Date of Final Oral Examination (Defense)

5-2012

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Hydrologic Science

Department

Geosciences

Major Advisor

James McNamara

Second Advisor

Shawn Benner

Third Advisor

Hans-Peter Marshall

Abstract

Understanding the mechanisms by which catchments route vertical water inputs laterally to stream channels is central to the development of accurate predictive models of watershed processes. It is commonly assumed that lateral redistribution occurs as overland or subsurface flow. Lateral flow can also occur within the snowpack during rain-on-snow (ROS) events or spring melt, sometimes resulting in surface expressions commonly called "runnels." This thesis examines lateral flow through snow and the role of the snowpack as a rapid down-slope water delivery mechanism, with the goal of determining if lateral flow through snow is an important control on streamflow generation and soil moisture.

To quantify the flux of lateral flow through snow, we installed two identical 4 m2 snowmelt lysimeters side-by-side on a 20 degree slope in the snow dominated Dry Creek Experimental Watershed, near Boise, Idaho. One lysimeter was blocked from lateral upslope inputs (control site) while the second lysimeter was not (experimental site). Both lysimeters were blocked on the downslope side. The experiment was designed so the total volume of water routed laterally through the snowpack could be estimated from the difference between the two plots. Through the 2010-2011 snow season, the experimental lysimeter collected ~47% more meltwater than the control lysimeter with ~34% of the total difference between the plots occurring during one major ROS event in mid-January, 2011. Further, results of a snow vs. soil tracer comparison provide evidence that the snowpack serves as an effective down-slope water delivery mechanism that may help contribute to streamflow generation and soil moisture variability.

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