A Simple Procedure to Estimate Reference Evapotranspiration during the Irrigation Season in a Hot-Summer Mediterranean Climate

The Food and Agricultural Organization of the United Nations (FAO) Penman–Monteith (PM) method is widely regarded as most effective reference evapotranspiration (ETo) estimator; however, it requires a wide range data that may be scarce in some rural regions. When feasible relative humidity, solar radiation wind speed are unavailable, temperature-based useful to estimate ETo provide suitable support irrigation management. This study has evaluated accuracy two estimations methods: (1) locally monthly adjusted Hargreaves–Samani (HS) equation; (2) simple procedure only uses maximum temperature adjustment coefficient (MaxTET). Results show that, if (kRs) calibrated for each site, acceptable (RMSE R2 equal 0.79 entire region) can achieved. also based on performs acceptably, when compared with estimation using PM equation = 0.83 mm day−1 0.77 Alentejo). comparing these results ones attained adopting HS method, MaxTET proves an accurate estimator. both methods used weather scarce.