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Riverbed infiltration galleries

1,357 bytes added, 18:47, 6 April 2012
→‎Construction, operations and maintenance
==Construction, operations and maintenance==
* 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.
* The top of the gallery should be ideally 1.5 metres minimum from the riverbed surface. This is so that:
#There is at least a minimum of infiltration that occurs from surface water during the wet season when the river is flooded.
#That there is less chance that the well shaft and pipework will be washed away in a flood event. Sand becomes mobile to a certain depth which differs for different rivers but has been recorded to be normally between 0.66 and 2 metres in seasonal riverbeds.
* Graded gravel needs to be placed under and over the pipe to minimize clogging with sediments.
Winona
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