“I don’t think South Africa is prepared for the possibility of a Gauteng Day Zero drought,” said Professor Francois Engelbrecht, director of the Global Change Institute at the University of the Witwatersrand.
Professor Engelbrecht was a keynote speaker at a session of the Southern African Mountain Conference 2022, held in the Drakensberg earlier this year and supported by, among others, the Afromontane Research Unit at the University of the Free State (UFS). The session, hosted by the international network, GEO Mountains, looked at Long-term monitoring activities and associated data availability for climate change-related applications across Africa’s mountains: status quo and next steps.
The professor went on to say we came very, very close in the 2015-2016 drought when the Vaal Dam dropped to 25% of capacity. Had it dropped just a bit more, to 20%, the most densely populated province in South Africa, our economic hub, would have been in serious trouble, as there would have been too little water to enable pumping the last dregs into the province.
What’s the link between a Day Zero event in Gauteng and data about mountain environments?
Think of the water towers that dot the Highveld landscape in Gauteng, very visible to residents of the suburbs. Mountains can be seen as massive ‘water towers’ that provide water to people hundreds, even thousands, of kilometres from their foothills. As Dr James Thornton of GEO Mountains, co-host of the session, explained, mountains provide a flow of ecosystem services; water provision is just one of them, but it is of critical importance. “The mountains are crucial for this, due to the orographic enhancement of precipitation.” The shape and topography of mountains (their orography), force moist air upwards into cooler air at higher elevations – an effect called ‘orographic uplift’ – so that vapour is held in the air condenses into water.
So as moisture-laden air sweeps in from the warm Indian Ocean to the east of us, it encounters the upward thrust of the long Drakensberg chain of mountains, from the Eastern Cape through Lesotho and KwaZulu-Natal and on, up to the Wolksberg Mountains in Limpopo. The upward movement of the air into colder regions triggers precipitation – rain, mist, sometimes snow.
And that moisture, falling on the soil and rocks in cool mountain air, is also less likely to evaporate and return rapidly to the atmosphere, as it might do on the coastal plains and lowlands.
The result? The most obvious consequence is waterfalls glittering in the mountain cliffs and swollen streams rushing down the slopes. Look at maps and you’ll see rivers springing from mountain sources everywhere in the world, like the Tugela heading east and the Orange flowing west from the Drakensberg in South Africa and Lesotho, or the Ganges and Indus rising in the Himalayas and the Rhine and Rhône rising in the Alps.
Mountain water also seeps into the ground, making its way through soil and rocks and recharging the groundwater within and beyond the mountains and their foothills. This recharge of the water table from high up in the mountains also contributes to streams and rivers that supply so much of our water needs, scientists have shown.
Mountain water in Gauteng
Gauteng residents are well aware of the role of the Vaal River in the Vaal Water Supply System, but do we understand just how much of our water originates in the Drakensberg? According to the Water Research Commission “transfers from the Maloti Drakensberg (34.4%) and the Northern Drakensberg SWSA (18.9%)” are critical to our water supply. That’s a little more than half our water in Gauteng coming from the Drakensberg.
Engelbrecht and his co-authors wrote a few years ago: “Except for the Southern Cape, the Drakensberg is the single most important source of water in Southern Africa and supplies regions where the bulk of the population resides.” (The Drakensberg Escarpment as the Great Supplier of Water to South Africa, S.J. Taylor, et al, in Developments in Earth Surface Processes Volume 21, Mountain Ice and Water, Investigations of the Hydrologic Cycle in Alpine Environments.) But, they added, due to population growth and other pressures, “In South Africa, it is now expected that demand for water will exceed supply by 2025 if nothing is done to supplement current water resources.”
That in itself is reason enough to focus on monitoring our mountains, and to support scientists observing and gathering data there. But add that to Professor Engelbrecht’s prediction that “multiyear El Nino-type droughts may plausibly occur from the mid-century (2030-2060) onwards” due to the climate change crisis, and it’s clear that we desperately need to understand the detail of how our mountains provide us with water; we urgently need to understand what is changing in the mountains.
The ongoing and rapid changes we’re seeing in these very sensitive environments, from changing precipitation patterns, to changing land-use, to increases in population, is why we really need to “monitor and track these changes, to understand the biophysical processes and their interaction with society, and to be able to better estimate the chance, for instance, of future extreme droughts on a more local scale so we can develop measures for mitigation and adaptation,” said Dr Thornton. Better management of upstream water resources – such as the massive ‘water tower’ in the Drakensberg and elsewhere – is one tactic we should be vigorously pursuing.
There is a paucity of data about our precious mountainous areas across the world, but especially in Africa, and one of the messages of this workshop and of the conference as a whole was the importance of not just doing the monitoring and gathering of data, but making it readily accessible to all.
Dr Susan Janse van Rensburg (of the South African Environment Observation Network or SAEON, a national facility of the National Research Foundation) spoke about the in situ environmental monitoring that is being done in important mountain areas, including Cathedral Peak, the heart of the Central Drakensberg where the conference was being held. She introduced SAEON’s new Data Portal for researchers to access and share data about mountains – and not just in South Africa, but across the whole continent.
Omar Seidu gave a presentation on an initiative called Digital Earth Africa which collates and curates satellite data – including data on mountains. And GEO Mountains itself runs inventories which “seek to identify, link up, and make accessible existing data and information resources across the world’s mountains”.
“We’re trying to make it straightforward for researchers on the ground to make their datasets available to anybody if they choose to do so,” said Dr Thornton.
Research, observations and data-gathering on the ground (and from satellites) is the foundation for intelligent analysis, which results in solid evidence that can guide policymakers and the public to make the best choices. Mountains, our water towers, have perhaps not been enough of a focus for society in the past; information about their vital role in something as basic as water provision, and better understanding of the processes that furnish us with water, will surely help us to both mitigate and adapt to a future in which water scarcity looms so large.