SUMMARY
As in all areas of the North, including the Maghreb Africa, the region of the Great Basin Mellegue has experienced over the last twenty years a very intense and persistent drought. This drought is characterized by a significant lack of rainfall has had a very negative impact on the flow regimes wadis and springs and the aquifer recharge.This hydro rainfall deficit has affected all socio -economic activities in the region especially in its agricultural development. More over, this phenomenon has an ecological impact and degrading treatment, in general, the environment and promoting particular, water pollution and decline of the natural environment.Given the gravity of this situation, comes at a time when, the demand for water for different uses has increased significantly, it is important to develop a policy that would enhance and protect our water resources.In order to locate the areas vulnerable to pollution and origin of water sampling and piezometric measurements campaigns were conducted during periods of High and Low water years 2005, 2006. The contamination index calculated enabled us to develop vulnerability maps on which identified three areas increasing degree of contamination.