Iwaya Dam
A blue-green lake flanked by forested mountains stretches out before the observation deck at Iwaya Dam in Gero’s Kanayama district. The dam was built to generate hydroelectric power, prevent flooding, and ensure a supply of water for surrounding communities. Construction began in 1966 and lasted ten years. The dam contributes to the local community, and the lake is a destination for leisure activities and wildlife enthusiasts.
Iwaya Dam is a rockfill dam that measures 127.5 meters in height and 366 meters in length. The dam’s reservoir, Lake Tosenkyo Kanayama, is the largest artificial lake in the Hida River basin, with a capacity of 150 million cubic meters. The lake is a popular spot for water sports like kayaking and stand-up paddleboarding.
During heavy rains, Iwaya Dam can accommodate up to 2,400 cubic meters of new water per second, discharging 300 cubic meters per second while safely storing the remainder. It distributes water for agricultural, industrial, and residential use to Gifu, Aichi, and Mie Prefectures and the city of Nagoya. Water from the dam is used by local power plants to generate enough electricity for around 110,000 households.
An exhibition hall near the dam provides information, including infographics, about its construction, function, and features. An augmented reality experience is available by downloading an app and scanning a card in the facility. There is an observation deck above the exhibition hall.
The reservoir and the forested slopes surrounding the dam are home to many plants and animals. Colonies of Asian fawn lilies (Erythronium japonicum) and orchids called Japanese cypripedium (Cypripedium japonicum) grow on the banks of the reservoir. Yellow-patterned Gifu butterflies (Luehdorfia japonica) emerge in spring, and forest green tree frogs (Zhangixalus arboreus) spawn in trees along the water’s edge between April and July. The majestic mountain hawk-eagle (Nisaetus nipalensis) can be spotted year-round, soaring through the surrounding skies.
