Using DC resistivity method to characterize the geometry and the salinity of the Plioquaternary consolidated coastal aquifer of the Mamora plain, Morocco

The Direct Current resistivity method was applied to the consolidated coastal Plioquaternary aquifer of Mamora plain, located on the Atlantic coast of Morocco. The aim is to determine the depth of the base of the saturated zone in the aquifer and to help in imaging lateral and vertical distribution of groundwater salinity. The geoelectric survey showed four geoelectric formations with the following electrical resistivities from top to bottom: 20-80, 200-2000, 200-300 and 5-70 Ohm m. The latter designates the basement of the aquifer constituted of marls and sandy marls. The mean resistivity of 250 Ohm m designates the aquifer formation. It decreases to less than 25% of its initial values for the soundings near the shore, reflecting the oceanic impact on the aquifer formation resistivity. The contour map shows that the basement of the saturated zone in the aquifer is deeper in the Northwest near the Sebou River estuary with values up to 70 m below sea level. This results in a larger thickness of the saturated zone of the aquifer leading to a consequent hydraulic potential. On the other hand, it has been deduced that the extent of marine intrusion inside the continent can be governed by human activities, natural properties and substratum geometry of the aquifer as well as by ecological factors. An optimal network of electrical soundings has been proposed for the monitoring of saltwater intrusion.