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Newsletter and Technical Publications

<Sourcebook of Alternative Technologies for Freshwater Augumentation in Africa>

3.1.1 Groundwater Harvesting

Technical Description

Borehole depths vary, depending on geological formations. In sedimentary rock formations, depths of between 25 and 200 m are common. Technically, borehole or well development starts with a geophysical investigation to identify a suitable site. Subsequently, the borehole is drilled through the overburden, weathered surface rock, and fractured bedrock. Usually during the drilling process, slotted screens and solid casings are installed to improve the integrity of well. When groundwater is harvested for industrial use, high yield boreholes and wells are drilled on industrial premises and fitted with pumps, powered by either electricity, oil, or solar energy, to deliver water for use within the production lines of the industry.

Extent of Use

Groundwater harvesting is widely used by breweries and and in the canning industry, among others, in water short areas of Africa.

Operation and Maintenance

The principle operation and maintenance requirements of a groundwater harvesting system relate to the pumping system and associated distribution network. Solar panels, although requiring less regular maintenance, have high capital costs. All pumping systems can be maintained at the maintenance section of the industry with back up support from the manufacturers.

Level of Involvement

This technology is typically implemented at the local level by individual industries.

Costs

Costs vary considerably according to size of the industry, its demand, pumping rate, type of pumping system, pump efficiency, energy costs, and other related factors that are industry and site specific.

Effectiveness of the Technology

Groundwater generally supplies a significant percentage of the water needs in industries using this technology.

Suitability

This technology is suitable for use in areas of water shortage, or where municipal supplies are expensive. The abstraction of groundwater, however, may be regulated by the government in times of drought or emergency.

Environmental Benefits

Few negative environmental impacts have been recorded, but regulation of pumping rates may be necessary to avoid overpumping. In karstic areas, such regulation may be needed to minimise the potential for the creation of sink holes.

Advantages

Water is made available on site in an appropriate quantity, and groundwater is generally of high quality. Use of groundwater resources over municipal supplies can result in significant saving in costs of production.

Disadvantages

Uncontrolled pumping may have a negative impact on the environment.

Cultural Acceptability

Use of groundwater is culturally acceptable.

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