Evaluation of evapotranspiration models

This study was performed to assess the suitability of Ten empirical methods with penman monteith method. The Penman Monteith method was taken as standard/reference method. Statistical analysis was conducted to test the performance of these methods, compared to Penman montieth method. The computer software CROPWAT was used to estimate Penman Monteith reference evapotranspiration. Ten years climatic data provided by Regional Agromet Centre, Tandojam, Ditrict Hyderabad. The suitability of different evapotranspiration ET methods was checked in reference to Penman Montieth method using statistical analysis, regression analysis, root mean square error (RMSE) and absolute deviation (AD). The analysis indicated that radiation method Jensen and Haise and priestly Taylor underestimated ET by 25 to 45 %, and 0.5 to 5 % respectively. FAO radiation and pen evaporation methods overestimated by 10 to 15 %. Pan evaporation based evapotranspiration approach also overestimated ET by 5 to 15 %. The most of the combination methods showed good agreement with Penman Monteith estimated ET. The Penman kimberly 1982 method showed very good ET estimates and ranked first in this study. As Penman Monteith method require very detailed crop and climatic data, therefore 1982 Penman kimberly method can be used as an alternative method to estimate ET for local conditions. The further studies are also required to develop local wind functions for 1982 Penman kimberly method in order to get more accurate results. The graphical and statistical analysis also supported 1982 Penman Kimberly method. It was concluded that Kimberly Penman 1982 method showed very good agreement with Penman Monteith method CROPWAT and it can be an alternative method where limited data is available. Kimberly Penman 1982 produced low Root Mean Square Error (RMSE) and absolute deviation (AD) values ranging from 0.05 to 0.33 mm/day and 0.19 to 0.43 respectively. averaged Hargreaves method, overestimated evapotranspiration ET by 15 to 50 % compared to Penman montieth method. Jensen Haise ET priestly Taylor methods underestimated evapotranspiration ET compared Penman Montieth Method.