Hydrostratigraphy and hydraulic characterisation of the shallow coastal aquifer, Niger-Delta Basin: a strategy for groundwater resources management

The groundwater from shallow coastal aquifers in Nigeria has been reported to be under intense stress resulting from both natural and anthropogenic impacts ranging from saltwater intrusion, contamination and pollution from effluent-related to oil spillage, gas flaring, municipal, industries and agriculture. Here we characterize the hydro-stratigraphy and hydraulic characteristics of the shallow coastal aquifers of the Niger Delta Basin and assess the resilience of groundwater to both natural and anthropogenic impacts. Fifty-two borehole logs were analysed from which lithological section were used to generate cross-sections along with four profiles. The system is more complex than previously reported, a unit of silty sand was observed in the western part of the basin thins out leaving the eastern part of the basin as an unconfined aquifer underlain by multiple thin beds of the sand aquifer. A layered sand aquifer occurs in the northern parts of the basin which hold freshwater in this area, and is interbedded by clay layers which serve as aquitards. The relatively higher Hydraulic conductivity of Benin formation units compared to those of the Deltaic formation leave it with weaker climate change resilience and more vulnerable to pollution and contamination. While groundwater remains the dominant source of fresh water in the northern part of the basin, a strategic approach is needed to access potable water from the southern part where contaminated surface water directly appears to interact with groundwater of the uppermost unconfined aquifer. Management of waste and effluent-related to oil spillage, municipal, industries and agricultural in this should be engineered to protect the groundwater resources of this aquifer.