Soil Moisture Dynamics During Snowmelt

TitleSoil Moisture Dynamics During Snowmelt
Publication TypeConference Proceedings
Year of Conference2014
AuthorsSutcliffe, Kent
Conference Name82nd Annual Western Snow Conference
Series TitleProceedings of the Western Snow Conference
Date Published2014
Conference LocationDurango, Colorado
Keywordsactive melt, diurnal fluctuation, snow, snowmelt, soil moisture

Little research exists examining soil moisture characteristics under a snowpack, especially during the active meltout period. Unlike snow water equivalent (SWE) and snow depth, which has been measured by the Snow Survey Program for 80 years, soil moisture changes during meltout have been difficult to monitor and analyze. Advances in sensor technology, increased deployment of instrumentation, and longer period of records present new opportunities for analysis and a better understanding of soil moisture dynamics under snowmelt. Three characteristic annual soil moisture patterns are discussed. Analysis of hourly soil moisture, SWE, and precipitation data have resulted in the observation of new relationships between daily snowmelt and soil moisture. At most SNOTEL sites, snowpack melt results in diurnal soil moisture fluctuations. At well-drained sites, during periods of rapid melt, fluctuations of up to 10 percent soil moisture by volume are observed. Typically, fluctuations are expressed by all three sensors through the 50 cm measurement zone during the entire meltout period, or until saturation is reached. Diurnal fluctuations in soil moisture scale in magnitude with the SWE loss during the same period. At sites with well-drained soils and no run-in from adjacent areas, the volume of water transmitted through the entire 50 cm zone correlates well with the volume of SWE loss on a daily basis. Four select sites with different soil properties and geographic areas within Utah and California are examined and the correlation between SWE and soil water flux is quantified and found to range from an R2 of 0.50 to 0.76. Analysis of diurnal soil moisture fluctuation provides a valuable window into the significant water flux occurring during the melt cycle and may assist in making soil moisture a quantitative input in statistical-based streamflow forecasting.