A headwork is a barrage across a river with regulators that take water into canals. Punjab's are at Madhopur on the Ravi, Ropar and Harike and Hussainiwala on the Sutlej, and Ferozepur.
Madhopur, from 1859, feeds the Upper Bari Doab Canal. Ropar feeds the Sirhind Canal system into the Malwa. Harike, built 1952, feeds the Rajasthan Feeder and the Ferozepur Feeder. Hussainiwala feeds the Eastern and Bikaner canals.
These are the physical points at which Punjab's water becomes somebody's allocation. Every water dispute in the region is finally a dispute about the setting of a regulator at one of five places.
The 1947 boundary was drawn with these structures in view, whatever the Boundary Commission said about its principles, and the Ferozepur and Madhopur awards are the most contested parts of the line.
They are guarded installations. Most Punjabis have never seen one and every Punjabi's living depends on them.
A regulator setting is a number in a register, changed by an executive engineer on instructions. The whole apparatus of tribunals, treaties and court orders exists to determine what that number should be on any given day.
Harike, at the meeting of the Sutlej and the Beas, feeds the canal into Rajasthan and the Ferozepur feeder, and the wetland behind it is a Ramsar site.
These structures were designed for irrigation and are operated for it. Their flood role is secondary in the rules that govern them, which is what the 1988 and 2023 floods turned on.