Comparison of three evapotranspiration models to Bowen ratio-energy balance method for a vineyard in an and desert region of northwest China

The accurate determination of vineyard evapotranspiration (ET) in the and desert region of northwest China is important for allocating irrigation water and improving water use efficiency. Taken a vineyard at the Shiyang river basin of the Hexi corridor of Gansu Province as an example, this study evaluated the applicability of the Bowen ratio-energy balance (BREB) method in the and desert region of northwest China, simulated the variation of vineyard ET by Penman-Monteith (P-M), Shuttle-Wallace (S-W) and Clumping (C) models in this region and compared the estimated ET by the three models with the measured ET by the BREB. Results indicated that the BREB could provide the accurate measurement of vineyard ET from the and desert region when the Bowen ratio instrument with higher accuracy was correctly installed. Generally, the variation of the estimated ET from P-M, S-W and C models were similar to that of the measured ET by the BREB method. However, the P-M model overestimated the ET significantly; the estimated ET from the S-W and C models, especially from the C model was approximately equal to the measured ET by the BREB. After a rainfall, the performances of the S-W and C models were also good. Therefore, among the three models, the C model was the optimal model in simulating the vineyard ET in the and region of northwest China. However, after a frost, the C model significantly overestimated the evapotranspiration because the canopy resistance did not fully reflect the dramatic decrease of grapevine transpiration. (C) 2008 Elsevier B.V. All rights reserved.