Spatial Properties of Snow in an Alpine Basin, Colorado Front Range

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precipitation, wind redistribution of snow, and surface energy fluxes during the accumulation and

ablation season. No widely suitable method yet exists to directly measure the spatial distribution of

SWE in rugged mountain regions. The problem of determining the volume and distribution of snow-

pack water storage within mountain basins remains acute. The test basin used in this study was the

Green Lakes Valley (8 km2), which lies in Colorado's Front Range, just west of the city of Boulder.

Intensive snow surveys were carried out in GLV on two dates near maximum snow accumulation of

the 1996 water year. More than 550 depth measurements were taken and 17 snow pits were excavat-

ed for density during the two field sessions. Snow depths were measured using aluminum sounding

probes. Snow density was measured in snow pits. Data from intensive field surveys are statistically

analyzed to determine inherent spatial properties. We quantify the relationship between spatial vari-

ability of SWE and variability in the controlling physical factors, such as topography and net solar

radiation, which have correlated with SWE distribution. Classic spatial statistical methods are em-

ployed to determine spatial characteristics and uncertainty in estimations of SWE distribution. The

data set is used to further test scale effects on a model (SWETREE) developed for distributing SWE

in complex terrain. SWETREE uses binary decision trees (regression trees) to determine the spatial

distribution of SWE by relating physically based independent variables (net solar radiation, topogra-

phy, soil and vegetation cover type) to measured SWE to estimate SWE over a gridded domain. This

research improves our understanding of spatial scaling properties of snow water equivalence from

point to basin scales.

Colorado State University, Department of Earth Resources, Fort Collins, Colorado 80523, USA

National Weather Service, 1735 Lake Drive West, Chanhassen, Minnesota 55317, USA