Freshwater National State Of The Environment Report

National State of the Environment Report - South Africa Freshwater Systems and Resources (http://www.ngo.grida.no/soesa/nsoer/issues/water/index.htm)

Summary South Africa's available freshwater resources are already almost fully-utilised and under stress. At the projected population growth and economic development rates, it is unlikely that the projected demand on water resources in South Africa will be sustainable. Water will increasingly becoming the limiting resource in South Africa, and supply will become a major restriction to the future socio-economic development of the country, in terms of both the amount of water available and the quality of what is available. At present many water resources are polluted by industrial effluents, domestic and commercial sewage, acid mine drainage, agricultural runoff and litter. To augment supplies, South Africa is looking towards water sources in other southern African countries (e.g. Lesotho) to assist in providing sufficient water for projected future demands. However, the risks of international dependency on such a priority resource are high. Other possible sources of water, such as desalinisation of seawater and water from icebergs, may be potential options in the long-term, although currently they are too expensive to exploit. It is imperative that South Africa develop both a water-efficient economy together with a social ethic of water conservation and ultimately a culture of sustainability of water resource use. Authors: Walmsley Dr R D, Walmsley J J, Mzuri Consultants, Silberbauer M, Department of Water Affairs and Forestry The overview of freshwater systems and resources is described under the following headings: • • • • • • •

Background information What are the driving forces affecting our freshwater ecosystems? What are the pressures of human activity on our freshwater resources? What is the status of our freshwater systems and resources in South Africa? What are the impacts on our freshwater systems and resources? What are our responses to change in our freshwater systems and resources? Outcomes Data issues

Background information South Africa is a semi-arid country. Freshwater is our most limiting natural resource. South Africa receives only around half the average rainfall of other countries, and this is

spread disproportionately across the country from east to west. Water availability now and in the future is heavily dependent on climate, water use and management and landuse practices. What are the driving forces affecting our freshwater ecosystems? There are three main driving forces affecting South Africa's freshwater environment. Firstly, the natural conditions, particularly climate (see Climate and Atmospheric Change section), which is characterised by low rainfall and high evaporation rates. Together these create low available run-off. Second is the rapid population growth (see Social Dimensions section), and need for economic development and meeting of basic needs. These socio-economic activities drive water use and lead to greater water demand and increased pollution of available resources. The third driving force is the policy pertaining to national management of water resources, which determines the approach taken by relevant authorities at all levels of government to managing our freshwater resources (see Policy). Indirectly, policy pertaining to land-use practices throughout the country impact on water quality and availability. What are the pressures of human activity on our freshwater resources? Population growth, increased economic activity and intensification of land use practices all lead to increased water demand, and increasing degradation of the resource. Already the freshwater resources of the country are under stress (Davies et l. 1993). For instance, most of the country's major rivers have been dammed to provide water for the increasing population; in most areas wetlands have been converted for other land-use purposes, with more than 50% of the country's wetlands already lost; industrial and domestic effluents are polluting the ground- and surface waters, and changes in habitat have affected the biotic diversity of freshwater ecosystems. Despite this extensive degradation of our freshwater resources, an estimated overall increase in demand of some 52% over the next 30 years is predicted.

Pressures affecting freshwater systems and resources in South Africa: The pressure of freshwater systems and resources is described under the following headings: 1. 2. 3. 4. 5. 6. 7. 8.

Climate Water demand Pollution Surface water Groundwater Previous legislation and policy Hydrological pressure Pollution pressure

9. Land use change Climate:

The characteristics of South Africa's aquatic ecosystems are largely determined by the interaction between climate, rainfall and the landscape over which water flows (see Introduction to this report - figures on general characteristics of country). For South Africa, the warm Agulhas current on the east coast, the cold Benguela current on the west, coupled to the topography of the sub-continent, have created an overall theme of aridity (Preston-Whyte and Tyson, 1988). Climatic features affecting South Africa's aquatic environment include (from Walmsley, 1991): • • •

• •

low precipitation- with an average rainfall of 497 mm, the country is well below the world average of 860 mm. high temporal climatic variability with distinct seasonal rainfall patterns (see Climate and Atmospheric Change section). high spatial climatic variability - the country has six rainfall regions with higher rainfall occurring on the East coast, and the country becoming progressively more arid towards the West (see Introduction). high solar radiation due to a low degree of cloudiness. high evaporation rates - except for small areas on the coast and certain escarpments, evaporation exceeds rainfall (see Introduction).

Figure 3.2 Mean annual precipitation and evaporation

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Figure 3.2 plots mean annual precipitation (MAP) against mean annual evaporation (MAE) for the major South African catchments. Evaporation exceeds precipitation in all cases.

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severe and prolonged droughts which are often terminated by severe floods. During any one season certain areas may experience drought whereas others experience severe flooding.

Figure 3.3a-e shows the high rainfall variability for each of the five aquatic eco-regions of the country (see Box 3.1, Allanson et al. 1990)

Fig 3.3a Annual precipitation for Fig 3.3b Annual precipitation for eco-region 1. eco-region 2.

Fig 3.3c Annual precipitation for Fig 3.3d Annual precipitation for eco-region eco-region 4. 3. Fig 3.3e Annual precipitation for eco-region 5.

Box 3.1 Aquatic eco-regions of South Africa

Region 1: A sub-tropical coastal plain incorporating the Eastern Transvaal lowveld, Mozambique and northern KwaZulu/Natal, in which the marine influence is strong, and aquatic ecosystems have variable salinity. Region 2: The summer rainfall region of the highveld and south eastern coastal plain, incorporating Gauteng, the Northwest Province, the Free State, southern KwaZulu/Natal and the northern section of the Eastern Cape. The Vaal-Orange, Tugela and Limpopo rivers are all included in this region. Region 3: The alpine mountain region of Lesotho. This area experiences high rainfall, and is characterised by clear mountain streams. Region 4: The western and southern Cape Mediterranean climate region. This area is one of winter rainfall. It has temperate, unbuffered, acid waters, arising principally from the Table Mountain Sandstone in the mountainous regions. Marine influences in the low-lying areas increase the buffering capacity of waters and raise the pH. There are two types of waters: the "peatstained" acid waters draining the seaward slopes (e.g. the Steenbras, Palmiet and Storms rivers), and the colourless acid waters draining from the landfacing slopes (e.g. Olifants, Great Berg and Breede rivers). Region 5: The arid western region stretching north from inland of Port Elizabeth into Namibia and southern Botswana. The western part of this region is dry, waters are temporary, alkaline and carry very high dissolved solids and sediment loads. The eastern section is characterised by short steep, geologically young rivers with permanent flows, neutral to alkaline waters and moderate levels of dissolved solids.

Water demand:

Population growth (see Social Dimensions section), increased economic activity (see Economic Dimensions section) and changes in land use (see Terrestrial Ecosystems section) all lead to increased water demand. Sectoral water requirements in South Africa are presented in Table 3.1. There is an estimated overall increase in demand of 51.7% over the next 30 years. The environment is presently the smallest sector, and only changes by 7.5% compared with the estimated increase of the urban and domestic sector to almost three times the present day usage. Table 3.1: Summary of sectoral water requirements for 1996 and 2030 (estimated) (adapted from Basson et al 1997) Sector Urban & domestic

% Contribution to GDP* -

1996 (106 m3 a-1) 2 171

2030 (106 m3 a-1) 6 936

Percentage increase 219,5%

Mining and industrial Irrigation & afforestation

37%

1 598

3 380

111,5%

6%

12 344

15 874

28,6%

Environmental

-

3 932

4 225

7,5%

TOTAL

-

20 045

30 415

51,7%

Figures for water use efficiency for each sector are not available, but agriculture is considered to be the least efficient in economic terms (production per m3) and commercial forestry the least efficient in environmental terms. Groundwater demand has also increased, from approximately 1 790 million m3 a-1 in 1980 to about 2 000 million m3 a-1 today. Seventy eight per cent of this water is utilised by the irrigation sector (Figure 3.4). The demand for water does not necessarily co-incide with the spatial distribution of water.

Figure 3.5 Availability of surface water per capita for South Africa

Figure 3.4 Groundwater use per sector

Figure 3.5 shows the availability of surface water per capita for South Africa.

This indicates that the country'surban and industrialised areas (Cape Town, Port Elizabeth, East London, Pietermaritzburg, Bloemfontein, Pietersburg, and Gauteng) are the most water stressed, and will become more so as the population increases and the demand for water in the urban and domestic sector increases. Because of the spatial variability of water resources and the scarcity of water throughout the country, in many catchments the need for water exceeds the supply of water. In 1996 the water requirements in the Vaal, Lower Orange, Sundays, Great Fish, Olifants (Mpumalanga) and Crocodile/Limpopo rivers exceeded the amount of water available (Figure 3.6). This situation is likely to rapidly worsen, and by 2030 the Breede/Berg basin will be added to this list and the discrepancies between water requirements and available balance in the other water-scarce catchments will become larger (Figure 3.6b).

Figure 3.6 Water balance for major catchments in South Africa, 1996

Information on the abstraction of water from surface- and ground-waters, coupled with return flows, gives an indication of local water budgets. However, this information is not readily vailable and is not presented here.

Figure 3.6b Water balance for major catchments in South Africa, 2030

What is the status of our freshwater systems and resources? South Africa is an arid country with only 8.6% of the rainfall available as surface water. This is one of the lowest conversion ratios in the world. The mean annual runoff (MAR) for South Africa is estimated at some 50 million m3 a-1. This is not distributed evenly throughout the country, with the Eastern seaboard having some 80% of the country's runoff, whilst the western regions tend to have low runoff. Nor is it consistent over time, with great variability between years. Similar to surface waters, South Africa's groundwater resources are relatively limited compared to world averages. The scarcity of freshwater resources and highly variable hydrological conditions have led to every major river in South Africa being regulated in order to ensure adequate water supply for development. However, because of the spatial variability of water resources and the scarcity of water throughout the country, in many catchments the need for water exceeds the supply. This situation is likely to worsen as the discrepancies between water requirements and availability in other water-scarce catchments increase. The scarcity of water is compounded by pollution of the surface- and ground-water resources. Typical pollutants of South Africa's freshwater environment include industrial effluents, domestic and commercial sewage, acid mine drainage, agricultural runoff, and litter. As many of these sources are spreadout across the country, it Mine drainage activities is difficult to estimate the magnitude of the pollution problem. However, Western Cape, Eastern Cape, KwaZulu-Natal and the Vaal rivers have

major problems with Total Dissolved Solids (TDS), and most of South Africa's rivers have an eutrophication problems. What are the impacts on our freshwater systems and resources? The indigenous aquatic fauna and flora of South Africa are well-adapted to the variable climatic conditions, and many are reproductively opportunistic as a result. The high levels of natural variability ensure that high biological diversity and habitat integrity are maintained. However, whilst most freshwater systems in South Africa are not negatively affected in the long-term by natural fluctuations, they must also endure increasing negative human-induced stresses, to which they are not adapted. Ecological changes to freshwater ecosystems occur because of catchment degradation (see Terrestrial Ecosystems section); regulation of flow by impoundments; pollution; over-extraction of water; and the breakdown of natural biogeographical barriers, typically through interbasin transfers. The primary results of these are extensive habitat loss, a decrease in biodiversity and an increase in invasive and pest species. In extreme cases, these can result in ecological collapse of the functioning of the natural systems. Additionally, riverine habitats have been so changed, that little remains of natural freshwater systems in South Africa. Many perennial rivers have become seasonal (e.g. Limpopo, Levuvhu, Letaba); floodplains that rely on regular flooding which has been attenuated have become less productive (e.g. Pongola) and many estuaries no longer have natural opening of the estuary mouth (e.g. Mfolozi).

Impacts Positive impacts:

The water resources of the country inherit much of their character from the climate and their flow behaviour mirrors the erratic rainfall patterns (see Pressures). However, the indigenous aquatic fauna and flora of South Africa are well-adapted to the variable climatic conditions. Hydrological variability has strongly influenced the evolutionary character of the biota. Many indigenous species are highly-tolerant of environmental extremes and are reproductively opportunistic as a result. The level of perturbation caused by natural fluctuations ensure that high biological diversity and habitat integrity are maintained. However, whilst most freshwater systems in South Africa are not affected in the long-term by natural perturbations, they must also endure the increasing human stresses mentioned previously (see Driving Forces and Pressures), to which they are not adapted and which have negative impacts.

Negative impacts:

Negative impacts on the freshwater environment may be divided into ecological impacts and impacts on human use of the resource. Ecological impacts:

Ecological changes to freshwater ecosystems occur because of catchment degradation (see Terrestrial Ecosystems section); regulation of flow by impoundments; pollution; over-extraction of water; and the breakdown of natural biogeographical barriers. The primary results of these are extensive habitat loss; a decrease in biodiversity and an increase in invasive and pest species. In extreme cases, negative impacts can result in collapse of the functioning of the natural systems. A good example of extensive habitat loss is that of natural wetlands. There is little documented information with regards to the extent of wetland loss throughout South Africa, although isolated examples can be quoted: •

• • •

• •

The Mfolozi Swamp, forming the largest fluvial plain in South Africa, by 1988 had been reduced through agricultural development to 43% of its previous extent (Begg 1988). In the Siyaya catchment in northern KwaZulu/Natal, 93% of the wetlands had been lost by 1966 (Begg 1988). Cape Town City Square was once a wetland, as was Louis Botha Airport in Durban (Begg 1988). In the semi-arid regions of the country, in the riverine lowlands it was estimated that 90% of the wetland areas had been severely eroded (Department of Agriculture and Technical Services 1972). The extent of wetlands in the upper Mgeni catchment has been reduced by 66% (D Kotze, Institute for Natural Resources, pers. comm.). Wetlands have been reduced by 21% in the Wilge and Klip rivers, in the Vaal catchment.

Kotze et al. (1995) hypothesized the extent of natural wetland loss in South Africa, based on isolated reports and climatic and physiographic information (Figure 3.23). It is estimated that parts of the Western Cape, Eastern Cape and KwaZulu/Natal have less than 50 % of the natural wetlands left. Additionally, riverine habitats have been so changed, that little remains of natural systems in South Africa. Many perennial rivers have become seasonal (e.g. Limpopo, Levuvhu, Letaba);

Figure 3.23 Hypothesised extent of wetland loss, based on the extrapolation of information from isolated reports and using climatic and physiographic information

floodplains that rely on regular flooding which has been attenuated have become less productive (e.g. Pongola) and some estuaries can no longer rely on natural opening of the estuary mouth (e.g. Mfolozi). 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. The effects of biodiversity loss have been debated extensively, and aquatic ecologists generally agree that long-term biodiversity loss has a negative impact on ecosystem sustainability. An indicator of loss of biodiversity is the number of threatened aquatic plants and animals, known as "Red Data Book" species. Lists of Red Data Book species were compiled for South Africa in the 1970s and 1980s. A list of threatened freshwater estuarine plant and animal species is available in Noble and Hemens (1978). Little information is available on loss of aquatic invertebrates (represented by a single dragonfly species), but 24 plant species, 25 fish species, 6 amphibians, 2 reptiles, 24 birds and 2 mammals are included in the Red Data Book list. Of these, one fern, Christella altissima is now extinct. Invasive or pest species may be alien to an area, introduced either accidentally or deliberately, or indigenous to an area, but become invasive when habitat changes create perfect conditions for their habits and life cycles. De Moor and Bruton (1988) have compiled an atlas of all known alien and translocated indigenous aquatic animals in South Africa. There are 42 known alien species (16 invertebrates, 23 fish, 1 reptile and 2 birds) in South African waters and at least 74 translocated indigenous fish species with the number of invertebrates unknown . Of these, 37 have a known detrimental effect on the environment (De Moor and Bruton 1988).

Fig 3.24a Distribution of the four most important alien aquatic macrophytes in South Africa - Eichhornia crassipes

Fig 3.24b Distribution of the four most important alien aquatic macrophytes in South Africa - Azolla filiculoides

Fig 3.24c Distribution of the four most important alien aquatic macrophytes in South Africa - Myriophyllum aquaticum

Fig 3.24d Distribution of the four most important alien aquatic macrophytes in South Africa - Salvinia molesta

Some alien aquatic macrophytes have flourished because of changes in flow regime and hypertrophic conditions. This has severe economic implications for South Africa as they cover and choke vast areas of standing and slow-running waters. Of special concern are water hyacinth (Eichhornia crassipes), parrot'sfeather (Myriophyllum aquaticum,) Kariba weed (Salvinia molesta) and the water fern, Azolla filiculoides. Distribution maps of these species are shown in Figures 3.24. Impacts on use:

Changes in habitat and quality of the freshwater environment in South Africa also leads to a change in access to the resources available. In some cases it leads to depletion in harvestable resources (e.g. reeds for weaving, fish, medicinal plants) with direct economic consequences. In other cases, the quality of life of people is affected. For instance, recreational opportunity is diminished, or health is affected (through poor sanitation and increasing pollution (see Social Dimensions section). Additionally, the over-utilisation of surface and groundwaters has led to conflict between users as demand outstrips supply (E Braune, DWAF, pers. comm.) What are our responses to change in our freshwater systems and resources? There are various responses at different levels in order to manage our water resources in a sustainable manner, including developing and adhering to international initiatives, setting relevant policy through legislation, implementing policy at an operational level (institutional arrangements; enforcement and monitoring) and implementation of special programmes to combat specific problems (see Policy). South Africa is a signatory to or abides by several international protocols that are important to water management. Most legislation pertaining to the environment affects water resources, either directly or indirectly. The most important are the Water Services Act (Act 108 of 1997) and the National Water Act (Act 36 of 1998), which fall under the authority of the Minister of Water Affairs and Forestry.

In the light of the uneven distribution of the water resources of the country and previous inequitable policies, the Water Services Act is important in ensuring that people's basic needs are met, i.e. water supply and sanitation. It ensures that there is sound planning and that water service providers are set up country-wide to cater for everyone. The National Water Act has replaced the old Water Act (Act 54 of 1956) of 40 years standing. It has completely reformed the water law in South Africa, bringing into legislation aspects of policy that are at the forefront of sustainable resource use thinking internationally. The Act is based on the principles of sustainability of use and equity of distribution.