Water resources in semiarid regions are one of the principal limiting factors for economic development. In that light, the protection of groundwater resources becomes a priority for concerned authorities. A map of aquifer vulnerabilities of the lower western chelif basin in Algeria was produced using several methodologies, among them SINTACS, a methodology developed by Professor Massimo Civita and successfully realized using ArcView GIS. The vulnerability map shows us the zones to be protected as well as zones where artificial supply is possible to supplement aquifer supply.