Ecology, Environment and Conservation Paper

COMPARISON OF REFERENCE EVAPOTRANSPIRATION METHODS: CASE STUDY FROM A SEMI-ARID CONDITION

P.R. Anjitha Krishna and R. Lalitha

Abstract

Reference Evapotranspiration (ETo) methods are widely used for the estimation of evapotranspiration (ET), an important component of hydrologic cycle. The performance of the empirical methods is different in different climatic conditions. The present study aims to evaluate selected empirical equations for ETo estimation against the standard FAO-56 PM method within a semi-arid taluk in Trichy district, Tamil Nadu. The statistical analysis of the methods showed that Pan Coefficient based methods and Makkink Radiation method are the best performing methods in the study area. Thornthwaite method with a single input parameter (temperature) showed highest RMSE, MAE and PE of 3.87 mm/day, 3.6 mm/day and 143% respectively followed by Hargreaves Method (RMSE-2.5 mm/day, MAE-2.4 mm/day and PE-109%) and Makkink Radiation method (RMSE-0.89 mm/day, MAE-0.79 mm/day and PE-38.3%). Local calibration of ETo equations is essential in terms of efficient water management in semi arid locations.