Ikehara Dam, Arch dam in Nara Prefecture, Japan

Ikehara Dam is a 110.0-meter-high arch dam on the Kitayama River in Shimokitayama, Nara Prefecture. Its pale gray concrete face curves between forested slopes, with a walkway and low parapet along the crest and green Japanese characters painted on the upper right. The dam creates the Ikehara Reservoir, also called Lake Ikehara, in Yoshino-Kumano National Park.

Planned from 1954 as the core of the Kumano River development scheme, the dam was first conceived as the 95 m Zenkiguchi gravity dam before being redesigned as an arch dam. Work began in March 1962 and finished in March 1965, after a rockfall killed four workers; the reservoir submerged nine settlements and 529 households. The power station started partial operation in 1965 and ran at full capacity from October 1966, once the Shichikyo Dam below it was finished.

The reservoir, called Ikehara Lake, was chosen as one of Japan's Dam Lake 100 in 2005 and lies within Yoshino-Kumano National Park. Green Japanese characters are painted on the upper right of the dam face, a detail visible from across the water. The lake is stocked for fishing, and the dam's water also feeds the pumped-storage plant shared with Shichikoro Dam downstream.

The dam is reached by National Route 169 through the mountains of Shimokitayama; the crest walkway with its low parapet is open to pedestrians. The reservoir, Lake Ikehara, lies in Yoshino-Kumano National Park, and the dam is paired with Shichikyo Dam downstream for pumped storage. Expect narrow mountain roads and slippery footing near the water in wet weather.

The concrete structure follows the natural shape of the narrow valley using compression to distribute the weight of the water onto the rocky sidewalls. This design allowed for a thinner wall compared to other approaches and made the project a technical achievement in the 1960s.