The Volta River system drains three quarters of the country. The Black Volta and White Volta flow southward from Burkina Faso and form the Volta River in central Ghana. The Volta and its tributary, the Oti, feed Lake Volta. It was formed in 1966 behind the Akosombo Dam, which supplies hydroelectric power for Ghana. In the southwest the Pra, Tano, and other small rivers flow from the Kwahu Plateau to the Gulf of Guinea.
Rain is concentrated in the spring and fall.
Tropical forests are in the southwest and the Akwapim-Togo Mountains. The principal trees are silk-cotton, mahogany, ebony, and camwood. Savannah grasslands and light woods with scrub underbrush cover the Volta Basin and northern Ghana. Demands for food and fuel have degraded the natural vegetation. Deforestation is widespread in the south.