Paper Details

Saltwater intrusion is a global phenomenon which threatens freshwater aquifer and thereby make it difficult in the coastal environment to tap freshwater for sustainable groundwater exploitation and management. Lagos State has witnessed a tremendous population growth and rapid urbanization, which in turn has culminated into over-abstraction of groundwater resources, thereby making the coastal aquifers vulnerable to seawater intrusion owing to the nearness of the boreholes to the sea-shore. A GIS GALDIT dependent index, consisting of six (6) hydrological, hydrogeological and geomorphological parameters, based on assigning weights and ranges, has been used to assess the vulnerability of the coastal aquifers to seawater intrusion in Apapa area of Lagos State. The method involved obtaining GALDIT parameters and Index scores for all the boreholes and classifying the boreholes into vulnerability classes of high, low and moderate vulnerability. In this study, a total of ten (10) boreholes were assessed. The GALDIT Index obtained ranged from 6- 6.5, which implied moderate vulnerability class. The results indicated that all the boreholes were moderately vulnerable to saltwater. This might be due to distance of the boreholes to the sea shore and consequent migration of saltwater into the coastal aquifers. The distance of the boreholes to the seashore ranged from 16 to 331m and the average distance of the boreholes to the seashore was 200m .It can be concluded from the study that Apapa has been affected by saltwater intrusion from the adjoining sea, which makes any boreholes located in the area vulnerable. Keywords: GALDIT Index, Vulnerability, Coastal aquifer, Groundwater, Seawater intrusion