Fuzzy Genetic Approach for Modeling Reference Evapotranspiration

This study investigates the ability of fuzzy genetic (FG) approach in modeling of reference evapotranspiration $\left({\text{ET}}_0\right)$ . The daily climatic data, solar radiation, air temperature, relative humidity, and wind speed from three stations, Windsor, Oakville and Santa Rosa, in central California, are used as inputs to the FG models to estimate ${\text{ET}}_0$ obtained using the FAO-56 Penman-Monteith equation. A comparison is made between the estimates provided by the FG and those of the following empirical models: the California Irrigation Management System Penman, Hargreaves, Ritchie, and Turc methods. The FG results are also compared with the artificial neural networks. Root-mean-square errors (RMSE), mean-absolute errors (MAE), and correlation coefficient statistics are used as comparing criteria for the evaluation of the models’ performances. The comparison results reveal that the FG models are superior to the ANN and empirical models in modeling ${\text{ET}}_0$ process. For the Windsor, Oakville, and Santa Rosa stations, it was found that the FG models with ${\text{RMSE}}_W=0.138$ , ${\text{MAE}}_W=0.098$ , and $R_W=0.999$ ; ${\text{RMSE}}_O=0.144$ , ${\text{MAE}}_O=0.102$ , and $R_O=0.999$ ; and ${\text{RMSE}}_S=0.167$ , ${\text{MAE}}_S=0.115$ , and $R_S=0.998$ in test period is superior in modeling daily ${\text{ET}}_0$ than the other models, respectively.