• The impounded water in the reservoir has to be regulat through outlet works to use it usefully.
  • Outlet works are required for following purposes

(i) Feeding water for power generation.

(ii) Discharging heavily laden silty water D/S.

(iii) Supplying water to irrigation channels.

(iv) Supplying water for water supply purpose.

(v) To evacuate the water from the reservoir in anticipation of flood inflow.

Outlet works consist of three component parts.

1. Water way.

2. Gates to control the flow of water.

3. Intake structures.

  • A pipe or tunnel passing though the dam is the water way.
  • It is sometimes also know sluice way.
  • In concrete gravity dams the sluice ways may be made in the body of the dam whereas in case of earth dam they are set up outside the limits of the embankment.
  • If sluice way has to be provided in the body of the earth dam, the sluice way should have projecting collars at regular interval.
  • Collars prolong the seepage path and prevent the failure of the dam.
  • The inlet of the sluiceway should further be placed at the minimum reservoir level.

Gates. Rectangular vertical lift gates are mostly used for exercising control on the entry of water.

Sometimes sideway sliding gates may also be use.

Intake Structures. It is a structure place at the entrance of the sluiceway.

  • The main purpose of the intake structure is to allow only that water to pass through the sluiceway which is clear of grit, floating debris, etc.
  • It has several openings at various heights.
  • All the openings are cover with the screen.
  • A trash rack is also one of the devices which prevents the entrance of objectionable material in the sluiceway.
  • It also prevents any heavy body from hiring the outlet.