Abstract
Evapotranspiration (ET) is an important component of the surface water cycle. In this study, we analyzed the differences between the estimated ET using the crop coefficients (kc) recommended by the Food and Agriculture Organization (FAO) and the measured ET with a lysimeter in Loess Plateau spring wheat (Triticum aestivum L.) from 2010 to 2012. Results showed that ET estimated from FAO-recommended crop coefficients (kc-FAO) was significantly overestimated (55%) compared with measured ET by lysimeter. Evapotranspiration was sensitive to the relative available water (Raw), and kc were strongly dependent on drought stress in semiarid area (p < 0.001). Relative available water dependence of kc increased with the decrease in Raw. An improved kc model based on kc-FAO integrating drought stress factor was developed, and then an empirical ET model derived from the kc approach was established based on the Penman–Monteith equation and the improved kc model. The ET data measured by lysimeter from June of 2004 to May of 2005 were used to validate the proposed ET model. The estimated ET showed satisfactory consistency to measured ET with a linear regression coefficient of 1.01. Evapotranspiration modeling performance derived from the improved kc model integrating drought stress factor was superior to that derived by kc-FAO directly in semiarid area.
- © 2019 by the Soil and Water Conservation Society
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