Geoelectrical investigation of saline water intrusion into freshwater aquifers: A case study of Nador coastal aquifer, Tipaza, Algeria

Abstract

The groundwater in Nador coastal plio-quaternary aquifer had high salinity in 1995, due to a seawater intrusion, where the Electrical Conductivity (EC) exceeded 9000 μS.cm-1. After the implementation of Boukourdane’s dam, a pumping reduction of groundwater occured, and the irrigation was ensured by the dam and the water resulting from the sewage treatment plant. The physico-chemical analysis of the groundwater quality for the year 2013 shows that there is a dilution of the salinity compared to 1995 with values of EC less than 4400 μS.cm-1. It also shows that more than 45% of the physico-chemical parameters have values above the permissible limits of the WHO standard for drinking purpose. The geophysical study is aimed mainly to understand the geophysical characteristics of groundwater in Nador plain by studying the electrical resistivity distribution of the subsurface saturated layers by applying the Vertical Electrical Sounding (VES) and Electrical Resistivity Tomography (ERT) techniques. A total of 47 VES and 3 profiles of ERT were carried out to understand the resistivity distribution of the area. The interpretation of the results has identified a highly saline coastal aquifer and delineates the freshwater in the upstream at more than 2 km.