To prevent the lowering of the ground water level on the downstream side by partitioning a water permeable layer under the ground with a cut-off wall to form a ground water storage section on the upstream side and, at the same time, providing an opening and closing device to an opening section provided to the cut-off wall.

A watter permeable layer 2 between an underground surface layer 1 and a non-permeable layer 3 is partitioned with a concrete cut-off wall 4, and a ground water storage section 5 is formed on the upstream side of the cut-off wall 4. An opening section is provided in the cut-off wall 4, and the opening section is opened and closed with an opening and closing device. The opening and closing device is constituted of a pipe-like member 6 forming silt-like opening and an inside member 7, the inside member 7 is rotationally controlled with a control member 8 extended to the ground to open and close the openings of the pipe-like member 6. Accordingly, the flow of ground water to the downstream side of the cut-off wall can be controlled by opening and closing control of the inside member.