Sensitivity Analysis of Reference Evapotranspiration (ETO) Models for Irrigation Requirement of Crops and Impact of Irrigation on Climate Changes in Semi-arid Region of India

Estimation of simple reference ETo model is being received considerable attention over the globally accepted FAO56 Penman-Monteith model, because the data generated from the fitted sensors of weather stations are questionable. To solves this problem in research field of water management, we tested five ETo models and compared with FAO56- PM by using 22 years weekly weather data (1975 to 1996) of irrigation command (CCA 80,800 ha) of semi-arid area of Maharashtra, India(long. 740 18′, lat. 190 45′, alt. 435 m). The Modified Penman model of FAO24 is quite effective against the FAO56 PM model but the former model requires both radiation and aerodynamic parameters for estimating ETo. The next temperature-based Hargreaves and Blaney Criddle model provided very significant effect as these models have expressed minimum RMSE, MBE, RE and high D-agreement. Development of water resources and irrigating seasonal field and horticultural crops in this semi-arid area has changed the physiological and physical attributes of vegetations. Due to more vegetation cover and cooling effect in irrigated area, the relative humidity has increased and evaporation rate, wind speed has decreased. When it was regressed with various weather parameters the temperature, wind speed, relative humidity and duration of bright sunshine have expressed positive effect and rainfall has shown negative effect on water loss from pan evaporimeter.