(355) Evaluation of Three Models for Estimated Potential Evapotranspiration under Sonoran Desert Conditions

The main crops in Caborca, Sonora, Mexico, in the Sonoran Desert, are grapes, asparagus, olive, and vegetables, such as melons and green beans. The growers in this area normally do not use methods to calculate water requirements of the crops, although in a desert region water use management needs to be as efficient as possible. A reason for using some of the models is the need to fit water requirements to regional conditions, or some stress could be caused in the crops. Recently, studies have been made in northwestern Mexico that indicate it is feasible to adapt the use of the Makkink model. Three models for estimated potential evapotranspiration (Eto) were evaluated: Penman-Monteith, Hargreaves, and Makkink, and were compared with the Class A pan method (control). Measured variables were the correlation coefficient ( R 2 ) between the models and the control; and the daily average difference between the models and the control. The results indicate that a low R 2 exists between the three evaluated models and the control (0.55, 0.67, and 0.54 for Hargreaves, Penman-Monteith, and Makkink, respectively). The average difference of the daily Eto in the course of 75 days of evaluation was of 0.62, 0.5, and 0.81 mm/day for Hargreaves, Penman-Monteith, and Makkink, respectively. This represents almost 6–10 cm less of potential evapotranspiration with the models, for a cycle crop of 120–130 days.