DEPARTMENT OF WATER AFFAIRS & FORESTRY WATER QUALITY STATUS REPORT: UPPER VAAL MANAGEMENT AREA 2000-2005
Riana Munnik
Pvt Bag X995, Pretoria 0001. E-mail:
- UPPER VAAL WATER MANAGEMENT AREA
The Upper Vaal Water Management Area is one of nineteen Water Management Areas (WMA) in South Africa.
The water management area includes towns as far as Breyten, Harrismith, Johannesburg and Potchefstroom.
STRATEGIC MONITORING IN THE UPPER VAAL WATER MANAGEMENT AREA
The Sub-Directorate Water Quality Management of the Gauteng Region conducts monthly water quality sampling in nine sub catchments of the Upper Vaal Water Management Area.
All the water quality-monitoring programmes are registered on the Department’s Water Management System (WMS). This information is used to generate compliance reports and trend graphs.
The Department has selected nine points in the main stem of the Vaal River at key locations as Strategic monitoring points. These points are located downstream of confluences with major tributaries and inflows from transfer schemes, as well as downstream of the Grootdraai Dam, Vaal Dam and the Vaal Barrage.
MAP OF STRATEGIC MONITORING POINTS IN THE UPPER VAAL WATER MANAGEMENT AREA.
SCHEMATIC DIAGRAM OF STRATEGIC MONITORING POINTS IN THE UPPER VAAL WATER MANAGEMENT AREA
WATER QUALITY ISSUES OF CONCERN
3. WATER QUALITY ISSUES OF CONCERN.
There are two major issues of concern namely salinity and eutrophication, or nutrient enrichment.
Salinity is evaluated by looking at variables such as Electrical Conductivity (EC), as an indication of dissolved salts, such as Sulphate (SO4), which is related to coal- and gold mining activities.
Examples of point sources of salinity are industrial and mine water discharges, and the diffuse sources of salinity are seepages from mine dumps and other discard and disposal facilities.
Eutrophication is evaluated by looking at nutrients such as Phosphate (PO4) and Nitrate (NO3).
Examples of point sources of nutrients are discharges from sewerage works and the diffuse sources are informal settlements.
The water quality trends for the abovementioned variables for the period 2000 to 2005 as recorded on the Department’s Water Management System (WMS), and presented as concentration over distance graphs are as follows:
CONCLUSIONS:
Is is clear that the biggest impact on water quality in terms of salinity and eutrophication is from the Vaal Barrage catchment as measured at Point VS8.
There is a huge inflow of phosphate and nitrate from the tributaries of the Vaal Barrage, namely the Klip River, the Leeu Taaibos spruit, the Blesbok Spruit and Suikerbosrand River, and the Riet Spruit.
The huge impact on water quality in the tributaries of the Vaal Barrage can be attributed to the huge loads of salts and nutrients that are discharged. The following table summarise only a couple of the discharges that actually takes place.
DISCHARGE FROM SEWERAGE WORKS INTO THE VAAL BARRAGE BASED UPON DRY WEATHER FLOW AS IN OCTOBER 2005
Name of company / Catchment / Flow Ml/day / Tons PO4 per annum / Tons of NO3 per annumERWAT 12 Waste Water Treatment Works (WWTW) / Blesbok Spruit / 138.22 / 98,7 / 198,0
ERWAT 4 WWTW / Klip River / 224,36 / 57,6 / 224,3
JO’BURG WATER 3 WWTW / Klip River / 507,55 / 61,06 / 851,18
TOTAL / 870,13 / 217,36 / 1273,48
DISCHARGE FROM MINES AND INDUSTRY INTO THE VAAL BARRAGE BASED UPON DRY WEATHER FLOW IN SEPTEMBER 2005
NAME OF COMPANY / CATCHMENT / FLOW Ml/DAY / TONS SO4 PER ANNUMSappi Enstra / Blesbok Spruit / 24,44 / 892
Petrex: Grootvlei Mine / Blesbok Spruit / 75 / 30 331,5
There are peaks of nitrate and phosphate observed in the Upper Vaal River and that is due to pollution from dense settlements near Breyten and small sewerage works not functioning properly in Ermelo, Bethal and Amersfoort.
The impact of the Mooi River and Wonderfontein spruit can be seen at point VS9.
The expansion of mining activities in the Ermelo area to provide coal for power generation impact on salinity and sulphates as seen for VS1 – VS4.
ACTIONS AND INTERVENTIONS
The saline point source discharges from mines and industry are regulated through water use licences.
The diffuse source seepages from slimes dams and other disposal facilities, especially those from abandoned mines need to be addressed.
The Waste Discharge system, which will be implemented in the near future, will also address these discharges.
Eutrophication is caused by the points source discharges from sewerage treatment works. These sewerage treatment works are regulated by the Department through water use licences.
Diffuse source seepages from informal settlements, overflowing pump stations and blocked pipelines also contribute to the nutrient enrichment of the water resources.
The biggest issue is the lack of co-operative governance and final effluent from sewerage works not complying to specified standards.
It is proposed to refine the strategic monitoring programme to address the lack of information on nutrients in the system by looking at Total Phosphorus, Total Nitrogen, and Chlorophyll and to include continuous monitoring at the strategic monitoring points.
The strategic monitoring system must also be extended to the Lower Vaal River system.
The Department also needs to improve on communications between water quality and water services sections in the various regional offices and the various provinces.
There has to be an ongoing drive from the water pollution control officials, with limited capacity, to address water services problems, establish communication with local authorities, raise awareness, send letters to councillors and to arrange meetings in order to influence the IDP’s of Municipalities in order to address the problems with service delivery.
The non-compliance of sewerage works managed by local authorities need to be addressed and is receiving attention at the highest level.
High level intervention is taking place at Emfuleni, but similar measures will be needed to address the full extent of the problem throughout the water management area.