TN-79 : Estimation of evapotranspiration losses from agricultural lands- climatological approach

Abstract

Evapotranspiration from agricultural lands forms an important part in the root zone water balance study. For last few years due to continued occurrence of drought conditions, it has become important to conserve soil moisture from rainfed crops. Knowledge of water requirements (or ET) of crops has values in several areas of agronomy, including irrigation, evaluation of drought severity and in hydrological studies. Evapotranspiration can be determined from direct measurements, empirical climatic formulae, or by using evaporation measurements as indices. Direct measurements are performed by many techniques including tanks and lysimeters, soil water depletion, field plots, energy balance and water balance methods etc. In this report it has been envisaged to review all available methods for estimating evapotranspiration from agricultural lands and present status of these methods, limitations, adaptability and usefulness in terms of data availability including recommendations for further research under Indian conditions.