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, aqua ...

on the

Nakatsu River The is a river in Iwate Prefecture, Japan. It flows through the city of Morioka, where it enters 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 79 ...

, a main

tributary A tributary, or an ''affluent'', is a stream or river that flows into a larger stream (''main stem'' or ''"parent"''), river, or a lake. A tributary does not flow directly into a sea or ocean. Tributaries, and the main stem river into which they ...

of the

Sagami River The is a river in Kanagawa and Yamanashi Prefectures on the island of Honshū, Japan. The upper reaches of the river in Yamanashi prefecture are also sometimes known as the , and the portion near the river mouth as the . The river overall was ...

in Aikō District,

Kanagawa Prefecture is a Prefectures of Japan, prefecture of Japan located in the Kantō region of Honshu. Kanagawa Prefecture is the List of Japanese prefectures by population, second-most populous prefecture of Japan at 9,221,129 (1 April 2022) and third-dens ...

, Japan. It straddles the border between the village of Kiyokawa, town of Aikawa and the former town of Tsukui (now part of the city of

Sagamihara is a city in Kanagawa Prefecture, Japan. , the city has an estimated population of 723,470, with 334,812 households, and a population density of 1,220 persons per km2. The total area of the city is . Sagamihara is the third-most-populous city ...

History

The potential of the Sagami River for

hydroelectric power Hydroelectricity, or hydroelectric power, is Electricity generation, electricity generated from hydropower (water power). Hydropower supplies 15% of the world's electricity, almost 4,210 TWh in 2023, which is more than all other Renewable energ ...

development began to be developed in the 1930s, with the growth of industry and electrical consumption in the

Yokohama is the List of cities in Japan, second-largest city in Japan by population as well as by area, and the country's most populous Municipalities of Japan, municipality. It is the capital and most populous city in Kanagawa Prefecture, with a popu ...

Kanagawa is a Prefectures of Japan, prefecture of Japan located in the Kantō region of Honshu. Kanagawa Prefecture is the List of Japanese prefectures by population, second-most populous prefecture of Japan at 9,221,129 (1 April 2022) and third-dens ...

industrial belt. Work on the

Sagami Dam The is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa, Sagamihara, Kanagawa Prefecture on the island of Honshū, Japan. History The potential of the Sagami River valley for hydroelectric power development began to ...

, the first dam on the main stream of the Sagami River began in 1938; however, lack of funding and the advent of

World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...

delayed completion until after the end of the war. Work on the

Shiroyama Dam The is a multi-purpose dam on the main stream Sagami River in Sagamihara, Kanagawa Prefecture on the island of Honshū, Japan. History The potential of the Sagami River valley for hydroelectric power development began to be developed in the 1930s ...

was completed in 1965. The growth in population of nearby

Atsugi is a city located in Kanagawa Prefecture, Japan. , the city had an estimated population of 223,960 and a population density of 2400 persons per km2. The total area of the city is . While the name "Atsugi" is often associated with the United ...

and increased need for industrial and drinking water spurred plans for additional dams on the Sagami River's tributaries. Plans for the Miyagase Dam were finalized in 1969 with work commencing in 1971. Due to the huge size of the dam, and the need relocate some 300 households from the area flooded by the dam, construction was not completed until the year 2000.

Design

The Miyagase Dam is a hollow-core concrete

gravity dam A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by using only the weight of the material and its resistance against the foundation. Gravity dams are designed so that each section of the dam is ...

. It was designed and built by a consortium of the

Kajima Construction is one of the oldest and largest construction companies in Japan. Founded in 1840, the company has its headquarters in Motoakasaka, Minato, Tokyo. The company is known for its DIB-200 proposal. The company stock is traded on four leading Japa ...

, Obayashi Corp. and the Toda Corporation. The dam was designed as a multi-purpose dam. In addition to providing

flood control Flood management or flood control are methods used to reduce or prevent the detrimental effects of flood waters. Flooding can be caused by a mix of both natural processes, such as extreme weather upstream, and human changes to waterbodies and ru ...

, it provides 90% of the tap water to two-thirds of the population of Kanagawa Prefecture, including the cities of Kawasaki,

and

Yokosuka is a city in Kanagawa Prefecture, Japan. , the city has a population of 373,797, and a population density of . The total area is . Yokosuka is the 11th-most populous city in the Greater Tokyo Area, and the 12th in the Kantō region. The city i ...

. It also provides water to the associated Aikawa Hydroelectric Power Plant, which has a rated capacity of 24,000 KW of power. The tall dam is the second tallest in the

Kantō region The is a geography, geographical region of Honshu, the largest island of Japan. In a common definition, the region includes the Greater Tokyo Area and encompasses seven prefectures of Japan, prefectures: Chiba Prefecture, Chiba, Gunma Prefe ...

. Miyagase Dam is the highest and the largest

roller-compacted concrete Roller-compacted concrete (RCC) or rolled concrete (rollcrete) is a special blend of concrete that has essentially the same ingredients as conventional concrete but in different ratios, and increasingly with partial substitution of fly ash for po ...

dam in Japan. The reservoir created by the dam, is a popular recreation spot in Kanagawa Prefecture.

Surroundings

Public access to the dam and its lake is provided by National Route 412.

References

* Japan Commission on Large Dams. ''Dams in Japan:Past, Present and Future''. CRC Press (2009). * Takeuchi, Kuniyoshi. ''Sustainable Reservoir Development and Management''. IAHS Press (November 1998).

External links

National government website

Local website)
{{Dams in Kanagawa Prefecture Gravity dams Dams in Kanagawa Prefecture Hydroelectric power stations in Japan Dams completed in 2000 Aikawa, Kanagawa Sagamihara Kiyokawa, Kanagawa 2000 establishments in Japan