Hydrogeology and groundwater evaluation of a shallow coastal aquifer, southern Akwa Ibom State (Nigeria)
2017
The rapid expansion of economic activities in coastal parts of Nigeria has triggered an uncoordinated development of groundwater leading to stress on the resource. Hence a study was conducted to assess the hydrogeological characteristics of the shallow coastal aquifer of southern Akwa Ibom State, Nigeria. Emphasis was on the hydraulic characteristics, quality with respect to domestic and irrigation purposes and influence of seawater. The study result revealed that the aquifer consist of intercalations of clayey sand and sand. The aquifer is characterized by high hydraulic conductivity and transmissivity values. The groundwater flow direction is southwards with higher groundwater depletion in the dry season. Groundwater samples from hand dug wells and boreholes were evaluated based on World Health Organization standard and some indices, respectively, for drinking and irrigation uses. The groundwaters are fit for drinking and domestic uses. However, more than 70 % of the pH values are not within the allowable limits of between 6.5 and 9.2 for drinking and domestic use. Therefore, it is recommended that neutralizing filter containing calcite or ground limestone should be applied to raise the pH of the groundwater. Of the 10 parameters used to assess the water for irrigation use, only sodium adsorption ratio (SAR), magnesium hazard (MH) and magnesium ratio indicated the excellent quality of these waters. Na⁺-K⁺-HCO₃ ⁻ constitute the dominant water type. Total dissolved solids and ratios of Na⁺/Cl⁻, Mg²⁺/Cl⁻, and Ca²⁺/SO₄ ²⁻ and saltwater mixing index (SMI) suggest some level of seawater intrusion in the area.
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