Comparison of potential evapotranspiration methods in Ethiopia

Abstract

The Food and Agricultural Organization method for estimating reference crop evapotranspiration (ETo), FAO56, is the standard method across the globe. Daily ETo estimated using seventeen potential evapotranspiration (PET) methods that has less data requirments were compared with FAO56 at five sites in Ethiopia (Bahir Dar, Bale Robe, Hawassa, Metehara, and Nazareth). The average rank of five model validation metrics namely standard deviation, RMSE, MAPE, NSE, and correlation were used to compare the methods. By taking the areal average ETo and PET, ten methods, Wen, Ant, Pen, Mak, PT, Ha5, Ha4, Tho, Rad, and Enk, having correlation > 0.57 and MAPE < 28% were ranked 1st to 10th, respectively. Also, at each site, the above ten PET methods were compared. By taking the average ranks of the five sites, Wen, Pen, Ant, PT, and Mak & Ha5 ranked 1st to 5th, respectively. Wen & Ant methods which are applied in Ethiopia for the first time had shown the best performance.