The South African government and its organs must play the leading role in directing efforts to halt and turn around the progressively deteriorating state of freshwater in the upper Olifants River catchment, eventually impacting on the water quality in Loskop Dam.
CSIR senior researcher Dr James Dabrowski taking samples from a heavily contaminated site in the Klip River just outside Witbank.
Loskop Dam supplies water to the second biggest irrigation scheme in South Africa.
According to the executive summary of the first year’s report of the CSIR-study on the chemical pollution of the upper Olifants River catchment, the Olifants and Klein Olifants rivers are eutrophic, while the upper catchment was found to be highly contaminated with microbial pollutants, disease-causing micro-organisms and endocrine disruptors. The other main stressor impacting on water quality in the catchment and eventually Loskop Dam is acidic water containing heavy and trace metal ions and sulphate, attributable to abandoned mining and industrial activities.
Saving this catchment and others like it will require “a truly collaborative approach between government, water resource managers, business and communities. However, government must play the leading role in directing efforts and evaluating success or failure,” the report reads.
Since November 2009 a multidisciplinary team of more than 30 scientists have been working in the upper Olifants River catchment and Loskop Dam to assess the eutrophication and chemical pollution of one of the hardest-working – but also the most polluted – rivers in South Africa. The three year-study, now in its second year, is funded by the Olifants River Forum.
The catchment of the Olifants River rises in the Highveld grasslands and covers about 54 570 km². It provides water to more than 200 dams, irrigating about 110 000 hectare, while Loskop Dam provides water to the second largest irrigation scheme in South Africa.
The report, Risk assessment of pollution in surface waters of the upper Olifants River system: implications for aquatic ecosystem health and the health of human users of water, emphasises the “acute need for greatly improved processes of land use development and management in the catchments of all the river tributaries in the upper Olifants River catchment, to counter the current situation of poor water quality and to halt or (preferably) reverse the existing pattern of progressively increasing eutrophication and contamination. This is a fundamental building block for the protection of water quality in all the rivers draining into Loskop Dam, and to prevent the propagation of adverse water quality impacts further down the Olifants River, as well as a key consideration for all catchment areas in South Africa.”
The report recommends the following action points:
- Refine and implement effective shoreline zoning along all rivers and watercourses, with firm stipulations that all land uses should be set back from the bank of any watercourse by at least 20 metres and even further in erosion-prone zones.
- All on-site sewage treatment and disposal systems used by industries and mines must be upgraded where necessary and managed carefully to consistently meet or perform better than the 1 mg/ℓ orthophosphate-phosphorus effluent discharge standard set under South African water law. The current effluent orthophosphate discharge standard of 1 mg/ℓ is too high for the upper Olifants River catchment or many other catchments in South Africa. The phosphorus target management level of 130 µg/ℓ that has been set for reservoirs in South Africa has not been validated by reliable limnological studies and this phosphorus concentration is more than twice the level at which South African reservoirs show symptoms of intense and undesirable eutrophication.
- Maximise the recycling and re-use of wastewater for other purposes at or close to the point where the wastewater is generated. These principles must be incorporated into water resource management plans for all land use activities. This will reduce the quantity of effluent that is discharged directly to the aquatic systems in the upper Olifants catchment and help to reduce eutrophication and contamination of these aquatic systems.
- Encourage the use of phosphate-free detergents throughout South Africa. The use of phosphate-free detergents is now mandatory in Europe and the USA and has reduced the phosphorus loads reaching wastewater treatment works by 30%.
- Protect and rehabilitate natural wetlands in the upper Olifants River catchment. Wetland plants and soils have a natural ability to trap phosphorus and thereby reduce the phosphorus loads that enter river and lake systems. This “phosphorus trapping” ability provides an effective “polishing mechanism” that helps to reduce the likelihood of nuisance algal blooms occurring; this is particularly important during the summer months.
- Every activity that causes or leads to an increase in aluminium concentrations in the upper Olifants catchment needs to be reduced or avoided as far as possible. The Criterion Continuous Concentration (CCC) for aluminium (the estimate of the highest concentration to which aquatic communities can be exposed to Al indefinitely without unacceptable effects) is 87 µg ℓ-1 at a pH value between 6.5 and 9.0. This CCC value is far lower than the average aluminium concentration recorded at certain of the study sites.
- Four key perspectives need to be embraced if the current process of cultural eutrophication (i.e., eutrophication processes that are accelerated by human activities) is to be halted and reversed. These principles are:
- The process of cultural eutrophication is reversible, though it may take time to achieve and require medium to large investments;
- There is no “quick fix, one-size-fits-all” solution. The problem requires a well-planned and effectively implemented long-term approach;
- The issue requires a truly collaborative approach between government, water resource managers, business and communities. However, government must play the leading role in directing efforts and evaluating success or failure; and
- The issue cannot be solved by a single, short-term technical intervention. Solving the problems will require the implementation of a suite of social, economic and technical interventions.
According to CSIR limnologist and project leader, Dr Paul Oberholster, the research team’s focus will now shift towards looking at possibilities of rehabilitation and remediation. This includes the establishment of artificial wetlands and the restoration of existing wetlands in the upper Olifants River catchment in conjunction with the South African National Biodiversity Institute’s (SANBI) Working for Wetlands programme.
The executive summary is available on the Olifants River Forum website at http://www.orf.co.za/welcome.html