Geostatistical methods for estimating snowmelt contribution to the seasonal water balance in an alpine watershed
Date
2006
Authors
Hultstrand, Douglas M., author
Fassnacht, Steven R., advisor
Stednick, John, advisor
Doesken, Nolan, committee member
Musselman, Robert, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
The performance of nine spatial interpolation models was evaluated to estimate snowmelt contributions to streamflow in the West Glacier Lake watershed (0.61 km2), in the Snowy Range Mountains of Wyoming. Streamflow from the West Glacier Lake watershed has been previously estimated at 40% to 130% greater than measured precipitation inputs. Additional input into the watershed had been attributed to a permanent snowfield in the upper portion of the watershed covering approximately 2.4% of the watershed area. However, the excess output may be a result of inaccurate estimation of water quantities using current precipitation and stream gauging methods. In April 2005, near peak accumulation snow depth measurements and snow density measurements were collected within West Glacier Lake watershed. The distribution of snow water equivalent (SWE) was calculated as the product of snow depth, snow density, and snow-covered-area (SCA). Snow depths were spatially distributed throughout the watershed through nine spatial interpolation models. Snow densities were spatially distributed through a multiple linear regression. The nine spatial snow depth models explained 18% to 94% of the observed variance in the measured snow depths. Co-kriging with solar radiation produced the best results explaining 94% of the observed variance in snow depth measurements. The annual water balance, expressed as equivalent water depths for water year 2005, was total precipitation (1,481 mm), snowpack sublimation (251 mm), and streamflow (1,000 mm), resulting in an evapotranspiration estimate of 230 mm. Estimated SWE from the field survey data was 67% greater than precipitation gauge estimates and accounted for 85% of the annual streamflow. Summer precipitation was not a significant contributor to the annual hydrograph and was also less than snowpack sublimation. Precipitation gauge values were unrepresentative of actual precipitation depths, and several spatially distributed snow depth models provided better estimates of precipitation inputs.