Comparison and Evaluation of Estimating Reference Evapotranspiration Methods in Three General Categories Based on Temperature, Radiation and Mass Transfer (Case Study: Lorestan Province)

Accurate estimate of reference evapotranspiration is very important not only in planning andcomputing irrigation frequency, but also in studies related to water balance modeling in eacharea. The purpose of this study is to compare and evaluate nine different methods of estimatingthe reference evapotranspiration based on three general categories of temperature, radiation andmass transfer at nine study stations in Lorestan province from 1999 to 2019. The results of thesemethods were compared with the results of the FAO Penman Monteith. The performance ofdifferent methods was evaluated using R2, RMSE and CRM statistics. The results showed that inmost of the study stations, among the temperature-based methods, the Hargreaves Samani,among the radiation based methods, the Makkink and among the mass transfer methods, theWMO showed the best performance with the highest R2 and lowest RMSE. Also using ArcGISsoftware, spatial zoning was performed and maps of each category was presented.