For the last twenty years, the needs of water has increased and implied an overexploitation of the aquifer causing an important drop of the water table. The principal objective of this study, included in the multidisciplinary project "SudMed", a French and Moroccan cooperation, is the estimation of water volumes used to irrigate cultivated surfaces and to quantify the total catchment by pumping. First, a better knowledge of the land cover of the plain is necessary. For this purpose, the use of remote sensing proves to be necessary. This land cover map allows us to calculate surfaces of the main crop types, then to estimate the water needs for irrigation.