A study in Onitsha, Nigeria used a method called vertical electrical sounding to find out about the groundwater in the area. They did 11 surveys and found that the aquifer layers are between 21 and 78 meters deep, with resistivity ranging from 20 to 5600 ohm-m. The water-saturated sandstone units are good for producing groundwater, with transmissivity between 2.55m2/day and 29.01m2/day. Boreholes can be drilled at depths of 40 to 110 meters for sustainable water supply, and the water quality is suitable for domestic and municipal use.