Aimata Dam - History

History

In the wake of the massive damage sustained by the Tonegawa River system from 1947's Typhoon Kathleen, the Economic Stabilization Board's consultative flood prevention committee proposed the construction of a reservoir as the pillar of a cumulative plan for developing flood prevention infrastructure. The Ministry of Construction's Kantō Regional Development Bureau drafted the "Tonegawa River Repair and Improvement Plan" in response to this proposal; the plan was based on the construction of (originally) 9 multi-purpose dams on the Tonegawa River system. These eventually became the Tonegawa River 8 Dam Cluster, with one of the dams on the main Tonegawa River—Fujiwara Dam—being already under construction.

Preliminary studies for dam construction were begun on the Akaya River in 1948. Afterward, the dam project's operation was turned over to Gunma Prefecture, rebranded as the auxiliary "Akaya River Cumulative Project"; construction began in 1952, and completed in 1956. However, during initial impoundment (in which the dam is partially filled to test for abnormalities), leakage through the bedrock on the left bank was discovered, and Gunma Prefecture requested repairs from the Ministry of Construction. That same year, concrete work was started to enable seepage control on the left bank. Repairs were completed three years later in 1959, and construction was finalized. Aimata Dam was placed under the direct management of the Ministry of Construction, and became the second of the Tonegawa River 8 Dam Cluster.