Rainwater harvesting/Groundwater recharge/Tube recharge
Tube recharge is a low cost technology that combines manually filled holes with drainage tubes that pass through the compacted topsoil layer. Rainwater that normally evaporates or runs off into rivers now penetrates into the ground and replenishes aquifers.
The tube recharge system consists of a plastic hose or PVC tube with a diameter of 20-30 mm. These tubes are placed in manually drilled holes, upstream of a production well and at a location where water collects naturally or in an artificially constructed pond. When the pond is filled up after the rain, some hours must pass before opening the drainage tube, in order to settle the dirt. Before the water enters the tube, it is filtered by a filter tube. The length of the tube is 5 to 10 m, depending on the size of the compact topsoil. They do not go into the aquifer itself.
Each rain event will recharge the aquifer with about 2-10 m3, depending on the size of the pond. The capacity and flow patterns of the groundwater determine the extent to which recharged water can be pumped up during the dry season.
The local geological situation dictates specific requirements, costs and time: if there are no stones or boulders, a 10 m hole can be made in one day or less with a drill such as a step auger or Hand auger - general.
Construction, operations and maintenance
- Prior to placing the recharge tubes, testing is needed to determine the best sizes of tube, depth, maximum capacity of recharge, etc.
- Maintenance consists of unclogging the drainage tube by swabbing: moving a stick with a cloth up and down the drainage hole.
- Before recharge systems are applied on a larger scale, their effectiveness in a given context should be further investigated by means of smaller pilot systems.
- Total costs per system (drilling, tubes, labour): US$ 5 - 30.
- Step auger or Baptist drill set for holes up to 12 m (can be used for many holes): US$ 75.
If the holes are drilled by families themselves, the costs can be minimised.
Draft Short Manual On Tube Recharge Methodology. Arrakis, 2006.
- Smart Water Harvesting Solutions: Examples of innovative, low cost technologies for rain, fog, and runoff water and groundwater. (or alternative link) Netherlands Water Partnership, Aqua for All, Agromisa, et al. 2007.
- Original Akvopedia.org article and more images: akvopedia.org/wiki/Tube_recharge