Ogouchi Reservoir (Lake Okutama)

Public Relation

The Landmarks of Tokyo Waterworks

　Ogouchi Reservoir (Lake Okutama) is the largest reservoir exclusively for water supply in Japan located at Okutama Town, Tokyo (65km from the center of the city). Its catchment area with the water source from the upstream area of Tama River, stretches over 4 cities and towns of Okutama Town, Tokyo along with Tabayama Village, Kosuge Village, and Koshu City of Yamanashi Prefecture. The 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 Reservoir 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 embankment. Then it is withdrawn at Ozaku Intake Weir and Hamura Intake Weir to become sources of raw water. The raw water is sent to Higashi Murayama Purification Plant and Sakai Purification Plant, passing through places such as Murayama and Yamaguchi Reservoirs and the channels of Tamagawa Josui by gravity flow. Afterwards, it is sent to Ozaku Purification Plant by water conveyance pumps. Also from Higashi Murayama Purification Plant, it is sent to 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 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 earthquake that can be predicted,which is confirmed by the earthquake resistance inspection results.

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General Information

Name	Ogouchi Reservoir (Lake Okutama)
Overview of the facility	Construction Completed　November 1957 Type Concrete Gravity Dam Height of Dam　149ｍ Length of Dam　353ｍ Available Storage Capacity　185,400,000m³
Location Access	5 Hara, Okutama Town, Nishitama County, Tokyo JR Ōme Line, Okutama Station, Buses to “Okutama-ko(Lake Okutama)”, “ Kamosawa-nishi”, “Taba”, “ Kosuge-no-yu”, “Minedani”, or “Tozura” (Get off at ”Okutama-ko(Lake Okutama)” bus stop） Free parking lots available nearby.