Nyumba ya Mungu reservoir, Tanzania: The general features

Abstract

Nyumba ya Mungu reservoir was completed in 1965 in northern Tanzania. By 1970 there was a thriving tilapia fishery but it declined catastrophically in subsequent years. A team of biologists surveyed the lake in 1974, and this paper outlines their hydrological, geographical, and climatic findings. The dam, constructed across a north/south Neogene fault-trough 80 km south of Mt. Kilimanjaro, has produced a reservoir about 180 km2 with a mean depth of 6 m. The catchment area is extensive but the main source of water is from Mt. Kilimanjaro. The lake is situated in an arid area, and over one quarter of the input water evaporates from the lake's surface. The outflow is regulated by a hydro-electric power station and is practically constant. At full capacity the retention time of the lake is one year but due to abnormally low rainfall, the reservoir was not full, and the retention time was nearer nine months. The lake is polymictic and a deep wind-driven current is maintained by the Trade Winds for most of the year. The general features of Nyumba ya Mungu are briefly compared with other man-made and natural lakes in Africa.