Abstract
Koka Reservoir in the Ethiopian Rift Valley (altitude about 1600 m) appears to be similar to natural lakes in the region. Its water is turbid because of suspended inorganic material. At the time of measurement it was supersaturated with oxygen to a depth of about 8 m, and displayed a pronounced conductivity stratification, due probably to the incomplete mixing of two inflows. The phytoplankton was dominated by Microcystis. The zooplankton was of low diversity but abundant. There was a large population of benthic invertebrates.
Finchaa Reservoir in west central Ethiopia (altitude about 2200 m) is very different. It covers the former Ch'omen Swamp and so contains many floating islands and large quantities of decomposing vegetation, causing undersaturation with oxygen even at the surface. The water is somewhat turbid owing to the presence of organic debris, of low conductivity, slightly acidic, and apparently calcium-dominated. A species of Microcystis was the most abundant phytoplankter. The zooplankton was sparse and of very low diversity. There were almost no benthic invertebrates.
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Mesfin, M., Tudorancea, C. & Baxter, R.M. Some limnological observations on two Ethiopian hydroelectric reservoirs: Koka (Shewa administrative district) and Finchaa (Welega administrative district). Hydrobiologia 157, 47–55 (1988). https://doi.org/10.1007/BF00008809
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DOI: https://doi.org/10.1007/BF00008809