Abstract
The study on 10 lakes within the Ethiopian Rift Valley during March–May 1991 covered a range of conductivity (K25) between 286 and 49100 µS cm−1. HCO3 − — CO sup2−inf3 and Na+ were the dominant ions in all the lakes. Concentrations of K+, Cl− and SO sup2−inf4 increased with increasing salinity and alkalinity, whereas Ca2+ and Mg2+ decreased. Comparison of these data with previous records showed that a ten-fold dilution of total ionic concentration occurred over 30 years in Lake Metahara and about three-fold increase occurred over 65 years in Lake Abijata. Concentrations of soluble silica were generally high (12–222 mg SiO2 1−1) and increased with increasing salinity, except for Lake Chamo which showed SiO2 depletion (to < 1 mg SiO2 1 −1) over the past three decades.
The relationship between ionic concentration and phosphorus was irregular although high phosphorus concentrations generally corresponded with increasing salinity. Fitting data to the Dillon & Rigler (1974) chlorophyll a — total phosphorus relationship suggested that lakes Zwai, Awassa and Chamo are phosphorus-limited, whereas others have surplus phosphorus.
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Kebede, E., Mariam, Z.G. & Ahlgren, I. The Ethiopian Rift Valley lakes: chemical characteristics of a salinity-alkalinity series. Hydrobiologia 288, 1–12 (1994). https://doi.org/10.1007/BF00006801
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DOI: https://doi.org/10.1007/BF00006801