Olifants River faces extreme warming by 2100, threatening fish and macroinvertebrates

TheOlifants River, one of South Africa’s most troubled waterways, is facing an escalating threat fromclimate change. Already heavily polluted, overused and ecologically stressed, new research suggests that the river could experience dramatic warming over the coming decades, with potentially devastating consequences for freshwater ecosystems. Thestudy, published in the latest issue of theSouth African Journal of Science, models how rising air temperatures could affect the Olifants under a high-emissions scenario.

The authors said the simulations presented in their study suggest that rising air temperature because of climate change will translate into rising water temperature in the Olifants River, with both daily and monthly water temperatures rising by up to 5°C by 2100. The study projects that by the end of the century, daily water temperatures on some extreme days could reach 42°C to 44°C, while monthly averages could rise by about 3.6°C and daily averages by about 3.7°C. Summer temperatures could regularly reach 34°C to 35°C.

The researchers warn that these results do not just indicate a large rise in water temperature but allude to the Olifants River undergoing other changes, such as increased evaporative losses and possible changes in flow regime. “The river will experience changes in both thermal and physical habitats, which will have detrimental effects on the survival and breeding of freshwater species which are sensitive to disruptions in flow regime and temperature change.” The scientists, from the University of Pretoria’s department of zoology and entomology, the Mammal Research Institute and the Association for Water and Rural Development, focused on a stretch of the river flowing through Kruger National Park – a section that remains ecologically important despite heavy pressures accumulating upstream. Rather than directly measuring future water temperatures, the researchers used validated statistical water-temperature models that estimate river temperatures from air temperatures.

[paywall]

They then applied future climate projections from 16 general circulation models under representative concentration pathway (RCP) 8.5, a high-emissions or “business as usual” scenario in which greenhouse gas emissions remain elevated and warming continues largely unchecked. The researchers modelled both monthly and daily average water temperatures from 2025 to 2100 in the heavily polluted and over-abstracted Olifants River in the Kruger.

[/paywall]