• It is a masonry or concrete structure, constructe at the head of the canal taking off from the river.
  • It is constructe U/S of the under sluices and located in one bank.
  • Its alignment is kept at an angle varying from 90° to 120° with the axis of the weir.
  • The head regulator consists of a number of spans separat by piers and each span is fitted with a steel gate which can be move up or down.
  • In the grooves made in the piers, with the help of either manual labour or winches.
  • In old regulators, the spans use to be quite small, but the modern trend is to use larger spans of 8 to 18 m.

Following are the functions of a main canal head regulator.

(i) To open or close the discharge in the canal and when require.

(ii) To check the silt entrance into the canal.

(iii) To prevent river floods entering the canal.

Design of head Regulator

1. The water way of head regulator should be adequate.

Q = 1.7 (L – knH) H3/2 where Q = Discharge in cumecs

L = Water way length of regulator in metres

H = Head causing flow

n = Number of end contractions.

k = A constant, whose value depends upon the shape of the nose of the pier.

  • Its value varies from 0.01 to 0.03. 2.
  • The angle of alignment of a head regulator with the axis of the weir maybe 90° to 120°.
  • The greater angle is preferre from the point of view of the smooth entrance of water.
  • The crest level of the head regulator should be about 1 m above the crest level of under sluices.
  • If some silt excluder device is to be locat U/S of the head regulator in the river, this difference may be increase to about 2 m.
  • Design of slop glacis and impervious floors is done in a similar way as for weirs.
  • D/S cut off must be provid to keep exit gradient well within the limits.
  • To prevent high flood water, spilling into the canal, R.C.C. breast wall should be provid on the U/S side of the regulator, from reservoir level to well above the H.F.L.
  • This wall is support on piers and is a design by considering its own weight and the water pressure from U/S.

Fig. 15.13. Main canal head regulator.

  • A high bridge is normally provid over the piers and winches and cranes are operate from the bridge for lift and drop the gates.
  • Length of D/S Talus should be about 4 to 5 times the depth of water in the canal and its thickness about 1 m.
  • It is made of concrete or stone blocks.