Intakes are the structures used for collecting the water from the surface source.
The basic function of the intake structure is to assist in safely collecting or withdrawing water from the surface source over a predetermined pool levels then to convey this water either by gravity or pumping to the treatment plant via intake conduits.
Generally, an intake may be a concrete or masonry structure and it mainly contains opening, grating or strainer through which the raw water from river, canal or reservoir enters and is carried to a sump well by means of conduits.
Water from the sump well is pumped through the rising main to the treatment plant.
The site for the intake should be selected carefully, keeping the subsequent points in mind :
- The intake must be located at an area when it can draw water even during the driest period of the year. If possible should be located sufficiently inside the shore line.
- Site should be as almost the treatment works as possible. it’ll reduce the conveyance cost from source to the treatment work.
- The intake must be located within the purer zone of the source in order that the simplest quality of water is out there , thereby reducing the load on the treatment plant.
- As far as possible the intake shouldn’t be located at the downstream or within the vicinity of the purpose of disposal of waste water (so that the water isn’t contaminated). When it becomes necessary to locate the intake within the close proximity of the disposal point, a weir should be constructed upstream of the disposal point and therefore the intake should be located within the upstream of the weir.
- The location should be such intake work can draw more quantity of water if required in future i.e. there should be sufficient scope for future additions and expansions.
- The intake should never be located near the navigation channel as there are chances of intake water getting polluted thanks to the discharge of refuse and waste from ships and boats. Also there are chance of accidents.
- The intake site should remain easily accessible even during floods.
- In meandering rivers, the intakes shouldn’t be located on the curves or atleast sharp curves. If they need to be located on curves, it’s better to locate them on concave banks instead of locating on convex banks as water will remain available on the concave side.
- At the location there shouldn’t be heavy current of water which could endanger the security of the intake works.