Omachi Dam

Omachi Dam stands as a concrete gravity dam on the Takase River in Nagano Prefecture, located in the scenic Takase Valley region west of Omachi city. Construction began in 1975 and was completed in 1985, making it one of the modern engineering projects in the Japanese Alps. The dam was built in response to severe flooding that occurred in August 1969, serving the dual purpose of flood control and water supply. The structure rises to a height of 107 meters and supports a 13 MW hydroelectric power station owned by TEPCO.

The dam's reservoir is known as Lake Ryujin or Dragon God Lake, named after local folklore of the region. One of its most distinctive features is the lake's striking emerald green color, which results from fine sulfur particles flowing from the upper reaches of the Takase Valley mixing with the water. The dam sits within the Takase Valley area alongside two other dams, Takase Dam and Nanakura Dam, forming a comprehensive water management system surrounded by the towering 3,000-meter peaks of the Hida Mountains.

Visitors can explore the dam through several unique experiences. The Omachi Dam Information Center provides educational exhibits about the dam's role and the surrounding natural environment using panels and computers. These tours take guests through the inspection gallery, which maintains a cool temperature in summer and warmth in winter, leading to viewing points where visitors can look up at the dam structure and observe water discharges up close. The museum operates from 8:30 a.m. to 5:30 p.m. throughout the year. An observation park near the information center offers panoramic views of the dam lake framed by the Northern Alps.

The area surrounding Omachi Dam is renowned for its natural beauty across all seasons. Between May and October, wildflowers bloom throughout the valley, while late October to early November brings spectacular autumn foliage displays. The dam serves as a gateway to the deeper Takase Valley, where visitors can access hot springs including the historic Kuzu Hot Springs, said to have a 300-year history.

To reach Omachi Dam, travelers typically arrive at JR Shinano-Omachi Station via the Oito Line, which takes approximately one hour from Matsumoto. From Nagano Station on the Hokuriku Shinkansen, express buses reach the area in about one hour and 10 minutes. The dam is most easily accessible by private car, as it sits along the road leading deeper into Takase Valley. Local buses and taxis are available from Shinano-Omachi Station. Admission to the dam area is free, and visitors can collect Omachi Dam Cards at the information center.