The measurement of actual evapotranspiration, a key term in the water balance equation, has become a very important issue. Many good methods exist for estimating actual evapotranspiration; however, most of these require complicated inputs. Here, a simple but robust model for estimation of actual evapotranspiration in arid areas of western China is proposed. This model is a visual system with a user-friendly interface in the STELLA (a commercial software package for building numerical models) environment combined with two existing water balance equations and local soil and climate data to ensure its easy application in developing areas. Validation with field measurements revealed that the estimated values of actual evapotranspiration obtained using the model are in agreement with the observed values. Both the established Choudhury model and the proposed model produced similar estimates when the actual annual evapotranspiration is below 200 mm, but the model proposed simulates real-world conditions more precisely when the actual annual evapotranspiration is greater than 200 mm. Another advantage of the proposed model is that it uses simple and reliable climate data that are readily available from the network of weather stations in China. The simulation results could serve as a relatively good reference for water resource management in this area.

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