South Africa: Groundwater – Key to Mitigating the Effects of The Climate Crisis #AfricaClimateHope

The scene before me was a stark contrast to the world we had known. Empty pools, people lining up for hours for daily rations of water, and dry, parched vegetation, all served as a reminder that we were facing an existential threat. Cape Town faced a drought from 2016 to 2018 when the city came within 90 days of running out of water.

We were forced to conserve water in every way we could. We stockpiled water in buckets and basins, took shorter showers, and turned off the tap when we brushed our teeth. We even felt guilty about flushing our toilets. My colleague went a step further and built a compost toilet. We used the water that had been used for cleaning or cooking for other purposes, such as watering plants or washing our cars. We knew that every drop of water was precious, and we had to make sure we were using it wisely.

Day Zero was our water Armageddon.

The dams were at critically low levels, and there was no rain in sight. If we had reached “Day Zero“, as it was called, residents would have been forced to line up for daily rations of water. The city would run out of water and have to turn off the taps. Businesses would have closed, and the economy would have ground to a halt. It would have been a complete disaster.

It was a whole new reality for us.

The drought was a wake-up call that rattled us to the core. It revealed our vulnerability to water scarcity and highlighted the clear and visible link between water and climate change. We saw first-hand how our water resources can be depleted, and how our lives can be upended by a lack of water. Many people reduced their water use, reused greywater, and increasingly turned to groundwater to meet their needs.

Although the drought may seem like a distant memory, we must remember that climate change is making water scarcity a more pressing issue than ever before.

Millions of people around the world are already experiencing water shortages, and this is only going to get worse. Climate change is disrupting the natural water cycle, causing more extreme weather events like floods and droughts. These events are displacing millions of people and negatively impacting agriculture and access to safe drinking water. It is important to take action now to manage our water resources wisely, or we will face water shortages in the future.

The climate crisis is changing the way weather works, making extreme weather events more common and unpredictable. This is leading to water shortages, which is threatening the health and development of communities around the world, reports UNICEF.

By 2040, almost 1 in 4 children will live in areas of extremely high water stress, according to UNICEF.

The World Health Organization projects that the climate crisis is expected to cause the deaths of an additional 250,000 people every year between 2030 and 2050. This will be caused by climate-linked malnutrition, malaria, diarrhea, and heat stress, all while continuing to jeopardise clean air, safe drinking water, and sufficient food supply.

Access to clean and safe water is a basic human right that is essential for life, well-being, and a sustainable future. The world is not on track to achieve Sustainable Development Goal 6, which aims to ensure universal access to safe and affordable drinking water by 2030. This is a major challenge, as the climate crisis is expected to make water scarcity and pollution worse. The international community must speed up its action to ensure that everyone has access to clean water. This is a moral imperative, as well as a critical step for building a sustainable future.

Despite the challenges we face, groundwater, which is hidden under our feet, helped us to overcome water scarcity and provide a critical source of water during the drought.

Risks to preserving local aquifers

Cape Town is home to three major aquifers: the Table Mountain Group Aquifer, the Cape Flats Aquifer, and the Atlantis Aquifer. These aquifers store a vast amount of water, which is essential for the city’s water supply. The aquifers are recharged by rainwater. However, climate change is likely to have a significant impact on the Cape Flats Aquifers, a vital groundwater resource for the metropolitan region of Cape Town.

allAfrica’s Melody Chironda spoke to hydrogeologist Dr. Reynolds Chow to learn more about the city’s groundwater resources and the severity of the crisis. Chow is a hydrogeologist with over 10 years of experience in groundwater modeling, mining, environmental impact assessments, water pollution, and teaching. He is currently a lecturer in hydrogeology at the University of Stellenbosch in the Department of Earth Sciences.

“Groundwater is like a precious resource that we must protect. It is not an infinite supply, and we need to carefully monitor how much is available to ensure that there is enough for our own use, as well as for the environment,” said Dr Chow.

“Groundwater feeds into our rivers and wetlands. If we take out too much groundwater, we will not be ensuring that there is enough for these ecosystems. This will have a negative impact on the biodiversity of these areas, such as fish, plants, and waterfowl.”

Groundwater is stored underground in aquifers, which are rock and sediment layers that act as underground reservoirs. Groundwater can be accessed via wells and boreholes. It is the largest source of freshwater on earth, comprising 99% of the world’s liquid freshwater. The 2022 United Nations World Water Development Report titled ‘Groundwater: Making the invisible visible’ reports that groundwater which accounts for 99% of the planet’s freshwater supplies – is poorly understood and consequently undervalued, mismanaged, and even abused. It also described the challenges and opportunities associated with the development, management, and governance of groundwater across the world.

Chow warned that Cape Town is already over-exploiting its groundwater resources.

The Cape Flats Aquifer is a ticking time bomb. This shallow, unconfined aquifer is the main source of drinking water for Cape Town, a city of over 4 million people. But it is also prone to flooding, which can contaminate the water supply and make it unsafe to drink. The climate emergency is expected to make this problem worse.

Chow is concerned that the Cape Flats aquifer is being overdrawn. If too much water is withdrawn from the aquifer, it could collapse, leaving people and ecosystems without water. He says that it is important to manage the use of groundwater carefully to ensure that it is not overexploited.

The climate crisis can increase the risk of groundwater contamination and degrade groundwater quality. Chow said that the aquifer is vulnerable to contamination because it is unconfined, meaning that it is open to the atmosphere. This means that pollutants from surface water, such as sewage and industrial waste, can easily infiltrate the aquifer.

“Climate change could exacerbate risks of groundwater contamination in the Cape Flats aquifer,” he said. “This is because climate change is expected to lead to more extreme weather events, such as floods and droughts. Floods can carry pollutants from surface water into the aquifer, while droughts can dry out the soil and make it more likely to erode and carry pollutants into the aquifer.”

A study published in Science Direct conducted by researchers from the University of the Western Cape (UWC) found that temperature increases, along with fluctuating and sometimes sparse precipitation, can have significant hydrologic consequences that significantly impact groundwater quality through increased nutrient and sediment loading to underlying aquifers. The study found that these changes in climate are likely to lead to a decrease in groundwater availability in the Cape Flats Aquifers by up to 20% by 2050. This could have a significant impact on the water supply for Cape Town, which is already facing water shortages.

Chow, referring to the study, said that the aquifer is likely to experience a reduction in groundwater storage over the long term due to climate change. The study found that climate change is expected to lead to more frequent and severe droughts in the Western Cape, which will impact the aquifer’s ability to recharge. The study also found that the most recent drought in the Western Cape was likely made worse by climate change. Chow noted that it is easy for people to forget about the problem of water scarcity in Cape Town, especially after a wet winter. However, he warned that the problem is not going away. Climate change is only going to make the problem worse, and we need to start planning for a future with less water.

“The literature suggests that the droughts that the Western Cape has experienced in recent years, such as the one between 2015 and 2018, are likely to become more frequent and severe in the next 10 to 20 years due to climate change. This is consistent with what I have seen in my own research,” he added. “The paper supports the findings of other studies that have predicted that the climate in the Western Cape will become more extreme in the next few decades.”

Advances in groundwater hydrology, such as the use of remote sensing and numerical modeling, are providing new insights into the movement and storage of groundwater, which can be used to better manage this vital resource.

The UWC researchers used the hydrological model (WaterWorld model) to simulate the hydrologic conditions in the Cape Flats watershed for the period 1950-2000. The model predicted a significant temperature increase of 1.9°C–2.3°C over this period. The researchers then used a geographic information system (GIS) to assess the impact of climate variability on groundwater quality. The GIS modeling analysis showed that the southern and central suburbs of the study area are more susceptible to groundwater contamination. These areas have high surface runoff and higher average temperatures, which can lead to the infiltration of pollutants into the groundwater.

Chow added that there have been a number of advances in groundwater modeling in recent years. One of the most significant advances is the integration of groundwater models with other hydrologic models, such as surface water models and atmospheric models. This allows for a more holistic view of the hydrologic cycle and can be used to predict how groundwater levels will be affected by changes in surface water, climate, and other factors.

He said that another major advance is the increasing power of computers. This has allowed groundwater models to become more complex and comprehensive and has made it possible to simulate the movement of groundwater in 3D. This is important for accurately predicting how groundwater will be affected by changes in the environment.

“The combination of these advances has made groundwater modeling a powerful tool for understanding and managing this vital resource. Groundwater models can be used to identify areas of groundwater depletion, predict the impact of climate change on groundwater resources, and plan for sustainable groundwater use,” he said.

“Groundwater acts like kind of like a battery, where it’s storing up the water and then gradually releasing water to rivers over time.”

Chow spoke about the role of groundwater in supporting river systems and wetlands. He said that groundwater acts as a “battery” for surface water, storing up water during wet periods and releasing it during dry periods. This helps to stabilise the flow of rivers and to maintain wetlands, which are important ecosystems that provide a variety of benefits to people and wildlife.

Enforcing existing laws

He also addressed the challenges of enforcing groundwater protection laws in South Africa.

Chow pointed out that there are many good laws in place, but that the problem is getting people to follow them. He uses the analogy of a milkshake to illustrate the problem: if everyone sticks a straw into the same milkshake, it will eventually run dry. The same is true for groundwater aquifers. If too many people pump groundwater out of the same aquifer, it can be overdrawn and depleted.

He also notes that the problem is particularly acute in areas with intensive agriculture. This is because agriculture is the largest user of groundwater in South Africa. In the Western Cape, for example, agriculture accounts for over 80% of all groundwater use. This means that even a small amount of over-abstraction can have a significant impact on aquifers.

“It’s not that the science isn’t up to date, people understand how to preserve and protect groundwater. It’s whether or not you can get all of the people that are using it to actually abide by those rules,” he added.

Can conserving groundwater be a solution to climate change?

Chow said that groundwater can be a solution to climate change if it is managed sustainably. “Groundwater is like a storage bank of water that we can draw upon in times of drought. This helps us to overcome periods of drought and gives us some resilience to the shock of those droughts. However, if groundwater is not managed sustainably, there is a danger that it will not be enough when we need it,” he said.

“Groundwater is recharged naturally by rainfall. However, if we have a number of years of lower-than-average rainfall, the groundwater aquifers can deplete. This is because there is not enough rainfall to recharge the aquifers. If we continue to draw upon groundwater during a drought, the aquifers can run dry,” he added. “So it helps buffer to some extent. But it really depends on whether or not you’re getting that recharge that you’re expecting every single winter.”

Groundwater resources can be impacted by a variety of factors, including land use change, population growth, and pollution.

Chow is concerned about the impact of urbanisation on aquifers. He believes that population growth, informal settlements, industrial land use, and paving over large areas of land are all contributing to the depletion of aquifers. He is encouraged by the fact that some cities are starting to design with infiltration features in mind, but he believes that more needs to be done to ensure that aquifers are protected from the effects of urbanisation.

Chow pointed out that the City of Cape Town is basically a “concrete jungle”  with a lot of concrete and asphalt, which can have a negative impact on aquifers. “In large urban areas, where everything is paved over, water cannot infiltrate into the ground and recharge aquifers. Instead, it runs off the surface, is collected in drainage pipes, and is piped out to the ocean. This means that water that would have naturally recharged aquifers is instead lost to the sea.”

But can we go back and undo the damage already been done?

“Yeah, that’s actually a tricky part,” said Chow.

He explained that it is much easier to prevent groundwater contamination than it is to clean it up after it has happened. This is because groundwater contamination can be very difficult to remove from the subsurface. Once contaminants are absorbed into the soil or rock, they can be very difficult to extract. Groundwater also moves slowly, so it can take a long time for contaminants to travel through the subsurface and reach the drinking water well. This means that by the time contamination is detected, it may have already spread to a large area.

For these reasons, Chow recommends that we focus on preventing groundwater contamination from happening in the first place. This can be done by identifying areas that are vulnerable to contamination and taking steps to protect them. For example, we can designate groundwater protection areas where certain activities, such as industrial development or the disposal of hazardous waste, are prohibited.

“If you’re in this area, you’re not allowed to build a factory, if you’re in this area, you’re not allowed to have a petrol station. Why? Because those are sources of contamination,” he said.

Is desalination an alternative to using groundwater?

Desalination is the process of removing salt from seawater or other saline water to produce water that is suitable for human consumption or irrigation.

“That was explored during the drought,” said Chow. “But it is expensive and energy-intensive. It is also not always effective, as the quality of the water produced can vary depending on the salinity of the seawater.”

Chow explained that a desalination plant was built in Cape Town during the drought, but it was not operational when it was needed. This was because the specifications of the plant were not correct for the seawater in Cape Town. He also said that the cost of desalination can be prohibitive, especially if the water quality is poor. He compared the cost of desalination to the cost of drilling a borehole and pumping out groundwater. He said that drilling a borehole is usually much cheaper, but the cost of pumping the water out increases as the water gets deeper.

He also mentioned the problem of saline intrusion. This is when seawater enters a freshwater aquifer, making the water salty and unusable. Saline intrusion can be a problem for coastal areas, where groundwater is often used for drinking water. He said that desalination is a viable solution for water scarcity, but it is important to consider the cost and environmental impact before investing in a desalination plant.

Call to Action

Chow is concerned that people have forgotten about the drought and are going back to their old water usage habits. He believes that this is a dangerous trend, as it could lead to Day Zero, a situation in which Cape Town would run out of water. He argues that people need to start using water more conservatively and that policymakers need to implement water usage restrictions and measures to help people change their habits.


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