Constraining Kilometer-Scale Mountain Snow Transport and Snowshed Areas

Snow transport (wind drifting and avalanches) can concentrate a large amount of water into a relatively small area, in contrast to precipitation, which is spatially smoother. I develop a framework to constrain the minimum effective seasonal transport necessary to explain observed snowpack patterns. In the Wind River Range, Wyoming, extensive deep snow (4–6 m snow water equivalent, >0.01 km²) is the result of long-distance transport, with about half of the seasonal accumulation originating >1 km upwind. Cirque glaciers on the downwind margins of alpine plateaus can accumulate snow from contributing source areas exceeding 2–3 km². Interbasin snow transport augments local snowfall by at least 22% in a glaciated first-order stream catchment (2 km²), with the upwind “snowshed” doubling the effective catchment area. Snow imported across topographic divides is equivalent to 7% of annual streamflow in a 125 km² watershed. Kilometer-scale snow transport is an underappreciated driver of mountain snowpack heterogeneity.