Lake Chivero is a man-made lake and the fourth largest impoundment in Zimbabwe. It was formed in 1952 by the Hunyanipoort Dam and is situated on the Hunyani River some 37 km southwest of Harare. It is a lake of many aspects: being a popular recreational site, the City's primary water supply reservoir, a source of irrigation water to downstream farms, an important fishery ground, and, until the 1970s, the receptacle of Harare's sewage effluent. It is, in short, typical of so many urban lakes in Africa and throughout the world. Lake Chivero is also unique, being amongst the first of the major man-made lakes on the continent to suffer from what is known as cultural eutrophication, and the first to be rehabilitated to a mesotrophic state through a rational programme of lake management.

Lake Chivero's physical limnology is controlled by the climate. The primary factors determining the surface and internal movements of the water are air temperature and winds, with river inflows becoming significant during the rainy season. Maximum air temperatures are in October and November and maximum wind strengths are in September and early October. River inflows are moderate or large during the period from January to March and negligible during the months May to November. Lake levels normally vary within a range of about 2 m of full supply level per annum largely in response to abstraction by the City of Harare for water supply purposes and to satisfy downstream demands. The lake is fairly typical of most southern African manmade lakes in terms of its inorganic chemistry. Most inorganic ions follow similar seasonal trends, with maximum values being recorded in spring and summer, and minimum in winter. This pattern is closely related to the hydrological regime and reflects concentration by evaporation during the hot spring and summer months as well as dilution by riverine inflows during late summer and winter.

Because of its proximity to Harare, the lake is an important recreational centre and the surrounding land was proclaimed as a National Park soon after the lake was formed. Angling is a major attraction and a commercial fishery was established in 1956. From 1960, periodic algal blooms appeared in the lake and caused purification difficulties at the works. But during the years 1976-78, phosphorus concentrations in the lake decreased to pre-eutrophic levels by a nutrient diversion programme by the City of Harare (1-3, 6-17).