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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

Research on cactus pear grabs attention of food, cosmetic and medical industry
2015-02-18

Cactus pear
Photo: Charl Devenish

The dedicated research and development programme at the UFS on spineless cactus pear (Opuntia ficus-indica) – also known as prickly pear – has grown steadily in both vision and dimension during the past 15 years. Formal cactus pear research at the UFS started with the formation of the Prickly Pear Working Group (PPWG) in June 2002. It has since gone from strength to strength with several MSc dissertations and a PhD thesis as well as popular and scientific publications flowing from this initiative.

According to Prof Wijnand Swart from the Department of Plant Sciences, the UFS is today recognised as a leading institution in the world conducting multi-disciplinary research on spineless cactus pear.

Cactus pear for animal feed

Increasing demands on already scarce water resources in South Africa require alternative sources of animal feed – specifically crops that are more efficient users of water. One alternative with the potential for widespread production is spineless cactus pear. It is 1.14 x more efficient in its use of water than Old man saltbush, 2.8 x more efficient than wheat, 3.75 x more efficient than lucerne and 7.5 x more efficient than rangeland vegetation.

“Studies on the use of sun-dried cactus pear cladodes suggest that it has the potential to provide some 25% of the basic feed resources required by South Africa’s commercial ruminant feed manufacturing sector,” says Prof HO de Waal of the Department of Animal, Wildlife and Grassland Sciences at the UFS.

Until recently, research has focused extensively on the use of cactus pear as drought fodder. However, this is now beginning to shift, with growing interest in the intensive production of spineless cactus pear for other types of animal feed. One example is the spineless cactus pear fruit, produced seasonal, yielding large quantities of fruit in a relatively short period of a few months in summer. Unless kept in cold storage, the fruit cannot be stored for a long period. Therefore, a procedure was developed to combine large volumes of mashed cactus pear fruit with dry hay and straw and preserve it for longer periods as high moisture livestock feed, kuilmoes – a high water content livestock feed similar to silage.

Cactus pear and Pineapple juice
Photo: Charl Devenish

Cactus pear for human consumption

“In addition to its use as a livestock feed, cactus pear is increasingly being cultivated for human consumption. Although the plant can be consumed fresh as a juice or vegetable, significant value can be added through processing. This potential is considerable: the plant can be pickled; preserved as a jam or marmalade; or dried and milled to produce baking flour. It can also serve as a replacement of egg and fat in mayonnaise,” said Dr Maryna de Wit from the Department of Microbial, Biochemical and Food Biotechnology.

The extraction of mucilage from fresh cladodes can form a gelling, emulsifier, and fat-replacing agent commonly found in food products such as mayonnaise and candy. During an information session to the media Dr De Wit and her team conducted a food demonstration to showcase the use of the cladodes in a juice, chicken stir-fry, biscuits and a salad.

The extrusion of cactus pear seed oil provides a further lucrative niche product to the array of uses. These include high-value organic oil for the cosmetic sector, such as soap, hair gel and sun screens.

The cladodes and the fruit also have medicinal uses. It has anti-viral, anti-inflammatory, pain killing and anti-diabetic agents. It is also high in fibre and can lower cholesterol. The fruit also prevents proliferation of cells and suppresses tumour growth and can even help to reduce a hangover.

In South Africa the outdated perception of cactus pears as thorny, alien invaders, is rapidly disappearing. Instead, farmers now recognise that cactus pear can play a vital role as a high yielding, water-efficient, multi-use crop, said Prof de Waal and the members of the Cactus Pear Team.

Facebook photo gallery
Dagbreek interview with Dr Maryna de Wit  

Research on cactus pear (read the full story)

For more information or enquiries contact news@ufs.ac.za

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