The Oulja Coastal Aquifer is part of Sahel Doukkala System Aquifer, is one of the main groundwater coastal aquifers in Morocco. It covers about 160 km2 and has a significant role in satisfying water needs for agriculture and potable water supply in the region. Over years, the need for agricultural water has increased, overexploitation of groundwater resources can put their quality under stress. It could be based on rapid disturbance in groundwater level leading to saltwater intrusion in this coastal aquifer.
To evaluate extent of the threat of the seawater intrusion. The present study is an attempt to map the vulnerability of the groundwater in Oulja Coastal Aquifer of against this intrusion by means of modeling coupled with GIS. The methodology used in the study consists of assessment of vulnerability using GALDIT method, is based on the most important factors controlling seawater intrusion, that is, four intrinsic hydrogeological parameters, one spatial parameter and one boundary parameter including Groundwater occurrence (aquifer type), Aquifer hydraulic conductivity, depth to groundwater Level above the sea (hydraulic head), Distance from the shore, Impact of seawater intrusion and aquifer’s Thickness.
Assigning each map an appropriate weightages and ratings, and the overlaid of the six thematic maps has allowed to produce vulnerability map. The result of the study indicates a high vulnerability to seawater intrusion due to excessive groundwater withdrawals, especially in the Oulja coastal zone. This vulnerability is more witnessed in the South near the Oualidia Lagoon than in the North of the studied area. The outcomes of this study provide useful insights on effective groundwater management for the Oulja Coastal Aquifer.