Akiba Dam

The potential of the Tenryū River valley for hydroelectric power development was realized by the Meiji government at the start of the 20th century. The Tenryū River was characterized by a high volume of flow and a fast current. Its mountainous upper reaches and tributaries were areas of steep valleys and abundant rainfall, and were sparsely populated. However, the bulk of investment in hydroelectric power generation in the region was centered on the Ōi River, and it was not until the Taishō period that development began on the Tenryū River. Private entrepreneur Fukuzawa Momosuke founded the Tenryūgawa Electric Power (天竜川電力, Tenryūgawa Denroku), which later became Yasaku Hydroelectric (矢作水力電気, Yasaku Suiroku Denki) before it was nationalized into the pre-war government monopoly Japan Electric Generation and Transmission Company (日本発送電株式会社, Nippon Hassoden K.K.) in 1938. The first dams on the main stream of the Tenryū River were built in Nagano Prefecture. To develop of the hydroelectric potential of the river in Shizuoka Prefecture, the post-war Japanese government turned to the Electric Power Development Company. The new company, in part through foreign aid loans from the United Nations, and with the use of new dam technologies completed the huge Sakuma Dam in the 1956, at the time the 10th largest in the world. The Akiba Dam was designed as a pumped-storage hydroelectricity facility, with the discharge from Sakuma Dam discharging through a penstock into a lake created by the smaller Akiba Dam downstream. The reversible turbine generators at the Sakuma power plant were designed to function as either electrical power generators, or as pumps, to reverse the flow of water back into the reservoir in times of low demand. Construction began in 1954 and was completed in 1958 by the Kumagai Gumi.