The system for varying flows in closed circuit open channel is disclosed. The system comprises a set of jet-mixer-ejectorsdriven by primary water jets, as a means of inputting additional mass flow, and associated momentum and energy by a pump to operate the jet- mixer-ejector system, an adjustable overflow gate to remove excess water to the pump inlet sump tank, preferably by gravity. The mixing zone to efficiently mix the water flow, and a plurality of guide surfaces to ensure effortless turning in the two end loops and screens to endure uniform flow. Plurality of ˜half™ ventury inserts are provided in the system which create various test sections to define the contraction of the flow width. Preferably, the closed circuit open channel facility is an oval shaped, which may also be called as ˜Endless pool� at various appropriate places in the description, due to the closed nature of open channel flow.
