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Water Portal / Rainwater Harvesting / Groundwater recharge / Wells, shafts, and boreholes

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[[Image:Wells,_shafts,_and_boreholes_icon.png|right|80px]][[Image:RechargePit.jpg|thumb|right|300px200px|Recharge pit constructed for recharge of surface runoff. Rajasthan, India. <br> Photo: [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDgQFjAB&url=http%3A%2F%2Funesdocunesdoc.unesco.org%2Fimages%2F0014%2F001438%2F143819e/images/0014/001438/143819e.pdf&ei=uqt8T9_sL6ibiQKTqdzFDQ&usg=AFQjCNFjJrN8OJHYuNSZrDZIrDtZxc_LRg&sig2=J7p3YnDub8Ixn2n4DU-uBw ''Strategies for Managed Aquifer Recharge (MAR) in semi-arid areas.''] UNESCO.]]  '''Wells, shafts, and/or boreholes''' are holes (often human-made) in the ground at various depths used for the purposes of storing water for later use.

Large diameter wells and smaller diameter boreholes can be used to directly recharge or dilute shallow aquifers where low permeability strata (rock) overlies the aquifers and where other infiltration methods are not effective. The important thing is that water of high enough water quality is used for this purpose. Although this method of recharge is practised with deep and high-yielding boreholes, this technique mainly describes recharge at the family level in areas where hand dug wells run dry at the end of the dry season or where groundwater is saline.

In loosely consolidated material, recharge pits and trenches are also used in cases where low permeability material overlies the aquifer, which occurs at trench-able depth, approximately 5-15m. Structures are excavated sufficiently deep to penetrate the low permeability strata, in order to provide direct access to the aquifer. Trenches or pits can be built to maximise the side-wall surface area and minimise the bottom surface area in order to facilitate horizontal movement of recharge water into the aquifer. The facilities should ideally be covered to keep out sunlight, animals, and people.

===Suitable conditions===

* Site only in areas where rainwater does not infiltrate fast enough where there is high runoff.

* '''Avoid''' where there is a risk of chemical contaminants entering the well, e.g. fertilizers and pesticides from agriculture, and when the final

water abstracted will be used for drinking, unless you have the ability to apply an appropriate filter.

 {{procontable | proborder="1" cellpadding="5" cellspacing="0" align="center"|-! width="50%" style="background:#efefef;" | Advantages! style="background:#f0f8ff;" | Disadvantages|-| valign="top" | - Can assist recharge of shallow wells. Allows groundwater aquifers to be treated as massive storage tanks where in times of surplus, the aquifer can be recharged while in times of drought the water can be extracted. One example of this is the “water bank” concept for Windhoek’s water supply in Namibia. <br>

- Can reduce salinity in groundwater <br>

- Low cost and simplicity enables it to be replicable by users without donor funds<br>

| convalign= "top" | - Water quality requirements of recharge water are high <br>

- A good understanding of the hydrogeology of the aquifer is needed<br>

- Technology needed to construct these structures can be quite complex, requiring engineering skills.<br>}|}

 ===Resilience to changes in the environment===

====Drought====

'''Effects of drought''': Water levels reduce in wells & boreholes that are being recharged. <br>'''Underlying causes of effects''': Less recharge.

'''Underlying causes of effects'''More information on managing drought: Less recharge[[Resilient WASH systems in drought-prone areas]].

====Floods====

Shallow wells in areas with a high water table are more prone to contamination from flooding than deep boreholes. Wells near rivers can be contaminated and filled with sand during flash floods.

===Construction, operations and maintenance===

'''General advice on cement''': A common cause of cracks in structures and linings (e.g. in tanks, dams, waterways, wells) is errors in mixing and applying the cement. First of all, it is important that only pure ingredients are used: clean water, clean sand, clean rocks. The materials have to be mixed very thoroughly. Secondly, the amount of water during mixing needs to minimal: the concrete or cement needs to be just workable, on the dry side even, and not fluid. Thirdly, it is essential that during curing the cement or concrete is kept moist at all times, for at least a week. Structures should be covered with plastic, large leaves or other materials during the curing period, and kept wet regularly.

[[Image:RoofToAquifer.jpg|thumb|right|300px200px|Roof to aquifer recharge. Click image to zoom. <br> Drawing: Unicef/Ara Centro. (2009)]]

====Water source considerations====

Some chemical pretreatment of the water may be required to prevent flocculation of iron, CaCO3, etc. and chlorination of other disinfection may be needed to prevent microbial growth. Clogged wells may need to be recovered at regular intervals using surging and pumping to remove fines and bacterial growth physically and the use of a wetting agent to remove air in an air-clogged well. Carbonate aquifers exhibit the least amount of clogging due to the gradual dissolution of calcite by a slightly acidic injectant, if periodic backflushing is observed.

==Costs=Field experiences===<br>{|style="border: 2px solid #e0e0e0; width: 40%; text-align: justify; background-color: #e9f5fd;" cellpadding="2"<!--rsr logo here-->|- style="vertical-align: top"|[[Image:akvorsr logo_lite.png|center|60px|link=http://akvo.org/products/rsr/]]<!--project blocks here-->|- style="vertical-align: bottom"|[[Image:project 467.jpg |thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org//project/467/ RSR Project 467]<br>Community Water and Sanitation Project</center></font>|link=http://rsr.akvo.org//project/467/ ]] |[[Image:project 427.jpg |thumb|center|140px|<font size="2"><center>[http://rsr.akvo.org//project/427/ RSR Project 427]<br>Scale up of Sustainable Water Access</center></font>|link=http://rsr.akvo.org//project/427/ ]] |}

==Field Experiences==<br>

==References manuals=Manuals, videos, and links===* [http://www.trustindiawaterportal.org/alertnetarticles/newswell-revival-effort-sees-many-other-benefits Well revival effort sees many other benefits] A community drive to revive wells in Mokhla talab near Udaipur results in water security for longer periods of time as well as making leaders out of women.* [http:/namibian/www.indiawaterportal.org/articles/experiments-capitalcommunity-needswells Experiments with 'community wells'] Mobilized farmers in Dhule, Maharashtra, show how communities can use groundwater as a common resource in an organised and collective manner.* [http://www.indiawaterportal.org/articles/battling-water-banksscarcity-borewell-recharge Battling water scarcity with borewell recharge]* [http://www.reuters.com/article/2011/10/26/us-fornamibia-drywater-times idUSTRE79P41B20111026 Namibian capital needs "water banks" for dry times]. Reuters. 26 Oct 2011.* [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=7&ved=0CFQQFjAG&url=http%3A%2F%2Fwww.ewisa.co.za%2Fliterature%2Ffiles%2F087/literature/files/087.pdf&ei=WCJ9T_DCOKnTiAKC193qDQ&usg=AFQjCNEFu8pC-bYhIJPvRSBd6YDEtYDHOg&sig2=irq8wEj0CslXGXA5l2w__Q ''Planning Water Resource Management: The Case for Managing Aquifer Recharge''], by E.C. Murray and G. Tredoux.* [http://www.indiawaterportal.org/nodearticles/6270 Recharge Wellaugmenting-groundwater-basics-how-construct-recharge-well Augmenting groundwater: Cost and CautionThe basics on how to construct a recharge well]. India Water Portal. Includes materials and costs.* Commercial product: [http://www.kentainers.com/wp-content/uploads/2013/01/Permawell.pdf PERMAWELL]. Made by AquaSanTec.

===Acknowledgements===* CARE Nederland, ''Desk Study : [[Resilient WASH systems in drought -prone areas'']]. October 2010. * Gale, Ian, [http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&ved=0CDgQFjAB&url=http%3A%2F%2Funesdocunesdoc.unesco.org%2Fimages%2F0014%2F001438%2F143819e/images/0014/001438/143819e.pdf&ei=uqt8T9_sL6ibiQKTqdzFDQ&usg=AFQjCNFjJrN8OJHYuNSZrDZIrDtZxc_LRg&sig2=J7p3YnDub8Ixn2n4DU-uBw ''Strategies for Managed Aquifer Recharge (MAR) in semi-arid areas.''] UNESCO's International Hydrological Programme (IHP), 2005.

* [http://www.uniteforsight.org/environmental-health/module4 Water: The Water Crisis.] Unite for Sight.

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