Published Paper Details:

Evapotranspiration (ET) is the combined process of evaporation from soil surfaces and transpiration from plant tissues. Its rate is a very significant factor for supporting irrigation management decision. ET is one of the most important components of hydrologic cycle which is calculated from records of climatic data and geographical attributes of a metrological station. Reference Evapotranspiration (RET) is an important index of hydrologic budgets at different spatial scales. This can be treated as a complex process in the hydrological cycle that influences the quantity of simple RET model survey widely according to regional climate conditions. It is often an important variable in estimating Actual Evapotranspiration (AET) in rain fall- run off and ecosystem modelling. Many RET estimation methods have been developed for different types of climatic data, and the accuracy of the method varies with climatic conditions. The international commission for irrigation and drainage(ICID)and food & agriculture organization (FAO) of the united nations have proposed using the Penman- Monteith method a the standard method for estimating Reference Evapotrapiration (RET)and for evaluating other methods. The objective of the present study is to estimate daily, monthly, annual Reference Evapotranspiration(RET) and to compare different RET models with hat of standard equation Penman-Monteith to ensure the sensitivity. Sensitivity analysis is a useful and common way to study o n regional and seasonal behavior of RET in response to changes in climatic variables. The results were then calibrated with statistical variations like Root mean square error (RMSE),Mean bias error(MBE), Mean percentage error(MPE),Nashco-efficiency of Efficiency (NCE). In this study RET estimated by the Turc (R2=0.254& NCE = 89.96%) method yielded better comparison onto that of standard Penman-Monteith method.