On the Role of Spatial Snow Distribution on Alpine Catchment Hydrology

The spatial distribution of alpine snow is largely governed by topographic complexity through shading of solar radiation and wind redistribution. While radiative shading is relatively consistent between years, wind redistribution is more variable, capable of producing anomalous areas of deeper snow that can persist into the late-summer and early-fall months. In a warmer future climate, we hypothesize that snow will become wetter and heavier than in the current climate, leading to less wind redistribution and a more homogeneous snowpack. This study seeks to investigate how the relative degree of snow redistribution will impact total streamflow generation in an alpine environment. A distributed hydrologic model is applied together with remotely sensed spatial estimates of snowpack in order to quantify the impact of spatial variability of snow water equivalent on streamflow. Preliminary findings for the Green Lakes Valley within the headwaters of the Boulder Creek watershed in Colorado, 2001–2014, show that more uniform snow distributions lead to earlier melt-out of 47 days on average and tend to produce less overall streamflow, with maximum decreases as large as 9.5% relative to the natural case. Overall, this analysis aims to provide insight into how warming-mediated changes in snow distribution will impact water resources in critical streamflow generating headwaters catchments.