Submitted to: American Geophysical Union
Publication Type: Abstract Only
Publication Acceptance Date: 9/5/2004
Publication Date: 12/7/2004
Citation: Gupta, R., D.G. Chandler, J.P. McNamara, and G.N. Flerchinger, 2004. Elevation controls on timing and quantity of water yield from a semi-arid catchment. Abstract H13C-0442 In: EOS Transactions Supplement. American Geophysical Union, Washington.D.C. (85):47 CD-ROM
Technical Abstract: Water supply in many semi-arid regions is derived from mountain precipitation, which varies in depth and phase with elevation. Predicting water yield from mountainous regions depends on the spatial and temporal distributions of the source area precipitation, and energy balance, which controls both snowmelt and evapotranspiration. The Simultaneous Heat and Water (SHAW) model was developed to simulate the response of the water balance at the component level to weather and soil. The SHAW model was applied to 4 years of weather station and soil moisture and temperature data at two elevations (1610.5 m and 1142.4 m) in Dry Creek watershed near Boise, ID to determine the annual variability in elevational controls on water yield. In particular, we were interested in improving our ability to better predict water yield for low snowpack conditions. Precipitation fell primarily between October and April at both elevations. The average annual precipitation was 57 cm and 33 cm at the upper and lower sites respectively. The maximum daytime air temperature at the lower site was generally higher than at the upper site but the nighttime temperatures were similar. Evapotranspiration was greater at the upper site, which remained wetter longer, due to the greater precipitation. No surface runoff was measured over the four year period. Water yield was equated with deep percolation from the soil column which was seasonal, and occurred from January through March at both sites. The onset and duration of deep percolation at both sites was dependent on the timing of increasing air temperature and extent of spring precipitation. Whereas total winter precipitation was found to be a first-order control on water yield, timing of spring rains was found to be an important second order control on deep percolation and runoff generation.