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The is a river in central
Honshū , historically called , is the largest and most populous island of Japan. It is located south of Hokkaidō across the Tsugaru Strait, north of Shikoku across the Inland Sea, and northeast of Kyūshū across the Kanmon Straits. The island ...
, Japan. With a length of , it is Japan's ninth longest river. Its source is
Lake Suwa is a lake in the Kiso Mountains, in the central region of Nagano Prefecture, Japan. Geography The lake is the source of the Tenryū River. It ranks 24th in lake water surface area in Japan. The cities of Suwa and Okaya and the town of Shim ...
in the
Kiso Mountains are a mountain range in Nagano and Gifu prefectures in Japan. They are also called the and they combine with the Hida Mountains ("Northern Alps") and the Akaishi Mountains ("Southern Alps") to form a group collectively known as the Japanese Al ...
near Okaya in
Nagano Prefecture is a landlocked prefecture of Japan located in the Chūbu region of Honshū. Nagano Prefecture has a population of 2,052,493 () and has a geographic area of . Nagano Prefecture borders Niigata Prefecture to the north, Gunma Prefecture to the n ...
. It then flows through Aichi Prefecture and western
Shizuoka Prefecture is a prefecture of Japan located in the Chūbu region of Honshu. Shizuoka Prefecture has a population of 3,637,998 and has a geographic area of . Shizuoka Prefecture borders Kanagawa Prefecture to the east, Yamanashi Prefecture to the north ...
.


Geography

The Tenryū River is the only river exiting Lake Suwa. It follows a generally southern course. The upper reaches of the river in the Ina Basin of Nagano Prefecture is a rich agricultural area. The river exits through a gap between the
Kiso Mountains are a mountain range in Nagano and Gifu prefectures in Japan. They are also called the and they combine with the Hida Mountains ("Northern Alps") and the Akaishi Mountains ("Southern Alps") to form a group collectively known as the Japanese Al ...
(Central Alps) and the
Akaishi Mountains The are 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 ("Northern Alps") and the Kiso Mountains ("Central Alps") to form the Japa ...
(Southern Alps), which forms the border between Shizuoka and Nagano Prefectures . This area is characterized by heavy rainfall (up to 3000 mm per year) and deep V-shaped valleys. Continuing south through Shizuoka Prefecture, the river drains a wide coastal plain noted for fruit and rice production. The city of
Hamamatsu is a city located in western Shizuoka Prefecture, Japan. the city had an estimated population of 791,707 in 340,591 households, making it the prefecture's largest city, and a population density of . The total area of the site was . Overview ...
is near the
river mouth A river mouth is where a river flows into a larger body of water, such as another river, a lake/reservoir, a bay/ gulf, a sea, or an ocean. At the river mouth, sediments are often deposited due to the slowing of the current reducing the carryin ...
at the
Philippine Sea The Philippine Sea is a marginal sea of the Western Pacific Ocean east of the Philippine archipelago (hence the name), the largest in the world, occupying an estimated surface area of . The Philippine Sea Plate forms the floor of the sea. Its ...
.


History

The Tenryū River is mentioned in
Nara period The of the history of Japan covers the years from CE 710 to 794. Empress Genmei established the capital of Heijō-kyō (present-day Nara, Nara, Nara). Except for a five-year period (740–745), when the capital was briefly moved again, it remai ...
records as the for its fast, turbulent flow and its propensity to flood. The upper portion of the river (in
Shinano Province or is an old province of Japan that is now Nagano Prefecture. Shinano bordered on Echigo Province, Echigo, Etchū Province, Etchū, Hida Province, Hida, Kai Province, Kai, Kōzuke Province, Kōzuke, Mikawa Province, Mikawa, Mino Province, Mi ...
) was referred to as the Tenryūgawa, whereas the lower portion (in
Tōtōmi Province was a province of Japan in the area of Japan that is today western Shizuoka Prefecture. Nussbaum, Louis-Frédéric. (2005). "''Tōtōmi''" in . Tōtōmi bordered on Mikawa, Suruga and Shinano Provinces. Its abbreviated form name was . The or ...
) was often referred to as the . In various entries in the national historical chronicle ''
Shoku Nihongi The is an imperially-commissioned Japanese history text. Completed in 797, it is the second of the '' Six National Histories'', coming directly after the '' Nihon Shoki'' and followed by '' Nihon Kōki''. Fujiwara no Tsugutada and Sugano no Ma ...
'', flooding of the river is mentioned in the years 710 CE and 765 CE. Records through the
Heian period The is the last division of classical Japanese history, running from 794 to 1185. It followed the Nara period, beginning when the 50th emperor, Emperor Kanmu, moved the capital of Japan to Heian-kyō (modern Kyoto). means "peace" in Japanese ...
and
Kamakura period The is a period of Japanese history that marks the governance by the Kamakura shogunate, officially established in 1192 in Kamakura by the first '' shōgun'' Minamoto no Yoritomo after the conclusion of the Genpei War, which saw the struggle bet ...
are sparse, but from the
Muromachi period The is a division of Japanese history running from approximately 1336 to 1573. The period marks the governance of the Muromachi or Ashikaga shogunate (''Muromachi bakufu'' or ''Ashikaga bakufu''), which was officially established in 1338 by ...
, increasing efforts at
flood control Flood control methods are used to reduce or prevent the detrimental effects of flood waters."Flood Control", MSN Encarta, 2008 (see below: Further reading). Flood relief methods are used to reduce the effects of flood waters or high water level ...
were made by various warlords and landholders along the river by construction of dikes,
levee A levee (), dike (American English), dyke (Commonwealth English), embankment, floodbank, or stop bank is a structure that is usually earthen and that often runs parallel to the course of a river in its floodplain or along low-lying coastl ...
s, and channels. With the occupation of Hamamatsu Castle by
Tokugawa Ieyasu was the founder and first ''shōgun'' of the Tokugawa Shogunate of Japan, which ruled Japan from 1603 until the Meiji Restoration in 1868. He was one of the three "Great Unifiers" of Japan, along with his former lord Oda Nobunaga and fel ...
, considerable efforts were made to increase the revenues of Tōtōmi Province through creation of new rice fields with irrigation from the Tenryū River. However, flooding remained a problem, including a great flood in 1674 which washed away many of the earthen works of previous centuries.


Transport

During the
Edo period The or is the period between 1603 and 1867 in the history of Japan, when Japan was under the rule of the Tokugawa shogunate and the country's 300 regional ''daimyo''. Emerging from the chaos of the Sengoku period, the Edo period was character ...
, the Tōkaidō (road) developed as the major highway linking
Edo Edo ( ja, , , "bay-entrance" or "estuary"), also romanized as Jedo, Yedo or Yeddo, is the former name of Tokyo. Edo, formerly a ''jōkamachi'' (castle town) centered on Edo Castle located in Musashi Province, became the ''de facto'' capital of ...
with
Kyoto Kyoto (; Japanese: , ''Kyōto'' ), officially , is the capital city of Kyoto Prefecture in Japan. Located in the Kansai region on the island of Honshu, Kyoto forms a part of the Keihanshin metropolitan area along with Osaka and Kobe. , the ...
, and ''
daimyō were powerful Japanese magnates, feudal lords who, from the 10th century to the early Meiji period in the middle 19th century, ruled most of Japan from their vast, hereditary land holdings. They were subordinate to the shogun and nominall ...
s'' from the western domains were forced to travel on a regular basis to Edo to attend to the ''
shōgun , officially , was the title of the military dictators of Japan during most of the period spanning from 1185 to 1868. Nominally appointed by the Emperor, shoguns were usually the de facto rulers of the country, though during part of the Kamakur ...
'' in a system known as ''
sankin-kōtai ''Sankin-kōtai'' ( ja, 参覲交代/参覲交替, now commonly written as ja, 参勤交代/参勤交替, lit=alternate attendance, label=none) was a policy of the Tokugawa shogunate during most of the Edo period of Japanese history.Jansen, M ...
''. However, the
Tokugawa shogunate The Tokugawa shogunate (, Japanese 徳川幕府 ''Tokugawa bakufu''), also known as the , was the military government of Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in ...
prohibited the building of bridges over major rivers as a security measure. As depicted in contemporary ''
ukiyo-e Ukiyo-e is a genre of Japanese art which flourished from the 17th through 19th centuries. Its artists produced woodblock prints and paintings of such subjects as female beauties; kabuki actors and sumo wrestlers; scenes from history and folk ...
'' prints by artists such as
Hokusai , known simply as Hokusai, was a Japanese ukiyo-e artist of the Edo period, active as a painter and printmaker. He is best known for the woodblock print series '' Thirty-Six Views of Mount Fuji'', which includes the iconic print ''The Great ...
, travelers crossed the river on
ferryboat A ferry is a ship, watercraft or amphibious vehicle used to carry passengers, and sometimes vehicles and cargo, across a body of water. A passenger ferry with many stops, such as in Venice, Italy, is sometimes called a water bus or water ta ...
s, as the current was too fast and too deep for fording. In cases of bad weather or high waters, they were forced to stay several days (or even several weeks) beside the river at post stations (''shukuba'') such as Mitsuke-juku. The river was bridged shortly after the
Meiji Restoration The , referred to at the time as the , and also known as the Meiji Renovation, Revolution, Regeneration, Reform, or Renewal, was a political event that restored practical imperial rule to Japan in 1868 under Emperor Meiji. Although there were r ...
by road and railroad bridges. Today the
Tōkaidō Shinkansen The is a Japanese high-speed rail line that is part of the nationwide Shinkansen network. Along with the Sanyo Shinkansen, it forms a continuous high-speed railway through the Taiheiyō Belt, also known as the Tokaido corridor. Opened in 196 ...
express train An express train is a type of passenger train that makes a small number of stops between its origin and destination stations, usually major destinations, allowing faster service than local trains that stop at most or all of the stations along ...
crosses the river in a few seconds.


Hydroelectric development

The potential of the Tenryū River valley for hydroelectric power development was realized by the
Meiji government The was the government that was formed by politicians of the Satsuma Domain and Chōshū Domain in the 1860s. The Meiji government was the early government of the Empire of Japan. Politicians of the Meiji government were known as the Meiji ...
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 Fukuzawa (written: 福澤 or 福沢) is a Japanese surname. Notable people with the surname include: *, Japanese actor *, Japanese writer, translator and journalist *, Japanese businessman *, Japanese volleyball player *, Japanese golfer {{surname ...
founded the , which later became before it was nationalized into the pre-war government monopoly in 1938. The first dam on the main stream of the Tenryu River, the
Yasuoka Dam Yasuoka Dam ( ja, 泰阜ダム) is a dam in the Nagano Prefecture, Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the we ...
was completed in 1935. This was followed by the
Iwakura Dam Iwakura Dam ( ja, 岩倉ダム ) is a dam in Urugi, Nagano Prefecture, Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the ...
in 1938. The Hiraoka Dam was started in 1938, but completed until 1951 due to the start of
World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the World War II by country, vast majority of the world's countries—including all of the great power ...
. After the end of World War II, the American occupation authorities ordered the dissolution of Nippon Hassoden, which was divided into regional power companies. Central Japan came under
Chubu Electric Power , abbreviated as Chuden in Japanese, is a Japanese electric utilities provider for the middle Chūbu region of the Honshu island of Japan. It provides electricity at 60 Hz, though an area of Nagano Prefecture uses 50 Hz. Chubu Elect ...
, which inherited the various dams and projects on the Tenryū River, all of which were located in Nagano Prefecture. For develop of the hydroelectric potential of the river in Shizuoka Prefecture, the government turned to the Electric Power Development Company. The new company, in part through
foreign aid In international relations, aid (also known as international aid, overseas aid, foreign aid, economic aid or foreign assistance) is – from the perspective of governments – a voluntary transfer of resources from one country to another. ...
loans from the
United Nations The United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmonizi ...
, and with the use of new dam technologies completed the huge
Sakuma Dam The is a dam on the Tenryū River, located on the border of Toyone, Kitashitara District, Aichi Prefecture on the island of Honshū, Japan. It is one of the tallest dams in Japan and supports a 350 MW hydroelectric power station. Nearby a ...
in the 1956, at the time the 10th largest in the world. Further dams were completed in the 1960s and 1970s until the completion of the
Funagira Dam The is a dam on the Tenryū River, located in Tenryū district, Hamamatsu city, Shizuoka Prefecture on the island of Honshū, Japan. History The potential of the Tenryū River valley for hydroelectric power development was realized by the T ...
in 1976 brought development of the Tenryū River to a close.


Environmental consequences

These dams have altered the once abundant flow of the Tenryū River, and the lower reaches of the river near its mouth are almost dry. This has had the unexpected effect of greatly increased erosion on the coastline of Shizuoka Prefecture, near Hamamatsu, especially around the
Nakatajima Sand Dunes are located at the southern part of Hamamatsu, Shizuoka Prefecture at the Pacific Ocean coast of Japan. The sand dune area measures approximately 0.6 km from north to south and 4.0 km from east to west. It is considered one of Japan ...
. Meanwhile, at the same time, the vast amount of sand and silt trapped in various dams upstream have resulted in greatly lowered operational lives than originally projected. Methods to increase dredging in dams and to channel the silt and sand downstream to the ocean via a series of pipelines have been explored.


Tourism

The Tenryū River Valley is partially within the
Tenryū-Okumikawa Quasi-National Park is a quasi-national park in the Tōkai region of Honshū in Japan. It is rated a protected landscape (category V) according to the IUCN. The park includes the Tenryū-kyō Gorge of the upper Tenryū River in Iida, Sakuma Dam and its surrounding ...
with the Tenryūkyō Gorge as a nationally designated
Place of Scenic Beauty is a collective term used by the Japanese government's Law for the Protection of Cultural Properties to denote Cultural Properties of JapanIn this article, capitals indicate an official designation as opposed to a simple definition, e.g "Cultural ...
in Iida,
Nagano Prefecture is a landlocked prefecture of Japan located in the Chūbu region of Honshū. Nagano Prefecture has a population of 2,052,493 () and has a geographic area of . Nagano Prefecture borders Niigata Prefecture to the north, Gunma Prefecture to the n ...
, Japan. The Tenryū Hamanako Railroad Tenryū Hamanako Line runs along the lower reaches of the Tenryū River valley, whereas the Iida Line runs along the upper reaches of the river into upper Shizuoka and Nagano prefectures, with a stop at
Sakuma Station is a railway station on the Iida Line in Tenryū-ku, Hamamatsu, Shizuoka Prefecture, Japan, operated by Central Japan Railway Company (JR Central). Lines Sakuma Station is served by the Iida Line and is 63.5 kilometers from the starting poi ...
near the namesake dam.


See also

*, led by *
Japanese Alps The is a series of mountain ranges in Japan which bisect the main island of Honshu. The peaks that tower over central Honshu have long been the object of veneration and pilgrimage. These mountains had long been exploited by local people for raw m ...


References


External links


Ministry of Land, Infrastructure and Transport
(mouth) {{DEFAULTSORT:Tenryu River Rivers of Shizuoka Prefecture Rivers of Aichi Prefecture Rivers of Nagano Prefecture Akaishi Mountains Kiso Mountains Japan Alps Minami Alps National Park Rivers of Japan