Submitted to: American Geophysical Union
Publication Type: Proceedings
Publication Acceptance Date: 9/8/1999
Publication Date: N/A
Technical Abstract: The purpose of this study is to understand hydrologic behavior at a small semi-arid mountainous watershed in order to construct a hydrologic model, which can later be scaled up to larger watersheds in the same region. We take a data intensive approach to understand the hydrologic processes acting in the watershed. Measurements used include maps of snow water equivalence surveyed manually on a 30 m grid, streamflow, precipitation, weather and radiation. Wind driven snow drifting combined with variable radiation exposure on rough terrain produces a consistent (from year to year) spatial distribution of snowpack in the watershed. Spatial variability of surface water input is identified as the dominant hydrologic process in this watershed. We use the drift factor approach to parameterize wind blown snow drifting in the watershed. The drift factors are obtained by calibration using manually surveyed snow water equivalence maps during the accumulation and drift period. Earlier studies have examined annual water balance at this watershed by dividing the watershed into three zones based on drift patterns, oil types and vegetation. We show that these zones can be obtained from the distribution of calibrated drift factors. The timing of surface water input on the zone corresponding to deep drifts on the north-facing, leeward slope corresponds closely with the timing of streamflow at the outlet. A lumped hydrologic model is developed which consists of (a) simple parameterization of evapotranspiration, (b) infiltration into the soil zone and recharge to the saturated zone, and (c) subsurface storage-discharge function. This model, applied to each of the three surface water input zones individually is shown to be sufficient to parameterize the volume and timing of runoff from this watershed.