COMPARATIVE STUDY ON ESTIMATION OF VARIOUS EVAPOTRANSPIRATION TECHNIQUES WITH PENMAN-MONTEITH METHOD

Evapotranspiration (ET) is one of the important parameter in hydrology and development of watershed. Concept of ET is crucial mainly in water requirements to crops and planning of any water resources structures. ET is the combined processes of evaporation from soil and plant surfaces and transpiration from plant tissues. Several methods are described by Food and Agricultural Organisation (FAO) and The International Commission for Irrigation and Drainage (ICID): of which Penman – Monteith Method (PMM) was considered as a standard method to evaluate Potential Evapotranspiration (PET). Various methods were adopted in this paper to estimate PET based on temperature, radiation and physical methods. Thus, values of PET for the study area were estimated from all the above said methods. It is a clear known fact that all the metrological parameters may not be obtained from all the corresponding metrological stations and thus some empherical formulas which are described on above classification quite difficult in order to estimate PET and there by based on the obtained PET values are thus validated and compared with R2 value. Finally, the suitable method on par with standard Penman – Monteith method for the selected watershed is Turc method as value of R2 = 0.813 (81.3 %) which yields better when compared to that of methods