The SUD-MED project aims at monitoring water resources over Mediterranean semi-arid regions. As part of the project, this paper presents a method we developed for the monitoring of cereal evapotranspiration and water supply. The method is based on the STICS crop model. The model is first calibrated and evaluated at field scale from an experiment that has taken place in the Yaqui Valley (Mexico). The performance of the model was found satisfactory on this semi-arid area. The calibration procedure is then applied using eight images acquired by the SPOT-5/HRVIR sensor during the 2001/2002 agricultural season. The test site is located in the Haouz plain surrounding Marrakech (Morocco). The time series of satellite data allows us to furnish some key-parameters of the STICS model. The map of seasonal evapotranspiration appears consistent with the drought observed during the 2001/2002 agricultural season.