Noun
regulator consisting of a valve or gate that controls the rate of water flow through a sluice
a gate upstream from a lock or canal that is used to control the flow of water at the upper end
Source: WordNetPagano said it was important the design not interfere with the use of the diversion’s head gate that controls water flowing from the river into a canal. Source: Internet
A project to repair the head gate at Reservoir F Dam is currently underway. Source: Internet