South Africa's water requirements are anticipated to increase from 20 045 x 106 m3.a-1 in 1996 to 30 415 X 106 m3.a-1 by the year 2030 (Basson, 1997). The increase in demand can be attributed to population growth and economic development (Shackleton et al., 1996). The South African population has increased from 22.273 million in 1970 to 40.584 million by 1996 (Orkin, 1998) at an average rate of increase of 2.4 % per annum between 1970 and 1995 (Anon, 1996). The economically active population has increased at an average rate of 1.99 % between 1991 and 1995 with employment in the manufacturing, construction and trade sectors increasing at average rates of 1.4%, 0.6% and 0.8% per annum respectively between 1970 and 1995 (Anon, 1996). The focus of this section will be on identifying how the specific sectors of the economy will demand water in future.
The historical development of water resources in South Africa has led to an uneven population distribution that reflects the physical, political, economic and social status of the past. This has led to the development of water resources according to a socio- economic scenario that favoured, for example, the reservation of water for irrigation and industries, including those involved in the production of synthetic fuels, viz. coal (Barta, 1999). Water demand in South Africa is currently shifting away from the dryland agricultural and irrigation sectors, which previously consumed the bulk of the surface water resources, towards the urban and industrial sectors as a result of a high rate of urbanisation and rapid industrial development (Table 3.1). In Table 3.1 it can be seen that the urban, domestic, industrial and mining sectors are expected to demand a far greater proportion of the total water supply by the year 2030 than in 1996. The greatest increase in demand comes from the urban and domestic sector, with a 12% increase. The irrigation, afforestation and environmental sectors, on the other hand, are going to have to make do with a smaller percentage of the total demand.
An increasingly important aspect in the demand for water in South Africa is that of . assurance of supply. Certain industries, modern power stations, mines, sanitation works and even large irrigation projects require certain minimum amounts of water to remain operationally viable. Hence, as the economy grows and activities in these industries increase, there will be a greater demand for a certain set minimum of water to be supplied (Conley, 1996).
Table 3.1 Comparison of the 1996 water requirements for various sectors of the economy to those projected for 2030 (after Basson, 1997)
Projected Projected
Water Percentage of
percentage of water
Sector of the requirements the total water
requirements the total water
Economy in 1996 requirement
in 2030 requirement
(106m3.a-1)
(106 m3.a-1)
in 1996
in 2030 Urban and
6936 22.8%
2 171 10.8%
domestic Mining and
1 598 3380 8.0 % 11.1 %
industrial Irrigation and
12344 15874 61.6 % 52.2 %
afforestation
Environmental 3932 4225 19.6% 13.9%
Total 20045 30415 100.0% 100.0%
3.2.1 Urban and domestic water demand
The National Water Act of 1998 sets aside a certain quantity of water known as the
"reserve". This reserve consists of two parts, the basic human need reserve and the ecological reserve. The basic human needs reserve provides for essential needs of individuals served by the water resource in question and includes water for drinking, for food preparation and for personal hygiene (National Water Act, 1998).
South Africa's increasing population will demand more water as a basic necessity. Rural communities are likely to place increased pressure on the groundwater and natural surface water supply as they demand their share of the reserve. However, rural . communities will need to manage these resources more efficiently, as supplying water to such diffuse communities is both expensive and often impractical. The growing urban population is demanding a larger amount of potable domestic water. Many of these urban centres, such as the Gauteng urban complex, are located far from large reliable water sources. This means that large water schemes need to be implemented to assure supply in such areas (Conley, 1996).
3.2.2 Ecological demand
The ecological reserve relates to the water required to protect and sustain the aquatic ecosystem of the water resource (National Water Act, 1998). A minimum share of the water resources. in South Africa is allocated to the environment. In South Africa, the protection of the natural environment is seen as a key factor in achieving sustainable development. Hence, the environmental demand will need to be factored in when assessing water supply schemes in the future (Shackleton et al., 1996). The calculation of this demand is still in an initial stage and it is as yet very difficult to anticipate with accuracy the impaCt this demand will have on the water resources within South Africa.
South Africa's high climate variability is echoed and amplified in river flow regimes (Schulze, 1997b), which are even more variable (by a factor of 2 - 5 compared with rainfall; Schulze, 2001). The indigenous and endemic biota that live in such rivers have adapted to this high variability and require it for their survival. In order to sustain these ecosystems, it is necessary not only to provide the basic minimum amount of water, but also to maintain the variability, which allowed these systems to develop and survive. The environmental demand is hence highly erratic, varying locationally, seasonally and inter-- annually. The complexity of the relationships and interactions inherent in any ecosystem makes the assessment of the environmental reserve a difficult and time consuming task.
3.2.3 Agricultural demand
Irrigation, using 54 % of the total water requirement, is the largest consumptive user of water in South Africa (Basson 1997). Food security is a major factor in the develop ment of any country. Agriculture therefore plays an important role in the economy. Perusal of Table 3.1 indicates that agriculture and forestry, both rainfed and irrigated, use approximately 62% of the current (1996) total water demand in the country (Basson, 1997). A major portion of the agriculture and forestry sectors relies on rainfall, thus making it prone to the vagaries of climate variability. Higher future demands for water in the other . sectors of the economy will increase the competition for water (Table 3.1). In the foreseeable future, the agricultural sector will have to give up the some of its share of water to the other sectors, making it a necessity for agriculture to optimise its water use (Watson, 1996).
3.2.4 Industrial demand
Industrial development is taking place at a rapid rate in South Africa. As the country develops so the industrial water demand increases. Industrial water use is predicted to increase from using 8% of the total water available in 1996 to using 11 % by the year 2030 (Basson, 1997). This translates into a doubling in actual consumption, from 1 598 x 106 m3.a-1 to 3 380 x 106 m3.a-1 (Table 3.1). Water demand for industrial processes is relatively constant throughout the year, increasing linearly over time as a result of industrial expansion. Most industrial processes need a set minimum amount of water and if this is not supplied then the industry is unable to operate. Hence, the economic stability of industrial regions depends on the stability and assurance of water supply throughout the year and between years.