Strategic Water Source Areas (SWSAs)

Definition and extent

Strategic Water Source Areas are defined as areas of land that generate a disproportionately large share of the country’s water resources relative to their size, either through high surface water runoff, high groundwater recharge, or a combination of the two. From a national planning perspective, these areas are considered of strategic importance for sustaining water supply to people, the economy and ecosystems.

Collectively, SWSAs cover approximately 8–10% of South Africa’s land area, yet they generate around 50% of the country’s surface water runoff. South Africa, Lesotho and Eswatini together share 22 surface water SWSAs, many of which are transboundary in nature, reflecting shared hydrological systems across national borders.

In addition to surface water SWSAs, Strategic Groundwater Source Areas have also been delineated. These groundwater SWSAs cover about 9% of South Africa’s land surface and contribute significantly to baseflow in rivers, particularly during dry seasons and drought periods, thereby stabilising water supply.

Geographic distribution and ecological characteristics

Surface water SWSAs are predominantly located in high‑rainfall, mountainous regions, including parts of the Drakensberg, Eastern Escarpment, Cape Fold Mountains, KwaZulu‑Natal midlands, Mpumalanga highlands, and Western Cape mountains. These areas generally coincide with headwater catchments, wetlands, and groundwater recharge zones that regulate downstream river flows.

Ecologically, SWSAs span key biomes such as Grassland, Fynbos and Savanna, which play an essential role in water regulation, sediment control, and water quality maintenance. Healthy ecosystems within SWSAs function as ecological infrastructure, working alongside dams, pipelines and treatment plants to deliver reliable water supply.

Importance for society and the economy

Despite their limited spatial extent, SWSAs support a substantial proportion of South Africa’s population and economy. It is estimated that around half of South Africa’s population and more than 60% of its economic activity depend directly or indirectly on water originating from these areas. Major metropolitan regions rely heavily on runoff generated in distant SWSAs.

SWSAs are also central to agricultural water supply, providing approximately 70% of the water used for irrigation, either directly or through downstream storage and transfer systems. As such, these areas are fundamental to food security, rural livelihoods and national economic stability.

Pressures and threats

Despite their importance, many SWSAs are under increasing pressure from land‑use change, mining, commercial agriculture, plantation forestry, urban expansion, invasive alien plant species, pollution and over‑abstraction of water resources. These pressures can compromise both water quantity and water quality, with impacts felt far downstream from the source areas themselves.

Formal protection levels remain relatively low. National assessments indicate that less than one‑fifth of surface water SWSAs are under formal protection, highlighting a gap between their strategic importance and the level of regulatory protection afforded to them.

Strategic significance under climate change

Climate change is expected to intensify rainfall variability, increase drought frequency and place additional stress on already limited water resources. In this context, protecting and restoring SWSAs is increasingly recognised as a cost‑effective, low‑risk climate adaptation strategy. Investment in ecological infrastructure within SWSAs can enhance resilience, reduce downstream water treatment costs, and buffer water supply during extreme events.

Conclusion

Strategic Water Source Areas form the backbone of South Africa’s water system. Although they occupy a small fraction of the landscape, they deliver a disproportionate share of the country’s water and support major population centres, economic activity and agricultural production. Securing these areas through improved land management, targeted protection, restoration and integrated governance is essential for long‑term water security, particularly in a changing climate.

- This overview draws on nationally recognised work by SANBI, CSIR, WRC and DWS on Strategic Water Source Areas.

See Also (Related WRO Pages) 

SWSAs are intrinsically linked to most other water resource topics on the WRO. The pages below are particularly relevant to understanding, monitoring, and managing these critical areas.

• Ecosystems — ecological integrity is fundamental to SWSA function

• Wetlands — wetlands within SWSAs are key hydrological regulators

• Biodiversity — SWSAs support high levels of endemic biodiversity

• Land Use Land Cover (LULC) — land use change is the primary threat to SWSA integrity

• Stream Flow — streamflow generation is the defining function of SWSAs

• Groundwater — groundwater SWSAs contribute to baseflow and dry-season water supply

• Erosion — erosion within SWSAs threatens downstream water quality and dam storage

• Climate and Weather Data — climate change projections are central to SWSA risk assessment

• Transboundary Water — many SWSAs are shared across South Africa's borders with Lesotho and Eswatini