Supporting article N: Water is the single very scarce resource in South Africa. Let us treat it with due care.
A SHARE-NET INITIATIVE
South Africa is extraordinarily rich in natural resources – except for water. Water is a vital, but scarce resource, distributed unevenly in time (frequent droughts alternate with periods of good rainfall) and space (the eastern half of the country is markedly wetter than the western half). Increasing demand for water, and decreasing water quality, make careful water management a priority in our country.
Our average rainfall is less than 500 mm a year, with the driest part of the country receiving less than 200 mm/year and the wettest receiving more than 2 500 mm/year! Rain does not always fall where it is most needed, and some areas of high demand, such as Gauteng, receive less water than they need. Most rain falls in the narrow belt along the eastern and southern coasts. The rest of the country receives only 27% of South Africa’s total rainfall. In addition, hot, dry conditions result in a high evaporation rate. Water is thus a very scarce resource in South Africa. Large scale engineering has been used to store water behind dam walls, and to distribute water from regions of plenty to regions of need (see “Intercatchment transfer”, below).
There are few natural lakes in South Africa. We depend on rivers, dams and underground water for our water supply. Approximately 75% of the water flowing from South Africa into the sea occurs along the eastern and southern seaboards where many short rivers occur. Flowing from east to west is the largest river in the country, the Orange River, which drains most of the rest of the country. Its water comes from sources in the Drakensberg and Maluti Mountains, and it flows into the Atlantic ocean on the West coast.
About half of South Africa’s annual rainfall is stored in dams. We have 550 government dams in South Africa, with a total capacity of 37 000 million m3.
Dams have both positive and negative ecological impacts. They can be beneficial in that they regulate the flow of a river, reducing flood damage, and contributing to a perrenial rather than seasonal flow. In addition, sediment is deposited in a dam, and the growth of aquatic plants means that excess nutrients are removed from the water. Thus water leaving a dam might be cleaner than water entering it. Negative ecological impacts include a reduction in strong water flow which reduces the river’s scouring ability. This, in turn, can lead to silting of estuaries.
South Africa’s landscape is not well suited to dams. There are few deep valleys and gorges, with the result that most dams are shallow with a large surface area. Together with the hot, dry, climate, this results in much water evaporating from dams. In addition, the high silt load (a result of an arid climate, steep river gradients and poor farming methods) of our rivers means that the capacity of South Africa’s dams is quickly reduced as they become silted. The rivers of the western Cape are an exception, and carry relatively little silt.
A growing problem for South Africa’s rivers is a lack of water! Reduction in river flow, owing to abstraction (removal), and damming, has affected many of our rivers, for example, those flowing through the Kruger National Park.
This involves the movement of water from catchments with good supplies and low demand, to those where demand is high and supply poor. There are seven intercatchment transfer schemes in operation, and a further eight are under construction or proposed. The largest operational scheme is the Orange-Fish River scheme where water gravitates from the Orange River at the Gariep Dam, and is piped through tunnels and canals to the Sundays and then the Fish Rivers in the eastern Cape. Other examples are the Tugela-Vaal (operational) and Lesotho Highlands-Vaal (under construction) schemes. Tentative plans have been put forward to buy water from neighbouring states, e.g. from the Okavango River in Botswana and the Zambezi River in Zimbabwe. As yet, little research has been carried out to establish the ecological consequences of intercatchment transfer.
Industrial and agricultural pollutants common in South Africa are: agricultural fertilizers, silt, toxic metals, litter, hot water, and pesticides. However, some of the most common pollutants come from urban waste water, particularly from informal settlements which lack sewage and water purification facilities. The resulting pollution contributes to serious health problems. For example, typhoid, cholera and gastroenteritis are transmitted by water contaminated with untreated sewage. Gastroenteritis is one of three main causes of death in South African children under the age of five. Between 1980 and 1987, between half a million and one million South Africans contracted cholera.
THE FUTURE – RECYCLING AND DESALINATION
Some large industries, such as SASOL and ESKOM, already recycle water for use in their plants. Regional water suppliers also recycle limited amounts of water, e.g. water supplied by the Rand Water Board contains less than 2% recycled water, and this is likely to increase as demand increases.
Desalination, currently thought to be too costly and thus not practised in South Africa, is a likely option as we come to realise the true value of water.
DID YOU KNOW?
* Most of South Africa’s water is used for irrigation, and for the vast majority of farmers water is free!
* Of the 4,5 million people in the Umgeni River catchment, 2,5 million have no direct access to potable water.
WHAT YOU CAN DO
* The quality and quantity of water in our rivers, lakes and dams is dependant on river catchment management. Work towards a local catchment management project in your area. Share-Net (address below), the INR (address below), and your regional agricultural extension officer are able to assist with aspects of catchment management.
* Save water by placing a brick (sealed in a plastic bag) in the cistern (water tank) of flush toilets to reduce the amount of water used; shower rather than bath – baths use five to ten times more water than a shower; and never wash under a running tap.
* Collect rainwater from the roof for gardening. Grow plants indigenous to your area as they usually need relatively little water. Water at night and mulch the soil around plants to reduce evaporation of water.
* Report water pollution to the Department of Water Affairs anf Forestry, address below.
* Never dump used motor oil onto the ground or into drains. Service stations collect used oil.
* Use the theme of water for school, wildlife club or university projects. Share-Net (address below) supplies a range of resources, including water test-kits and regional contacts to support water projects.
* “The biology and conservation of South Africa’s Waters” (details below) has a very useful chapter titled “What you can do”.