Contents preface (VII) introduction 1—37

13.10. CANAL HEAD REGULATOR
A canal head regulator is required to serve the following functions: (i) To regulate the discharge into the offtaking canal, and (ii) To control the entry of sediment into the canal.
The head regulator is usually aligned at an angle of 90° to 110° (Fig. 13.9) to the barrage axis (5). This orientation minimises entry of sediment into the offtaking canal and prevents backflow and stagnation zones in the undersluice pocket upstream of the regulator. The discharge through the regulator is controlled by gates. Steel gates of 6 to 8 m spans are generally used. However, larger spans can also be used in which case the gates are operated by electric winches.
The pond level in the undersluice pocket, upstream of the canal head regulator, is obtained by adding the working head of about 1.0 to 1.2 m to the designed full supply level of the canal. The level of the crest of the head regulator is obtained by subtracting from the pond level, the head over the crest required to pass the full supply discharge in the canal at the specific pond level. The crest of the regulator is always kept higher than the cill of the undersluices to prevent entry of sediment into the canal. If a sediment excluder is also provided in the undersluice pocket, the level of the crest of the head regulator should be decided keeping in view the design requirements of the sediment excluder in addition to the requirements of waterway, and the working head available.

Loose apron

Toe wall
Block protection
Upstream conc. floor

Axis of

barrage
Under sluices


Sheet pile
Pier

Axis of regulator

Slope	D/S conc. floor
1 in 2	D/S sheet pile

Inverted filter

Toe	Loose apron
wall
		Canal

Sloping floor

wallsupported	onbackfill
Wing