Evaluation of the impact of the phosphate-P standard on the water quality and trophic state of Hartbeespoort Dam

Abstract

This report deals with the phosphates in effluents released in the catchment of Hartbeespoort Dam and the quality of water entering, within and leaving Hartbeespoort Dam from 1985 to 1989 (March). It also describes the phytoplankton and zooplankton populations of the dam and how they have responded to changing conditions in the dam. Data on Hartbeespoort Dam dating back to 1980 have been used in the interpretation of results, which to a considerable degree, is concerned with the impact of the effluent phosphate standard on the dam. In 1985 a 1 mg 1-1 effluent orthophosphate-P standard came into effect in the catchment of Hartbeespoort Dam, although the largest effluent treatment plant was granted an exemption from the standard for three years. Effluent data are available only from the latter half of 1986, since when there has been insignificant change in the total mass of phosphates released in the catchment of Hartbeespoort Dam.

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