Comparison between Penman-Montieth Model and Pan Evaporation Model in the Estimation of Reference Evapotranspiration in Different Regions in IRAQ

Abstract

The objective of this research is to find the mean monthly values of reference  evapotranspiration (ET_O) in 22 stations distributed all over Iraq using (PM-1998) model which is widely used in the world and E_pan (class A) model during the period (1980-2010). The results showed high converge between the mean monthly values  of  reference  evapotranspiration calculated  by the two models in all stations. The results showed also very high  relation between (ET_O) calculated  by the two models in all stations where the  (R²) ranged between (0.961-0.996), as well as (MAE,RMSE) values are very low in  most of the stations. This demonstrates the accuracy of these correlations. Also correlation was found all over Iraq between the mean monthly values of (ET_O) calculated by the two models which give  high value of (R²) which is equal (0.931).

Keywords: FAO-56; PM-1998; Epan; ET_o