Daily reference evapotranspiration modeling by using genetic programming approach in the Basque Country (Northern Spain)

Evapotranspiration, as a major component of the hydrological cycle, is of importance for water resources management and development, as well as for estimating the water budget of irrigation schemes. This study presents a Gene Expression Programming (GEP) approach, for estimating daily reference evapotranspiration (ET0) in four weather stations in Basque Country (Northern Spain), for a 5-year period (1999-2003). The data set comprising air temperature, relative humidity, wind speed and solar radiation was employed for modeling ET0 using FAO-56 Penman Monteith equation as the reference. The GEP results were compared with the Adaptive Neuro-Fuzzy Inference System (ANFIS), Priestley-Taylor and Hargreaves-Samani models. Based on the comparisons, the GEP was found to perform better than the ANFIS, Priestley-Taylor and Hargreaves-Samani models. The ANFIS model is ranked as the second best model. (C) 2011 Elsevier B.V. All rights reserved.