A suitably designed regulator at the head of a canal is provided to regulate the supplies entering the canal as well as to control silt entry into the canal. It can also be used as a calibrated meter for assessment of the discharge entering the canal. Head regulators are provided at the head of a canal off-taking from a river or a branch canal taking-off from a main canal or a distributary sub distributary taking-off from a branch canal or a distributary itself as a case may be. The setting of alignment of the head regulator particularly in case of distributary canals vis-a-vis the alignment of the branch canal or a sub distributary from a distributary canal as the case may be needs to be given special attention. Notwithstanding the fact that the design of head regulator in the rehabilitation process is only confined to branch canals taking off from main canal or the distributary canal heads.
Designs both hydraulic and structural including the gate and hoist features of the existing head regulators are of interest in relation to the project area. Bureau of Indian Standards Code IS 6531:1994 – “Canal Head Regulator Criteria for Design” provides the general guidelines for design of head regulators for canals off-taking from a river diversion structure (weir / barrage). However, in case of distributary and branch canal heads though the best alignment of an off-take channel is zero angle with the parent channel in its initial length and then go out in a transition, in majority of the cases it is seen that the parent channel has to follow its course without any deviation and the off-take canal of the head regulator in such situations should be between 600 to 800 with the centre line of the parent channel. Whereas the general guidelines given in the above mentioned IS code may be relied upon in preparing the design for branch and distributary canal head regulators. Location specific details shall have to be decided on the basis of other relevant standards / references. The following procedure shall be adopted for design / redesign of head regulators.
(REF: http://idup.gov.in/wps/UpidHm/UPWSRP/WSRP_StandardsAndGuidelines/Canal%20Head%20Regulators.htm )