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Case Study V* - The Witbank Dam Catchment * This case study was prepared by S.A.P. Brown V.1 Introduction The Witbank Dam catchment is located in the upper portion of the Olifants River basin. The Olifants River is one of South Africa's major water resources. The water quality in the Witbank Dam catchment is rapidly deteriorating, mainly due to coal mining. If this trend were to continue, the water in the Witbank Dam would be unfit for use, for most of the recognised users, by the end of this century. Poor water quality in the dam has meant that power generation, which is the largest industrial activity in the catchment, already has to rely largely on other sources of water from outside the catchment. This case study describes the water quality management approach of the Department of Water Affairs and Forestry (DWAF) to ensure that the surface water quality in the Witbank Dam remains fit for use and that the resource is secured adequately for the future. Many aspects of this approach are currently still being implemented. Nevertheless, further deterioration in water quality has been arrested and has been evident since October 1993 (see Figure V.3). Indications are that the implementation of this approach will result in water fit for use in the Witbank Dam catchment for at least the next 10 years. Other strategies will have to be employed to address water quality in the longer term. V.2 Background information South Africa is a country of great diversity. Its society comprises underdeveloped, developing and developed components. The annual disposable income per capita for all population groups is approximately US$ 2,000, but varies between US$ 1,020 and 7,750 for different population groups. Furthermore, the country is characterised by great disparities concerning access to adequate water supplies. Water-related issues are, therefore, a central aspect in the country's political arena; so much so that water supply and sanitation for all the inhabitants of South Africa is a key element of the Reconstruction and Development Programme (RDP). This programme was initiated by the Government of National Unity to restore the social and economic imbalances in the country. Figure V.1 Location map of South Africa showing the Olifants River basin and the Witbank Dam catchment South Africa is, however, a semi-arid country with limited water resources. Water is geographically unevenly distributed throughout the country and is not consistently available throughout the year. Generally, more water is available in the eastern portion of the country and availability gradually declines westwards. The Olifants River, one of South Africa's major water resources, is situated towards the east. The availability of water is further compounded by the fact that the demography of the South African population is changing rapidly. Vast numbers of people are moving to cities where they live in areas of poor water supply and sanitation services, or none at all. The DWAF is the authority, in South Africa, responsible for overall water resource management and it has to ensure the supply of adequate quantities of water of acceptable quality to recognised water users. However, in practice, part of this responsibility is delegated to other levels of government, other agencies, water users and to those who have an impact on the water resource. As a result of the dynamic political situation in South Africa, roles and responsibilities are being redefined and reallocated. In carrying out its mandate, DWAF often has to reconcile, integrate and co- ordinate conflicting and diverse interests within the framework of sustainable and equitable use of South Africa's water resources. Figure V.2 Detailed map of the Witbank Dam catchment and its nine management units, showing urban development and major industrial and mining activities (After Wates, Meiring and Barnard, 1993) V.3 The Witbank Dam catchment The Witbank Dam catchment is located at the headwaters of the Olifants River (Figure V.1). A more detailed representation of the catchment is provided in Figure V.2 which indicates the location of Witbank Dam, urban development and major industrial and mining activities, as well as the nine management units (see section V.5.1). The Witbank Dam catchment covers an area of 3,256 km 2 and has a mean annual run-off of 125 × 10 6 m 3 a -1 . Land-use practices in the catchment are varied and include the following: • Agriculture, of which maize is of strategic importance to South Africa's national staple food supply. Dry-land cultivation of maize is practised on 24 per cent of the catchment area. • Power generation, which is the largest industrial activity in the catchment and includes four of the country's major coal-fired power stations. • Coal mining. A total of 29 major collieries and a number of smaller operations are active in the catchment, producing approximately 47 per cent of the country's coal production. • Urban development, which is limited to a number of smaller towns. V.4 Pre-intervention situation V.4.1 The strategy The general approach to pollution control and environmental management in South Africa entails a management strategy based on a single environmental medium which is either air, water or land. The regulatory authorities responsible for the management of the environment are organised as follows: • Air: Department of National Health. • Water: Department of Water Affairs and Forestry. • Land: Department of Agriculture together with various other Departments. For example control over mining activities is exercised by the Department of Mineral and Energy Affairs (DMEA). The three main regulatory authorities have developed different organisational structures to suit their regulatory approach. Furthermore, the present arrangement fails to recognise the transfer of pollution across environmental boundaries. It also does not provide for a regulatory mechanism to ensure that environmental management is effective and efficient. The result is the absence of clear responsibilities, the overlapping of institutional boundaries, the exclusion of areas which require attention and a duplication of effort. Prior to 1991, the water quality management strategy of DWAF was based on the Uniform Effluent Standards (UES) approach. In applying this strategy, the focus was mainly on point source effluents. Diffuse sources of water pollution and the receiving water body were not given the necessary attention. With respect to control over mining activities, these shortcomings were further compounded by several factors: • The DWAF addressed water quality management concerning mining in isolation, i.e. control of water quality in relation to mining activities was not integrated with other activities. This approach even included separate offices dealing with mining-related matters within the same management area. • There was a lack of co-ordination between DWAF and the DMEA which has the primary responsibility regarding the influence of mining activities on land use. • The mining community was not aware of the detrimental effect of coal mining on the water environment. V.4.2 Water quality issues Coal mining is a major potential source of diffuse water pollution. Sulphate is a good indicator of salinity arising from this form of pollution. Approximately 70-80 per cent of the sulphate load in the Witbank Dam catchment emanates from diffuse sources and can be attributed to coal mining. This increase in diffuse pollution has resulted in a gradual decline in water quality in the Witbank Dam catchment. Water quality in the dam itself has declined from 50 mg l -1 sulphate and 100 mg l -1 total dissolved solids (TDS) to over 150 mg l -1 sulphate and 400 mg l -1 TDS. The concentrations of these two variables over a 16-year period are given in Figure V.3. In some reaches of rivers and streams in the catchment this deterioration has been more pronounced and, in some cases, water quality has deteriorated from a natural baseline level of approximately 50 mg l -1 to over 1,500 mg l -1 sulphate. The other major water quality issues are: • Eutrophication. Phosphorus is the limiting nutrient in the dam and the concentration of total phosphorus has not changed significantly over the past decade. However, the transparency of the water in the dam has increased by an order of magnitude over the same period of time. This is mainly due to the increase in TDS which has enhanced the flocculation of clay particulates resulting in an increase in light penetration. • Elevated levels of compounds toxic to the natural aquatic environment occur in some reaches of streams in the catchment. These compounds are predominantly metals and ammonia. Acid mine drainage associated with coal mining mobilises metals. Aluminium, iron and manganese are the main metals of concern. Ammonia originates from sewage effluents. V.5 Intervention with a new approach During 1991, DWAF adopted a new water quality management strategy. This strategy focuses on the receiving water body and considers all sources of water pollution. Catchment water quality management plans and sectoral specific management strategies are central to the new strategy. As part of this strategy, the water quality management approach in the Witbank Dam catchment was reviewed. The aim of the new approach is to arrest deterioration of water quality, to ensure fitness for use by the recognised water users and to secure the water resource. The main thrust of this approach consists of: • Development and implementation of a catchment water quality management plan. • Prevention and minimisation of pollution arising from mining activities wherever possible. These two activities are inter-related and are implemented concurrently. The catchment water quality management plan has to provide, amongst other things, compliance requirements for each activity based on the level of pollution that can be accommodated by the water without impairing its suitability for use. Pollution prevention is a key issue in the catchment strategies embodied in the management plan to ensure that set water quality management objectives are met. Figure V.3 Total dissolved solids and sulphate concentrations in Witbank Dam, 1987-94 (After Wates, Meiring and Barnard, 1993) V.5.1 Catchment water quality management plan A catchment plan will provide a framework to manage water quality coherently and consistently; to influence present and future land use, particularly those uses over which DWAF does not have direct control; and to integrate other resource management efforts and environmental media issues with water quality. In order to provide this framework, the following steps were taken: • Water quality objectives were set at strategic locations in each catchment. The water quality objective at a particular location is a quantitative statement of the water quality that must be maintained at that particular point to ensure suitability for use. In the Witbank Dam catchment, the recognised water uses are domestic, power generation, mining, recreation, the natural aquatic environment and irrigation. • Flexible catchment strategies were formulated to ensure that water quality objectives can be attained. • Compliance requirements were set for those activities that could adversely affect water quality. Sites giving rise to both point and diffuse sources of pollution were considered "single" sources and the compliance requirements were determined and stipulated accordingly. • The collective powers and influence of other authorities, agencies and the public were co-ordinated in a co-operative manner to implement catchment strategies. This applies particularly to control over future land use and adjustment to existing land-use practices to reduce diffuse sources of water pollution. • Monitoring and auditing systems were provided to ensure the implementation of catchment strategies. The effectiveness of the catchment water quality management plan and of water quality management efforts undertaken by other role-players was also monitored. The catchment water quality management plan is being developed to such a level of detail that it specifies what must be achieved and implemented, where and when it will be implemented, how it will be administered and managed and who will be responsible for the specific activities. However, the catchment cannot be managed as a single management unit. Sub-catchments upstream of the dam have different water-use requirements. For this reason, the catchment was subdivided into nine management units on the basis of the sub-catchments (see Figure V.2). At the lower end of each management unit, in-stream water quality management objectives are set. The management strategies and water quality objectives embodied in the plan focus on: • Salinity, with sulphate as the selected indicator of salinity. • Eutrophication, with phosphorus as the limiting nutrient. • Toxic constituents, particularly heavy metals and ammonia. Salinity The sulphate management objective for the dam itself was set at 155 mg l -1 (95 percentile value). This is approximately 23 per cent lower than the user requirement of 200 mg l -1 . This margin allows for: • Further mining, industrial and agricultural development. • Potential malfunctioning of water pollution control systems. • Current knowledge gaps on the future potential impact of atmospheric deposits, high- extraction coal mining and open-cast mining technique. • Lack of adequate information to establish accurately water user requirements, particularly that pertaining to the natural aquatic environment. Attainment of the sulphate management objective depends on zero discharge from power stations, 45 per cent reduction in diffuse pollution from collieries and additional water imported into the catchment. The projected improvements resulting from applying these strategies are indicated in Figure V.4. The sulphate management objectives for the nine management units are outlined in Table V.1. Figure V.4 Present and predicted sulphate concentrations in Witbank Dam assuming power stations operating at zero discharge facilities and with a 45 per cent reduction in non-point source colliery pollution (After Wates, Meiring and Barnard, 1993) Eutrophication Eutrophication control is aimed at limiting the available phosphorus compounds in order to reduce algal growth in the Witbank Dam. Natural anthropogenic weathering and agriculture are the largest diffuse sources of phosphorus in the catchment. Substantial losses of phosphorus applied to agricultural land take place in the catchment; 32 per cent of this reaches the Witbank Dam. It was not considered practical to control these diffuse sources of phosphorus. Municipal sewage treatment plant effluents provide 38 per cent of the recorded catchment sources and 44 per cent of the recorded phosphorus discharge to the dam. Phosphorus control is principally aimed at these sources by means of imposing a special phosphate standard of 1 mg l -1 PO 4 -P on all sewage plant effluents. Table V.1 In-stream sulphate management objectives Management objective Management unit 1 Most sensitive user requirement (mg l -1 SO 4 ) 50 percentile 95 percentile 1 30 24 34 2 200 70 120 3 * 620 1,200 4 * 830 1,450 5 200 220 390 6 * 260 380 7 200 160 260 8 200 190 460 9 (Witbank Dam) 200 84 155 1 Management units are based on sub-catchments of the Witbank Dam catchment * None identified Source: Wates, Meiring and Barnard, 1993 Metals and ammonia Control of metals and ammonia will be effected by restricting the maximum allowable free and saline ammonia and metal concentrations in discharges from mining and industrial complexes. These maximum allowable concentrations are given in Tables V.2 and V.3. V.5.2 Prevention and minimisation of pollution The essence of the approach to pollution prevention and minimisation is the use of regulatory instruments which facilitate direct intervention to prevent pollution at source. The Water Act, which is the statutory component of the regulatory instruments applied by DWAF directly, has limited power to exert influence on land use affected by mining. Thus direct intervention to prevent diffuse pollution, in particular, is not always possible. In order to address this, as well as other shortcomings mentioned earlier in relation to mining activities, co-ordination between the regulatory systems of DWAF and DMEA was effected. Co-ordination was accomplished by participation within an integrated environmental management system for prospecting and mining activities. Table V.2 Maximum allowable concentrations of free and saline ammonia in discharges from mining and industry Free and saline ammonia concentration (mg l -1 NH 3 -N) pH of discharge 15°C 1 20 °C 1 25 °C 1 6.5 10.0 10.0 10.0 7.0 3.4 4.4 4.8 7.5 1.1 1.7 1.3 8.0 0.62 1.1 0.76 8.5 0.36 0.37 0.27 9.0 0.13 0.14 0.12 1 Temperature values apply to the effluent or discharge. Ideally, they should have been applied to the receiving water body. However, for prolonged periods the base flow in receiving streams can be very low to negligible and therefore the temperature requirement has been applied to discharges. Source: Wates, Meiring and Barnard, 1993 Table V.3 Maximum allowable concentrations of heavy metals in discharges from mining and industry Heavy metal Maximum allowable concentration (mg l -1 ) Aluminum 150 Cadmium 2 Chromium 200 Copper 20 Iron 1,000 Lead 10 Manganese 500 Mercury 0.1 Nickel 100 Selenium 30 Zinc 200 Source: Wates, Meiring and Barnard, 1993 The integrated system plays a key role in the regulatory systems of both departments in the following ways: • Placing the departments in a position to address anticipated effects on the water environment before mining proceeds. • Placing the departments in a position to ensure that environmental objectives are met constantly. • Ensuring that mining proponents have understood the magnitude and nature of the effect which their activities will have on the environment, and have committed [...]... related to water pollution The water supply system provides about 60 m3 s-1 for this area, about 80 per cent of which is returned untreated to the main water courses Water quality problems are compounded by the fact that the rivers form part of a system designed exclusively for electric power generation This system requires the flow to be reversed and, consequently, a mixture of untreated wastewater and... extent that the second level of objectives have mostly been reached before implementation of the required long-term strategies V.8 References Wates, Meiring and Barnard 1993 Technical support document for Witbank Dam Water Quality Management Plan Prepared for the Department of Water Affairs and Forestry, South Africa Case Study VI* - The Upper Tietê Basin, Brazil * This case study was prepared by Roberto... implementation of the water quality management approach in the Witbank Dam catchment The following issues require attention: • The development of a catchment plant that focuses on water quality alone serves a limited purpose Water supply and demand issues must be included in the development of a catchment water management plan to ensure effective water resource management • Commitment to water- related issues... valley are principally involved in agricultural activities, complemented by livestock breeding Their standard of living is higher than that of the population without access to wastewater for use in irrigation (Romero, 1994) Irrigation districts 03-Tula and 100-Alfajayucan use raw wastewater from the metropolitan area of Mexico City (Figure VII.2) This wastewater has received no conventional treatment... Paulo Case Study VII* - The Mezquital Valley, Mexico * This case study was prepared by Humberto Romero-Alvarez VII.1 Introduction Mexico is a federal republic composed of 31 states and a federal district The country has a surface area of nearly 2 × 106 km2 and an annual rainfall of 777 mm, which is equivalent to 1,522 × 109 m3 a-1 of water This volume of water should be sufficient for all the needs of... collecting all the information, CETESB defined a system called STAR (Sistema de Tratamento de Águas Residuárias, or Wastewater Treatment System) which is an information protocol establishing the treatment processes for each industry together with the schedule for the implementation of the treatment and the permit system, under the agreement signed by CETESB and the industries The information gathered... addition, the demand for municipal water supply is growing exponentially, from 5 m3 s-1 in 1940 to a projected 65 m3 s-1 by the year 2000 (Figure VI.2) This region has the largest urban concentration in the whole of South America and the largest industrial complex in Latin America The industrial output is 27 per cent of the national total and 62 per cent of the State total The motivation for this rapid development... projected growth in population and water supply in the São Paulo region VI.3 Pre-intervention situation Geography and history have been influential in shaping early water resources development in the São Paulo metropolitan area The first large hydraulic project was conceived purely for the purpose of generating hydroelectricity and stemmed from the need to supply cheap energy for industry The system was designed... secondary level and, therefore, severe environmental problems were experienced The complexity of the system grew as the need to increase municipal water supplies resulted in some of the reservoirs (originally planned for hydroelectric generation, e.g the Guarapiranga reservoir) being used to supply water The untreated sewage, flowing through the main channels, was then used for power generation Figure... a task force with selected professionals from both of these companies and six other State departments The directive committee is chaired by the State Governor himself The Tietê Project began with a master plan for sewage collection and disposal which had been prepared during the period 198 3-8 7 Under this plan, five wastewater treatment plants were considered with a total capacity of 53.2 m3 s-1 This . and 7,750 for different population groups. Furthermore, the country is characterised by great disparities concerning access to adequate water supplies. Water- related issues are, therefore, a. development. • Potential malfunctioning of water pollution control systems. • Current knowledge gaps on the future potential impact of atmospheric deposits, high- extraction coal mining and open-cast. responsible for the specific activities. However, the catchment cannot be managed as a single management unit. Sub-catchments upstream of the dam have different water- use requirements. For this