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[[Image:RiverbedHandDugWell.jpg|thumb|right|350px| Hand-dug wells situated in riverbeds must be equipped with a well-head to prevent the well shaft being filled with sand during floods such as this hydro-dynamic well-head used in Sudan. It is shaped as a wedge to break the force of floods. © E. Nissen-Petersen, Kenya.]]
These are shallow wells which draw water from a natural or man-made aquifer specifically within a riverbed. The simplest version of these is a shallow hole dug every season in a riverbed which gets flooded with every flood event. Other versions allow the water to be accessed all year round through [[Handpumps]] or [[Small and efficient motor pumps]]. A bucket and rope can be used but risk of contamination increases. In such a case, household water treatment should be advocated.
==Suitable conditions==
* Wells need to be sited in riverbeds that are dry for part of the year, allowing construction to take place.
* There should be water remaining in the riverbed throughout the dry season.
- Can be difficult to sink to required depth especially in areas of flowing sand.
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==Resilience to changes in the environment==
====Drought====
'''Effects of drought''': Can dry up.
'''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:RiverbedWellWithHandpump.jpg|thumb|right|350px| Riverbed well with offset handpump. Eric Fewster, BushProof. <br> (Click image to zoom.)]]
Simplify construction methods while getting a more robust end product in a safer fashion. Pre-cast concrete rings can be used, but is more easily done with a cutting foundation ring and curved concrete blocks, some of which are made from porous concrete.