Re-Eutrophication and Pathenogenic Contamination of Lake Chivero

Lake Chivero illustrates a number of lake management issues. The lake is downstream to the City of Harare and its satellite urban settlements. About fifteen years after its filling the lake became hypereutrophic. The restoration measures taken to restore it were based on scientific data. Good management and investment in infrastructure and nutrient removal wastewater treatment technology resulted in reducing the trophic state to mesotrophic state by the end of the 1970s. From 1980 onwards, there was a surge in urban population, with a doubling period of about 12.5 years. Watershed runoff diminished, resulting in reduction of the flushing rate.. As the population grew, the proportion of wastewater returns to precipitation runoff inflows increased to the extent that wastewater return is the main inflow into the lake during the dry season. These developments, in the context of inadequate investment in wastewater treatment facilities, poor infrastructure maintenance, low operating capital and poor governance, have resulted in the lake reverting to hypereutrophic state, which now poses a health risk.