Mechanisms controlling the chemical composition of lakes and rivers: Data from Africa

Data for natural lakes, rivers, and springs in intertropical Africa indicate that the chemical compositions of these waters are controlled primarily by rock dominance (weathering reactions) and the evaporation-crystallization process (evaporative concentration and calcite precipitation). There are minor deviations from the primary pattern observed in Africa and elsewhere. They usually occur as a result of contamination by cyclic salts or salts ultimately derived from ancient lakes or oceans.