Tashiro Dam
Encyclopedia
The is a dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 on the Ōi River
Oi River
The is a river in Shizuoka Prefecture, Japan.-Geography:The Ōi River flows from the Akaishi Mountains, the branch of the Japanese Southern Alps which form the border between Shizuoka, Nagano and Yamanashi prefectures. These mountains, with peaks ranging from 2000–3000 meters, are characterized by...

 in Aoi-ku
Aoi-ku, Shizuoka
is one of three wards of Shizuoka, Shizuoka, Japan, located in the northern part of the city. Aoi-ku borders Suruga-ku in the south and Shimizu-ku to the southeast; the west faces Shimada, Fujieda and Kawanehon and its northern tip extends into the border between Nagano Prefecture and Yamanashi...

, Shizuoka
Shizuoka, Shizuoka
is the capital city of Shizuoka Prefecture, Japan, and the prefecture's second-largest city in terms of both population and area. It became one of Japan's 19 "designated cities" in 2005.-Geography:...

, Shizuoka Prefecture
Shizuoka Prefecture
is a prefecture of Japan located in the Chūbu region on Honshu island. The capital is the city of Shizuoka.- History :Shizuoka prefecture was formed from the former Tōtōmi, Suruga and Izu provinces.The area was the home of the first Tokugawa Shogun...

 on the island of Honshū
Honshu
is the largest island of Japan. The nation's main island, it is south of Hokkaido across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyushu across the Kanmon Strait...

, Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

. It was the first concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...

 gravity dam to be constructed on the Ōi River, and has a hydroelectric power generating station owned by the Tokyo Electric Power Company.

History

The potential of the Ōi River valley for hydroelectric power development was realized by the Meiji government at the start of the 20th century. The Ōi 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.

In 1906, a joint venture
Joint venture
A joint venture is a business agreement in which parties agree to develop, for a finite time, a new entity and new assets by contributing equity. They exercise control over the enterprise and consequently share revenues, expenses and assets...

 company, the was established, and began studies and design work on plans to exploit the potential of the Ōi River and Fuji River
Fuji River
The is a river in Yamanashi and Shizuoka Prefectures of central Japan. It is long and has a watershed of . With the Mogami River and the Kuma River, it is regarded as one of the three most rapid flows of Japan....

 in Shizuoka Prefecture. The British interests were bought out by 1921, and the company was renamed , for its plan to divert water from the Ōi River to the Hayakawa River in Yamanashi Prefecture
Yamanashi Prefecture
is a prefecture of Japan located in the Chūbu region of the island of Honshū. The capital is the city of Kōfu.-Pre-history to the 14th century:People have been living in the Yamanashi area for about 30,000 years...

 through a system of penstock
Penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....

s, and thus generate electricity. Work on the Tashiro Dam began in 1924 and was completed in 1928.

Hayakawa Electric was absorbed into , which was later nationalized and merged with other electrical producers into the . After the breakup of Nippon Hassoden at the end of World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 into various regional power utilities, the bulk of the dams on the Ōi River came under the control of Chubu Electric Power. However, only the Tashiro Dam was given to Tokyo Electric Power due to its previous owner, Tokyo Dento.

Design

The Tashiro Dam was designed as a solid core, non-overflow concrete gravity dam. The impounded water forms a lake called the , from which water discharges through a long penstock
Penstock
A penstock is a sluice or gate or intake structure that controls water flow, or an enclosed pipe that delivers water to hydraulic turbines and sewerage systems. It is a term that has been inherited from the technology of wooden watermills....

 under the Southern Japanese Alps
Akaishi Mountains
is a mountain range in central Honshū, Japan, bordering Nagano, Yamanashi and Shizuoka prefectures. It is also called the , as it joins with the Hida Mountains and the Kiso Mountains to form the Japanese Alps....

 into the Hayakawa River. Two hydroelectric power plants along this route produce 17,400 KW and 22,700 KW of power respectively.

Surroundings

Tashiro Dam is located in the very northern tip of Shizuoka Prefecture, surrounded on three sides by the high peaks of the Minami Alps National Park
Minami Alps National Park
is a national park in the Chūbu region, Honshū, Japan.The Minami Alps National Park was established on June 1, 1964. It extends along the border of Shizuoka, Yamanashi and Nagano Prefectures for a length of , and a maximum width of for a total area of...

, an area of high mountains, forests, and a popular vacation area. The dam is on a route for mountain climbers on the way to the Japanese Alps, and can be reached on foot. However, the dam itself and its associated electrical power plant are not open to the public, and access to the area by car is prohibited.
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