Climate change in South African rivers : a case study on the Olifants River in the Kruger National Park

Abstract

Freshwater systems are among the most endangered ecosystems, with anthropogenic climate change causing detrimental ecological and economic impacts. Due to climate change, increased air temperatures will translate into the warming of rivers, and at the same time will alter flow regimes and increase evaporation and stochastic events. In this study, we used validated statistical water temperature models that predict average water temperatures (WTavg) from air temperature to project monthly and daily WTavg from 2025 to 2100 CE in the heavily polluted and over-abstracted Olifants River, Kruger National Park, Limpopo Province, South Africa, under the ‘business as usual’ Representative Concentration Pathway 8.5 scenario. The results from 16 General Circulation Models showed that monthly WTavg is likely to increase by 3.6 °C and showed summer months reaching up to 34–35 °C by 2100 CE. The daily results showed a similar increase of 3.7 °C by 2100 CE, with some extreme days reaching 42–44 °C. These results support similar research conducted within the Olifants catchment of the Limpopo Basin and add to the limited knowledge of freshwater climate change, especially in Africa. Climate change will ultimately alter the thermal and physical landscape of the Olifants River and this forecast highlights the need for further research on the potential detrimental consequences on freshwater biota, including possible local extinctions.

SIGNIFICANCE • Increasing air temperature due to anthropogenic climate change will cause water temperatures to rise. • Statistical models can be used to predict future water temperatures from air temperature. • The projections show an increase in monthly average water temperature (WTavg) of 3.6 °C and an increase in daily WTavg of 3.7 °C by the end of the 21st century. • This drastic rise in water temperatures will ultimately have negative effects on freshwater biota.