Department of Water Affairs and Forestry
	Institute for Water Quality Studies

POLLUTION INCIDENT IN THE ROODEPLAAT DAM, May 2000

1. INTRODUCTION

This report was written as a result of a pollution incident in the Pienaars River, flowing into the Roodeplaat Dam. Prof. Cock, from the University of the Witwatersrand, reported the incident to the IWQS on 25 May 2000 after she used the impoundment for recreational purposes over the weekend of 20-21 May 2000. She noticed a foul smelling patch (Site A in Figure 1) in the Pienaars River upstream of the confluence with the Moreleta/Hartbees Spruit in the Roodeplaat Dam. Many complaints about the state of the water quality of the Roodeplaat Dam were received by DWAF, especially during the summer of 1998 – 1999 (Van Ginkel, unpublished).

In addition to the regular sampling being conducted on the Roodeplaat Dam, the IWQS conducted an ad hoc survey to investigate the reported pollution incident. This survey took place on the 26^th May 2000. Both the Pienaars River and the Moreleta/Hartbees Spruit were visited and samples were taken. The first sampling event was followed up by a second sampling trip on the 26^th June 2000.

Due to the belief of the authors that this pollution incident is merely a symptom of long-term pollution resulting in a water quality problem in the Roodeplaat Dam the report is structured to:

• Initially outline the historical and general water quality situation in the Roodeplaat Dam, and
• To detail the sample results from the ad hoc investigation conducted to ascertain the extent of the pollution problem.

The historical overview details the chemical, biological, microbiological and physical properties of the Roodeplaat Dam are given. The historical water quality assessment gives the background to the development of the pollution incident. Eutrophication in the Roodeplaat Dam is discussed in detail as it can be directly linked to the ‘pollution incident’.

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