Simulating Evapotranspiration on Semi-Arid Rangelands

by G. N. Flerchinger,
C. L. Hanson,
W. P. Kustas,
M. A. Weltz,

Document Type: Proceeding Paper

Part of: North American Water and Environment Congress & Destructive Water


Detailed simulations of the surface energy balance using the Simultaneous Heat and Water (SHAW) model were compared with measurements collected at the Reynolds Creek Experimental Watershed in Idaho and the Walnut Gulch Experimental Watershed in Arizona. Simulations were conducted for three vegetation types (low sagebrush, mountain big sagebrush and aspen) in Idaho and two vegetation types (grassland and creosote bush) in Arizona. Simulated diurnal variation in each of the surface energy balance components compared well with measured values for all sites. Timing and magnitude of evapotranspiration (ET) from the sites differed considerably. Measured and simulated ET for approximately 25 days of measurement at the Idaho sites were 41 and 44 mm, respectively, for the low sagebrush, 74 and 69 mm for the mountain big sagebrush and 85 and 89 mm for the aspen. Measured and simulated ET for 20 days of measurement at the Arizona sites were 66 and 48 mm for the creosote bush and 74 and 69 for the grass-dominated site. The variation in hourly simulated evapotranspiration accounted for by the model ranged from 56% for the creosote bush site in Arizona to 78% for the aspen site in Idaho.

Subject Headings: Vegetation | Evapotranspiration | Watersheds | Simulation models | Rangeland | Mountains | Energy measurement | United States | Idaho | Arizona

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