GEOELECTRICAL INVESTIGATION OF SEAWATER INTRUSION IN THE COASTAL AQUIFER OF NADOR (TIPAZA, ALGERIA)

Abstract

The Wadi Nador plain at the North of Algeria is very talented area for agricultural activities. It depends on underground water in its agricultural activities. The Plioquaternary aquifer in this plain has suitable thickness to be used as the main water source for different purposes. Due to the presence of the main aquifer in the area in contact with the Mediterranean Sea, the fresh coastal water is contaminated towards the western direction. The present study concerns the application of surface geophysical techniques to study the spreading out of seawater intrusion. The geoelectric study showed a variation in the electrical resistivity for two moments separated in time by more than 45 years. The fall in resistivity may be due to the seawater intrusion into the freshwater where the aquifer was strongly exploited during the period from 1980 to 1990. The resistivity surveys reveal two distinct sectors: the saturated aquifer in brackish and saltwater having resistivity values to 36-10 Ω.m, which extends nearly 1600 m inland, and the saturated aquifer in freshwater with resistivity values more to 36 Ω.m in upstream of the plain at more than 2 km.