Ohashi Dam
Encyclopedia
Ohashi Dam is a dam
built on the Yoshino River
in Agawa District
, Kōchi Prefecture
of Japan
. This concrete dam 73.5m high. It is a hydroelectric dam
of the Shikoku Electric Power Company
. It supplies water to the company's hydroelectric plant, Ohashi Power Station, which can produce up to 5,500kW. It is the lower reservoir for a pumped-storage hydroelectric plant
. The upper reservoir being Inamura Dam
. Water flowing between these two can produce up to 615MW. It is a public works which The Japan Society of Civil Engineers has recommended as a site of Public Works Heritage.
flows through Shikoku
with an abundant volume. In the upper reaches there are swift currents so it was a suitable place for hydroelectric power generation. In Ehime Prefecture
the Sumitomo Group
have many factories and the Besshi copper mine
. Tosa City
-Yoshino River Hydroelectric Company (currently Sumitomo Joint Electric Power Company) was founded to promote the construction of the hydroelectric power station, on the Yoshino River, in 1919, (Taishō period
8). The Takayabu Power Station, (14.3MW), was built at the Okuyoshino torrents of the upper reach of River Yoshino, and it commenced operation in 1930 (Shōwa period
5).
This company conceived of further developing the upper reaches of the river. Diverting the water flow of Yoshino River, separating the watershed, to the south flowing Edagawagawa River of the drainage system, and planned to perform hydroelectric power generation utilising that volume of water and the topography. However, in this plan, the diversion of water did not avoid the decrease in the volume of water flowing downstream. Because of this, a plan was made to regulate the quantity water flowing in the river by forming a large-scale artificial lake and building the Ohashi Dam between Takayabu Power Station and the upstream inflow.
In 1934 (Showa 9), the Tosa-Yoshino River Hydroelectric Company was renamed the Central Shikoku Electric Power Company, and from 1937 (Showa 12) work started on the Ohashi Dam. Engineers who took part in the Pujon River Dam on the Korean Peninsula
and the construction of the Senzu Dam
of the Ōi River
drainage system in Shizuoka Prefecture
were invited to the construction to study the concrete mix. The results of the geological survey were to confirm that rock suitable for concrete aggregate
could not be collected from around the dam's construction site. Therefore, an overhead freight-carrying cable
was built to in the Niyodo River Basin, 22km to the south and, rock was collected to and brought from there. The Ohashi Dam was completed in 1939 (Showa 14). In the same year, Ohashi Power Station, using water from the Ohashi Dam, started production (at that time 5.3MW).
After that, Central Shikoku Electric Power Company, went ahead with the construction of a diversion canal
from up stream of the Ohashi Dam to the Niyodo River. In 1940 (Showa 15) the First Diverted Water Power Station (26.6MW), and in 1941 (Showa 16) the Second Diverted Water Power Station (7.8MW), and Third Diverted Water Power Stations (10.9MW) started operation. However, in the mean time, the Japanese government had an eye on the state control of the electric utilities, and steadily advanced preparations for the establishment of the in 1939. The Central Shikoku Electric Power Company financed many hydroelectric power stations such as starting the Ohashi Dam and Diverted Water System Power Stations, the Japan Electric Generation and Transmission Company, and the
with electric distribution companies established under similar state control. In 1943 (Showa 18) it changed its name to the present Sumitomo Group of electric power companies. Japan Electric Generation and Transmission Company took over the development of the improving Central Shikoku Electric Power Company. In 1949 (Showa 24), upstream of Ohashi Dam, as well as Nagasawa Dam
(5.2MW), in 1950 (Showa 25) at the water diversion's lowest point the Fourth Diverted Water Power Station (8.1MW) was completed.
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...
built on the Yoshino River
Yoshino River
The Yoshino River is a river on the island of Shikoku, Japan. It is 194 km long and has a watershed of 3,750 km². It is the second longest river in Shikoku , and is the only river whose watershed spreads over the four prefectures of the island.It is regarded as one of the three greatest rivers of...
in Agawa District
Agawa District, Kochi
is a district located in Kōchi, Japan.As of January 1, 2008, the district has an estimated population of 35,108 and a density of 43.7 persons per km²...
, Kōchi Prefecture
Kochi Prefecture
is a prefecture of Japan located on the south coast of Shikoku. The capital is the city of Kōchi.- History :Prior to the Meiji Restoration, Kōchi was known as Tosa Province and was controlled by the Chosokabe clan in the Sengoku period and the Yamauchi family during the Edo period.- Geography...
of 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...
. This concrete dam 73.5m high. It is a hydroelectric dam
Hydroelectricity
Hydroelectricity is the term referring to electricity generated by hydropower; the production of electrical power through the use of the gravitational force of falling or flowing water. It is the most widely used form of renewable energy...
of the Shikoku Electric Power Company
Shikoku Electric Power Company
The is the electric provider for the 4 prefectures of the Shikoku island in Japan with few exceptions. Their image character is .On April 12, 1991 the company instituted Akari-chan as their image character and at the same time introduced the romanized nickname of Yonden .The company is also an...
. It supplies water to the company's hydroelectric plant, Ohashi Power Station, which can produce up to 5,500kW. It is the lower reservoir for a pumped-storage hydroelectric plant
Pumped-storage hydroelectricity
Pumped-storage hydroelectricity is a type of hydroelectric power generation used by some power plants for load balancing. The method stores energy in the form of water, pumped from a lower elevation reservoir to a higher elevation. Low-cost off-peak electric power is used to run the pumps...
. The upper reservoir being Inamura Dam
Inamura Dam
Inamura Dam is a dam in Kōchi Prefecture, Japan....
. Water flowing between these two can produce up to 615MW. It is a public works which The Japan Society of Civil Engineers has recommended as a site of Public Works Heritage.
Construction
The Yoshino RiverYoshino River
The Yoshino River is a river on the island of Shikoku, Japan. It is 194 km long and has a watershed of 3,750 km². It is the second longest river in Shikoku , and is the only river whose watershed spreads over the four prefectures of the island.It is regarded as one of the three greatest rivers of...
flows through Shikoku
Shikoku
is the smallest and least populous of the four main islands of Japan, located south of Honshū and east of the island of Kyūshū. Its ancient names include Iyo-no-futana-shima , Iyo-shima , and Futana-shima...
with an abundant volume. In the upper reaches there are swift currents so it was a suitable place for hydroelectric power generation. In Ehime Prefecture
Ehime Prefecture
is a prefecture in northwestern Shikoku, Japan. The capital is Matsuyama.-History:Until the Meiji Restoration, Ehime prefecture was known as Iyo Province...
the Sumitomo Group
Sumitomo Group
is one of the largest keiretsu, founded by Masatomo Sumitomo.-History:The Sumitomo group traces its roots to a bookshop in Kyoto founded circa 1615 by a former buddhist priest,...
have many factories and the Besshi copper mine
Besshi copper mine
The was a rich source of copper in Niihama, Ehime Prefecture, Japan. The deposits were discovered in 1690, and mining began in the following year. From then until the closing of the mine in 1973, Besshi produced about 700,000 tons of copper, and contributed to Japan's trade and modernization...
. Tosa City
Tosa, Kochi
is a city in Kōchi, Japan. It is located on the southern coast of the island of Shikoku.As of October 31, 2007, the city has an estimated population of 29,782 and the density of 325 persons per km²...
-Yoshino River Hydroelectric Company (currently Sumitomo Joint Electric Power Company) was founded to promote the construction of the hydroelectric power station, on the Yoshino River, in 1919, (Taishō period
Taisho period
The , or Taishō era, is a period in the history of Japan dating from July 30, 1912 to December 25, 1926, coinciding with the reign of the Taishō Emperor. The health of the new emperor was weak, which prompted the shift in political power from the old oligarchic group of elder statesmen to the Diet...
8). The Takayabu Power Station, (14.3MW), was built at the Okuyoshino torrents of the upper reach of River Yoshino, and it commenced operation in 1930 (Shōwa period
Showa period
The , or Shōwa era, is the period of Japanese history corresponding to the reign of the Shōwa Emperor, Hirohito, from December 25, 1926 through January 7, 1989.The Shōwa period was longer than the reign of any previous Japanese emperor...
5).
This company conceived of further developing the upper reaches of the river. Diverting the water flow of Yoshino River, separating the watershed, to the south flowing Edagawagawa River of the drainage system, and planned to perform hydroelectric power generation utilising that volume of water and the topography. However, in this plan, the diversion of water did not avoid the decrease in the volume of water flowing downstream. Because of this, a plan was made to regulate the quantity water flowing in the river by forming a large-scale artificial lake and building the Ohashi Dam between Takayabu Power Station and the upstream inflow.
In 1934 (Showa 9), the Tosa-Yoshino River Hydroelectric Company was renamed the Central Shikoku Electric Power Company, and from 1937 (Showa 12) work started on the Ohashi Dam. Engineers who took part in the Pujon River Dam on the Korean Peninsula
Korean Peninsula
The Korean Peninsula is a peninsula in East Asia. It extends southwards for about 684 miles from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan to the south, and the Yellow Sea to the west, the Korea Strait connecting the first two bodies of water.Until the end of...
and the construction of the Senzu Dam
Senzu Dam
The is a dam on the Sumata River, a tributary of the Ōi River, located in Kawanehon Town, Haibara District, Shizuoka Prefecture on the island of Honshū, Japan.-History:...
of 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...
drainage system in 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...
were invited to the construction to study the concrete mix. The results of the geological survey were to confirm that rock suitable for concrete aggregate
Construction Aggregate
Construction aggregate, or simply "aggregate", is a broad category of coarse particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates. Aggregates are the most mined material in the world...
could not be collected from around the dam's construction site. Therefore, an overhead freight-carrying cable
Aerial tramway
An aerial tramway , cable car , ropeway or aerial tram is a type of aerial lift which uses one or two stationary ropes for support while a third moving rope provides propulsion...
was built to in the Niyodo River Basin, 22km to the south and, rock was collected to and brought from there. The Ohashi Dam was completed in 1939 (Showa 14). In the same year, Ohashi Power Station, using water from the Ohashi Dam, started production (at that time 5.3MW).
After that, Central Shikoku Electric Power Company, went ahead with the construction of a diversion canal
Aqueduct
An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose....
from up stream of the Ohashi Dam to the Niyodo River. In 1940 (Showa 15) the First Diverted Water Power Station (26.6MW), and in 1941 (Showa 16) the Second Diverted Water Power Station (7.8MW), and Third Diverted Water Power Stations (10.9MW) started operation. However, in the mean time, the Japanese government had an eye on the state control of the electric utilities, and steadily advanced preparations for the establishment of the in 1939. The Central Shikoku Electric Power Company financed many hydroelectric power stations such as starting the Ohashi Dam and Diverted Water System Power Stations, the Japan Electric Generation and Transmission Company, and the
with electric distribution companies established under similar state control. In 1943 (Showa 18) it changed its name to the present Sumitomo Group of electric power companies. Japan Electric Generation and Transmission Company took over the development of the improving Central Shikoku Electric Power Company. In 1949 (Showa 24), upstream of Ohashi Dam, as well as Nagasawa Dam
Nagasawa Dam
Nagasawa Dam is a dam in Kōchi Prefecture, Japan....
(5.2MW), in 1950 (Showa 25) at the water diversion's lowest point the Fourth Diverted Water Power Station (8.1MW) was completed.