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Saltwater intrusion caused by groundwater over-exploitation from coastal aquifers poses a severe problem in many regions. The Fum Al Wad aquifer is located between Atlantic Ocean in the West and Laayoun in the East. This aquifer covers an area of 250 Km 2 , and represents an essential water resource for Laayoun city and the periphery regions. It is heavily exploited for water supply, agriculture and industry. The freshwater-saltwater interface is affected by groundwater extraction by public supplies, irrigation wells, and domestic wells in the coastal of this aquifer. The position of the interface is controlled by several factors: these include precipitation, recharge rate, dryness, evapotranspiration, hydraulic conductivity and hydraulic head. Landward migration of the interface freshwater-saltwater often results in a significant decrease in the water resources available for coastal communities. The volume pumped by public for irrigation and the domestic usage in 2010-2011 is estimated 2.5 Mm

The present work contributes to the multidisciplinary geological, hydrogeological, and geophysical exploration of groundwater in the Bir Tam-Tam region of the Fez-Taza corridor. Our main objective is to release water resources in our study area to supply drinking water in the region and irrigation of agricultural areas. Potential zones are located at the Lias fracturing zones. This study is interested in understanding the hydrogeological context of the study area through geophysical methods such as Electrical Tomography. The comparison of geological data, Drilling data, and the interpretation of the results of electrical Tomography have made it possible to highlight the geoelectric levels likely to constitute a potential aquifer and to locate possible structural accidents (faults) affecting the dolomitic limestone formations of Lias that could drain groundwater.

The Dayet Iffer belongs to the Dayets of tectono-karst origin of the Northern Middle Atlas. After its watershed genesis of middle altitude during the Quaternary, two lacustrine formations were deposited on the surface while other thick formations exist in depth. The detailed sedimentological study of the soltanian and holocene lithological sections on the surface and the 14C datings helped recognize part of the history of the watershed. The geophysical study allowed to detect the thickness of the superficial geological formations as well as the various geological phenomena (tectonic and/or karst) that affected them from the genesis to the present. The current shape of the watershed where the Dayet Iffer exists is only the result of an evolution where sedimentary, tectonic and karst phenomena interfere. The tomography obtained with Res2DInv software, performed for the first time at the Dayet Iffer, reveals the presence of three ranges which can be interpreted as three resistive, intermediate and conductive zones with a large set of faults. These results helped determine the thickness (over 160 m) of the sedimentary filling. This shows that the hydrological behavior of the Dayet Iffer takes into account both horizontal flows at the stratification and/or karstic joints and the movement of sub-vertical fractures.