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POLLUTION INCIDENT IN THE ROODEPLAAT DAM, May 2000

5. CONCLUSIONS

  1. The hyper-eutrophic state of the Roodeplaat Dam, with the associated symptoms of hyper-eutrophication, led to the development of yet another pollution incident that was reported.
  2. There are traces of microbiological pollution in both the Pienaars River and the Moreleta/Hartbees Spruit. Although the origin of this pollution in the Pienaars River seems to be from human wastes, in the Moreleta/Hartbees Spruit the origin seems to be from animal wastes.
  3. These incidents of toxic cyanobacterial blooms are a potential recreational health hazard as the conditions existing in the impoundment will lead to a more significant establishment of cyanobacterial blooms with their associated potential for toxicity problems.
  4. The increased nutrient concentrations that led to the incident can be explained by a variety of causes that are all associated with the hyper-eutrophic state of the impoundment. The origin of the extremely high and increasing nutrient loads into the system can be attributed to a) high nutrient containing discharges from WCW, b) diffuse land-uses (including intensive, agricultural feedlot wastes) and c) re-circulation of nutrients from the bottom sediments and decaying plant material. The contribution from these potential sources should be identified for management purposes.
  5. The incidence of cyanobacterial toxin production needs to be established in the Roodeplaat Dam in order to determine the potential health hazard that exists for recreational users.

6. ACKNOWLEDGEMENTS
  1. The authors want to thank the IWQS Laboratories for the dedicated manner of sampling analysis without which this report would not have been possible.
  2. Dr. P Kempster, Dr. A. Kühn, Mr. S. Mosai and Me A. Howman for their constructive comments.

7. REFERENCES

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ANON, (1988b) Special phosphate standard for sensitive catchments. Water sewage and Effluent, vol. 8, no. 4 pp 10-11. Pretoria.

CHORUS, I. and BARTRAM, J. ed. (1999). Toxic cyanobacteria in water. A guide to their public health consequences, monitoring and management. Published on behalf of the WHO. E & FN Spon. LONDON.

DU PLESSIS, B.J., HOWARD, M.R. and BRUWER, C.A. (1990). Eutrophication. The trophic Status of selected South African reservoirs. HRI Report No. N/0000/00/DEQ 1290. PRETORIA.

DWA, (1988) Important announcement on implementation of the Special Phosphate standard in sensitive catchments. IMIESA (Johannesburg), vol13, no. 9, p 35.

DWAF (1996). South African Water Quality Guidelines Volume 7 Aquatic Ecosystems. Department of Water and Sanitation. PRETORIA, South Africa.

HENDERSON-SELLERS, B. and MARKLAND, H.R. (1987). Decaying Lakes The origins and control of cultural eutrophication. John Wiley & Sons. New York. 254pp.

HOHLS, B.C., BELCHER, T., KEMPSTER, P.L. and VAN GINKEL, C.E. (1999). Assessment of the Water Quality in the Roodeplaat Dam since 1990. Draft Report No. N/A200/00/DEQ/2199. Institute for Water Quality Studies, Department of Water and Sanitation, PRETORIA, South Africa.

HOHLS, B.C., QUIBELL, G., DU PLESSIS, B.J. and BELCHER, T. (1998). Assessment of the implementation of the phosphate standard at the Baviaanspoort and the Zeekoegat Water Care Works. Report No. N/A230/01/DEQ/0797. Institute for Water Quality Studies, Department of Water and Sanitation. PRETORIA, South Africa.

IWQS (1999). Macro Elements Laboratory Test Methods and SOP Manual. Revised edition. Institute for Water Quality Studies. Department of Water and Sanitation. PRETORIA. South Africa.

IWQS (2000a). Biology Laboratory Test Methods and SOP Manual. Revised edition. Institute for Water Quality Studies. Department of Water and Sanitation. PRETORIA. South Africa.

IWQS (2000b). Trace Metal Laboratory Test Methods and SOP Manual. Revised edition. Institute for Water Quality Studies. Department of Water and Sanitation. PRETORIA. South Africa.

UTILKEN, H.C., OLIVER, L.R. and WALSBY, A.E. (1985). Buoyancy regulation in a red Oscillatoria unable to collapse gas vacuales by turgor pressure. Arch. Hydrobiol., 102, 319-329.

VAN GINKEL, C.E., HOHLS, B.C., BELCHER, A., VERMAAK, E. and GERBER, A. (2000). Assessment of the trophic status project. Draft Report No. N/0000/00/DEQ/1799. Institute for Water Quality Studies, Department of Water and Sanitation. PRETORIA. South Africa.

WALMSLEY, R.D. (1984) A chlorophyll a trophic status classification system for South African impoundments. Journal for Environmental Quality, 13 (1), 97-104.

WALMSLEY, R.D. AND BUTTY, M., (1980) Guidelines for the control of eutrophication in South Africa. Special Report, Water Research Commission, PRETORIA, South Africa.

WETZEL, R.G. 1983. Limnology 2nd Edition. Saunders College Publishing, Philadelphia. USA.

WWW.ag.ohio-state.edu/ ~ohioline/b795/b795_1.html (June 2000).

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