Performance of Some Evapotranspiration Equations in an Arid Region

Abstract

Estimation of evapotranspiration is necessary for planning, design and irrigation design and water resources management. In order to determine the best method to estimate evapotranspiration using data of Qom synoptic meteorological stations during the years 1987 to 2007 was statistically significant. The FAO Penman Monteith (FAO-56 PM) method has been accepted by many researchers and international institutes as the reference and standard method. Accurate difference methods include Blaney-Criddle, Hargreaves-Samani, Jensen-Haise, Linacre, Rn-based method, Thornthwaite and Turc were applied and then their results were compared with the FAO-56 PM method. In this study, using statistical indicators, the best method to estimate ET0 in Qom province was selected and found to be Blaney-Criddle (RSME = 0.690 mmd-1, MAE = 0.545 mmd-1, D = 0.998). The results indicate that ET0 increases from north to south, west to east in the province. The regression relationship between the mean temperature and FAO-56 PM method and evaporation from the pan were determined. Also comparison of the pan evaporation and monthly values of FAO-56 PM method, coefficient pan (Kp = 0.583) is calculated. doi:10.14456/WJST.2015.8

Keywords

• Qom province
• evapotranspiration
• statistical indicators
• FAO Penman Monteith
• Blaney-Criddle
• pan evaporation