Modified Hargreaves Equation For Accurate Estimation Of Evapotranspiration Of Diverse Climate Locations In India

Abstract

Standard model for estimation of reference evapotranspiration rate (ET0) is the FAO-56 version of Penman– Monteith. It needs a wide range of atmospheric parameters like solar radiations, wind speed, air temperature, humidity, vapor pressure and soil heat flux. All these datamay not be available at the majority of the locations. The estimation of evapotranspiration using the Hargreaves equation is a potential solution to this problem. It needs only temperature and radiation data to estimate ET0. But, simplification brings inaccuracy and need for regional calibration of the Hargreaves equation constants—CH and EH. Fuzzy logic based calibration of the constants CH and EH in the Hargreaves equation for diverse climate locations of India like— Bikaner, Calcutta,Kakinada,Coimbatore, Panjim-Goa, Kota, Deharadun, and Srinagar is performed and validated. Performance of modified Hargreaves equation (MHG) is compared withHargreaves equation (HG) and FAO-56 version of Penman–Monteith (PM-56). MHG resulted in improvement by reducing the error in ET0 estimates. The root mean square error (RMSE) values reduce with the range 0.36–0.92 mm/ day for MHG from 1.12 to 2.53 mm/day of HG. Location specific calibration improves the accuracy of the HG.