Evapotranspiration is the second most dominant component of the global water cycle behind precipitation, yet it remains one of the most difficult to measure and model. The numerous methods that have been developed for estimating evapotranspiration (ET) rates using climatological data vary in both complexity and spatiotemporal robustness. While the Penman-Monteith method has continually been shown to compare better with observed ET rates across more geographies and timescales than any other method, its high data requirements remain a barrier to use in many areas, and it is often desirable or necessary to make use of an alternative method. Daily reference ET estimates from the Penman-Monteith method were compared to ET estimates from seven alternative methods, which were generated using 14 years of observed weather records at five locations across the Midwestern United States. Then, a one-dimensional water balance model, DRAINMOD, was run at 362 locations across the Midwest using 50 years of synthetic climate data and three distinct sets ET inputs: 1) reference ET from the Penman-Monteith method, 2) potential ET generated from the Penman-Monteith reference ET and location-specific crop coefficient curves, and 3) potential ET from the Thornthwaite method. Results suggest that the best alternative method to Penman-Monteith varies by location, application, and timescale of interest, and that the misapplication of ET estimates for water balance model parameterization could have a dramatic impact on the accuracy of model predictions.
University of Minnesota M.S. thesis December . 2019. Major: Bioproducts/Biosystems Science Engineering and Management. Advisor: Gary Sands. 1 computer file (PDF); iii, 187 pages.
Comparison of Evapotranspiration Estimation Methods and Implications for Water Balance Model Parameterization in the Midwestern United States.
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