Greetings from the Director of the Osaka Prefectural Aigawa Dam Construction Office

Osaka Prefecture is engaged in a variety of projects to ensure the safety and security of its residents in the event of natural disasters, and the construction of the Aigawa Dam is considered one of the most important projects as the cornerstone of flood control measures in the Aigawa River basin in northern Osaka Prefecture.
Construction of the Aigawa Dam began in 2014, with the embankment raising completed in January 2022, the flood discharge and other major structures completed in April of the same year, and the foundation treatment work, which is critical to the dam's water storage function, completed, and initial impoundment began on September 5, 2022.
Dam projects require the acquisition of large tracts of land for the dam itself and waterlogged areas, and have a significant impact on the lives of local residents, including the relocation of those who live there and the provision of farmland for their livelihood. On the other hand, it is the downstream urban areas that will enjoy the benefits of the dam, not the residents of the construction site. For this reason, Osaka Prefecture spent a long time carefully explaining the Aigawa Dam to local residents, gaining their understanding and cooperation for the project, which is why the Aigawa Dam exists today. As a person involved in the project, I would like to keep in mind and cherish the sense of gratitude we owe to the local residents.
More than half a century has passed since the "Hokusetsu Torrential Rain Disaster" in July 1967 that triggered the dam concept, and the project is now nearing the final stage of completion. For the safety and security of the residents of the basin, all of us will work together to ensure that the dam is ready for use as soon as possible, and we will continue to steadily conduct initial impoundment and proceed with the remaining work toward the completion of the project with safety first.
The site of the Aigawa Dam is located approximately 7 km from the urban area of Ibaraki City, in an area rich in greenery, and when the dam is completed, a new lake will be created there, transforming the area into one blessed with water and greenery. We hope that the Aigawa Dam will be a local resource that will be enjoyed by the citizens of Ibaraki for many years to come, taking advantage of its unique location.

Until the Aigawa Dam was completed. ―Trace of construction and the future―
(1) Following the July 1967 Hokusetsu torrential rain disaster, which caused serious flood damage including 61 casualties, drastic flood control measures for the Aigawa river through river improvement and dam construction were seriously considered, and a construction plan for the Aigawa River Dam was drafted.
(2) Adopted in 1988 as a national government-subsidized project by the Ministry of Construction (at that time).
(3) In 1999 (Heisei 11), with the understanding of all local residents, the government of Osaka Prefecture began purchasing land for dam project use.
(4) In 2005, the function as a water source of municipal water supply was reviewed, and the dam height was changed to 6m lower than the initial plan (82.5m → 76.5m).
(5) In 2014, the groundbreaking ceremony for the dam construction was held.
(6) After excavation of the dam foundation started, various problems were encountered, such as a slope failure on the left bank side of the dam site and a rock slide behind the emergency spillway energy dissipator. In each case, experts and researchers in geotechnical engineering and geology were involved to conduct risk management as well as responding appropriately.
(7) Currently, it has passed about 30 years since the Aigawa Dam construction began. It reaches the high zenith of the construction works.

The north side of the dam is the interchange of the Shin-Meishin Expressway, and the southern area south side is an urban area, making it a rare urban dam in Japan. In addition to the original functions of dams such as flood control and water utilization of cause, it is also expected that the lakeside of newly result will become a base for the mingling of regional people and tourism.