Lake Okutama and Ogōchi Dam

photo by Guilhem Vellut · CC BY 2.0

1957 dam, Tokyo's largest water reserve: free observation tower, 10:00–16:00

The concrete gravity dam, 149 metres high and 353 long, holds back a reservoir of 185,400,000 cubic metres: the largest water reserve of Tokyo's waterworks. You can walk freely along the crest; the observation tower, five hundred metres from the Mizu to Midori no Fureaikan visitor centre, has a model of the dam on the second floor and an observation room on the third, with a view over the valley floor.

The Ogōchi reservoir was completed in November 1957 after nineteen years of work, begun in 1938 and suspended from 1943 to 1947 because of the war: it forced 945 families to relocate and cost 87 lives during construction. It holds three independent official distinctions: among the ‘100 dam lakes of Japan’ in 2005, among the ‘100 modern waterworks of Japan’ in 1985, and civil engineering heritage of the Japan Society of Civil Engineers in 2018.

ℹ️ The reservoir and the surrounding paths are always accessible, free. The dam's observation tower is open 10:00–16:00 (17:00 from 20 July to 31 August), closed from 28 December to 4 January; free entry. Several Nishi-Tokyo bus lines connect JR Okutama Station to the lake in about 20 minutes (among them, the 奥15 goes directly to the lake via Sakaibashi and Mizune; others continue towards Kamosawa-nishi, Tabayama or Kosuge, all passing the lake). The ‘Okutamako Ikoi no Michi’ path goes round the whole lake in about 12 km, 4 hours; the dam and tower alone can be visited in under an hour, according to a Jalan review.

🚉 Okutamako · 6 min walk

Sources: waterworks.metro.tokyo.lg.jp · gotokyo.org · nisitokyobus.co.jp

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