ASABE Technical Library - Abstract

Abstract. Accurate estimation of reference evapotranspiration is imperative for the water budget of irrigation schemes, water resources management and planning and other agricultural water management issues. In present study, the capabilities of Gama Test technique(GT) was evaluated for choosing the inputs combination for building a reliable smooth model to estimate reference evapotranspiration (ET0) using four separate sets of weather data from four locations representing different climatic patterns (including humid, semi-humid, arid, and semi-arid pattern). And also, this paper examined the performance of Gene Expression Programming (GEP) based models for estimating ET0 using the different combinations of climatic variables from GT. The daily data set (2008-2013) comprising air temperature, relative humidity, wind speed and solar radiation was employed for choosing the combination inputs for GEP and modeling ET0 using FAO-56 Penman Monteith equation as the reference. Overall, the results demonstrated that the GEP model with four meteorological variables as inputs had the best performance in Zhenghou station (semi-humid zone), Guangdong station (humid zone), Huhehaote station (semi-arid zone) in China, while that considering only two climatic variables resulted in the lowest accuracy in all stations. The GEP model with three climatic variables performed better than the GEP model with four variables as inputs in Dunhuang station (arid zone). All the GEP models with four variables and three variables exhibited high accuracy under all the climatic conditions including arid, semi-arid, humid and semi-humid conditions which provides more potential methods to estimate ET0 in someplace where cannot provide adequate climatic data to calculate ET0 using the FAO-56 Penman Monteith equation.