This article explores the water supply-demand relationship in the Middle Draa valley, under climate change and socio-economic scenarios; identifying some of the climate-hydrological variables that best express the vulnerability of hydrological resources at watershed level. The analysis utilizes the outputs of some general circulation models runs under different scenarios socio-economical and climate change (A2 and B2). We used the Statistical downscaling models (SDSM) that allow the observation of climate change at local level and the Water Evaluation and Planning System (WEAP), an integrated approach to simulate water systems and orient management policies. The results predict that under the scenario of climate change A2, the region will know more severe droughts than under B2 scenarios. The estimation of the water balance is made through WEAP model; which shows that the study area will know a lack in supply.