Sakuma Dam

The dam holds back the Tenryu River between Sakuma, Sakuma-cho, Tenryu-ku, Hamamatsu City, Shizuoka Prefecture (left bank) and Toyone-mura, Kitashitara-gun, Aichi Prefecture (right bank). It has a dam height of 155.5 meters, a dam length of 293.5 meters, an effective water storage capacity of 205,440,000 cubic meters, and a lake surface area of ​​7.15 square kilometers. Its upstream end reaches Hiraoka, Tenryu-mura, Shimoina-gun, Nagano Prefecture, about 33 kilometers upstream. It was built by Electric Power Development Co., Ltd. as part of the Tenryu-Higashi Mikawa Specific Area Comprehensive Development Project, and was completed in 1956 (Showa 31) after a construction period of three years and four months. It marked the beginning of the introduction of large civil engineering machinery and the construction of multipurpose dams in Japan. During construction, 248 homes were submerged, and the Iida Line was also relocated. The Sakuma Power Station has a maximum generating capacity of 350,000 kilowatts. In order to meet the sudden increase in electricity demand at that time, a frequency converter station was installed that could convert the frequency to 50 and 60 Hz, allowing electricity to be transmitted to both the Kanto and Kansai regions. The Akiba Dam in Tokura, Tatsuyama-cho, Tenryu-ku, Hamamatsu City, located downstream, is a dam that regulates the water volume of the Sakuma Dam, and the Shin Toyone Dam in Toyone Village, Aichi Prefecture, located along the tributary, the Oinyu River, is a pumped-storage hydroelectric power generation dam that serves as the upper reservoir of the Sakuma Dam, with a maximum output of 1.125 million kilowatts. The Sakuma Dam was built due to its abundant water volume and winding gorge location, but the landslides in the surrounding mountains and the transport of sediment from upstream have caused a large amount of sediment, reducing its water storage capacity. As a result, the dam is being treated to make more effective use of the dam, such as by installing a sediment removal facility. A 32,000-kilowatt second power plant was also built in 1982. It is 2.5 km from Chubu-Tenryu Station on the JR Iida Line.

[Kitagawa Mitsuo]

"Sakuma Dam: The Social Impact of Modern Technology," edited by the Japanese Society of Literature (1958, University of Tokyo Press)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

静岡県浜松市天竜区(てんりゅうく)佐久間町佐久間（左岸）と愛知県北設楽(きたしたら)郡豊根村(とよねむら)（右岸）との間の天竜川をせき止めたダム。堤高155.5メートル、堤長293.5メートル、有効貯水量2億0544万立方メートル、湖水面積7.15平方キロメートルで、上流端は約33キロメートル上流の長野県下伊那(しもいな)郡天竜村平岡に達する。天竜東三河特定地域総合開発の一環として電源開発により建設され、3年4か月の工期で1956年（昭和31）完成。日本における大型土木機械の導入による工法や多目的ダム建設の出発となった。建設にあたって248世帯が水没し、飯田線の付替え工事も行われた。佐久間発電所は最大出力35万キロワットの発電能力をもつ。また当時の電力需要急増に対応するために周波数を50ヘルツと60ヘルツに変換できる周波数変換所を付置し、関東にも関西にも送電できるようになっている。下流に位置する浜松市天竜区龍山町(たつやまちょう)戸倉の秋葉ダムは佐久間ダムの水量調節機能をもつダムで、支流大入(おおにゅう)川に沿う愛知県豊根村の新豊根ダムは佐久間ダムの上池として揚水発電を行い、112.5万キロワットの最大出力をもつ。佐久間ダムは豊富な水量と曲流する峡谷部を立地条件として建設されたが、周辺山地の崩壊や上流からの土砂送流により堆砂(たいさ)量も多く貯水能力は減少している。そのため、堆砂排除施設の整備など、ダムの有効利用のための処理が行われている。3万2000キロワットの第二発電所も1982年建設された。JR飯田線中部天竜駅から2.5キロメートル。

［北川光雄］

『日本人文科学会編『佐久間ダム――近代技術の社会的影響』（1958・東京大学出版会）』

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