[[Image:OmoRiver.jpg|thumb|right|400px|The Omo River in Ethiopia, Africa.]]
Channels take water from a riverbed to a collector well in the riverbank. They are often screens (slotted or perforated pipes) that are inserted horizontally into a riverbed, but also infiltration galleries can be made from channels with graded gravel as long as sediments are not washed into the collector well. Where screens are used, the screen diameter tends to be larger than that used normally for jetted/driven wells.
Riverbeds having catchments of flat farmland usually contain fine textured sand, that can only yield a maximum of 100 litres of water from 1 m3. of sand, i.e. an extraction rate of 10%. Stony riverbeds containing boulders and fractured rocks have the lowest potential for water extraction due to seepage caused by the boulders and fractured rocks. This seepage is, however, beneficial for replenishment of boreholes situated on riverbanks.
==Suitable conditions==
[[Image:InfiltrationGalleryDiagram.jpg|thumb|right|400px|Infiltration gallery Image courtesy of WEDC. © Ken Chatterton. In: Hussey, S.W. (2007) Water from sand rivers: guidelines for abstraction. WEDC, Loughborough University, UK.]]
[[Image:InfiltrationGalleryBuild.jpg|thumb|right|400px|Building an infiltration gallery. Infiltration Area: 1080 ft2 (100.3 m2). Cost - $9.33/foot2. Overseas supplier (AUS).]]
====How deep is the water table?====
Some rural people and most well-diggers know that water can only be found at certain places in riverbeds. They can also give a rough estimate on how deep they have to dig before reaching the water-table.Their knowledge is based on the fact that certain species of trees and vegetation must have roots reaching down and into the water-table in order to survive droughts. This traditional information is compiled in the table below.
[[File:WaterTableDepth.jpg]]
* The length of screen required will be greater for an infiltration gallery than for a jetted or driven well – in an infiltration gallery, water flows to the collector well under hydraulic head rather than being pumped out with a suction pump. Diameter of screen used is typically 75 – 300 mm PVC and varies from a few metres up to several hundred metres in length. Layouts vary according to the river widths. Yields are typically 15 litres/min/metre, but depends on depth from river to sump.
* Ensure that galleries are dug deep enough to allow enough flow during the dry season. In practical terms, this means aiming for at least 1 metre depth within the saturated zone. If more than one pipe are installed, distance between pipes should not be less than 3 metres.
