大井川
In 1906, a joint venture company, the was established, and began studies and design work on plans to exploit the potential of the Ōi River and Fuji River in Shizuoka Prefecture. The British interests were bought out by 1921, and electrical production nationalized under the aegis of the in 1938. The first dams on the Ōi River were completed in the late 1920s and early 1930s, but further work was suspended by the Great Depression of the 1930s, and World War II in the 1940s. However, by the early 1950s, Japan's need for electrical energy was growing exponentially, especially in the industrial belt near Nagoya. After the breakup of Nippon Hassoden at the end of World War II into various regional power utilities, the bulk of the dams on the Ōi River came under the control of Chubu Electric Power.