Healing South Africa’s ailing dams16 May 2013
A combination of factors have contributed to the poor health of the Hartbeespoort dam in South Africa. The 90-year-old dam has been described as one of the country’s sickest but a government initiated remediation programme is now having a positive effect.
The Hartbeespoort dam on the Crocodile River is described as being one of the most significant dams in the economic hub of South Africa's North West Province. Used for agricultural, industrial and recreational purposes it helps contribute to more than one-third of the country's gross domestic product.
Built in 1923, the 59.3m high dam's supply level was raised in 1970 through the installation of ten 10m x 2.4m crest gates on the spillway. Hartbeespoort is the lowest point of a catchment on the Crocodile River which starts in Johannesburg, Kempton park, Ekurhuleni, Tshwane and Centurion. According to the Department of Water Affairs these catchments contain informal settlements, and with their respective storm water challenges, the result is that "everything ends up at the Hartbeespoort dam".
Twenty six state dams are located in the region and seven of these are in a hypertrophic state. The Department of Water Affairs states that Hartbeespoort dam is the "sickest" in the area.
So what factors have had such a detrimental effect on the health of the South African dam? For many years, nine wastewater treatment works have discharged 720M litres of purified effluent into the Crocodile River each day and there has been an increasing load of phosphorus in the dam. With polluted storm water from the catchment this has intensified the occurrence of blue-green algae or cyanobacteria which, can not only pose a great risk to human health, but also have a detrimental impact on recreational activities and economic activity in the region.
Rapid urbanisation in the area has also led to increased runoff, sedimentation, erosion and solid waste entering the reservoir. Contrary to previous beliefs, it has also become evident that 15-20 years of pollution has become trapped in the sediments. This pollution is constantly in re-circulation and nutrients released from the sediment have affected reservoir biology.
For more than 30 years there also has been extensive and unrestricted growth of water hyacinth in the dam and upper catchment. While over the past three years the influx of litter and debris has become a growing problem which has escalated dramatically and can no longer be ignored. Finally during the provision of launching platforms for recreational vessels and unobstructed fishing areas, the shoreline has been cleaned and destroyed - becoming almost sterile.
“It is important for us to face the facts," the Department of Water Affairs stated. "We are the people causing the imbalance in our water resources and we have a responsibility towards dealing with it. The ordinary person does not realise what the actual cause is or what each and every one of our share of the problems are. In short: we are part of the problem and we need to become part of the solution."
Although Hartbeespoort dam has been in a eutrophic state since the 1980s it had gone unnoticed as the area was sparsely populated. However, as development increased, so did public pressure to address the dam's poor condition.
In 2005 the Department of Water Affairs (DWA) implemented the Hartbeespoort Dam Integrated Biological Remediation Programme (Harties Metsi a me which means my water). A thorough two-year study on the biological condition of the dam was undertaken and DWA appointed Rand Water as the implementing agent for the programme in June 2006. In May 2007 the programme was identified as a national priority to facilitate immediate full scale implementation and fast tracking. It forms part of the South African government's plan to target growth and development and generate employment.
The focus is to determine, optimise and manage the physical and biological conditions at the dam through a reduction in the levels of toxic algae, the removal of hyacinths and fish biomass amongst others.
AS DWA states the programme is focusing on short term results which will be implemented in parallel with longer term challenges. A three pronged approach is being taken:
• Firstly, symptomatic treatment, restorative action and the creation of a biological self-cleaning balanced ecosystem will be established in the dam basin. This involves establishing a natural balance in the dam by removing the bulk of the algae, hyacinths, unwanted fish, dead shorelines, litter traps and trapped sediments.
• Secondly, the natural filters of wetlands and riverbanks in the immediate catchment of the Hartbeespoort dam will be restored and protected.
• Thirdly, water use in the greater Hartbeespoort dam catchment will be regulated. There will also be enforcement on unlawful water use and the integration of interdepartmental efforts across the catchment to address the impacts on the dam.
Phase I of the remediation of the dam started in 2008 and has led to significant improvement. "We are very pleased that there has been a real improvement in the overall condition of the dam with no more unpleasant smells emanating from it and the water becoming clearer," Minister of Water and Environmental Affairs Edna Molewa said in September 2011.
Since 2007 the programme has employed up to 140 people and removed:
• 6400 tons of hyacinth.
• 2400 tons of litter and debris.
• 31M litres of algae.
• 190 tons of unwanted fish.
In addition more than 8500m2 of shoreline has been rehabilitated and 4800m2 of floating wetlands have been constructed to act as filters to clean the water. More than 11,500 tons of sediment has also been excavated with the dredging of 50 tons. The harvested plant matter, litter and debris were recycled and the organic matter composted with the use of earth worms. Local people even started up earthworm farms near the dam to help the programme. The quality of fish in the reservoir has also improved and it has now been established that they are in a class 1 and 2 state of health.
To inform and educate the general public about the role they can play in ensuring pollution of the dam is reduced, an Information, Communication and Knowledge Centre was established at the dam wall. More than 7000 visitors and 6000 learners have benefitted from this so far.
“What is more pleasing with these developments at this dam is that the general public can contribute to the solution by implementing waste minimisation and reuse options to reduce catchment impacts to the water resources, with the focus on addressing these impacts on a biological and more environmentally friendly manner," Minister Molewa said.
Phase II of the programme started in September 2012. In November DWA announced that R258M (US$) is to be spent during the 2013-14 financial year on O&M, fast tracking and full scale project implementation.
DWA says that the department remains committed to the fight against pollution and such efforts will go a long way in ensuring a more sustainable management of South African water resources.
For more information about the Hartbeespoort Dam Integrated Biological Remediation Programme see www.harties.org.zaFor more information about the Hartbeespoort Dam Integrated Biological Remediation Programme see www.harties.org.za