conference, 1980)
Accurate predictions of snowmelt runoff from high elevation watersheds are needed to properly regulate six multipurpose reservoirs on the main stem of the Missouri River. In order to improve snowmelt-runoff forecasts and thus reservoir operations, the SSARR model was calibrated and tested using the snow-band option on the Madison and Gallatin River Basins. The temperature-index method was used to compute melt. The model was calibrated on 8 years of daily streamflow data, selected randomly from a 14 year record. The remaining 6 years were used for verification. Computed and observed volumes, peak, and timing of peak charges were compared statistically. This study demonstrated that the prediction of streamflow volune forecasts can be improved with the use of the SSARR model.
Keywords: Forecasting, Reservoir regulation, Snowmelt, SSARR model

Undisturbed measurement of the energy and mass balance of a deep alpine snowcover - Davis, R.; Marks, D. (48th Annual Western Snow Conference, 1980)
The testing and development of energy balance snowmelt models requires the undisturbed measurement of various energy exchange components, snow mass balance, and snow and soil properties. A micrometeorological station providing such measurements has been established in cooperation with the U.S.F.S. at 2930 m on Mammoth Mtn. in the southern Sierra Nevada. This site has an average winter snow depth of around 3 m, and can be as deep as 8 m. Radiometers measure incoming and reflected solar radiation in two wavelength bands, and incoming and emmitted thermal radiation in one wavelength band. Surface fluxes of latent and sensible heat are determined with a very accurate dew point sensor utilizing the `condensation mirror approach', two anemometers, and the measurement of emitted thermal radiation. Snow-soil thermal interaction is estimated using thermistor arrays at fixed spacing. Snow water content and average density are obtained from a snow pillow and depth stake. Dynamic measurement of snow settlement, and temperature profiles is done using a sliding platter device similar to that described by Swanson (1968) which allow a depth location with temperature.
Keywords: Micrometeorological Instrumentation, Snow hydrology

Proposed metric snow samplers - Farnes, P.E.; Goodison, B.E.; Peterson, N.R.; Richards, R.P. (48th Annual Western Snow Conference, 1980)
In June 1978 the Western Snow Conference selected a committee to develop a plan and criteria for unified development and testing of metric snow samplers. The proposed design of metric snow samplers is presented. Field meaasurements made both with existing and proposed snow sampling equipment are tabulated. Comparisons between different cutters and the accuracy of each based on 1978-79 data are presented. Criteria for the proposed metric snow samplers and procedures that can be used to modify present equipment are discussed.
Keywords: Equipment, Metrication, Snow sampling, Snow Water Equivalent

Mapping snow surface temperature from thermal satellite data in the southern Sierra Nevada - Frampton, M.; Marks, D. (48th Annual Western Snow Conference, 1980)
Mapping snow surface temperature over a large alpine area is a useful tool for monitoring the surface evergy exchange. In this study, Tiros-M satellite data are used to measure snow surface temperatures over very complex terrain in the southern Sierra Nevada. The satellite data are compared to extensive field measurements collected at the time of satellite overpasses. The reliability of the data is very good in areas of total snowcover (0.99 degrees K), but is degraded in areas of mixed trees or rocks, and snow. Because the satellite data were received in Field Station Format, accurate geometric rectification and subsequent registration to terrain coordinates was not possible. An approximate registration allowed the satellite determined surface temperatures to be used to compute incoming longwave and net radiation over the Glen Pass area in the southern Sierra Nevada. This is done to illustrate that satellite derived surface temperatures can provide useful information on the energy exchange over snow in an alpine environment which may lead to improved snowmelt runoff prediction.
Keywords: Remote sensing, Snow hydrology

A calibration procedure for airborne gamma ray snow surveys - Glynn, J.E.; Grasty, R.L. (48th Annual Western Snow Conference, 1980)
Using an airborne gamma ray spectrometer, nine pre-snow and nine snow flights were carried out at different altitudes over a site in eastern Ontario, based on air attenuation coefficients, snow-water equivalents were calculated for the total count (0.41 - 2.81 Mev), potassium (1.36 - 1.56 Mev), and thorium (2.41 - 2.81 Mev) windows. An iterative procedure incorporating height dependent stripping ratios was used to correct for Compton scattering in the snowpack and in the air. Soil moisture corrections were also applied. The standard deviation in the calculated snow-water equivalent from the total count, potassium, and thorium windows for the nine snow flights had values of .1, 1.2, and 1.3 cm water respectively and the results agreed with ground measurements of 14 +/- 3 cm.
Keywords: Gamma ray snow survey, Remote sensing

Importance of water supply forecasts in power planning - Gordon, W.R.; Lamb, R.C. (48th Annual Western Snow Conference, 1980)
Planning the power operation of the Federal Columbia River Power System (FCRPS) is dependent on water supply forecasts at many points within the Pacific Northwest. These water supply forecasts in turn are dependent on appraisals of the snowpack and precipitation throughout the basin. This paper will describe the FCRPS and define how supply forecasts are used in planning the power operation of the FCRPS.
Keywords: Columbia River Power System, Power operations, Water supply

Areal determination of the influence of a forest canopy on the surface radiant energy exchange - Marks, B.; Marks, D. (48th Annual Western Snow Conference, 1980)
To accurately model the energy balance of an alpine snowpack, the influence of a vegetation canopy on the surface radiant energy exchange must be known. A number of studies have been conducted to determine the shading effects of a canopy at a point. This paper presents a new method of estimating canopy cover density which can be extended over a large area. Canopy shading functions, developed from photographic techniques, describe the proportion of the hemisphere surrounding a point which is partially obscured by vegetation. A general diffuse shading function and a beam shading function which account for changes in solar zenith are presented. Both functions account for changes in canopy cover density with variations in snow depth. The technique presented is to be modified and tested during summer, 1980, so that it can utilize Landsat satellite data to determine canopy densities over a large area. The shading functions can then be used in areal models of solar and terrestrial radiation.
Keywords: Alpine climatology, Remote sensing

Snow management for crop production on the Canadian Prairies - Steppuhn, H. (48th Annual Western Snow Conference, 1980)
About 60% of the total area comprising the Canadian Prairies is devoted to the production of dryland crops, chiefly spring-seeded cereals, oilseeds and forages. Summer-fallowing to achieve adequate soil water prior to seeding is commonly practiced and removes 30% of the cultivated land from production annually. Although the natural snowcover contributes significantly to the water economy of the region, greater utilization of the total snow resource available could vastly reduce the area summerfallowed and increase production. Snow management has shown the ability to gain an extra 50 mm of overwinter soil water recharge, which about equals the extra quantity gained by summerfallowing. Manipulation to enhance snowcover retention also benefits the survival of winter crops. Management practices designed to harvest wind-blown snow on the Prairies include distributing field-sited fences, maintaining tall crop stubbles, planting arborescent field barriers, modifying soil surfaces, and leaving unharvested crop strips.
Keywords: Dryland soil water, Semiarid - crop production, Snow management, Snowcover, Soil water enhancement

Surface wind structure in forest clearings during a chinook - Swanson, R.H. (48th Annual Western Snow Conference, 1980)
During a chinook wind period, 5-8 April 1979, horizontal wind speed and its vertical component at 2 m height were measured in 12 circular 1 to 6 tree height diameter clearings in 20 m tall lodgepole pine forest in Alberta. These values are compared with horizontal wind speed in the centre of a 400 X 400 m clearcut and at 10 m above the tree canopy. Wind speed in all of the small circular clearings averaged about 1/20 of that above the canopy; that in the square clearcut was approximately equal. Vertical motion in 4 and 6 tree height clearings was 4 X that in the smaller ones.
Keywords: Clearcuts, Forest climatology, Forest hydrology, Wind profiles

Studying snowdrifting problems with small-scale models outdoors - Tabler, R.D.; Jairell, R.L. (48th Annual Western Snow Conference, 1980)
Drifts formed by snow fences are geometrically scaled in proportion to fence height. This observation led us to try using small scale models outdoors (on lake ice) to study snow deposition and erosion, thereby circumventing many of the well-known problems associated with simulating blowing snow in wind tunnels and water flumes. This paper briefly summarizes the theory of natural scaling and presents examples of successful outdoor modeling of snowdrifts formed by topographic features, guard rails, buildings, surface roughness, and snow fences on modeled terrain. Practical aspects of outdoor modeling are discussed, including advantages and disadvantages, site selection and preparation, selection of model scale, methods of model construction, weather requirements, and measuring techniques.
Keywords: Blowing snow, Model studies, Snow control, Snow deposition, Snow fences, Snow management, Snowdrifts

A watershed information system - Thomsen, A.G.; Striffler, W.D. (48th Annual Western Snow Conference, 1980)
The simulation approach to snowmelt runoff forecasting for high mountain watersheds is discussed. This approach uses Landsat imagery as a basis and adjusts to current conditions using remote or conventional information.
Keywords: Forecasting, Satellite imagery, Simulation

The spectral albedo of snow: effects of age, depth, cloud cover, sun angle, and impurities - Wiscombe, W.J.; Warren, S.G. (48th Annual Western Snow Conference, 1980)
We present a method for calculating the spectral albedo of snow which can be used at any wavelength in the solar spectrum and which accounts for diffusely or directly incident radiation at any zenith angle. For deep snow, the model contains only one adjustable parameter, an effective grain size, which is close to observed grain sizes. The model agrees well with observations for wavelengths in the near-infrared above 0.8 micro m. In the visible and near-UV, on the other hand, the model for pure snow may predict albedos up to 15% higher than those which are actually observed. The discrepancy is due to the presence in snow of trace amounts of small highly-absorbing particles of desert dust or carbon soot. At concentrations of only 1 part per million by weight or less, they can lower snow albedo in the visible by 5-15%.
Keywords: Aerosols - effect on snow albedo, Albedo, spectral, Dust - effect on snow albedo, Snow albedo

1979 Title, Contents, and Minutes (47th Annual Western Snow Conference, 1979)

Mean and extreme semi-monthly northwestern hemispheric snow boundaries from satellite records (1966-1979) and some surface data comparisons - Berry, M.O.; Scholefield, P.R. (47th Annual Western Snow Conference, 1979)
Using twelve years of weekly snow and ice boundary charts produced by the National Environmental Satellite Service, mean and extreme positions of the most northerly continuous snow boundary were determined for the beginning and middle of each month over the northern hemiphere. Standard deviations of the latitudinal positions of the boundary at five degree longitudinal intervals were determined to analyse snow-boundary variability. The seasonal advance and retreat of snowcover boundaries deduced from satellite data was compared with that depicted by conventional analysis based on surface observing stations. Based on these analyses, the variability of snowcover on a regional basis is discussed, as is the use of the results to monitor anomalies in seasonal snowcover on a near real-time basis. Major differences between satellite and surface station analyses, which occurred in areas like the North Ameriacan Cordillera, are described and related to terrain and other factors.
Keywords: Snow-line measurement

Large-scale air-sea interaction and atmospheric circulation patterns - Born, R.M. (47th Annual Western Snow Conference, 1979)
A general discussion of the large scale circulation patterns to the atmosphere and several mechanisms which could influence their year-to-year variability is presented. Specific processes accounting for the bulk of energy exchange between the ocean and atmosphere and the resulting effects upon the general circulation are described. From this bakground, the overall problem of short-term (months to seasons) climatic forecasting is discussed with particular emphasis upon the role of the oceans.A descriptive analysis is made of the last three winters in the western United States as specific illustrations of the general concepts.
Keywords: Air circulation, Climate

Microwave measurements of snow stratigraphy and water equivalence - Boyne, H.S.; Ellerbruch, D.A. (47th Annual Western Snow Conference, 1979)
This paper reports on a study of electromagnetic surface and subsurface scattering properies of snow using an FM-CW radar system operating in the frequency range 8-12 GHz. The scattering properties are interpreted and compared with the measured physical properties of snow such as density, stratigraphy, hardness and equivalent moisture content. The electromagnetic scattering properies are measured in situ under natural environmental conditions and the physical analysis is done at each test site to correlate the physical properties of the sample with its electromagnetic signature. Correlation between the electromagnetic and physical properies of snow are discussed. In particular, it is shown that there is a simple relationship between the 'optical' depth of the snowpack and the snowpack water equivalence, where the 'optical' depth, the square root of epsilon * d, is the product of the square root of the average dielectric constant, epsilon, and the physical depth, d, of the snowpack.
Keywords: Microwave measurements, Snow measurement

Application of meteor burst telemetry to snow hydrology - Burroughs, H.F.; Patterson, P.E. (47th Annual Western Snow Conference, 1979)
With the successful implementation of two hydrometeorological data acquisition systems using meteor burst technology during 1978, a review of associated capabilities and limitations is appropriate for the purpose of evaluating the potential of such systems for other planned automations.Data transmission via ionized trails in the upper atmosphere is accomplished by means of specially designed equipment configured in a network consistent with the survey requirement, radio path characteristics, and site conditions. The equipment must provide for a proper power budget, appropriate antenna arrays, capabilities for RF analog signal processing, data handling through digital logic circuits, and flexible sensor interface logic. A well designed software package is required to effectively control and command the system and to collect, organize, and forward sensor data.
Keywords: Telemetering equipment

The weather modification advisory board report - Cleveland, H. (47th Annual Western Snow Conference, 1979)
The report of the Weather Modification Advisory Board, presented to the Secretary of Commerce in July 1978 after 14 months of work, is discussed. The Board was appointed in response to the National Weather Modification Policy Act of 1976, and was charged with investigating the present status of the subject and developing a national policy theron. The conclusions of the Board are discussed including the conduct of a national research and development program and the creation of a commission called the National Weather Resources Management Board.
Keywords: Weather modification, Weather modification evaluation

Hydrochemical separation of components of discharge in alpine catchments - Collins, D.N.; Young, G.J. (47th Annual Western Snow Conference, 1979)
Waters produced from the melting of snow and ice are characterised by low solute contents. According to routing across alpine catchments, some waters are enriched chemically by passing through different hydrochemical environments. Meltstreams draining from the snouts of temperate glaciers exhibit seasonal and diurnal variations of both discharge and solute concentration, determined by the variable proportions of total flow from different sources which have followed different routes within the basin.Electrical conductivity, used to characterise meltwater hydrochemistry, was monitored continuously to provide detailed records of temporal variations of water quality. Proportions of flow routed through different hydrochemical environments can be calculated from simple mixing models using water quality diagnostics. Temporal variations of calculated components of total discharge defined by flow routing provide an indication of runoff formation from water rapidly traversing the catchment after melting and that delayed in transit as a result of storage within snowpack and glacier.
Keywords: Chemical analysis, Glacier runoff, Meltwater

Application of snowcovered area to runoff forecasting in the southern Sierra Nevada - Hannaford, J.F.; Hall, R.L.; Brown, A.J. (47th Annual Western Snow Conference, 1979)
Long-term snowcovered area data from aircraft and satellite observation made it possible to analyze the effect of snowcovered area on water supply forecasting procedures in California's southern Sierra Nevada. Water supply forecasting procedures utilizing snowcovered area as a parameter were developed on the Kings River and Kern River under the sponsorship of the California Department of Water Resources and NASA. 1978 was the first season with major snowmelt runoff since the procedures were developed, and snowcovered area was used operationally in making and updating the forecast through the period of snowmelt runoff.The forecast procedures developed for the Kern River did show a substantial reduction in error as the season progressed. Results were far from dramatic on the Kings. During 1978 a series of storms throughout the winter with extremely high freezing levels produced snowpack in the order of 200 percent of normal at higher elevations. The relatively high snow lines and lighter snowpack at the lower elevations were not consistent with snowpack at upper elevations.
Keywords: Aerial measurement, Models-snowmelt, Photographic measurement, Snow measurement, Water supply forecasting

Operational and technical considerations regarding recent forecast seasons in California - Hannaford, J.F.; Howard, C.H. (47th Annual Western Snow Conference, 1979)
The past three runoff seasons in California have resulted in some very unusual situations with regard to the preparation and use of operational water supply forecasts in California's Sierra Nevada. The 1976 season was near record low, followind by 1977 which was record low at about 15 percent of average runoff. This was followed by 1978 at over 200 percent of average runoff in some southern Sierra watersheds. These contrasting seasons represented the record minimum season runoff, the record minimum two year runoff, and the second or third highest runoff of record in the southern Sierra Nevada. Preparaton of forecasts during these seasons posed certain technical problems in presentation and use of water supply forecast of operational purposes. In addition, very unusual climatologic conditions further complicated the problem of analysing forecast probability and updating forecasts to meet changing conditions. This paper documents some of the technical and operational problems encountered by forecasters during this sequence of seasons in California.
Keywords: Water supply forecasting

Volume forecasts using the SSAR model in a zone mode - Kuehl, D.W. (47th Annual Western Snow Conference, 1979)
The redesign of the elevation zone computation routines of the watershed model of the SSARR system will make possible operational continuous simulation of snow accumulation and ablation for various elevation bands. Volume runoff forecasts can be prepared by the model using the model conditions for any date and subsequent temperature and precipitation sequences of previous years.Correlation between snow course observed snow water equivalents and simulated snow water equivalents in model zones are excellent. These results suggest combined use of temperature and precipitation model and observed snow course data will produce improved water supply forecasts. The model results will be valuable for (1) evaluation of snow courses and network design, (2) definition of snow climatology, and (3) interpolation and extensions of snow course records.
Keywords: Models, Snow Accumulation, Snow depletion, Snow survey network design, Water supply forecasting

Evaluation of streamflow forecasting methods - Lettenmaier, D.P.; Garen, D.C. (47th Annual Western Snow Conference, 1979)
Choice of a seasonal snowmelt runoff forecast model represents a tradeoff between data availability and the level of model complexity which can be justified. The basin storage accounting method, based on a storage estimate derived as the difference between accumulated low altitude precipitation and winter season runoff, with a correction for snow water equivalent observations represents a fairly accurate, although simple approach to forecasting seasonal runoff. The worth of precipitation and snow course data during the winter snow accumulation season, and the worth of forecasts of runoff forecast period precipitation may be evaluated in a relatively straightforward manner for such models. The evaluation is made directly through comparison of split sample seasonal forecast accuracy as a function of the number of precipitation stations and snow courses used. Precipitation forecast accuracy worth is assessed through comparison of split sample runoff forecast errors using long term average precipitation and recorded precipitation in the runoff forecast season, representing the range from no precipitation forecast to perfect precipitation forecast accuracy.
Keywords: Comparative forecasting methods, Digital models, Water supply forecasting

Modernizaton of the hydrologic data telemetry network in California - McCullough, C.A. (47th Annual Western Snow Conference, 1979)
California's hydrologic data telemetry differs from those existing in other states because of the breadth in both kinds of data collected and in the muliple uses to which the data is put. The first telemetered data by DWR was a reservoir stage in the 1920s used for water rights administration. Today we telemeter streamflow, precipitation, wind, snow water content, temperature, water quality, and reservoir stage. Combinations of the data are used for flood (river) forecasting, water supply forecasting during the snow season, and project operation. Systems have progressed from radio callup with counting of beeps, telephone callup with beeps, interrogation of remote logic stations from a console, to computer automated callup of all types of stations with automatic assembly of data files therefrom. Event reporting stations are also interrogated by computer. Present systems use radio, ground-based systems for communications; except for ten precipitation stations and one snow sensor which are being operated experimentally on the GOES satellite.The replacement of the North Coast-North bay system in the spring of 1979 will include microprocessors at each remote station as bid.
Keywords: Telemetering hydrologic data

CROHMS - an example of successful interagency coordination in data collection - Speers, D.D. (47th Annual Western Snow Conference, 1979)
In October 1978 the central computer facility for the Columbia River Operational Hydromet Management System (CROHMS) was placed into operation, thus marking the completion of 10 years of coordination between agencies of the Pacific Northwest in developing a shared data collection system. The CROHMS system consists of a number of automated remote data collection networks, under ownership and operational responsibility of several federal agencies, including the SCS SNOTEL System. Data being collected include snow water equivalent, precipitation, streamflow, and operating data from dams. Data from network controllers are periodically relayed to the CROHMS Central Facility, an extensive data bank in portland, where it is validated, stored, and made available to interagency users on a near 'real-time' basis. Basic policies for the interagency coordination were established by a Memorandum of Understanding, signed in 1970, and implementation has been carried out through the Hydromet Data Committee of the Columbia River Water Management Group.
Keywords: Computer operations, Computer procedures, Telemetering - hydrologic data

Snow blowing and snow fall on the North Slope, Alaska - Wendler, G. (47th Annual Western Snow Conference, 1979)
Blowing snow is a fairly common phenomenon on the North Slope of Alaska. Monthly mean values for blowing snow for a 10-year period are as high as 20% and 25% for Barrow and Barter Island, respectively. The higher values at Barter Island are the result of the somewhat higher windspeeds which occur there. At Barrow ENE or WNW winds are most frequently associated with blowing snow, while at Barter Island there is a main maximum with W winds and secondary maximum with E winds.Barter Island receives more snow than Barrow. At Barrow, snowfall occurs most frequently with easterly winds; in contrast, at Barter Island most falling snow is observed with westerly winds and there is only a secondary maximum of winds from the east.Finally, an empirical formula was developed which gives the frequency of blowing snow from the wind velocity and the amount of snowfall on a monthly basis for the North Slope of Alaska.
Keywords: Blowing snow, Snowfall probabilities, Snowfall studies

Interagency coordination in water supply forecasting: progress and opportunities - Williams, K.L. (47th Annual Western Snow Conference, 1979)
The author presents a manager's view of the major issues and challenges affecting interagency coordination in water supply forecasting. The impact of recent initiatives in government reorganization, and the instruction to phase out snow surveys and water supply forecasting in the Soil Conservation Service are discussed as they might affect interagency coordination. The evaluation and use of water supply forecasts are described before a discussion of past efforts asnd progress in interagency coordination. The impact of new technology applications on interagency coordination and some of the basic policy and operational questions for achieving desired ojectives are discussed as they relate to the snow telemetry (SNOTEL) system of the Soil Conservation Service.
Keywords: Policy - reorganization, Snow survey organization

1978 Title, Contents, and Minutes (46th Annual Western Snow Conference, 1978)

The California two-year drought - Brown, A.J. (46th Annual Western Snow Conference, 1978)
The paper reviews the two-year drought condition experienced in California in sufficient detail to obtain an understanding and appreciation of the effects of drought on water conservation and distribution in the State. It covers the effects of drought on agricultural interests, municipal and industrial water, recreation, fish and wildlife, energy, and forests and wild lands. It discusses the decisions made and actions taken to cope with the effects of the drought by state and federal water projects, by the Drought Emergency Task Force appointed by Governor Brown, and by local agencies. Finally, the paper reviews quickly the problems and special conditions encountered in making water supply forecasts during record setting low flow conditions.
Keywords: Drought, Water management

Surveying snow in arctic Alaska...to determine its effects on reindeer herding - Clagett, G.P. (46th Annual Western Snow Conference, 1978)
Reindeer herding in Western Alaska is being upgraded with the introduction of modern management techniques. Alaskan Eskimos intend to maximize meat production of their herds to augment subsistence dependency on a dwindling caribou population. An intensive management plan is being produced for over 4.5 million acres of the Seward Peninsula based on soil, vegetation and snow surveys. 95% of the reindeer range is windy, treeless tundra where the snow cover is relatively uniform and shallow. However, relentless winds pack the snow into slabs and crusts that greatly limit forage availability during critical winter months. Data from the first year's snow measurements present an interesting picture of the wind induced effects and indicate a solid basis for establishing mangement guidelines. The main instrument used was a RAM Penetrometer which deliniates the location, thickness and relative hardness of the various layers within the snow profile.
Keywords: Snow cover, Snow hardness, Snow trafficability

The care and feeding of snow pillows - Cox, L.M.; Bartee, D.; Crook, A.; Farnes, P.E.; Smith, J.L. (46th Annual Western Snow Conference, 1978)
Soil Conservation Service appointed an Evaluation Team in 1977 to evaluate the adequacy of the snow pillows and identification of causes for failure when failures occurred. This paper is a result of some of these findings. Several different designs and types of snow pillows have been built and tested. Two major types have evolved, the butyl rubber pillow and the stainless metal pillow. The snow pillow has been accepted by SCS and the California Department of Water Resources as their standard snow water equivalent sensor. Several years of record have demonstrated the fact that the snow pillow can accurately measure the snow water equivalent. There is also documentation that there can be problems in using this device. Although pillows appear to be rather simple devices, they are quite complex. Trained personnel must be available to install and maintain these devices to obtain good quality data. Certain procedures must be followed in order to obtain a satisfactory operational record.
Keywords: Snow pillow operation, Snow pressure pillows

Future operations with SNOTEL - Farnes, P.E. (46th Annual Western Snow Conference, 1978)
The implementation of the SNOTEL (Snow Survey Telemetry) by Soil Conservation Service will cause many changes in the methods, training, and analysis of current snow survey techniques. Real time data will provide significant input to streamflow models, filling the historic void of good data from the main water producing zone. Calibration of ungaged or gaged watersheds for inputing extreme storm events will provide improved design data for reservoirs and land use planning. Accuracy of short range streamflow forecasts will be improved. The frequency of manual snow surveys at most unautomated sites can be reduced to once or twice a year. The date of manual snow surveys will become less critical. Estimates of water equivalent at manual snow courses can be made for the first of each month based on real time data from SNOTEL sites and correlation methods. Manual surveys at automated sites can be limited to times when a site is visited for maintenance after an initial calibration period between snow pillow and snow course has been established. Field snow surveyors will become fewer in number, more mobile and better trained. Reports will be more aligned with changes in water supply conditions than calendar dates.
Keywords: Hydrologic data, Telemetry

Developing techniques for measuring precipitation - Foehner, O.H. (46th Annual Western Snow Conference, 1978)
Although precipitation has been measured for thousands of years, its reliability has been frequently (and justifiably) questioned. Within Project Skywater, a variety of field programs from California to Kansas underwrite instrument development and testing to improve reliablility and accuracy of data collection over wide areas at reasonable cost. Skywater data collection systems range from fence post gages to satellites. Instruments such as auto siphons and digitally recording radar have been tested with varying degrees of success. When measuring snowfall, comparisons indicated that both the snow pillow and the heated tipping bucket gage tended to undermeasure, while standard weighing bucket gages are subject to bridging and in heavy snowfall areas do not have adequate capacity. Although large orifice, high capacity weighing bucket gages hold promise of avoiding these problems, additional field tests are needed. Data relay alternatives have also been investigated. The Landsat satellite has been tested and compared with more conventional telemetry. The limited periods of response available from orbiting satellites has led to a current test with GOES for more frequent interrogations.
Keywords: Precipitation gages

Canadian snowfall measurements: some implications for the collection and analysis of data from remote stations - Goodison, B.E.; McKay, D.J. (46th Annual Western Snow Conference, 1978)
A summary of the accuracy of different snow gauges used in Canada is given. The results of field experiments carried out at the Cold Creek Hydrometeorological Research Station near Toronto demonstrated that the non-recording MSC Nipher shielded gauge displayed a superior catch efficiency compared to the Alter shielded Universal or Fischer & Porter recording gauges. The Fischer & Porter gauge had the lowest catch ratio of all gauges tested; yet, it is one of the most suitable gauges for operation at remote stations. Some of the implications for obtaining comparable precipitaton statistics for use in areal analyses and hydrologic models are discussed. Current research and development work on the Fischer & Porter gauge to increase its resolution to 0.25 mm resolution and to incorporate a built-in processing facility to correct for gauge catch deficiency is summarized.
Keywords: Precipitation Gages, Snow measurements

Automatic hydrometeorological telemetry network of Alberta - Graham, D.R.; Kerr, W.E.; Grauman, R.J. (46th Annual Western Snow Conference, 1978)
The planning of the Alberta Environment remote telemetry system began in 1974 and the first precipitation remotes were installed in early 1976. This system was designed to support four distinct subsystems: a) Air quality Monitoring Subsystem, b) Water Quality Monitoring Subsystem, c) Water Level Monitoring Subsystem, d) Water Level and Precipitation Subsystem. All of the Precipitation Subsystem and most of the Water Level Subsystem was designed and built by local firms to operate in extreme environment conditions. The specifications for the precipitation remotes stated that the equipment must operate in an environment between -40 degrees C and +55 degrees C, with relative humidities up to 99%. There are three distinct parts to the system. a) Automatic Collection of the Data; b) Transmission of the Collected Data; c) Receiving, Storing and Editing Data. The intention of this paper is to outline the system showing its present and future capabilities.
Keywords: Hydrologic data, Telemetering data

Microwave studies of snowpack properties - Hall, D.K.; Chang, A.T.C.; Foster, J.L.; Rango, A.; Schmugge, T. (46th Annual Western Snow Conference, 1978)
Research involving the microwave characteristics of snow was undertaken in order to expand the information content currently available from remote sensing, namely the mesasurement of snow-covered area. Microwave radiation emitted from beneath the snow surface can be sensed and thus permits information on internal snowpack properties to be inferred. The intensity of radiation received is a function of the average temperature and emissivity of the snow layers and is commonly referred to as the brightness temperature (Tb). The Tb varies with snow grain and crystal sizes, liquid water content and snowpack temperature. Multifrequency passive microwave aircraft measurements as well as in-situ measurements were obtained in 1976 and 1977 at Steamboat Springs and Walden, Colorado. The Tb of the 0.8 cm wavelength channel was found to decrease more so with increasing snow depth than the 1.4 cm channel. More scattering of the shorter wavelength radiation occurs thus resulting in a lower Tb for shorter wavelengths in a dry snowpack. Longer wavelengths such as the 21.0 cm can be used to assess the condition of the underlying ground.
Keywords: Microwaves

A comparison of three snowmelt prediction models - Haverly, B.A.; Wolford, R.A.; Brooks, K.N. (46th Annual Western Snow Conference, 1978)
A comparison of three snowmelt models is presented to provide a basis for snowmelt and related runoff predictions in Minnesota. The three models, representing three levels of complexity, were: (1) an accumulated Degree Day Model, (2) the Corps of Engineer's Generalized Snowmelt Equations, and (3) a modified Leaf-Brink Snowmelt Model. The overall objective of this study was to determine the accuracy of each of the three modeling techniques relative to their data requirements. The availability and measurement problems of required input data for each model were investigated for streamflow forecasting applications and hydrologic studies. The potential application of snowmelt simulation results to hydrologic runoff models is also discussed.
Keywords: Model evaluation, Water supply forecasting

BPA's hydromet data management system - Hearn, R. (46th Annual Western Snow Conference, 1978)
The Bonneville Power Administration (BPA) markets the electric energy generated at 30 Federal dams in the Pacific Northwest. Knowledge of the hydromet conditions over the Columbia Basin is necessary to develop forecasts of electric loads and water resources. Hydromet data is received on an hourly and daily basis by BPA's Realtime Operations & Dispatch System (RODS) located at the Dittmer Power System Control Center in Vancourver, Washington. The data is received via the Columbia Basin Teletype, BPA's telemetering hydromet network, and relay from National Weather Service computers in Suitland, Maryland. The data is directly inputted to load and streamflow forecasting models. The output from the forecasting models, in turn, is input to a computerized model of the Columbia River hydro generation system. The RODS system displays hydromet data in various CRT formats. It also performs validity checks on the data and provides an exception alarm capability. Examples of the various hydromet information prepared by the RODS system are given together with a discussion of plans for the future.
Keywords: Hydrologic data, Telemetering

Metrication of field equipment and operations for British Columbia snow surveys - Letvak, B. (46th Annual Western Snow Conference, 1978)
Metrication of British Columbia snow survey operations began with the Summary of Snow Survey Measurements 1935-75, and the Snow Survey Bulletin published in metric since 1976. Field operations for the plans for equipment changeover were devised. This paper describes the planning and implementation of conversion to complete field operations in metric. Production of metric field notes and new Sampling Guide is discussed. The program of equipment modification, inluding re-marking the snow tubes by our own staff is explained, including a description of costs and logistics of the operation. The question of sampling tube cutter testing as it relates to metrication is considered, as well as the future of equipment design.
Keywords: Metric sampler tubes, Snow sampler tubes

Pilot tests of satellite snowcover/runoff forecasting systems - Rango, A. (46th Annual Western Snow Conference, 1978)
NASA instituted Applications Systems Verification and Transfer (ASVT) programs to demonstrate and test the usefulness of developing technology in remote sensing. Because results from satellite snow mapping and runoff correlations have been encouraging, a cooperative, quasi-operational, four-year test program was started with various agencies in four major snow zones of the Western U.S. These areas were selected to test the capability of satellite systems for mapping snowcover in various snow, cloud, climatic, and vegetation regimes. Different satellite snowcover analysis methods are being used in each of the study areas. The snowcover data have been employed in illustrations of the effects of drought, in regression methods to forecast seasonal runoff, and in hydrologic models for simulations of daily streamflows. The suitabiliaty of the satellites for snowcover mapping in the various regions and the applicability of the forcasting techniques are being assessed. The final year of testing (1978) and a proposed operational snowcover system will be described.
Keywords: Remote sensing, Satellite, Snow cover sensing

Extended streamflow prediction during the California drought - Twedt, T.M.; Burnash, R.J.C.; Ferral, R.L. (46th Annual Western Snow Conference, 1978)
The California drought, which entered its second season during water year 1977, afforded an excellent opportunity to test and evalutate the Sacramento River Forecast Center (RFC) version of Extended Streamflow Prediction (ESP) during extreme hydrologic conditions. Because of the severity of the drought and its possible consequences, a wide variety of water users and managers had high interest in reliable long-range predictions during the year. The Sacramento RFC utilized a combination of a traditional regression-type water supply forecast approach, the more recently developed ESP model, and the rational analysis of hydrologic records from previous drought periods to produce such predictions. This paper presents a brief description of the development and operation of the Sacramento ESP model and discusses the resultant forecasts from these combined approaches.
Keywords: Long range forecasting, Water supply forecasting

A review of operational water supply forecasting techniques in areas of seasonal snowcover - Zuzel, J.F.; Cox, L.M. (46th Annual Western Snow Conference, 1978)
Examples of seasonal and short-term operational water supply forecasting models in use during the last 20 years and the economic relationships between forecast accuracy and monetary benefits are reviewed and discussed. The importance of input variables associated with forecast models such as soil moisture, antecedent streamflow, wind and others, in addition to the common variables of snow-water equivalent and precipitation, is discussed. A comparison of a precipitation regression model, a water balance model, a pattern search model, a multiple linear regression model, and the Tangboran-Rasmussen Hydrometeorological Streamflow Prediction model is made for six forecast periods on the Middle Fork of the Boise River in southwest Idaho. Results indicate that multiple linear regression and pattern search produce the most accurate forecasts, although data requirements are more stringent when compared to the other models.
Keywords: Model evaluation, Water supply forecasting

1977 Title, Contents, and Minutes (45th Annual Western Snow Conference, 1977)

Comparative evaluations of four snow models - Baker, M.B. Jr.; Carder, D.R. (45th Annual Western Snow Conference, 1977)
Land management planning requires estimates of resource outputs for use in evaluating alternative management practices. Simulation models are useful tools for providing these estimates, but model testing is a necessary step in their evaluation. Results of operating four available models on a common data set to simulate an actual snow regime are presented, along with information on sensitivity of outputs to changes in the input parameters used to operate each of the models. The results show that the models are most sensitive to the basic climatic inputs: precipition and air temperature.
Keywords: Models, Snow simulation model

SNOTEL: an operational data acquisition sysem using meteor burst technology - Barton, M.; Burke, M. (45th Annual Western Snow Conference, 1977)
This paper describes the implementation and operation of the SNOTEL System, a snow data acquisition system operated by the U.S. Soil Conservation Service. The SNOTEL System collects snow and other hydrometeorological data from snow courses in 10 Western states. Remote snow course data is telemetered to two central data collection points via the forward scatter meteor burst technique, the first such use of meteor burst communications. Data is available to users in each state, in near-real-time, via land-line access to a central data processing and storage facility. This paper discusses the key SNOTEL implementation decisions and their rationale, reviews key project milestones to date, describes the design and operation of the SNOTEL System, and presents preliminary data concerning sensor and telemetry system performance.
Keywords: Telemetering, Telemetering equipment, Telemetry equipment

Acoustic emissions in the investigation of avalanches - Bowles, D.; St. Lawrence, W. (45th Annual Western Snow Conference, 1977)
This paper reports on the results of several years of investigations into the role of ultrasonic emissions in the deformation and failure process in snow. The origin of ultrasonic emissions in snow is discussed and the manner in which these emissions enter tnto the process of deformation is considered. The results of several laboratory experiments are presented. In the laboratory acoustic emission investigations were conducted in a frequency range from 30 KHZ to 300 KHZ. Snow samples were subjected to various load and deformation histories and the acoustic response recorded. Laboratory investigations were also conducted to study the pattern of acoustic activity as it relates to the failure properties of snow.In the field, a two-year investigation was conducted to determine if the acoustic patterns observed under laboratory conditions would also appear in natural snow slopes. This study indicated that although the acoustic activity is not as well defined in situ, certain patterned responses are detected which relate to developing stability and instability in the snow pack.
Keywords: Avalanche research, Research ice and snow, Settlement of snowpack, Snow avalanche research

Microwave characteristics of snow - Ellerbruch, D.A.; Little, W.E.; Boyne, H.S.; Bachman, D.D. (45th Annual Western Snow Conference, 1977)
A program is underway at NBS to measure the microwave scattering characteristics of snow. Microwave signals nondestructively penetrate snow, but they are modified by the material properties of snow (density, free moisure content, resistance, temperature). There is a distinct possibility of developing miniaturized microwave instrumentation to remotely sense and measure those undisturbed snow properties as a function of time and depth. A portable FM-CW system was developed to measure electromagnetic profiles of snow packs down to ground level. This system was used to monitor changes in snow stratigraphy as a function of time of day. An Automated Network Analyzer system was used to measure the elecromagnetic scattering properties of snow at discrete frequencies over the range 250 MHz - 18 GHz. the snow was physically analyzed in terms of resistance, temperature, and density profiles, and by visual characterization. Some experiments included measurement of global radiation and liquid water at the snow surface.
Keywords: Microwave, Snow measurement

Value of water supply forecasts to irrigated agriculture - Elliott, S.J. (45th Annual Western Snow Conference, 1977)
A linear programming model is applied to three study areas of irrigated agriculture to produce matrices of revenues at various combinations of forecast and actual water supplies. Optimization techniques reveal value of forecast accuracy and the impact of error on revenues. Empirical data indicate value of agricultural production, number of irrigated acres served and vulnerability to water shortages for each forecast point. Comination of these data reveal potential loss of agricultural production due to forecast error and to lack of forecast. For various assumptions as to supplemental water supply the model shows net benefit to irrigators of water supply forecasts.
Keywords: Economics of water supply forecasting, Snow survey economic benefits, Water supply forecasting

The Southwest's frozen assets: snowpack management - Ffolliott, P.F.; Thorud, D.B. (45th Annual Western Snow Conference, 1977)
In the arid Southwest, less than 20% of the average annual precipitation is recovered for use by man. However, water yield improvement experiments have demonstrated the feasibility of increasing runoff from snow accumulations on forested watersheds through various management practices. Based upon the hypothesis that greater accumulations of snow contribute to increased runoff, the effects of reducing forest densities and removing forest overstories upon the amount of snow trapped and subsequently recovered in the form of snowmelt runoff--have been assessed. In addition, studies have been designed to examine the behavior of intercepted snow, while, theoretical studies, which supplement other investigations, have been undertaken. Hopefully, these research efforts will provide guidelines for forest management to enhance snowmelt water yield and, at the same time, be compatible with wood, forage, and wildlife production, and recreational use of forest lands.
Keywords: Snowpack management, Watershed management

Weather modification - a major resource tool - Foehner, O.H. (45th Annual Western Snow Conference, 1977)
Weather modification has been identified as a significant source of new water in several major planning documents including the 'Westwide Study' and 'The Report on Water for Energy in the Upper Colorado River Basin.' Project Skywater's results support these conclusions. There is increasing evidence that the potential for increasing the water supply of the Western United States through snow augmentation is very good. Recent evaluation of winter experiments provides new support for the estimated potential increase in snowfall with cloud seeding. A study is now underway to identify seedability criteria and increase efficiency through better control of seeding operations. Both additional research and new operational application of the existing technology are progressing in a number of locations including California, Utah, and Colorado.The impact on energy production, irrigation, water quality, municipal and industrial use, and recreation is significant.
Keywords: Economic aspects of weather modificatio, Weather modification

Impacts of energy development on the waters of the northern Great Plains - Fogarty, W.J. (45th Annual Western Snow Conference, 1977)
Development of the energy resources, particularly coal, is now and will continue playing an ever increasing role in the future of the West. The main questions are where, when and to what extent will the development occur. One of the main restricting factors in answering these questions is the availability of water. In the Upper Missouri Basin estimates are that agriculture accounts for over 90% of the present consumptive water use, urban growth approximately 4% and mining far less than 1%. Projecting to the year 2000 when coal production could reach 400 million tons annually, water consuption due to mining is predicted at 7-14,000 acre feet, which represents only about 1/10th of the current water consumption for the region. Energy conversion facilities principally gasification and electric generating plants, are being projected to use approximately 77% of the total annual consumptive use in the Northern Great Plains region by 2000. In 1970, the average annual streamflows in the Upper Missouri Basin amounted to approximately 26 million acre feet.
Keywords: Water consumption for energy, Water management

The avalanche warning program in Colorado - Judson, A. (45th Annual Western Snow Conference, 1977)
Avalanche warnings for Colorado originate from the Forest Service's Rocky Mountain 'Forest and Range Experiment Station in Fort Collins. The current program, which began on an informal basis in 1962, has been operating formally as a joint venture with the National Weather Service since 1973. More than 150 avalanche warning bulletins have been issued during the past 3 winters. The warnings cover part or all of the State's high mountains west of the 105th meridian. Principle components of the warning system include a network of 55 mountain reporting sites, custom made mountain weather forecasts that feature predicted quantitative precipitation amounts from an orographic precipitation model, an avalanche warning center, and a communications system for disseminating avalanche warnings to the public. The program, now in its fourth winter, is running smoothly. Warnings have been well received by the public, and response has been good. Development of danger-rating models and fine tuning of the newly developed orographic precipitation model for the Colorado mountains will continue to aid the warning program.
Keywords: Avalanche warning

NAIWMC--impact on hydrometeorologic measurements - Keyes, C.G. Jr. (45th Annual Western Snow Conference, 1977)
In January 1975, attendees from twenty-three states, three provinces and Mexico formed the North American Interstate Weather Modification Council. The main purpose of this organization is to achieve and maintain state and local control of weather modification activities while endeavoring to attain a high degree of legislative uniformity and an effective information exhange mechanism.Several states and provinces are aware of the requirement to develop necessary cooperation and communication between states to solve problems of interstate weather modification activities. Other states have defined their awareness of relationships with federal programs dealing with research and funding of future weather modification activities. Estimates are derived as to the impact on hydrometeorological measurements required by winter orographic programs which are supported by the North American Interstate Weather Modification Council. State and Federal legislation that is required to carry out such programs is also discussed.
Keywords: Weather modification, Weather modification controls

The application of aerial and satellite snow-mapping techniques for multi-purpose reservoir system operations in Arizona - Kirdar, E.; Schumann, H.H.; Warskow, W.L. (45th Annual Western Snow Conference, 1977)
Multipurpose reseroir system operations in central Arizona requires timely and dependable snowmelt information. This requirement led to aerial snow-mapping on the Salt and Verde watersheds in late 1965. Snow maps have proven to be a valuable decision-making tool for system operations. The maps have also been used in verification and improvement of satellite snow-mapping technique which was successfully applied by the Salt River Project during the 1975-76 runoff season under the NASA-ASVT program. Preliminary hydrologic analysis of snowmelt runoff is being made. Timely satellite snowpack information is being integrated into the decision-makeing process for multi-purpose reservoir system operations in Arizona.
Keywords: Mapping photography satellite, Snow cover photo mapping, Snow measurement

Remote sensing: snow monitoring tool for today and tomorrow - Rango, A. (45th Annual Western Snow Conference, 1977)
Although still a developing technology, remote sensing from airplanes and satellites is proving to be a unique means for monitoring snow characteristcs over large areas. The results of an ongoing quasi-operational test of satellite-derived snow-covered area (SCA) in snowmelt runoff prediction methods by three state and six federal water agencies are reviewed. Early indications are that the inclusion of SCA can result in a significant reduction of runoff forecast error on specific watersheds. In order to further improve forecasts, research is underway at Steamboat Springs, Colorado to exploit microwave capabilities for the eventual remote determination of snow water equivalent, depth, and free water content. Both active and passive microwave systems are being tested to determine the appropriate sensors for future operational aircraft and spacecraft platforms. A futuristic look at a total snow monitoring system that will eventually lead to improved management of our snow resources is provided. This system will incorporate rapid data relay and processing, remote sensing from a variety of satellites supplemented by low and high altitude aircraft, and improvements in ground-based snow measurement technology.
Keywords: Aerial and photographic snow measurement, Radiomicrowave sensing, Snow cover management, Snow line measurement, Snow research programs

Application of a new hydrometeorological streamflow prediction model - Tangborn, W.V. (45th Annual Western Snow Conference, 1977)
A mathematical model to predict seasonal streamflow, using only low-altitude precipitation gages and streamflow gaging stations, is described. The main features of the model developed are: (1) It can be implemented in any basin that has a large snow storage component, historical streamflow records, and precipitation observations in or near the basin. (2) It is based on simple but rational premises: that basin storage is approximately equal to winter precipitation minus winter runoff, that the catch of a low-altitude precipitation gage is proportional to nearby upland precipitation, and that storage is eventually released as summer streamflow. (3) It does not require expensive high-altitude installations to obtain data. (4) It incorporates a method to test and revise the estimate of storage available for release as summer streamflow.Tests of the model to obain retrospective predictions for the past 10 to 15 years are shown for basins in the North Cascades of Washington, the South Central Sierra Nevada, and for Norway. These tests show that the model appears to be about 20 percent more accurate than existing methods.
Keywords: Precipitation data forecasting, Water supply forecasting with prec data

Avalanche zoning: current status, obstacles and future needs - Tesche, T.W. (45th Annual Western Snow Conference, 1977)
The rapid expansion of winter recreational facilities, housing subdivisions, highways, mining operations and energy lifelines into mountainous areas has dramatically increased the frequency of man's exposure to avalanche disaster. Currently, the limitations of access to hazardous areas during periods of high danger and control over the construction of structures in hazardous areas are the most promising means of mitigating avalanche hazards. This paper focuses upon land use zoning regulations pertaining to avalanche hazard and the need for expanded zoning efforts in the Western United States.With the exception of the State of Colorado, avalanche zoning in the United States, where it exists at all, is piecemeal and fragmented. The general lack of consistent land use policy for natural hazard areas, particularly avalanche areas, stems from complex interactions between local socioecomomic, legal and political pressures. Confounding the avalanche zoning problem are current scientific problems in delimiting the snow avalanche hazard, improving hazard recognition, estimating destruction potential and encounter probabilities, and avalanche zone mapping.
Keywords: Avalanche zoning

National weather service extended streamflow prediction - Twedt, T.M.; Schaake, J.C. Jr.; Peck, E.L. (45th Annual Western Snow Conference, 1977)
A new technique under development by various elements of the Office of Hydrolgy, National Weather Service, for providing water supply forecasts is described. The method, known as Extended Streamflow Prediction (ESP), provides probabilistic streamflow predictions during any user-designated time period for headwater catchments. The ESP model utilizes physically-based conceptual hydrologic models and long-term historical records of precipitation and temperature to simulate a set of possible streamflow regimes conditioned upon the current hydrologic conditions of the catchment. The set of regimes can be analyzed for the following properties: total volume, maximum mean daily flow, minumum mean daily flow, or average mean daily flow for the period of interest and probability distributions developed. Thus, streamflow can be related to a desired chance of occurrence during the period and forecasts for predicted streamflow properties at user-selected levels of probability can be provided for any time period in the future. Applications to test catchments and proposals for future development are presented.
Keywords: Water supply forecasting

1976 Title, Contents, and Minutes (44th Annual Western Snow Conference, 1976)

The application of isotopic profiling snow gauge data to avalanche research - Armstrong, R.L. (44th Annual Western Snow Conference, 1976)
The Institute of Arctic and Alpine Research (INSTAAR), University of Colorado, has been conducting research into the nature and causes of snow avalanches in the San Juan Mountains of southwestern Colorado. An isotopic profiling snow gauge has been operated in conjunction with the research during five winter seasons. Specifications and a brief history of the development of the two types of gauges which have been operated at the Red Mountain Pass snow study site are presented.The structure of the existing snowcover and the amount and rate of additional new snow accumulation are of critical importance in avalanche studies. Conventional methods for acquiring this tpe of information are compared with data available from the profiling snow gauge. Additional data analysis relating to the study of the physical and mechanical properties of snow is presented. Techniques regarding the location, installation and operation of a profiling snow gauge for avalanche forecasting and research are discussed.
Keywords: Avalanche research, Radioactive snow gauges, Snow gauges

An estimate of watershed efficiency for a Colorado alpine basin - Carroll, T. (44th Annual Western Snow Conference, 1976)
A two year project was conducted during 1973 and 1974 in a 3 sq km alpine basin located tweny miles west of Boulder in the city's watershed. The spring snow survey taken at peak accumulation indicated that 67 cm of snow water equivalent was held on the basin. subsequent ablation measurements revealed that slopes with a southern aspect contributed most per unit area to stream discharge. Stream stage was recorded at two locations within the basin from May until the end of september. Annual discharge from the basin was estimated to be 2.15 * 10(6)m(3), enough to fulfull the treated water requirement of boulder City for approximately two months. A water budget for the basin was established in terms of generated discharge, precipitation, and evapotranspiration. From the water budget, watershed efficiency (output expressed as a percentage of input) was estimated to be in excess of 90%. This estimage is in agreement with that other workers have found for watershed efficiencies in the Rocky Mountain alpine zone. Partially as a result of the high watershed efficiencies found in alpine areas, it has been suggested that these areas might be used to increase water supply to populated areas of the Western United States.
Keywords: Ablation of snowpack, Water supply forecasting, Watershed basin analysis

A method for determining sensible heat transfer to late-lying snowdrifts - Cox, L.M.; Zuzel, J.F. (44th Annual Western Snow Conference, 1976)
A method of sensible heat transfer was determined by measuring the amount of snowmelt and latent heat transfer from a snow surface shaded with a large pan filled with melting snow.Results for five 24-hr periods are compared with the Corps of Engineers and Sverdrup's methods for determining sensible heat transfer.The main advantage of this method is that the sensible heat transfer can be easily determined without making meteorological measurements. However, the method is restricted to use on late-season snowpacks.
Keywords: Heat exchange, Heat Transfer, Snow, Snowmelt research

Synoptic patterns associated with heavy spring snowfalls in southwestern Alberta - Janz, B. (44th Annual Western Snow Conference, 1976)
Several of the spring storms producing heavy precipitation in southern Alberta exhibit a remarkably similar synoptic pattern. The essential features common to these storms appear to be a moist southerly flow aloft over southern parts of the province coupled with a 'deep northeasterly upslope'.The topograghy of western Alberta is discussed in relation to its influence on spatial and time variations of heavy snowfall.
Keywords: Snow storm, Storm patterns

Snow pillow experiences in a prairie (Alberta) environment - Kerr, W.E. (44th Annual Western Snow Conference, 1976)
The use of snow pillows for measuring solid precipitation in a prairie environment has been seriously questioned. However, our experience indicates that this gauging device can provide valuable information even under very unfavourable conditions such as: 1) Shallow snow packs (snow depth 20 inches) 2) Heavy drifting 3) Chinook areas 4) Isolated locationsComparisons of total catch under these conditions are made with Fischer & Porter, Belfort, Sacramento and Nipher precipitation gauges, and also with Standard snow course measurements. Guidelines for selecton of representative sites for precipitation gauges and snow courses under prairie conditions are presented. Snow pillow operational costs are also discussed.
Keywords: Snow gauge location criteria, Snow gauges, Snow pressure pillow

Metrication of British Columbia snow survey operations - Letvak, D.B. (44th Annual Western Snow Conference, 1976)
This paper describes various aspects of the metrication of snow survey operations in British Columbia as directed by the Hydrology Division of the B.C. Water Investigatons Branch. As with any large widespread operation, a change of this kind must be spread out over a period of time. However, as far as the public is concerned, the change was immediate, beginning in early 1976 with publication of a summary of all existing snow survey data for the Province, followed by the 1976 Snow Survey Bulletins, all in S.I. units.This paper discusses the choice of units, and the conversion of back data with respect to precision of units, conversion errors, and computer programming difficulties. The 1976 operations in mixed units are described, that is, the field measurements in the old system converted to published snow data and volume flow forecasts in metric.Finally, the changes in field equipment (sampling tubes, weigh scales, notebooks, automatic recorders, etc.) are discussed with repect to recalibratation of existing equipment and design of new equipment.
Keywords: Metrication

The SIMPAK program, application to simplified streamflow forecasting - Lyons, R.O. (44th Annual Western Snow Conference, 1976)
A computer program for streamflow routing and simulation of reservoir operations is described. The program was developed for the Fraser River basin in British Columbia, but is completely general and can be applied to any river. Also described is a novel use of this program for short-term streamflow forecasting using only streamflow data. This type of forecasting was found to be very simple and useful in directing flood control operations.
Keywords: Forecasting - digital computers, Water supply forecasting

Snow creep investigations near the Snettisham transmission line in southeast Alaska near Juneau - Meyer, R.L. (44th Annual Western Snow Conference, 1976)
This paper describes the installation of snow creep measuring devices along the Snettisham transmission line in southeast Alaska near Juneau. The investigation was undertaken to determine the effects of snow creep pressure on transmission line towers after several towers had failed. Information was gathered on snow creep, depth, density, and on other environmental parameters including wind velocity, direction, and duration. This information was utilized in the analysis of the transmission tower failures and was also essential to the determination of design criteria for future transmission line construction.
Keywords: Snow creep, Snow creep loading, Snow creep measurement

Nuclear techniques applied to hydrology - Morrison, R.G. (44th Annual Western Snow Conference, 1976)
Background information and history of nuclear applications will be discussed with a review of limitations presented by the different techniques.A slide presentation will be made of the operating equipment showing physical limitations in snow water equivalent, soil moisture, and precipitation measurements with present technology.Trade-off considerations will be presented regarding accuracy, updating frequency and power consumption on given systems.Operating experience will be reviewed on systems operating in Idaho, Colorado, and California.
Keywords: Radioactive snow gauges, Snow gauges

Flood forecasting - Oldman river basin - Mustapha, A.M.; Samide, G.W.; Kuhnke, W.K. (44th Annual Western Snow Conference, 1976)
In areas subjected to flash flooding, timely flood warnings can reduce the damage to property and lessen the danger to life. This paper discusses the effect of snowcover on major floods in the Oldman River Basin in Southern Alberta. It describes the steps involved in the development of the existing forecasting model for the Oldman River Basin and the associated problems and limitations in the forecasting procedure development are discussed.The steps involved in the preparation of operational real-time forecasts are explained, from the receipt of meteorologic forecasts and hydrometeorologic data to the generation of the flood forecasts and the issue of the actual flood warnings. Specific reference is made to the generation of the forecast for the flood of June 1975 in the Oldman River Basin.
Keywords: Flood forecasts

Grid square runoff model - Obedkoff, W. (44th Annual Western Snow Conference, 1976)
Long-range water resources planning in the semi-arid Okanagan basin in British Columbia where there has been substantial water use development requires dependable analytical methods for estimating flows. A five kilometer grid square runoff model using temperature, precipitation, snow course and estimated evapotranspiration data was developed for the Canada-British Columbia Okanagan Basin Agreement, a comprehensive water resource study of the Canadian portion of the Okanagan River. The model was developed by incorporating two independent water balancetechniques into the grid square method to simulate snowmelt and runoff on a mean monthly basis. The simulated runoff was compared with observed runoff for the total Okanagan basin and four major sub-basins. Reasonably accurate mean monthly runoff estimates were obtained.
Keywords: Statistical methods, Water supply forecasting

Water in freshly-fallen snow - Stashko, E.V. (44th Annual Western Snow Conference, 1976)
Water equivalents of freshly-fallen snow are expressed as a function of representative surface air temperature and snowflake size. The relationship yields a method of approximating past snowfall water equivalents closer than the 10 to 1 rule.
Keywords: Snow water equivalent

Areal water equivalents for prairie snowcovers by centralized sampling - Steppuhn, H. (44th Annual Western Snow Conference, 1976)
Accurate estimates of water quantities stored as snow covering prairie lands can improve runoff forecasting and agricultural management. Centralized sampling offers an efficient shortcut for determining mean, error-qualified, areal water equivalents in shallow snowcovers. This method reduces sample size and retains accuracy (1) by exploiting the close relationship between rural landscapes and snowcover distribution, (2) by separating sampling for snow depth from sampling for verical density, and (3) by sampling for density selectively based on a central depth statistic. Snow data for 1972-75 from 23 areal landscapes in Saskatchewan showed that reducing sample numbers by 1/5 or less resulted in average deviation from the mean areal density of 3.3, 3.1, or 4.8% for the mean, mode,and median depth statistic, repectively. Centralized sampling will comlement any snow meaurement technique, including ground-based tube-coring and serial gamma-sensing.
Keywords: Snow cover analysis

Comparison of precipition-gauge and snow pillow data from a severe april snowstorm in a mountain watershed - Storr, D.; Golding, D.L. (44th Annual Western Snow Conference, 1976)
Snow pillow data for a severe April snowstorm are not in conflict with data from precipitation gauges when the theory of delayed response of the pillows is applied. However, there are other problems with abstraction of data from snow pillow charts for short period, such as the effects of atmospheric pressure and temperature. The storm isohyetal pattern suggests that convergence in the low pressure area is more important than orographic lifting in precipitating the atmospheric moisture. The 24-hour snowfall at one gauge site was over 50% greater than the 100-year return-period value that would have been expected from the 11 years of previous record.
Keywords: Snow gauge comparisons, Snow gauges

Snowmelt recharge on a shortgrass prairie site - Van Haveren, B.P.; Striffler, W.D. (44th Annual Western Snow Conference, 1976)
An analysis was made of the contribution of winter precipitation to soil water recharge for the 1970-71 winter period on the IBP Pawnee Site in northeastern Colorado.Soil water recharge was inferred from periodic measurements of soil water content with a neutron probe at 60 sampling locations. The sampling design included three grazing treatments, five levels of poition -on-slope, and two slope orientations. Indices expressing the importance of snowmelt recharge ot total soil water recharge (the 'snowmelt recharge ratio'), and the importance of snowmelt recharge to winter precipitation (the 'snowmelt recharge efficiency'), were computed and analyzed for treatment effects.
Keywords: Snow cover, Snow cover analysis

A portable profiling snow gauge - results of field tests on glaciers - Young, G.J. (44th Annual Western Snow Conference, 1976)
During the past two years a 'Digiray' portable profiling snow gauge used in conjunction with a Mt. Rose sampler has been tested for accuracy, reliablity and convenience on glaciers in Western Canada. There have been several small mechanical failures, but the electronics have on the whole proven reliable. The instrument has to be back-packed and this can be done conveniently if three men are available. The most important single limitation to the effectiveness of the system lies not in the accuracy, reliability or convenience of the probe itself but in the difficulty of cutting through very compact snow and ice lenses at depths exceeding 6 m with a Mt. Rose sampler. Despite several reservations about the system it is still regarded as a practical alternative to digging deep snow pits.
Keywords: Glacier coring, Glacier research studies, Radioactive snow gauges, Snow gauges

1975 Title, Contents, and Minutes (43rd Annual Western Snow Conference, 1975)

SNOTEL - automated snow surveys - Barton, M. (43rd Annual Western Snow Conference, 1975)
The Soil Conservation Service is currently in the process of implementing an automated westwide snow survey and related hydrometeorological data telemetry system called SNOTEL. This system, to be installed during the next 5 years, will be providing on-call data as frequently as once an hour from 500 key locations in the western United states. These data will be available on a 'near' real-time basis to users and cooperators.This paper describes the data network, type of sensors, communication system, telecommunications network, terminals, asnd computer control system which in total will make up the SNOTEL system.
Keywords: SNOTEL, Telemetering hydrologic data

Removal of nitrogen from snowmelt water by the soil-vegetation system, Lake Tahoe basin, California - Coats, R.N.; Leonard, R.L.; Loeb, S.L. (43rd Annual Western Snow Conference, 1975)
Most of the precipitation in the Lake Tahoe basin falls as snow between October and May. Fresh snow usually contains concentrations of inorganic and organic nitrogen that far exceed those found in highly oligotrophic Lake Tahoe. Algal productivity in the lake is most sensitive to additions of the nutrient ion, nitrate. Research by the Tahoe Research Group in the Ward Valley watershed near Tahoe City has revealed that over 80% of the nitrate-nitrogen in the snowpack is removed by the natural soil-vegetaton system prior to the entry of melt water into the stream and lake. Soil disturbance and vegetation removal can severely damage the effectiveness of the nitrogen removal process. Construction practices in this subalpine environment should be carefully controlled to minimize destruction of the natural protective cover on sensitive sites. We are attempting to identify such sites and to evaluate the impact of development on nitrate release to the aquatic sysem.
Keywords: Snow - Analysis - Chemical, Snowmelt research