Is there a global model to reliably predicting evapotranspiration?

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Spring Runoff Conference

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A reliable estimate of Evapotranspiration (ET) in river basins is truly important for the purpose of water resources planning and management. Therefore, the uncertainty in estimating ET can lead to the inaccurate prediction of water balance and water resources needs. The complementary methods, including Complementary Relationship Areal Evapotranspiration (CRAE), Advection-Aridity (AA), and Granger and Gray (GG) methods, have been used to estimate ET. These methods are attractive due to simplicity, practicability, and reliability in estimating ET (or total water loss) at regional scale using meteorological data only. These methods are applied to 34 FLUXNET sites representing different physical and climatic conditions in the globe. In comparison to eddy covariance (EC) fluxes of ET, the results indicate that further improvements to those methods can be performed. A wide set of model variations are developed and statistically tested in order to better simulate the latent heat fluxes of ET. The GG method was found to be promising once wet environment ET is calculated by the Priestley-Taylor equation and the basic complementary relationship is applied to the method. The results of the modified GG model are equal or even better than those of the most recent ET studies. Eventually, the objective of this study was achieved by developing a global, simple but robust, model using minimal data requirements to reliably estimate regional ET in a variety of ecosystems, climates, and environmental conditions.

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