Modeling daily reference evapotranspiration in middle south Saurashtra region of India for monsoon season using most dominant meteorological variables and the FAO-56 Penman-Monteith method

Abstract

Many methods are available to estimate reference evapotranspiration (ET_o) from                    standard meteorological observations. The FAO-56 Penman-Monteith method is considered to be the most physical              and reliable method and is often used as a standard to verify other empirical methods. However, it needs a                        lot of different input parameters. Hence, in the present study, a model based on most dominant meteorological            variables influencing ET_o is proposed to estimate ET_o in the Middle South Saurashtra region of Gujarat (India). The performance of five different alternative methods and proposed model is compared with the standard FAO-56 Penman-Monteith method.

         The five quantitative standard statistical performance evaluation measures, Nash-Sutcliffe efficiency coefficient (E), coefficient of determination (R²), refined Willmott’s index (d_r), root mean square of errors-observations standard deviation ratio (RSR) and mean absolute error (MAE) are employed in evaluating the performance of the selected methods and proposed model. The results show that the developed model and Hargreaves and Samani (1985) method with recalibrated parameters provide the most reliable results in estimation of (ET_o) and it can be recommended for estimating (ET_o) in the study region.