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High risk that water demand in Gauteng will exceed available resources

08 April 2025 | Story Andre Damons | Photo Andre Damons

DrSophie-Biskop_ProfFrancois-Engelbrecht — Dr Sophie Biskop from the Department of Geography at the Schiller University Jena, Germany, and Prof Francois Engelbrecht, a Professor of Climatology at the Global Change Institute (GCI), University of the Witwatersrand, at the Southern African Mountain Conference (SAMC).

The severe El Niño drought of 2015/16, which culminated in the Vaal dam reaching an alarming low water level (~25%), prompted scientists to try and predict whether climate change could bring a drought so severe and long lasting that Gauteng could run out of water.

Prof Francois Engelbrecht, a Professor of Climatology at the Global Change Institute (GCI), University of the Witwatersrand, is one of the scientists working on this project and says though they cannot predict a Day Zero drought with certainty, he thinks it is possible that Gauteng might run out of water in the 2030s or 2040s.

“This is the biggest climate change risk South Africa faces”, he said.

Prof Engelbrecht and Dr Sophie Biskop from the Institute of Geography at the Friedrich Schiller University Jena, Germany, together with other scientists are working on a project involving hydrological modelling to predict and prevent a Day Zero from happening. Dr Biskop presented their research paper titled ‘Projected hydrological futures of South Africa's mega-dam region’ at the second Southern African Mountain Conference (SAMC2025) in March, indicating there is a high risk that the water demand in Gauteng will exceed available water resources within the Integrated Vaal River System (IVRS) under future climate change.

Gauteng may be severely compromised

The IVRS, a large, complex water system comprising water resources of different river basins, and several mega-dams within, has been constructed to secure the water supply of the Gauteng province, the economic hub in South Africa.

According to the researchers, Southern Africa is a water-stress hot spot and is projected to become significantly warmer and likely also drier under global climate change, increasing the risk of devastating hydrological droughts. The IVRS, Dr Biskop told the attendees, is vulnerable to the occurrence of multi-year droughts as experienced between 2012 and in 2016. The alarming low water level of the Vaal dam after a period of drought of 2015/16 provided early warning that water security of Gauteng may be directly and severely compromised in a changing climate. Potential evapotranspiration will increase as a consequence of strong regional warming.

Answering questions

“There is consequently a high risk that the water demand in the Gauteng province will exceed available water resources within the IVRS under future climate change. This raises the question if under ongoing climate change the natural hydrological system (without considering water transfers between dam catchments) can maintain dam levels in South Africa’s eastern mega-dam region, and particularly within the Lesotho Highlands,” explained Dr Biskop.

“To answer this question, the aim of our study is to quantify future water balance changes of several dams under changing climate conditions using the Jena Adaptable Modelling System (JAMS), a software framework for component-based development of environmental models. For this purpose, we build process-based hydrological models for several dam catchments.”

She said an ensemble of high-resolution regional climate change projections is subsequently used as forcing, to generate future hydrological projections. The analysis of projected changes in hydrological system components (precipitation, evapotranspiration, run-off) provides probabilistic estimates of the occurrence of a regional climate change tipping point - when the natural water supply can no longer achieve the full storage capacity of the mega-dams which supply the Gauteng region.

Working to prevent Day Zero

According to Prof Engelbrecht, they are working with the City of Johannesburg, the National Department of Water and Sanitation and Rand Water on this project. Their hope for this research is to create awareness in order to try and prevent Day Zero from happening. They also hope to assist these role players in building resilience and help them prepare for Day Zero. Their work with the City of Johannesburg also includes helping the city to reduce water wastage and change water users’ behaviour as well as formulating a disaster management plan should Day Zero happen.

The Southern African Mountain Conference (SAMC) series is unique as it seeks to integrate science, policy and practitioner sectors for sustainable interventions in southern African mountains. SAMC events are conceptualised by the Afromontane Research Unit (ARU) of the University of the Free State (UFS), the African Mountain Research Foundation (AMRF) and Global Mountain Safeguard Research (GLOMOS), a joint initiative between Eurac Research and the UNU Institute for Environment and Human Security. These three organisations form the Primary Partners, with the SAMC series being implemented by The Peaks Foundation (a non-profit company). SAMC2025 is being held under the patronage of UNESCO.

News Archive

Africa's Black Rhino conservation strategy must change

2017-07-10

The black rhino is on the brink of extinction. The study that was
published in the Nature Scientific Reports reveals that the
species has lost an astonishing 69% of its genetic variation.
Photo: iStock

The conservation strategy of the black rhino in Africa needs to change in order to protect the species from extinction, a group of international researchers has found. The study that was published in the Nature Scientific Reports reveals that the species has lost an astonishing 69% of its genetic variation.

South African researchers took part
The researchers, which included local researchers from the National Zoological Gardens of South Africa (NZG), have highlighted the fact that this means the black rhino is on the brink of extinction. "We have found that there is a decline in genetic diversity, with 44 of 64 genetic lineages no longer existing," said Prof Antoinette Kotze, the Manager of Research and Scientific Services at the Zoo in Pretoria. She is also affiliate Professor in the Department of Genetics at the University of the Free State and has been involved in rhino research in South Africa since the early 2000s.

DNA from museums and the wild
The study compared DNA from specimens in museums around the world, which originated in the different regions of Africa, to the DNA of live wild animals. The DNA was extracted from the skin of museum specimen and from tissue and faecal samples from animals in the wild. The research used the mitochondrial genome.

"The rhino poaching ‘pandemic’
needs to be defeated, because
it puts further strain on the genetic
diversity of the black rhino.”

Ability to adapt
Dr Desire Dalton, one of the collaborators in the paper and a senior researcher at the NZG, said the loss of genetic diversity may compromise the rhinos’ ability to adapt to climate change. The study further underlined that two distinct populations now exists on either side of the Zambezi River. Dr Dalton said these definite populations need to be managed separately in order to conserve their genetic diversity. The study found that although the data suggests that the future is bleak for the black rhinoceros, the researchers did identify populations of priority for conservation, which might offer a better chance of preventing the species from total extinction. However, it stressed that the rhino poaching ‘pandemic’ needs to be defeated, because it puts further strain on the genetic diversity of the black rhino.

Extinct in many African countries
The research report further said that black rhino had been hunted and poached to extinction in many parts of Africa, such as Nigeria, Chad, Cameroon, Sudan, and Ethiopia. These rhino are now only found in five African countries. They are Tanzania, Zimbabwe, Kenya, Namibia, and South Africa, where the majority of the animals can be found.

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