Assessment of the cumulative impacts within the Kromdraai catchment area with a specific focus on the point source discharges
Van Dyk, Anna Aletta
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The purpose of this dissertation was to determine if the cumulative impacts from point source discharges in the Kromdraai Catchment area sigdicantly impacting on the fitness of use of the surface water resource. The Kromdraai catchment area is located within the Upper Vaal Water Management Area and includes the Upper and Lower Wonderfonteinspruit, the Mooi River and the Loopspruit. The catchment area stretches from Krugersdorp to the confluence with the Vaal River and includes the towns of Westonaria, Carletonville, FochviUe and Potchefstroom. Various dams are situated within the catchment area, these include the Donaldson Dam, Klipdrift Dam, Boskop Dam, Klerkskraal Dam and the Potchefstroom Dam. In order to calculate relevant salt loads reference was made to the Best Practice Guideline Document for the compilation of water and salt balances (DWAF, 1999b:16). The assessment made use of the concentration of salts discharged in kg per day (also referred to as the Total Dissolved Salts or TDS in mg/l) in order to assess the levels of impact. The said method described was utilised throughout the assessment. In order to establish an informed assessment the following methodology was applied. Collation of information in order to obtain: - Understanding the activities of point source discharge. - Localities of discharge. - Quantities and qualities of discharge. Site visits to: - Obtain and clarify information. - Obtain additional information. - Form a holistic view of the area. Review of information: - Missing information was sourced. - Personal contact with point source dischargers. Cumulative impact assessment: - Impact was calculated in accordance to the guidelines of DWAF. Conclusions - Based on the results certain cumulative impact assessments were made, limitations and problem areas were highlighted and certain recommendations made. The following point source dischargers discharge directly into the surface water resource: Merafong City Lou1 Municipality Oberholzer Sewage Works; Khutsong Sewage Works; Wedela Sewage Works; Welverdiend Sewage Works; Fochville Sewage Works; Mogale City Municipality Flip Human Sewage Works; Hannes van Niekerk Sewage Works; Potchefstroom Local Municipality Potchefstroom Water Care Works The following mining activities have a direct point source discharge point into the catchment area: GoldFieIds Limited - Hoof Gold Mine, Driefontein Consolidated Mines. AngloGold Ashanti - West Wits Durban Roodepoort Deep - Blyvooruitzicht Gold Mine Harmony Gold Mine - Deelkraal and Elandsrand, Randfontein Estates The conclusion that was formed based on the results of the different point source discharges was that: No single point of discharge can be identified as a major polluter. Certain of the point discharge sources were found to be discharging water containing waste with TDS concentrations above the acceptable Water Research Commission Guideline (1998: 59) for drinking water, however none of these point source discharges ever contained TDS concenhations of a magnitude that poses a risk to human health. The point source dischargers are cumulatively responsible for the raised levels of salts found in the surface water resource. It should be noted that this raised level is still not deemed to be a health risk to humans as per the standards. It was found that the state of especially municipal water care works is in need of urgent upgrading and maintenance as well as management. This was especially clear from site visits although not evident in the monitoring data. The assessment was done with data received from different point source dischargers. Throughout the assessment averaged figures were utilized. It should be noted that a great discrepancy exist in the methods used by the dischargers i.e. dates of sampling, times of sampling, methods of analysis, regularity of sampling and sampling methods. Final conclusion was that a uniform system of monitoring and analysis throughout the region would provide a much more accurate and clear indication of actual state and possible impact on the surface water resources.
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