The land ministry will establish a system of compensating for losses stemming from water release from dams in rivers managed by prefectural governments as a pre-emptive measure to minimize damage from torrential rains, sources have said.
The plan, similar to an existing one for water systems managed by the central government, is aimed at avoiding flood damage triggered by increasingly intense rains, the sources said.
There are some 2,700 Class B rivers, or water systems managed by prefectures, around the country. Dams have been constructed in around 350 of such rivers.
Most of the rivers have a smaller basin area than nationally managed Class A rivers, but recent torrential rains have caused some of them to overflow and flood residential areas.
The new system is intended for so-called water utilization dams, which are built for purposes other than flood control. Such dams are used for power generation or for channeling water from rivers for industrial, agricultural or tap use.
If water utilization dams release water ahead of torrential rains, the amount of generated electricity or water supply for human use will be low until the dams’ water level rises back after the torrential rains. This risk has prompted the ministry to devise a system to compensate for losses on the side of power utilities and others affected by the pre-emptive water release.
The compensation is expected to be paid for by the central and prefectural governments, and the ministry plans to hammer out the details in the future, the sources said.
The central government decided last December to sign agreements with the operators of water utilization dams and related parties to allow for the release of water before severe rains.
A compensation system for drops in power generation and water supply was introduced by the ministry for dams in Class A rivers in April, and agreements with all 99 water systems in the category with dams were signed by June.
Chief Cabinet Secretary Yoshihide Suga said that similar measures will be adopted for Class B rivers, during a visit to the Sudagai dam in the town of Minakami in Gunma Prefecture, eastern Japan, on Aug. 12.