Abstract: A rotary valve assembly is disclosed for regulating the flow through two ts to control the filling and emptying of a lock. The valve assembly includes a plurality of planar elements, rotatable about a vertical axis within a cylindrical housing, and disposed at predefined angles as viewed in a horizontal plane, determined by the angles of intersection with the housing of a plurality of fluid conduits. Controlled rotation of the valve positions the planar elements relative to the fluid conduits, to direct flow from a source conduit into a lock chamber to fill it with water, to direct flow from the chamber to empty the lock, or to prevent flow altogether.