A Review of the Assessment of Spatial and Temporal Variations of Groundwater in South Africa

Deep beneath the surface of the Earth, hidden within cracks in rock and spaces between grains of sand, lies a vast reservoir of fresh water. This is groundwater, a resource that does not sit in a visible lake or river but is stored inside the geological layers of the planet. In many parts of the world, this invisible water is the only reliable source of life, especially when the rains fail and surface rivers run dry. In South Africa, a nation where droughts are becoming more frequent and severe, this hidden water is critical. It provides 60% of water for rural homes and a significant portion for farms. However, because it is buried underground, it is difficult to see, measure, and understand. The water levels can rise and fall, and the quality can change, depending on the type of rock it sits in, the weather above, and how much water people are pumping out.

For years, scientists have studied these hidden waters in South Africa, but their findings were scattered across hundreds of separate reports, each looking at a small piece of the puzzle. Some studies focused on the dry Karoo region, others on the wet coastal areas, and many looked at specific problems like pollution from farms or mines. No one had yet brought all these pieces together to see the full picture of how the water is changing across the entire country. Without a complete view, it is hard for leaders to make the right decisions about how to protect this vital resource for the future.

To solve this, a researcher led by Emmanuel Oisakede at the Durban University of Technology decided to gather every relevant study published between 2020 and 2025. They acted like librarians of science, searching through thousands of records to find 95 high-quality papers that contained real measurements of groundwater levels and water quality. They carefully checked each one to ensure the data was reliable, then combined the results to look for patterns that no single study could reveal on its own. Their goal was to map out where the water is, how fast it is disappearing, and how its quality is changing, all while understanding the forces driving these changes.

The researcher found that the ground in South Africa is far from uniform. The depth of the water table—the distance from the surface down to the water—varies wildly depending on the local geology. In the sandy, riverbed areas of the lower Orange River, the water is relatively close to the surface, sitting just about 6 meters down. In contrast, in the fractured rock formations of the Karoo, the water is buried much deeper, often reaching depths of over 44 meters. This difference matters greatly for people who need to drill wells; finding water in the deep, cracked rock requires much more expensive equipment and effort than tapping into the shallow river sands. Furthermore, the study revealed that the depth of the water does not necessarily predict its quality. While one might expect deep water to be cleaner or more mineralized, the researcher found no clear link between how deep the water is and how salty or polluted it is. In some places, the deepest wells contained water too salty to drink, while in others, shallow wells were contaminated by human activity.

Over the last few years, the situation has become increasingly urgent. The analysis showed that groundwater levels across the country are dropping. On average, the water level in wells is falling by between 0.28 and 0.51 meters every year. This decline is not happening everywhere at the same rate, but it is widespread. In the fractured rock aquifers of the Karoo, the drop is most severe, with nearly three-quarters of the wells showing a significant downward trend. In the dolomitic rock areas of Gauteng, where the water moves quickly through large underground channels, the decline is slightly slower but still concerning. The alluvial aquifers, which are the sandy deposits along rivers, are also losing water, though they show a bit more ability to recover when heavy rains occur. The primary drivers of this drop are a combination of less rain due to climate change and increased pumping for agriculture and industry. The researcher noted that during severe droughts, the water levels can plummet, and even when the rains return, the levels often do not bounce back to where they were before.

While the quantity of water is shrinking, the quality is also deteriorating. The study tracked several key chemicals and found that the water is becoming more polluted. Nitrate levels, which often come from fertilizers used on farms and from sewage, have risen sharply. In the agricultural heartlands, the amount of nitrate in the water has increased by nearly 12 percent each year. This is a serious health risk, particularly for infants, as high nitrate levels can prevent blood from carrying oxygen effectively. Salt levels are also rising, especially in coastal areas where seawater is pushing inland and in dry inland areas where evaporation concentrates salts. The water is becoming slightly more acidic as well, a change linked to mining activities and the burning of coal. These changes are not just numbers on a page; they mean that water that was once safe to drink is becoming unsafe, and wells that used to provide enough water for a family are now running dry.

The researcher also looked at how different types of rock react to these pressures. They found that the fractured rock aquifers of the Karoo are the most vulnerable to losing water volume, while the coastal aquifers are the most vulnerable to becoming salty. The dolomitic aquifers, which hold a lot of water, are particularly sensitive to nitrate pollution because the water moves through them so quickly that it carries contaminants from the surface straight down to the supply. The study highlighted that the current way of managing water is not keeping up with these changes. Many areas are being overused, and the monitoring systems that track water levels are too sparse to give an accurate picture of what is happening. In many parts of the country, there are simply not enough wells being measured to know if the water is safe or if it is running out.

To address these challenges, the author proposes a new approach to managing groundwater. They recommend expanding the network of monitoring wells, especially in the Northern Cape and Northwest provinces, which are currently under-studied. They suggest using modern technology, such as satellites and automated sensors, to get a clearer and more frequent view of the water levels and quality. The study also calls for stricter rules on how much water can be pumped out, particularly in areas where the water is already low, and for better protection of the land above the water sources to prevent pollution. Finally, they emphasize the need to involve local communities in monitoring, as farmers and residents are often the first to notice changes in their local wells.

The picture that emerges from this review is one of a resource under significant stress. South Africa's groundwater is a lifeline for millions, but it is being depleted faster than it can be replenished, and its quality is slipping away. The study does not claim that the situation is hopeless, but it makes it clear that the current path is unsustainable. Without a systematic effort to monitor the water more closely, manage the pumping more carefully, and protect the land above the aquifers, the country risks losing a critical part of its water security. The findings serve as a call to action, urging policymakers and scientists to work together to ensure that this hidden resource remains available for future generations.