The is a

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, a ...

on the Toyosawa River, a tributary of the

Kitakami River The is the fourth largest river in Japan and the largest in the Tōhoku region. It is long and drains an area of . page 793 It flows through mostly rural areas of Iwate and Miyagi Prefectures. The source of the river is the Mount Nanashirug ...

system, located in the town of Shiwa,

Iwate Prefecture is a prefecture of Japan located in the Tōhoku region of Honshu. It is the second-largest Japanese prefecture at , with a population of 1,210,534 (as of October 1, 2020). Iwate Prefecture borders Aomori Prefecture to the north, Akita Prefectur ...

in the

Tōhoku region The , Northeast region, or consists of the northeastern portion of Honshu, the largest island of Japan. This traditional region consists of six prefectures (''ken''): Akita, Aomori, Fukushima, Iwate, Miyagi, and Yamagata. Tōhoku retains a ...

of the island of

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 separa ...

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 west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. It completed in 1952.

History

The need for storage reservoirs in the Kitakami River valley for irrigation purposes was recognized 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 o ...

at the start of the 20th century, due to repeated crop failures and conflicts between various communities over water rights, dating even from the early

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 characteriz ...

. The river also suffered from severe environmental problems with acidic runoff from upstream mining operations. Plans for a series of dams was initiated in 1941 by the Ministry of Agriculture and Forestry, but all work was halted during

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 vast majority of the world's countries—including all of the great powers—forming two opposin ...

. The plan was revived after the war, and the Sannōkai Dam was the first to be constructed.

Design

The Sannōkai Dam was started in 1947 and was completed in 1952 as a 37.4-foot high

earthen Soil, also commonly referred to as earth or dirt, is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Some scientific definitions distinguish ''dirt'' from ''soil'' by restricting the former term ...

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...

. However, due to aging and concerns over safety, it was completely rebuilt starting in 1977 as a

rock-fill dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, tap water, human consumption, Industri ...

, with its height raised to 61.5 meters. The new dam was completed in 2001.

References

*Japan Commission on Large Dams. ''Dams in Japan: Past, Present and Future''. CRC Press (2009).

External links

photo page with data
(
Official home page
Dams in Iwate Prefecture Dams completed in 2001 Embankment dams Shiwa, Iwate {{Iwate-geo-stub