Olifants river study under way to identify potential stressors

16 March 2010, Engineering News
URL: http://www.engineeringnews.co.za/article/olifants-river-study-under-way-to-identify-potential-stressors-2010-03-15

Johannesburg:  Some 30 researchers from the Council for Scientific and Industrial Research (CSIR), as well as a number of South African universities, are undertaking an intensive multidisciplinary study of the upper Olifants river and its tributaries.

The study will eventually identify the sources of different stressors to the river system, develop and refine appropriate water quality management responses, decision-making processes, and remediation measures for the rivers in the catchment area.

The stressors are many. Owing to the amount of human interference in terms of mining, power generation, industry, agriculture and sewage treatment in the catchment area of the Olifants river, it has been described as one of the most polluted rivers in Southern Africa.

Pressing concern over pollution in the Loskop dam is viewed as a symptom, and researchers said that they could not remediate the dam without assessing the impacts and causes in the upper catchment area.

CSIR research group leader Dr Paul Oberholster explains that the study takes a holistic approach to the entire upper catchment area, and analysis of samples from various sites will be done on: endocrine disrupting contaminants activity; bacteria, viruses and pathogens in the water; single cell organisms; invertebrates; fish; and algae found in the water.

"Pollution is difficult to measure as it quickly moves through the river and becomes dissolved. However, traces of how pollution has affected an area can be found and analysed by looking at indicators such as phytoplankton and algae in the sediments, macro-invertebrates and fish, while isotope studies will give an indication of the possible accumulation of heavy metals and fish and invertebrates," he says.

The study will identify the critical variables in the upper Olifants river and its tributaries, and determine their thresholds by making use of a set of ecological indicators, at different trophic levels (the position that an organism holds in the food chain). It will also use molecular techniques that give accurate estimates of the ecosystem health in the study area.

Although the upper Olifants river is affected by many variables, the CSIR notes that such a system is usually driven by a few controlling variables, such as heavy metals from acid mine drainage, industry and power generation, and high total phosphate concentrations from the inflows of untreated or partially treated sewage. Associated with these variables are threshold concentrations that contribute to the resilience of the system and its ability to withstand and recover from various stressors.

Funding for the first year of the project has been secured through the Olifants River Forum. This group was formed in the mid-1990s by a number of participants, largely from the mining industry, but also from heavy industry, the agricultural sector, and the Parks Board, which wished to improve the catchment area as a whole.

It is hoped that funding for a further two years will be sourced, as the study will require more than only one year of research.

In April, the CSIR will also start a human health risk assessment, piggy backing off the Olifants river research project.

The Olifants river flows north through Mpumalanga province before reaching the Loskop dam. It then flows on through the Kruger National Park, and eventually through Mozambique where it enters the Indian Ocean at Xai-Xai north of Maputo.

In 2007, there was a 14-ton fish die off in the Loskop dam, and, despite being one of the few inland rivers that can accommodate crocodiles, the number of crocodiles in the Loskop dam has declined from about 80 in 2003 to 4 in 2009.

Although water sampling in the Loskop dam has been focusing on the inorganic components of water quality for the past 20 years, little biological sampling research has been done on Loskop dam, and the best study was conducted in 1968. A number of people are experiencing a growing concern for the water quality, and water from the Loskop dam has now been sampled for the last three years.

The Loskop dam nature reserve covers about 22 850 ha, in which, about 2 350 ha surface area of the dam is included. Mpumalanga Parks and Tourism Agency regional ecologist Jannie Coetzee explains that the wilderness zone of the dam is now one of the most polluted areas of the dam. "The conservation area of the dam is on the receiving end of the upstream pollution." And the pollution in the dam is bad for tourism, which is what drives conservancy.

"There is a risk of this lake becoming like Hartebeespoort dam - that is why we must look at the upper catchment area. We will try our best to sort it out. The farmers are relying on the CSIR because their livelihood depends on it," explains Oberholster.

Hartbeespoort dam is renowned for its poor water quality. It suffers from severe eutrophication resulting from the high concentrations of phosphates and nitrates in the Crocodile river inflow. The pollution sources are industrial and domestic effluent from Gauteng. The eutrophication is evident in the excessive growth of algae and cyanobacteria, as well as macrophytes like water hyacinth.

Cyanobacteria are now also evident in sections of the Loskop dam. Oberholster explains that there are three or four different microcosms of phytoplankton and environmental conditions in the one dam. At the area where the Olifants river flows into the dam, the pH is about six, while in the transitional zone of the dam, the pH is about eight or nine.