Infiltration galleries

Can infiltration galleries be used for drinking water? Infiltration galleries may be used for artificial recharge of the surface water to supplement the natural recharge of the groundwater aquifer.

Infiltration galleries are covered from two angles:

1. spring water
2. groundwater

Spring water tapping

Where the spring aquifer is of limited thickness but wide and the yield limited (so not a real spring 'eye') then a tunnel could be constructed to collect the flow from the wide spring. [1]

Fig. 1. Tunnel for tapping gravity overflow spring

Groundwater Recovery

Infiltration drains and tunnels are more costly to build, and their design is more complicated. Drains may be subject to clogging. The advantage of drains and tunnels is that these collectors are completely underground so that the collected water is protected against any contamination from the ground surface.[1]

Fig. 2. Infiltration drain

F ig. 3. Infiltration tunnel

In situations where a thick water-bearing ground formation is present at shallow depth, either vertical and horizontal water collectors, or a combination of these, can be appropriate. The technical feasibility will largely depend on the local geological conditions. A much more difficult situation exists when groundwater has to be withdrawn from a thin aquifer situated at a considerable depth. In view of the small saturated area of such an aquifer, boreholes should not be used. Ditches and drains are not appropriate since they would require an excessive amount of excavation work. Sometimes, in consolidated ground, tunnels may be suitable. For unconsolidated ground, radial collector wells may be considered. However, such wells require specialist design and construction and they are, therefore, generally less suited to small-scale water supplies. [1]

Fig. 4. Battery of boreholes

Fig. 5. Radial collector well or "Ranney Well"

You will also find a technical description of infiltration galleries in the UNEP/SOPAC - Source Book of Alternative Technologies for Freshwater Augmentation in Small Island Developing States, available on the Internet at: http://www.siwin.org/reviews/swr0004/swr0004b212.html and http://www.unep.or.jp/ietc/Publications/TechPublications/TechPub-8d/galleries.asp

For a list of other reports on this topic you can search on "infiltration galleries" in the IRC library database IRCDOC

Notes

[1] Chapter 10: Groundwater withdrawal by Okuni, P. & Farr, J. in: Smet, J. & Wijk, C. van (eds). (2002). Small Community Water Supplies: Technology, People and Partnership, (Technical paper series / IRC; no. 40). Delft, The Netherlands : IRC International Water and Sanitation Centre.
Contents page, introduction and chapter 4 on water quality is available online at http://www.irc.nl/page/1917

Price hard copy: EUR 34.00, order your copy, order code: TP40-E

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Date: Aug 2002

This response has been provided by the WELL Resource Centre Network with funding from the UK Department for International Development (DfID).

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