The lake occupies the site of the former Ogouchi village, which was submerged during the dam's completion in 1957.
The construction of the reservoir required the relocation of 945 households and the dismantling of historical shrines.
The Ogouchi Dam is one of the largest water supply dams in Japan, designed to hold up to 189 million cubic meters of water.
The lake functions as a stabilizer for the Tama River's water flow, preventing floods and droughts in downstream regions.
During extremely low water levels, ruins of the original village occasionally become partially visible near the shoreline.
Lake Okutama, officially known as Lake Ogouchi, is a man-made reservoir created by the Ogouchi Dam on the Tama River. It serves as a primary water supply source for Tokyo's metropolitan area. The area features extensive hiking trails, including the scenic Okutama Mukashi-michi, which retraces historical trade routes. Visitors can cross the Ogouchi-ko floating bridges, which are anchored pontoons providing direct access across the water. The surrounding Okutama-chō region is part of Chichibu-Tama-Kai National Park. The lake's surface area spans approximately 4.25 square kilometers depending on water levels. It is a focal point for autumn foliage viewing in western Tokyo.
The observation deck near the Ogouchi Dam for panoramic views of the water framed by mountains.
Wear sturdy, broken-in hiking boots if planning to traverse the mountain trails surrounding the perimeter.
Check the local water level status before arrival, as significant fluctuations change the visibility of the floating bridges.
Carry extra layers, as the mountain elevation results in temperatures significantly cooler than central Tokyo.
Attempting to walk the entire perimeter in a single day, as the lake's shape and rugged topography make it physically taxing.
Carry out all trash as there are limited disposal facilities; stay on marked trails to protect the watershed environment.
