Identification of Best Potential Evapotranspiration model for Estimating Reference Evapotranspiration for sub temperate climate: Almora, Uttarakhand

FAO-56-Penman-Monteith is regarded as a standard method worldwide for calculation of ET. However due to requirement of detailed meteorological data, its application is often constrained under data scarce region. Under such situation, a suitable alternative method with equivalent efficacy to that FAO56PM needs to be identified. The present study is undertaken to evaluate 13 different ETo model from temperate, radiation and combined method using monthly long-term (1985-2010) meteorological data from VPKAS, Experimental farm located in mid Himalaya region of Uttarakhand state of India with respect to standard (FAO56PM) method. The result revealed that combination method, Penmen-Monteith was found most suitable (r=1, RMSE= 0.04 mm/ month ) followed by 1972 Kimberly Penman (r=0.99, RMSE= 0.13 mm/month) . Among radiation method Turc ETo model (r=0.71, RMSE= 0.12 mm/month) was found most appropriate followed by Hargreaves et al., (1985) (r=0.4, RMSE= 0.99 mm/month) in temperature based method. In general, combination method for estimation of PET followed by radiation-based and temperature-based method