Investigating the ability to use the evaporation pan coefficient to calculate the evapotranspiration of the reference plant in Khorramabad region

Estimation of evapotranspiration of the reference plant is one of the important components in the design of irrigation systems and water management for irrigation of plants. In this study, four coefficients of evaporation pan Schneider (1992), Aurang (1998), Allen and Perot (1991) and Konica (1989) to estimate the reference evapotranspiration compared to the FAO-Penman-Monteith model using indices RMSE, MAE, AARE, MR and Spearman coefficient were evaluated. Information required for different coefficients for estimation (ETo) was collected from Khorramabad synoptic station. The results of statistical evaluation showed that in the daily period, Orang (1998) and Schneider (1992) pan coefficients with RMSE equal to 1.004 and 1.13 (mm.day-1), respectively, as the most appropriate and Allen and Prot coefficients ( 1991) and Konica (1989) were selected as the most unsuitable coefficients with RMSE of 1.83 and 1.47 (mm.day-1), respectively. On the other hand, the results of statistical evaluation for the 10-day period of Konica (1989) and Schneider (1992) pan coefficients with RMSE of 6.01 and 8.25 (mm.day-1), respectively, as the most appropriate coefficients and coefficients of Allen and Perot (1991) and Aurang (1998) were selected as the most unsuitable coefficients with RMSE of 13.90 and 9.43 (mm.day-1). Spearman correlation test also showed that the results of all coefficients have an acceptable correlation with the reference method.