Agricultural production in the six oases in the Drâa Region in Southern Morocco is highly dependent on irrigation using mainly traditional irrigation channels or pumps. The basin has been suffering enormously from a continuing drought during recent years. Declining rainfall and high evapotranspiration rates in the semi-arid region lead to lower flow in the Drâa River. Aggravating this situation, farmers increasingly pump groundwater with motor pumps, leading to a rapidly drop in the aquifer. However, agricultural production is economically inefficient and based on subsistence farming. The income a farmer gets by selling a share of his production on the local markets hardly covers the variable costs for fertilizers and irrigation water. Farmers do pay only the pumping cost estimated at 0.58 Dh/m3. To prevent a further drop in the groundwater table, and hence to conserve water resources, the introduction of a water charge is evaluated with the MIVAD River Basin Model) RBM). This shows that imposing a water change of 0.42 Dh/m3 leads to stable groundwater table, but with a drop in cropped area by 50%.