Sourcebook of Alternative Technologies for Freshwater Augumentation in Africa


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<Sourcebook of Alternative Technologies for Freshwater Augumentation in Africa>

2.1.7 Artificial Groundwater Recharge

Technical Description

Artificial recharge is the use of infiltration basins (Figure 33) or injection wells (Figure 34) to recharge groundwater resources. Infiltration basins can take many forms. For example, a storage dam can function as an infiltration basin under certain conditions. With infiltration basins, it is essential to construct the pond on an infiltration zone lying above an impermeable layer.

Extent of Use

Infiltration basins and injection wells have been implemented in Botswana, Egypt, Tunisia, and Algeria. In Zimbabwe, small infiltration dams are being developed.

Figure 33. Recharge by infiltration basin.

Operation and Maintenance

There is need for a source of the water to be recharged. Groundwater recharge using infiltration basins in areas with high evaporation rates is not likely to be effective. Likewise, the presence of clay lenses covering parts of an aquifer can be a problem as they can prevent the infiltrated water from reaching the aquifer. Both problems can be overcome through the use of injection wells, which allow the recharge water to be inserted into an aquifer under pressure.

Figure 34. Recharge by injection well.

Level of Involvement

Construction of recharge basins can be undertaken by local personnel with experience in well digging. Government assistance may be required to identify appropriate recharge sites.

Costs

The costs are moderate, depending on the scale of operations.

Effectiveness of the Technology

Recharged water may take on the qualities of normal groundwater, as impurities are removed within the soil profile. However, there is also the possibility of introducing contaminants into the groundwater system through the use of this technology, depending on the source of the recharged water. Groundwater recharge as a stormwater management technology creates the least cause for concern, and ensures the reliability of water supplied from nearby wells.

Suitability

This technology is appropriate for arid regions lacking alternative water sources. Water reclaimed in this fashion may be used as an alternate source of drinking water. Recharge may be appropriate in areas where behaviour of naturally-occurring groundwater is uncertain.

Environmental Benefits

The construction of infiltration basins may help to control soil erosion. The basins are usually appropriate habitat for a number of birds and wild animals.

Advantages

Groundwater recharge, especially using injection wells, conserves water through reduced evaporation. Clean drinking water may be recovered from wells in the vicinity of the recharge field without using complicated treatment systems.

Disadvantages

The water from a recharged aquifer cannot be used without a system of abstraction. There is also a possibility of polluting the aquifer with the recharged water.

Cultural Acceptability

The technique is culturally acceptable.

Further Development of the Technology

There is limited scope for further development of technology, especially in terms of ensuring the quality of the recharged water and the prevention of groundwater contamination.

Information Sources

Gustafsson, P. and J. Johansson s.d. A Study of Water Resources in Botswana. Department of Geology, Chalmers University of Technology and University of Goteborg, Goteborg, Sweden.

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