SUMMARY
This paper presents the first application of the COP method for the vulnerability mapping in Mefrouch catchment (Tlemcen, Algeria). This method has been developed for the intrinsic vulnerability of carbonates aquifers in the frame of the European COST action 620(Zwahlen 2004). It takes into account three factors: the concentration of flow (C factor), the overlaying layers above the water table (O factor) and the precipitation (P factor). Since the method is intended for the karstic medias, it takes into account karst specific characteristics such as swallow holes and sinking streams. The vulnerability map established in this work shows that Meffrouch catchment is composed of five vulnerability classes. The method classifies 27% of the total area of the catchment as zones of high to very high vulnerability. This percentage reveals that anthropic actions can seriously affect the groundwater of the region. In order to prevent pollutants from reaching this vital resource, the established map can be used for the delineation of zones to be protected.