Mapping of the vulnerability to marine intrusion “in coastal Cherchell aquifer, Central Algeria” using the GALDIT method

Abstract

Located in the south of the western Mediterranean, in the central Algerian region, the Cherchell coastal aquifer has participated over time in the economic development of the region (agriculture and seaside tourism). The construction of the Boukerdene dam in the watershed of the region, thus the exploitation of the aquifer in response to the excessive demand of agriculture and the potable water supply, has caused the piezometric level of the aquifer to decline and threatens its sustainability and makes it more vulnerable to marine intrusion, noting that no work has been realized in this study area despite the inestimable value of this aquifer in the region, it's the only aquifer in Cherchell town. The aim of this paper is to map the vulnerability of this aquifer to marine intrusion, based on the proven methodology of the GALDIT model for coastal aquifers combined with Geographic Information Systems (GIS). The GALDIT methodology requires six input parameters: groundwater occurrence (G), aquifer hydraulic conductivity (A), groundwater head above sea level (L), distance from the shore (D), impact of the existing status of seawater intrusion l'impact (I), and thickness of the aquifer (T).The results indicate low to moderate vulnerability upstream and high vulnerability downstream. This high vulnerability can be as much as 700 m from shoreline inland. This vulnerability is mainly due to the hydrological disruption linked to the construction of the Boukerdene dam, which reduces surface water inflows. These results provide a basic tool for local managers and decision-makers, for future management and protection strategies for the Cherchell area aquifer in the face of marine intrusion.