Comparison and analysis of Hargreaves equation and Penman-Monteith equation during the different hydrological years in the semi-arid region

The reference crop evapotranspiration of four typical hydrological years was calculated by Hargreaves equation and Penman-monteith equation in Xinxiang city in Henan Province. The results of Hargreaves equation were analyzed by using the results of Penman-monteith equation as standard. The results show that the error of Hargreaves equation is increased with the increase of annual precipitation. While the ET0 values of ten day by two equations are no remarkable difference during the 1st ～12th and the 31st～36th 10-day. During the 13th～30th ten day of four typical hydrological years, the ET0 values calculated by Hargreaves equation are greater than that calculated by Penman-Monteith equations, the regression relation between two equations was established during the 13th～30th ten day. The result shows that Hargreaves equation can be applied in Xinxiang City. The researches results provide the reference for reference crop evapotranspiration calculated by Hargreaves equation in the sililar semi-arid region.