Akwa Ibom State is located in the Niger delta region of Nigeria. The coastal plain sand aquifer, which underlies the area, is the major source of potable water for domestic, agricultural, and industrial use. The increase in demand for water has led to an increased exploitation of the aquifer in the last few years. Hence it is essential to quantify the amount of exploitable water in the aquifer. To achieve this goal, a regional numerical groundwater flow model using MODFLOW was calibrated under steady-state conditions to determine the aquifer’s hydraulic conductivity (K) and the recharge characteristics of the area. The hydraulic conductivity and recharge values from the pilot points calibration ranged from 1 to 75 m/d and 5.89 × 10-6 m3/d to1.23 × 10-4 m3/d. The calculations of the model showed that the average recharge rate amounts 0.40l/s/km2 or 12.60 mm/year. The estimated recharge suggests a high groundwater potential for the area. This is the first time that such a study has been carried out in the area, and it will serve as an important basis for future groundwater management and simulation of transient groundwater flow modeling in Akwa Ibom State.
Akwa Ibom State was founded 26 years ago. According to the census figures, the population was 2,409,613 inhabitants in 1991, while in 2006, 3,902,051 people lived in the area. This growing population alongside expansion of urban, agricultural and industrial activities has led to an increase in the demand for water in the area. The demand is partly achieved by the indiscriminate sinking of boreholes by individuals, communities, private organizations, government at local, state and federal levels and donor agencies including UNICEF, EU, ADB, the World Bank, etc. All these activities result in an increase in groundwater abstraction from the main hydrogeological unit, the Coastal Plain Sand aquifer.
What worsens the situation is the lack of a law enabling the control of the abstraction of groundwater in the area. Hence, there is a need for an effective management document to be in place for conserving and controlling the use of the available groundwater resource. This study therefore is the first attempt to numerically model groundwater flow under steady-state conditions in Akwa Ibom State. The main objective is to develop a regionalscale steady-state groundwater flow model for the area. Minor objectives include the determination of hydraulic conductivity and recharge characteristics using available hydrogeological information and applying inverse modeling technique based on the pilot point and zonation techniques.
Akwa Ibom State shown in
The geology of the Akwa Ibom area has been extensively studied by [
The area has three hydrostratigraphic units including the Alluvial Deposit, Coastal Plain Sand and Lower Sand Aquifers [
Based on the knowledge of hydrogeological system, a steady state mathematical model of the coastal plain sand aquifer was developed. The area of study is 7081 km2, therefore the model has a regional character. The hydrogeological conditions were defined from more than 200 boreholes drill log. Borehole data were obtained from [