Comparison of Different Empirical Methods for Estimating Daily Reference Evapotranspiration in Mediterranean Climate

The estimation of reference evapotranspiration (ET0) is very important for the management of water resources and the determination of the water budget, especially under arid conditions. The applicability of simple forms of Penman equations that were recently developed by Valiantzas is investigated in this study. The new empirical equations are applied to daily climatic data from four stations located in the Mediterranean region of Turkey: Adana, Antalya, Isparta, and Mersin. The results are compared with the ET0 values obtained by Food and Agricultural Organization 56 Penman-Monteith and the following empirical equations: Copais, Turc, Hargreaves-Samani, Hargreaves, Ritchie, and Irmak. Root mean square errors, mean absolute errors, and determination coefficient statistics are used for comparison of the empirical models. The results indicate that the Valiantzas equation with full weather data performs better than the other empirical methods at stations in Adana, Antalya, and Isparta. In the Mersin station, however, the Copais equation perform the best out of the nine methods. The worst estimates are generally obtained from the Turc method.