Changes

==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.