The Lake Chad basin has important groundwater resources. There are vast areas underlain by sedimentary formations (sands and sandstones) containing continuous water-table aquifer systems and deeper confined or semi-confined aquifers. The most used aquifer systems in the basin are those found in the younger sedimentary formations with widely varying compositions. There are Quaternary formations bearing free groundwater and Lower Pliocene and Continental Terminal formations containing artesian aquifers. Groundwater flow in the Quaternary aquifer was analysed in some parts of the the Lake Chad basin due to a number of localised pilot initiatives measuring the water levels in village wells and piezometers. Furthermore, various groundwater extraction mechanisms are used in the basin, ranging from simple holes, over open cemented wells to boreholes with solar-powered pumps. The cemented wells were mainly dug in the colonial period to supply water for human consumption and livestock. These types of wells are being replaced by boreholes with hand pumps, pedestal pumps and solar-powered pumps in cities, towns and villages to supply drinking water. In some cities in Nigeria and the Niger, the drinking water supply comes from artesian wells. Some wells of this kind are also used for irrigation purposes.