A liquid management unit uses a substantially horizontal rotor device partially submerged in a liquid so that at least a portion of a rotating component or the rotor device moves a liquid above the surface of the body of water and is then collected in a container for filtering, irrigation, or other purposes. A flap may be used with the container for opening and closing the container to incoming liquid. A control device such as an endless screw, chain, or rod may be used for opening and closing the flap especially when it is located on the interior of a shroud. A flow restriction unit can also be used with the liquid management unit to provide increased velocity to incoming liquid. The flow restriction unit is formed as a U-shaped member with an open inlet and opposite open outlet end. The inlet end cross sectional area may be increased by angling the sides outward at the inlet or slanting the bottom downward from the outlet to the inlet ends. The flow restriction unit can also be used in conjunction with a baffle and especially an articulated baffle to control the cross-sectional area through which the liquid flows.