3.1.2 Surface water harvesting

Technical Description

Water demands in industrialized areas tend to out grow the available water supply. Thus, in order to meet demand, it is necessary to transfer of water to the site from another basin. Such inter-basin transfers (IBTs), although expensive, are becoming the only solution to meeting industrial and mining water demands. The technique involves building large reservoirs to capture runoff in watersheds that may be several hundreds of kilometres away from the centre of activity, and transferring this water by pipeline or canal to the area of use.

Extent of Use

Due to large financial investment required, this technique is limited to economically-viable projects such as the Lesotho Highlands project in South Africa and the water projects of Libya.

Operation and Maintenance

These systems have high operation and maintenance costs. There is usually a need for large and powerful pumping systems as well as extensive networks of pipelines and canals.

Level of Involvement

Highly qualified engineers and technicians are required to plan, design, implement and operate inter-basin transfer schemes.

Costs

This technology has high capital and operational costs.

Effectiveness of the Technology

This technology is generally effective in ensuring a reliable supply of water to areas that would otherwise be classified as water short areas. It is dependent, however, on the rainfall and availability of water in the remote catchment area, which may be subject to the same vagaries as the surface water resources in the centre of activity.

Suitability

This technology is suitable for use in areas where the rate of financial return is high, such as in the mining complexes of South Africa or the oil fields of Libya.

Environmental Benefits

There are numerous drawbacks with the use of this technology. Many affect the biodiversity of the waterbodies connected by the transfer scheme, and often include public health impacts, especially where there are open water transfer canals that can serve as water-borne disease vectors.

Advantages

This technology provides water where it is most needed for economic production, and can assist in bringing development to remote places.

Disadvantages

Water provided using this technology is expensive and, hence, the water may not be affordable by the poor. There are also potential biodiversity and public health impacts that must be monitored and contained.

Cultural Acceptability

This technology is culturally acceptable and is widely used in water-poor regions of Africa.

Further Development of the Technology

Options need to be thoroughly analysed before embarking on project. Development of an economic and environmental assessment protocol would be beneficial.

Information Sources

Department of Water Affairs and Forestry, Private Bag X313, Pretoria 0001, South Africa.