Riet River health in Mokala National Park after the Jagersfontein tailings dam collapse
MOKALA NATIONAL PARK AND ITS RIET RIVER ECOSYSTEM IS VULNERABLE TO UPSTREAM DISTURBANCES AS EVIDENCED BY EFFECTS OF THE COLLAPSED MINE TAILINGS DAM AT JAGERSFONTEIN
A primary aim of protected areas is to conserve biodiversity and ecosystems. For linear riverine ecosystems this is extremely challenging, with many freshwater systems under pressure from water abstraction, development and pollution. Furthermore, the location of some protected areas makes conservation of riverine ecosystems challenging when they are located downstream of industrial or other significant developments.
These challenges became very apparent in September 2022 when a tailings dam located in the Riet River catchment 220 km upstream of Mokala National Park collapsed and negatively affected river macroinvertebrates and water quality variables. For instance, seven macroinvertebrate families that were frequently found in Mokala before dam collapse disappeared and the macroinvertebrate average SASS5 score decreased by 17%.
The collapse of a mine tailings dam at Jagersfontein, more than 200 km upstream from Mokala National Park on a tributary, had negative impacts on the Riet river in Mokala National Park (Map: Abel Matsapula).
The tributary of the Riet River near Jagersfontein, clogged with siltation from a collapsed mine tailings dam. This incident happened 220 km upstream of Mokala National Park, in the catchment of the Riet River which flows along the border of the park (Photo: Hendrik Sithole).
Effects of a mine tailings dam collapse on the Riet River in Mokala National Park, both macroinvertebrate score and water quality decreased (increased dissolved solids
and decreased water clarity).
Furthermore, in the aftermath of the dam collapse, concentrations of total dissolved solids (TDS) in the park increased, although they were still lower than sites upstream of the park. TDS are a measure of dissolved organic and inorganic materials such as metals, minerals, salts, and ions and concentrations provide an indication of water quality. Surprisingly, the Modder River, a tributary of the Riet River below the Jagersfontein dam and not affected by the collapse, had even higher TDS concentrations, and hence did not dilute TDS in the Riet River in Mokala National Park.
We also observed a decline in the clarity of the water as a result of an increase in suspended particles as a result of the spillage. Water clarity was also not improved in the Modder River due to its high concentrations of suspended particles.
Elevated TDS concentrations and low water-clarities are expected to have longer-term negative impacts on macroinvertebrates in the Riet River, as these and other elements of river biodiversity struggle to adapt to poor water quality. Ongoing monitoring is important to track the changes and responses and can assist stakeholders to lobby for more responsible upstream water use.
This article was written by Hendrik Sithole, Roxanne Erusan and Jerome Snyders and originally published in the 2022/2023 Research Report.
