Lateral Water Redistribution During Spring Snowmelt and Simulated Rain-On Snow Events

Publication Date

Summer 2009

Type of Culminating Activity


Degree Title

Master of Science in Hydrologic Sciences



Major Advisor

James P. McNamara, Ph.D.


Lateral water movement through snow is a process that is often presumed to be induced by the occurrence of ice layers within the snowpack that serve as impermeable boundaries to vertical infiltration. We present evidence that lateral movement of water occurs in several different snowpack types, and that lateral water movement was often an important process in snowpacks where ice layers were either non-existent or rare. In snowpacks where considerable lateral movement of water was observed, water was routed laterally due to micro-scale stratigraphic variability, or increased liquid water within the snowpack, rather than from ice layers. We investigated the occurrence of lateral flow in a melting snowpack by performing passive dye tracer experiments during the spring of 2007 and 2008. These experiments showed that dye traveled distances on the order of several meters down slope before reaching the base of the snowpack with the majority of lateral flow occurring along saturated layers within the snowpack. We also performed rain-on-snow simulation events over four different snow pack types (representing three different snowpack types) within the Shafer and Sinker Creek watersheds northeast of Boise, Idaho. Rain-on-snow simulations were performed over a 4.0 m2 plot, with an average rainfall intensity of 18.81 mm-hr-1. The results from these experiments show that liquid water from snow melt or rain-on-snow events often does travel laterally through the snowpack, and that the snowpack does not drain water solely from the base during spring melt, nor do they store all water from rain-on-snow events within the snowpack.

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