Measurement and simulation of the water storage pit irrigation trees evapotranspiration in the Loess Plateau.

• The evapotranspiration mechanism of the water storage pit orchard is revealed. • An evapotranspiration model of the water storage pit irrigation trees (SWp) is established. • The mechanism of the simulation error of the SW P model is illustrated. Accurately predicting the evapotranspiration of the orchard is of great significance for improving the water use efficiency of orchard and optimizing the water management of orchard. Based on both the evapotranspiration mechanism of the water storage pit irrigation orchard and the Shuttleworth-Wallace dual-source evapotranspiration model, an evapotranspiration model S W p suitable for water storage pit irrigation trees was established in this study. The evapotranspiration measured by the thermal diffusion sap flow meter and mic-lysimeter methods during 2018 were used to verify the performance of the PM model, the SW model and the S W p model under the water storage pit irrigation conditions. The results show that: (1) an evapotranspiration model of the water storage pit irrigation trees is established, and the Nash efficiency coefficient of the model is 0.93; (2) the diurnal variation of the evapotranspiration obtained by the three models of P M , S W , and S W p are the same as the measured value. The simulated value of P M model is 11.45% lower than the measured value, the simulated value of S W model is 24.01% higher than the measured value, and the simulated value of S W p model is 5.55% higher than the measured value; and (3) sensitivity analysis is performed on the six resistance variables in the S W p model, which reveals the mechanism of the simulation error of the S W p. model. Thus the S W p model significantly improved the accuracy against the PM and SW models and can be used to estimate the evapotranspiration under the water storage pit irrigation conditions. [ABSTRACT FROM AUTHOR]