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Ogouchi Reservoir (Lake Okutama)

Ogouchi Reservoir (Lake Okutama)

The Ogouchi Reservoir (Lake Okutama) is the largest exclusive water supply reservoir in Japan located at Okutama Town Tokyo (65km from the center of the city). The catchment area with the water source from the upper basin of the Tama River stretches over 4 cities and towns of Okutama Town Tokyo along with Tabayama Village, Kosuge Village, and Koshu City of Yamanashi Prefecture. This area is 26,288ha which is equivalent to about 40% of the 23 Wards in Tokyo.
The Construction of Ogouchi Dam began in November 1938. After an interruption due to the war, it was completed in November 1957 over the course of 19 years with relocation of 945 households, ultimate sacrifices of 87 people, and the total construction cost of 15 billion yen.
The water stored at Ogouchi Dam is discharged into the Tama River after it is used to generate electricity at the Tamagawa I Power Plant (under the jurisdiction of Bureau of Transportation Tokyo Metropolitan Government) , which is directly beneath the dam. Then it is withdrawn at the Ozaku Intake Weir and Hamura Intake Weir to become sources of raw water. The raw water is sent to the Higashi Murayama Purification Plant and Sakai Purification Plant, passing through places such as the Murayama and Yamaguchi Reservoir and the channels of Tamagawajosui Headrace by gravity flow. Afterwards, it is sent to the Ozaku Purification Plant by water conveyance pumps. Also from the Higashi Murayama Purification Plant, it is sent to the Asaka Purification Plant and Misono Purification Plant with the raw water connecting pipes.
You can enjoy the fabulous beauty of Okutama’s nature throughout the seasons including the sakura cherry blossoms in spring. The view from the Miharashi-no-oka is also magnificent.
In addition, even though it has been over 60 years since the establishment, Ogouchi Dam is safe against the greatest possible earthquakes that can be predicted. This is confirmed based on the earthquake resistance inspection results.

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General Information

Name Ogouchi Reservoir (Lake Okutama)
Overview of
the facility
Construction Completed December 1957
Type Concrete Gravity Dam
Height of Dam 149m
Length of Dam 353m
Available Storage Capacity 185,400,000m3
5 Hara, Okutama-Machi, Nishitama-gun, Tokyo
JR Ome Line, Okutama Station, Buses to“Okutamako”,“Kamosawanishi”,“Taba”“Kosugenoyu”,“Hachiya”, or“Tozura”
(Get off at ”Okutamako” bus stop)Free parking space available nearby.