Summer soil moisture loss at Utah SNOTEL sites and streamflow recession at nearby gauges: variability in runoff generation and the potential for flow forecasting

Abstract

This analysis compares decreases in soil moisture (SM) at Utah snow telemetry (SNOTEL) sites during the summer months with discharge at nearby stream gauging locations using data from water years 2008–2012. The following characteristics were evaluated: (1) the influence of the SM loss at mid-depths (20 cm) on hydrograph recession, (2) the influence of moisture loss from deeper portions of the soil (50 cm) on late-season baseflow and (3) the timing of this transition. Thirty-four pairings were used between SNOTEL sites and nearby stream gauges 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 gauges (e.g. >30-km, >1000-m elevation difference for the best pairing). At such sites, transition timing in 2013 (between predominantly 20- vs 50-cm SM loss) was well predicted from 2012 data given the similarity in water years, with discharges at the transition point less than 30% different than observed values in 2013. An index of the robustness of each pairing was generated to determine where this type of analysis might be most successful; however, results suggest that identification of high-quality pairings may need to be site by site. Published 2015. This article is a U.S. Government work and is in the public domain in the USA.