Numerical Groundwater Flow Modeling of the Coastal Plain Sand Aquifer, Akwa Ibom State, SE Nigeria

Abstract

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 m 3 /d to1.23 × 10 -4 m 3 /d. The calculations of the model showed that the average recharge rate amounts 0.40l/s/km 2 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.