Predicting Streamflow Hydrograph Recession from Soil Moisture Loss at Utah SNOTEL Sites

TitlePredicting Streamflow Hydrograph Recession from Soil Moisture Loss at Utah SNOTEL Sites
Publication TypeConference Proceedings
Year of Conference2014
AuthorsClayton, Jordan
Conference Name82nd Annual Western Snow Conference
Series TitleProceedings of the Western Snow Conference
Date Published2014
Conference LocationDurango, Colorado
KeywordsSNOTEL, Snow water equivalent, soil moisture, streamflow recession, Utah, Water supply forecasting

This analysis uses decreases in soil moisture (SM) at Utah SNOTEL sites during the summer months to predict discharge at nearby stream gaging locations during the recessional portion of the annual hydrograph using data from water years 2008-2012. The following characteristics were evaluated: (a) the influence of the SM loss at mid-depths (8”) on hydrograph recession; (b) the influence of moisture loss from deeper portions of the soil (20”) on late-season baseflow; and (c) the timing of this transition. Thirty-four pairings were used between SNOTEL sites and nearby stream gages in select locations throughout Utah, for 3-5 years each depending on data quality, to generate 143 total comparisons of soil moisture loss and stream discharge. Regressions were fairly strong (r2 > 0.8) where the SNOTEL site was in a location with slow meltout rates, ample infiltration, and minimal summer precipitation. In a few cases the correlation was remarkably strong (r2 > 0.95), even for SNOTEL sites located far from respective stream gages (e.g. >20 mi, >3500’ elevation difference for the best pairing). At such sites, transition timing in 2013 (between hydrograph recession and baseflow, and between predominantly 8” vs. 20” SM loss) was well predicted from 2012 data given the similarity in water years, with discharges at the transition point predicted from SM loss in 2012 less than 30% different than observed values in 2013. Conversely, predictions of discharge were poor where timing was not coincident between soil moisture and discharge due to poor infiltration, intense summer precipitation, flow control structures, or other factors. An index of the robustness of each pairing was generated to attempt to develop predictive relations for where this type of analysis might be most successful for a given type of water year (normal, abnormally dry, or abnormally wet) based on watershed characteristics (e.g. average peak SWE, basin runoff production, etc.); however, results suggest that identification of high quality pairings may need to be site-by-site.