The Water Resources of Central Africa

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Abstract
Investigations of the importance of the swamp or dambo in the conservation of water in Central Africa were made around Lake Bangweulu and the outflowing Luapula River. Dense growth of papyrus (Cyperus papyrus) gives a very slightly inclined surface to the extensive swamps which are actually a part of the lake. Irregularly clogged drainage due to floating masses of papyrus probably account for the hitherto unexplained fluctuations of the lake level and the submergence of previously cultivated sand banks within the swamp area. Similar long-term fluctuations in the level of Lake Nyassa from an 8.5-ft. lake gauge reading in 1915 to a 23.5 ft. max. in 1938, superimposed on a regular seasonal fluctuation of about 3 ft., were found to be due to gradual accumulation of papyrus-induced sandbars in the outlet Shire R. A subsequent lowering to 19 ft. in 1945 was due to channel cutting in these bars by water from the overfull lake. Two controlling factors are the phenomenal rate of growth of aquatic vegetation such as papyrus, and the tremendous floods in the rainy season which bring down silt from the mountains. A remedy for the Lake Nyassa fluctuations in level would be a regulating barrage near its outlet on the upper Shire R.

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