Groundwater Potential Assessment of the Sedimentary and Basement Complex Rocks of Ogun State, Southwestern Nigeria

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Seventy borehole data were used to appraise the groundwater resources of the sedimentary and Basement Complex rock terrains of Ogun State, Nigeria. Borehole depth, static water level, discharge and drawdown were evaluated to determine the hydrogeological and hydraulic properties of the aquifers. Specific capacity of the boreholes was estimated at one hour using discharge and drawdown values. Most boreholes in the sedimentary terrain explored shallower aquifers of < 100 m, while most boreholes in the Basement Complex rock terrain explored deeper aquifers > 100 m. The sedimentary rock aquifers had thinner groundwater storage of 65.28 m and average borehole yield of 43.51 m³ hr⁻¹, while the Basement Complex rock aquifers had thicker groundwater storage of 95.02 m and average borehole yield of 5.53 m³ hr⁻¹. The average efficiency of boreholes in the sedimentary and Basement Complex rock terrains were 0.66 and 7.14 m² hr⁻¹, respectively. Boreholes within Basement Complex rocks had higher efficiency than those within sedimentary rocks. Adequate groundwater occurs in the sedimentary and Basement Complex rock terrains for domestic, industrial and agricultural purposes. The groundwater is weakly acidic with small amount of TDS, hence falls within the fresh water category. The groundwater is not potable but could serve domestic and general purposes.