Dams and lakes are constructed for several reasons:
Water supply for example dams are constructed near urban centers so that the water can pumped, treated and used for domestic and industrial use.
Irrigation purposes-for example near farms and estates such as sugar cane in Hippo Valley which would be impossible to grow in that climate without supplemental water.
Hydroelectric power for example Lake Kariba which generates most of the electricity for Zimbabwe and Zambia as well as Lake Cahora Bassa which generates and supplies most of the electricity in Mozambique.
Inland Navigation-some dams are used by small ships to transport cargo.
Flood control-dams are used to regulate water flow and thus control and prevent flooding.
Tourism- dams and lakes are used for tourist and recreational activities.
Fishing- lakes are an important source of fish which provides required protein intakes for the adjacent population as well as whole countries for example Kapenta fish from Kariba and Cahora Bassa. Fishing is also an important source of livelihood.
The availability and supply of water for industrial and domestic use.
Electricity generation through Hydro Electric generators being installed on dams.
River transport and the carrying of cargo.
Irrigation increases food and crop production.
Livelihood through activities such as fishing and boat tour operators.
Tourists bring in foreign currency.
Joint ownership of resources empowers local communities.
Improved accessibility of certain areas.
Towns may even grow as a result of these dams e.g. Kariba and Livingstone.
Improved standards of living.
Less likelihood of flooding.
Displacement of the local people e.g. the Tonga people from the Zambezi valley.
Destruction of animal habitats.
Disruption of local ecosystems.
Water conflicts may result as people downstream fight for their right to access water from the river.