There are three major dams in Niger State, Nigeria. The Kainji Dam built in 1968, Jebba Dam built in 1985 and Shiroro Dam built in 1990. A fourth dam is being built at Zungeru, also in Niger State. These are all hydroelectric dams and generate a potential combined power output of 1,900 megawatts.
The 1976 geo-technical activities carried out included geological mapping, marine geophysical surveys, land and marine drilling and sampling, soil overburden and rock core sampling, test pits for clay core borrow materials, on site soil laboratory setup and testing, groundwater level and seepage monitoring, testing of loose river alluvium, data collection and analysis, bore hole logs and geologic cross sections for preliminary feasibility studies.The Kainji Dam has a concrete main dam with rock-fill embankments and a saddle dam. The saddle dam protects the main dam during flooding. There are four spillway with hydraulic operated gates of 15.2 x 15.2 m (50 x 50 ft), which could be opened to control flood and release water for use at the Jebba Dam downstream.
Kainji Dam is 85.5 m (215 ft) in height and about 8 km (5 miles) in length. The lake is supplied with water from the upper Niger River and it flows from Futa Djarlon Island through Guinea, Mali, Sierra Leone, Senegal and Niger. The reservoir lake stretches some 136 km upstream and has a breadth of 24 km at its widest point. The maximum head elevation is 141.7 m (465 ft) and maximum tail elevation is 104m (330 ft). The lake has a total capacity of 15 billion cubic meters covering an area of 1270 square kilometres. The dam which took almost five years to construct was built at the cost of N175 million by Impregilo, a consortium of three Italian firms. It took 20,000 men of nine different nationalities to build it.