A THEORETICAL STUDY ON EVAPORATION AND EVAPOTRANSPIRATION

Abstract

A knowledge of evapotranspiration is necessary in water resources planning and management and also in vat~ious allied fields relating water. Various theoretical, semi- empirical and empirical methods are available for estimating evapotranspiration. Theoretical methods requires sophisti-cated instrumentation and constant attendance by s►.tilled personal. On the other hand, empirical methods can not be used unless they simulate the climatic conditions for which they were originally developed. To check their adtvtability for the area under study, experimental methods are to be sa carried out. The present study was conducted to estimate evapotranspiration from some selected meteorological stations of Nepal and India. Computer programme based on empirical and semiempirical methods has been developed. Consumptive use of wheat and maize crop for the area around Dehradun(India) have been calculated and compare with the measured data. Con-sumptive use of maize crop estimated by empirical and semi-empirical is 372 mm against measured ET — loss from lysimeter 33.5 mm, However for wheat all methods underestimate.