Estimation of reference evapotranspiration for southern region of Saudi Arabia

The reference crop evapotranspiration (ET,) for four areas in Saudi Arabia was estimated using five different methods: FAO-Penman, Jensen-Haise, Blaney & Criddle, pan evaporation, and calibrated FAO-Penman under local conditions (Penman(-SA)). Comparison was also made between the estimated ETr and the measured ETr of alfalfa grown in lysimeters in the Riyadh area. Regression analysis revealed that estimated ETr values were highly correlated with measured ET, values. In addition, linear regression relationships between ETr values estimated by the Penman(-SA) method and other methods were determined. The results of this study indicated that the calibrated Penman(-SA) method can be transferred successfully to other locations, and this method could be used for the estimation of ETr values in all areas in the southern region of Saudi Arabia.