Evaluation of evaporation pan coefficients for empirical methods to Estimate Reference Evapotranspiration

Reference evapotranspiration (ETo) is one of the main parameters in water resource planning and water management. Pan coefficient Class A (Kp) is an important factor for calculation of reference evapotranspiration (ETo). There are several ways to estimate Kp using different parameters such as wind speed, relative humidity and vegetation. In this study, using daily meteorological data for 4 years period from Shahrekord Meteorological Station using different equations such as Cuenca, Allen Pruitt, Snyder, Orang and Pereira, pan coefficient was estimated. Then, those values were estimated FAO-Penman-Monteith, Penman-24, Turk, Blaney-Cridle and Hargreaves-Samani equations. Results were comprised to lysimeter data collected from this region. Also for choosing the best model, between three parameters, Root mean square error, Mean absolute error and Standard Estimation Error rank test was performed. Results showed that pan evaporation methods had better accuracy compared to empirical methods. In addition, Turk equation ranked as the best and most accurate method and Penman-24 was the worst one.