INLAND WATER

Water is an indispensable natural resource, fundamental to life, the environment, food production, hygiene and sanitation, industry and power generation. In South Africa it is recognised as a crucial element in the battle against poverty, the cornerstone of prosperity, and a limiting factor to growth (DEA&T, 1999).

South Africa is a semi-arid country, where water is scarce. Wise utilisation of this resource in a sustainable manner is essential for the future of the country. Already the freshwater resources of the country are under stress. For instance, most of the country's major rivers have been dammed to provide water for the increasing population; in some areas over 50 % of the wetlands have been converted for other land-use purposes; industrial and domestic effluents are polluting the ground- and surface waters, and changes in habitat have affected the biotic diversity of freshwater ecosystems.

There are two main driving forces affecting South Africa's freshwater environment: natural conditions, particularly climate, and development through economic activities (Figure 1). These place pressure on inland waters, resulting in changes in amount of water available (i.e. quantity of ground and surface water), and the quality of the water resource. This in turn affects the ecological functioning and human use value of water resources in the country.

Figure 1:   Driving forces and pressures affecting South Africa's inland water resources. These result in impacts on the ecology and human use value of water resources (adapted from DEA&T, 1999).

Although Figure 1 provides a valuable framework to develop relevant indicators, not all the issues pertaining to inland waters are equally important. Priority issues for South Africa were identified from a literature review of policy and legislation in South Africa, and from discussions and workshops with specialists and stakeholders. The issues identified were:

 Environmental Issues:

1. Limited freshwater resources (surface and ground water). Limited is defined here in the sense of the ability to utilise inland waters for social or environmental purposes.
2. Changing freshwater quality (surface and ground water).
3. Degradation and loss of freshwater ecosystem integrity.
4. Flood and drought management of inland water resources.

 Socio-Economic & Political Issues:

5. Inadequate and Inequitable distribution of services (reflected on inland waters).
6. Conflicting interests over water sharing (national and international) (reflected on inland waters).

In assessing the issues, it became evident that many of the priority issues are sub-issues of other identified issues (Figure 2). This is obviously an oversimplified representation of the relationship between issues, however it highlights the key issues of concern, namely limited freshwater resources and changing freshwater quality and the secondary impacts on inland water resources.

Figure 2:   Relationship between identified issues of concern.

The issues of concern were used as the basis for developing environmental indicators for inland waters. Since the terms of reference for identifying indicators was to "identify issues pertaining to environmental sustainability", (CSIR et al., 2001) only issues 1-4 were used to develop indicators. Issues 5 and 6 were identified as socio-economic / institutional issues, which although impact upon the freshwater resource, could not be managed by means of environmental indicators. These issues are addressed through individual indicators located in other specialist themes.

DESCRIPTION OF ISSUES

Limited Freshwater Resources

South Africa is a water scarce country, with a hydrological regime that is characterised by low water runoff and high variability (DEA&T, 1999). The MAR for South Africa is estimated at 50 150 million m³ a^-1, and only 8,6% of the rainfall is available as surface water. This is one of the lowest conversion ratios in the world (DEA&T, 1999).

Similar to surface waters, groundwater is relatively limited compared to world averages (E Braune, DWAF, pers. comm.). There are no aquifers or groundwater sources large enough to supply any of the larger urban areas or irrigation schemes with water (Basson et al. 1997), and groundwater can only be abstracted on a sustainable basis at a rate less than, or equal to, the long-term average recharge of the resource through infiltration of rainwater.

Freshwater resources are also limited by their distribution throughout the country. Rainfall is not distributed evenly, with the eastern seaboard having high rainfall, whilst the western regions are considerably drier. In addition, water resources are typically not located where the demand is, resulting in the need for water supply and transfer schemes, such as the Lesotho Highlands Scheme

Changing Freshwater Quality

With the limited water resources available, efficiency of use and the management of impacts upon the quality of water resources are essential. Changing water quality results in impacts upon its effectiveness for use, as well as upon the ecosystem integrity.

Although water quality improvement is possible, the greatest area of concern is a deterioration of water quality due to pollution. Freshwater pollutants originate mainly from industrial, mining, domestic and agricultural sources. Those of greatest concern include organic and inorganic chemicals, plant nutrients, oxygen-demanding wastes, radioactive materials, sediment and microbiological contaminants (DEA&T 1996). The type and amount of pollution will vary from catchment to catchment, depending on the land-use and development patterns within each catchment. The main water quality problems in South Africa include: salinisation, enrichment by plant nutrients, microbiological contamination, siltation and acidification (DEA&T, 1999)

Ecosystem Integrity

Ecological changes to freshwater ecosystems occur because of catchment degradation; regulation of flow by dams; pollution; over-extraction of water; and the breakdown of natural bio-geographical barriers. Any anthropogenic changes to a natural ecosystem, will have a negative impact on the balance of that ecosystem, i.e. it will affect the functional integrity of the system (Walmsley 2002). This may take the form of invasion by alien species, increase in the numbers of pest species, decrease in biodiversity, and inability of the system to clean itself etc. In most of these cases, the result will have direct or indirect economic consequences.

In South Africa most riverine habitats have been so changed, that little remains of natural systems. Many perennial rivers have become seasonal (e.g. Limpopo, Levuvhu, Letaba); floodplains that rely on regular flooding have become less productive (e.g. Pongola) and some estuaries can no longer rely on natural opening of the estuary mouth (e.g. Umfolozi). In addition, it is estimated that more than 50% of the natural wetlands in parts of Western Cape, Eastern Cape and KwaZulu-Natal have been destroyed (DEA&T, 1999).

Loss of or changes in habitat have resulted in changes in biotic composition. These changes may be characterised into two main types: loss of biological diversity and introduction of invasive species. Biodiversity loss have a long-term negative impact on ecosystem sustainability, and invasive species alter the ecosystem functioning to such an extent that indigenous biota can no longer compete.