Intake definition, components, river intake

Definition

An intake is a structure built in or near a water source (river, lake, reservoir, canal or spring) to draw water safely in the required quantity and send it to the conveying main, pump well or treatment plant.

Components of an intake

1. Intake opening / port with a bell-mouth entry, placed at one or more levels.
2. Coarse screen (trash rack) with bars 20 to 50 mm apart to stop large floating objects, and a fine screen (6 to 12 mm mesh) to stop small debris.
3. Intake well / tower / chamber that houses the gates and valves and lets water settle.
4. Sluice gates / valves to regulate or cut off flow.
5. Conveying (intake) pipe or conduit from the well to the pump house or main.
6. Sump or pump well (for pumped schemes) and a foot bridge for access.
7. Protection works: pitching, groynes, wing walls, embankment, guard rails, and a flushing / scour pipe for removing silt.

General river intake

A river intake is a tower or well built in (or at the edge of) the river with openings at different levels. Water enters the openings through screens, passes into the well and then flows by gravity (or is pumped) through the intake pipe to the treatment plant.

   Foot bridge
  =========|===========
           |   Intake tower
 HFL ~~~~~ |  [ ]  gate/valve
           | __|__ upper port
 NWL ~~~~~ |/  |  \  <-- screens
           |   |__ middle port
 LWL ~~~~~ |   |
           |___|__ lower port
  River bed ///|\\\
              \|/ intake pipe to
                   pump well/treatment

Working

• Ports at two or three levels let the operator draw the clearest water at any river stage: the upper ports when the river is high (the surface water carries less silt), and the lower ports when the river is low.
• Coarse and fine screens at the ports stop floating matter, leaves, fish and debris.
• Gates or valves on each port regulate flow and isolate a port for repair.
• The water travels from the intake well through the intake pipe to the pump well or the plant.
• The entrance velocity is kept low (0.15 to 0.3 m/s) so that little silt and debris are drawn in. A foot bridge gives access for operation and cleaning.