South Africa’s water – where are we?

Water is arguably South Africa’s most vital and precious natural resource. It is integral to the survival of human life, the functioning of ecological systems, food and energy production, transportation, waste disposal, and industrial development (1–4). But as human populations grow, consumption patterns change, and economies develop, the pressures on natural water resources continue to increase.

Here, in South Africa, we are in the midst of a serious drought – water scarcity is a reality, and issues of water quality are that much closer to home. It is thus fitting to provide a brief synopsis of South Africa’s natural water resources (as brief as possible, as this is a massive topic), highlighting water availability; the demands for water; and the state of the country’s associated ecological infrastructure (rivers and wetlands).

It must be kept in mind that water-related challenges will increasingly be overlaid by the negative impacts of climate change – in most parts, rising temperatures, shifting rainfall patterns, and increasing variability in rainfall.

This reinforces the need to recognise the limits of our water use and manage the quality and supply of our finite freshwater resources as effectively and sustainably as possible.

 

Natural availability

Classified as a semi-arid country, South Africa has an average annual rainfall of just 465mm – far below the global average of 860mm (1,5). Additionally, there is huge variation in the distribution of this rainfall: “approximately 20% of South Africa receives less than 200mm, and 47% receives less than 400mm per annum” (4,6), represented in Figure 1 below.

 

South Africa's Mean Annual Precipitation (MAP) (Source: Schulze 2011)

Figure 1: South Africa’s Mean Annual Precipitation (MAP) (Source: Schulze 2011)

 

In terms of surface runoff, which contributes to the flow of rivers, and the recharge of wetlands, lakes, dams and aquifers, only about 8% of South Africa’s land produces about 50% of the total surface runoff (4) . Conserving these ‘water factories’ is absolutely crucial (2).

However, not all surface runoff is available for use on a sustainable basis – accounting for annual variability, a considerable portion needs to be available to support natural ecological systems. Within this is the required ‘ecological reserve’: the water that needs to remain in rivers and wetlands in order to maintain their ecological functioning (5).

 

Water Demand

With its large agricultural base, approximately 60% of SA’s total surface water use is comprised of irrigation agriculture, followed by urban (25%), with the remaining use split between rural; mining and bulk industrial; power generation; and afforestation (5,6). See Figure 2 below.

 

SA water use by sector. (Data Source: DWAF 2000)

Figure 2: SA water use by sector. (Data Source: DWAF 2000)

 

Importantly, water use for irrigation agriculture takes place on just 1.1% (approximately) of SA’s total land surface area, “often in relatively low rainfall areas, where either supplementary irrigation is very high or total irrigation is practiced, much of it still using relatively inefficient modes of irrigation” (6).

In some of South Africa’s major catchments, local water demands far exceed reliable local yields. This is demonstrated in Table 1 below, where, back in 2000, 11 of the 19 catchments listed already had a negative water balance (5).

Table 1: Reconciliation of water availability and requirements for 2000 (million m3/amnum) (Source: DWAF 2000) (* refers to the amount that can be reliably provided 98 years out of 100, with ecological reserve requirements already subtracted.)

Table 1: Reconciliation of water availability and requirements for 2000 (million m3/amnum) (Source: DWAF 2000) (* refers to the amount that can be reliably provided 98 years out of 100, with ecological reserve requirements already subtracted)

 

Our Rivers and Wetlands

Our rivers and wetlands are responsible for the provision of a number of invaluable ecosystem services. River ecosystems are vital for storing and transporting water, where, together with manmade transfer schemes, they “bring water to rural and urban areas, irrigate croplands, take away waste and provide cultural and aesthetic services” (2).

According to a number of criteria, a scary 57% of South Africa’s river ecosystem types are considered to be threatened (25% critically endangered; 19% endangered and 13% vulnerable). This proportion also rises substantially when only lowland rivers are included, in which the negative impacts of irrigation agriculture; industrial activities; and domestic water use are far more prevalent.

Wetland ecosystems can be extremely effective in regulating water flows; filtering and purifying water; and mitigating the impacts of droughts and floods. In addition, wetlands tend to support a diverse range of species, with both intrinsic and economic value.

Approximately 300 000 wetlands remain in South Africa, comprising 2.4% of the country’s land surface area. .” A disturbing 65% of wetland ecosystem types are threatened (48% critically endangered, 12% endangered and 5% vulnerable), making wetlands the most threatened of all ecosystems” (2).

 

Conclusion

Summarising the points above, the availability of freshwater “is one of the major limiting factors to South Africa’s development” (4). In addition, from Schulze (2011), the generally poor state of South Africa’s water quality is cause for major concern as it provides a “threat to human health, to ecosystems and to water security alike”. It is exceedingly clear that our consumption of, and negative impacts on water resources need to be carefully measured and managed.

At 60% of SA’s total water consumption, irrigation agriculture has a huge footprint. Not only is its use significant, but cultivated lands flank most of the country’s riparian zones, containing both river and wetland systems. With significant technological evolvements – pump metres ; soil water probes; drones; remote sensing data; and wastewater treatment solutions – we are increasingly able to make informed decisions about water use.

We need to use these ‘tools’ to identify and operate within these resource limits, and act responsibly, in order for agricultural water use to be sustainable.

 

 

References

  1. Pitman W. Overview of water resource assessment in South Africa : Current state and future challenges. Water SA. 2011;37(5):659–64.
  2. Driver A, Sink KJ, Nel JL, Holness S, Van Niekerk L, Daniels F, et al. National Biodiversity Assessment 2011: An assessment of South Africa’s biodiversity and ecosystems. Pretoria; 2012.
  3. Gleick PH. Water and Conflict: Fresh Water Resources and International Security. Int Secur. 1993;18(1):79–112.
  4. Colvin C, Haines I, Nobula S. An introduction to South Africa’s Water Source Areas [Internet]. 2013. Available from: http://awsassets.wwf.org.za/downloads/wwf_sa_watersource_area10_lo.pdf
  5. DWAF. Chapter One: Overview of the South African Water Sector. Governing Board Induction Manual. 2000.
  6. Schulze RE. A 2011 Perspective on Climate Change and the South African Water Sector. 2011.