Snow Water Equivalents Modeled at the Mesoscale
with Geographic Information Systems
Jason Carey1
Snow water equivalent (SWE) is spatially distributed within the mountainous basins of climates
marked by a seasonal snowpack. This distribution is directly linked to mesoscale physiography such
as slope, solar aspect, elevation, canopy, wind transport zones and avalanche tracks, and to time. In
the Oquirrh Mountains near Salt Lake City, the SWE distribution of seven subbasins has been mod-
eled with Geographic Information System technology and a Digital Elevation Map of the area. The
purpose of the model is to obtain accurate estimates of SWE for smaller basins. The modeled subba-
sins are on the order of 1 km2. Individual maps of mesoscale physiography were developed as the
controls of SWE distribution. Daily water-year 1997 data from three SnoTel stations were compared
with the SWE physiographic maps. Using snow accumulation theory and a statistical analysis of
ground measured data, individual SWE distribution models were fit with the mesoscale maps of
solar aspect, elevation, vegetation, and basin area. The SWE distribution models, representing either
loss or gain, were then combined in chronological order to model total snow accumulation for a
period. Peak SWE was calculated for March 7, 1997, using the mesoscale accumulation model. A
total SWE of 1882.74 acre-feet, 35.6% of average Bingham Canyon annual precipitation, was calcu-
lated for peak. Modeled site locations had a very good linear correlation (0.97) with measured site
data. A ridge line cornice model contributed 51.99 acre-feet SWE, 2.7% of peak. The Snow Estima-
tion and Updating System (SEUS) is implemented by the Colorado Basin River Forecast Center for
macroscale SWE calculations. SEUS modeled 3569.35 acre-feet, 190% of the mesoscale model, for
the same area and period. This study shows that the scale of the study area determines the influence
of the mesoscale distribution on basin-wide SWE determination.
1
University of Utah, 1250 W. Winchester, Salt Lake City, Utah 84123, USA
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