The Ogouchi Dam (小河内ダム) is located in Okutama Town, Tokyo (about 65km from the city center) at an altitude of 530m. The catchment area, which has its water source in the upper reaches of the Tama River, spans four municipalities: Okutama Town, Tokyo, Tabayama Village, Yamanashi Prefecture, Kosuge Village, and Koshu City. The Okutama Dam groundbreaking ceremony was on November 12, 1938. However, due to the increasingly fierce battlefield, construction was canceled on October 5, 1943. The construction resumed in September 1948. It was completed on November 26, 1957. Today, it plays an important role in ensuring stable water supply for residents.