To efficiently dissolve oxygen in a water having a variable α factor by changing a rate of gas to liq. stream according to a calculated α factor or parameter and providing a flow changing means for keeping a dissolution high in efficiency within a prescribed range.

In a movable oxygenation system for a river, a pump 12 for sucking water in a liq. conduit 14 provided with a gas introducing means having a shape of a Venturi tube 16 is provided. An oxygenated water in which the oxygen is incorporated in a water accelerated under an action of an impact wave made at a downstream of a throat part of the Venturi tube 16 is returned to the river via a perforated dispersion pipe 24 having plural outlet nozzles 26. At that time, in a controlling system 36, an output signal of a measurement means 38 measuring the α factor of the water is inputted and a controlling for pumping and/or oxygen supply is started, and this controlling is executed through an oxygen valve and actuators 40 and 42 and/or motor speed/operation controlling 44.