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[[Image:InfiltrationWell.JPG|thumb|right|250px|Infiltration well in Madagascar. Eric Fewster, BushProof.]]
Also called interception wells, these are shallow wells which draw water from a natural aquifer outside of a riverbed, but which have a partial lining. They can be used to either drain a catchment area or recharge groundwater, especially where recharge of the aquifer is low due to low rock/soil permeability (the well penetrates through this). Infiltration wells do not have to have a direct inlet (although they can have one). Without an inlet, they can become a larger hole and be filled with porous natural materials to increase the ground's infiltration capacity and, in most cases, have a coiled drain between the soil surface and the underground piping. Rocks, coarse wood chips or straw can be used as filtering material. Wells made of straw are constructed like permeable trenches and do not have a coiled drain, which can limit their infiltration capacity. Water extraction can be done with [[Handpumps]] or [[Small and efficient motor pumps]]. Handpump cylinders will need to physically be able to fit inside the screen that has been installed.
==Suitable conditions==
* Site where water table is within 5 metres of ground surface, and where soils are stable.
* Site where water demand is low, e.g. for small communities.
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==Resilience to changes in the environment==
====Drought====
'''Effects of drought''': Less recharge of aquifer due to less rainfall; Increasing population & water demand; Size of aquifers – e.g. limited sand volume; Wells not sunk deep enough into water table; Incorrect siting; Graded gravel around pipe not correctly done.
'''Underlying causes of effects''': Less recharge of aquifer due to less rainfall; Increasing population & water demand; Size of aquifers – e.g. limited sand volume; Wells not sunk deep enough into water table; Incorrect siting; Graded gravel around pipe not correctly done.
'''To increase resiliency of WASH system''': Increase volume through construction of groundwater dam; Sink wells/pipes deeper; De-water wells during caissoning within the water table; Construct during the latter half of the dry season; Site in riverbeds that are dry for part of the year, where water remains in the riverbed throughout the dry season; Increase flow by use of porous concrete & perforated pointed steel pipes driven horizontally into the aquifer (riverbed wells) and graded gravel (infiltration galleries & jetted wells); Site in a degrading river section where there is no deposition (infiltration galleries); Put graded gravel around pipes to minimize clogging and increase flow.
==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.
'''Specific advice''':
[[Image:StrawInfiltrationWell.jpg|thumb|right|300px|Infiltration well filled with straw. <br> Source : Georges Lamarre (MAPAQ)]]
* Construction involves digging a hole to the water table in stable soil that has no risk of collapsing. Digging should not go deeper than 5 metres for safety reasons.
