Ogouchi Dam 小河内ダム, home of the Lake Okutama reservoir 奥多摩湖 (1957). (Tokyo Metropolitan Government Ogochi Dam)

For further reading see: Splashing around Tokyo’s water infrastructure

To see where this dam places in relation to other water infrastructure projects, see: Tokyo Metropolitan Waterworks Map 東京都水道地図 and Murayama-shimo dam 村山下ダム