3 5 7 8 and 10 and shown in vertical longitudinal section on a plane v v of fig6 fig7 is a view through a third gate implementing disposition numbers 1 2 3 4 5 7 9 and 10 shown in section on a longitudinal vertical plane vii vii of fig8 fig8 is a fragmentary plan view of the third gate the characteristics common to the gate shown in fig5 to 8 are described below both of these gates are disposed on a canal and each of them separates an upstream reach 3 from a downstream reach 4 by means of a metal plate 1 which moves in a concrete channel 2 the plate is carried at the end of the upstream branch 6 of a frame oscillating about a transverse horizontal axis 5 the upstream branch also carries immediately downstream from the plate a cylindrically shaped compensation tank 11 the downstream branch 7 has a float 8 in the form of a sector of a torus at its end this float moves inside a tank 31 which communicates with the downstream reach via an orifice 37 the float has an access hatch 29 enabling solid ballast to be inserted therein in addition the frame carries a correction tank 13 at.