PURPOSE: To utilize the energy of water without requiring a special location for installation by a method wherein a movable dam is arranged on an underwater weir provided in a river and a draft tube, passing below the underwater weir from the bottom of the river at the upstream of the underwater weir, is provided to install a hydraulic generator on the entrance of the draft tube.

CONSTITUTION: The underwater 1 is provided at a proper position in the river and the movable weir 2 is provided thereon. The draft tube 3, penetrating below the diving dam 1 from the bottom of the river at the upstream of the underwater weir 1, is bored to install the hydraulic generator 4 at the entrance thereof. The generator 4 is consisting of a water introducing tube 4A and the main body 4B of the generator while the axial lines thereof are vertical. An intercepting gate 6 is equipped at the entrance of the draft tube 3 to open and close in accordance with the beginning and the stop of the generation of electricity. This constitution does not require a special acquisition of a land for the installation of the generator and a small installation fee is enough to install it, therefore, the energy of water, which has been neglected so far, may be utilized effectively.