A liquid level control system employs a flap gate for discharging liquid, but with a midstream headloss inducing device between the basin or tank and the flap gate. The flap gate opens when liquid level in the basin rises, and the opening of the gate is controlled by a counterweight positioned so as to decrease closing force as the gate opens farther, thus managing the outflow of liquid to efficiently return the basin to a design level. If flow from the basin is generally constant, the system will reach a point of equilibrium of gate opening and closing forces while liquid flows out from the basin.