Strategic Water Source Areas: Combining surface and groundwater to enhance water security

South Africa is among the driest countries in the world with an average yearly rainfall of about 490 mm, only about 10% of which ends up in our rivers. A situation which has been highlighted by the recent droughts and water shortages across the country. The limitations on our water resources have been known for a long time - initiatives aimed at protecting water resources date back to the 1800s and were strengthened after severe droughts in the 1920s and 1930s. In the 1960s a national commission identified more than 60 areas in the country which were characterised by their high water production. A subset of these areas was highlighted again by a study of the state of South Africa’s rivers which found they generally were in poor condition and that the headwater catchments were vital for maintaining their ecological condition. This message was reinforced by a study that found that just 8% of the land area produced 50% of the water in our rivers (1) – and highlighted 21 Strategic Water Source Areas (SWSAs). The water from these areas sustains most of our larger towns and cities as well as most of the irrigated agriculture. The findings of this study were so striking that the importance of protecting these areas was included in the 2013 National Water Resources Strategy (2).

Draft surface and ground water Strategic Water Source Areas in South Africa, Lesotho and Swaziland.

All of these studies only examined surface water production and sources – i.e. the water in our rivers and streams, wetlands and flowing from springs. The CSIR has now partnered with ΔH Water Systems Modelling and the Water Research Commission (who are funding the study) to produce an updated assessment. This includes revising the original national surface water SWSAs and bringing in groundwater SWSAs. This project is also being guided by inputs from a range of stakeholders including water specialists from across the country.

Why is it important to include groundwater areas? Groundwater plays vital roles in sustaining the ecosystems which are critical for our survival. Water entering the soil that is not used by the vegetation typically percolates down to the water table and recharges the groundwater. Most of this water continues to move through below the surface to emerge in springs or seep into wetlands and rivers. These groundwater outflows sustain rivers and streams during periods when it does not rain and into or throughout the dry season. Groundwater also is the only reliable source of water for many towns and agricultural areas, especially in the arid and west and centre of South Africa. The map shows a working version of the ground and surface water SWSAs in South Africa, and highlights the fact that groundwater SWSAs are prominent in the drier parts of South Africa.

This study is due to be completed by December 2017 and will demonstrate how vital both the ground and surface water SWSAs are to the security of our society and our economy.

1: Journey of Water - http://journeyofwater.co.za/watersourceareas

2: National Water Resource Strategy - https://www.dwa.gov.za/nwrs/NWRS2013.aspx