Submitted to: Western Snow Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 10/1/1997
Publication Date: N/A
Interpretive Summary: In western North America, the majority of much needed surface water supplies, and floods with their associated hazards, come from melting mountain snowpacks. Daily snowmelt rates are highly correlated to subsequent runoff, however,detailed information about snowmelt characteristics over wide areas and different climatic zones is historically lacking. Snow data from 94 sites located in nine topographical regions within the western United States were analyzed. The general patterns of snow build-up or accumulation and depletion or melt,are quite similar throughout the study area. However, the timing of snow accumulation, and particularly snow-melt, varied considerably depending on the peak amount of snow accumulation and site conditions such as aspect and exposure. Maximum daily snow-melt rates generally occurred late in the snow-melt season when temperatures were warmer and most of the nearby snow cover had melted. Maximum daily snow-melt rarely exceeded 90 millimeters per day. More detailed and accurate information on snow-melt characteristics can be used for improving estimates of snow-melt runoff volume and peak flow amounts. Improved water supply forecasts would allow reservoir managers to allocate available resources with increased efficiency, saving both natural and financial resources.
Technical Abstract: Snowmelt is affected by a number of factors including elevation, slope, aspect, exposure, snowpack depth, surface reflectance and climatic or meteorologic variables such as solar radiation, temperature, wind speed, vapor pressure, and precipitation. Snowmelt models attempt to account for these factors in various degrees from simple empirical relationships based on air temperature to detailed energy balance procedures. Detailed energy balance models should be superior in estimating snowmelt,but ade- quate data sets are rarely available to use these methods without making simplifying assumptions. Unfortunately, these simplifications usually reduce the models' ability to account for the meteorologic factors that cause snowmelt to occur. Thus the models produce estimates of snowmelt based on the input data available and the assumptions required, but these estimates may not relate to actual snowmelt in timing or rate. Since actual snowmelt data is very limited, it is seldom possible to compare model simulated melt rates with actual values. This paper is significant because it presents an analysis of snowmelt data under a variety of conditions encountered at representative SNOTEL sites selected from nearly 600 locations in the western United States. It thus provides a range of snowmelt information including average and maximum snowmelt that can be used to compare with snomelt model simulations and other uses.