Hiraoka Dam

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Hiraoka Dam
Hiraoka Dam free flow.jpg
Location Tenryū, Nagano, Japan
Construction began 1938
Opening date 1951
Dam and spillways
Type of dam Concrete gravity dam
Impounds Tenryū River
Height 62.5 m
Length 258 m
Dam volume 252,000 m³
Total capacity 42,425,000 m³
Catchment area 3,650 km²
Surface area 258 ha

Hiraoka Dam (平岡ダム, Hiraoka damu) is a dam in Tenryū, Nagano Prefecture, Japan, completed in 1951.[1] It is located on the Tenryū River upstream from the Sakuma Dam.

During the Second World War prisoners of war held at Tokyo #2D (Mitsushima) Prisoner of War Camp provided labour to build the penstock tunnel to the powerstation, collect aggregate, and mix cement for the construction of the dam between November 1942 and August 1945. Fifty seven prisoners died from diseases relating to poor sanitary, diet, and climate conditions.

See also[edit]


Coordinates: 35°16′57″N 137°50′48″E / 35.28250°N 137.84667°E / 35.28250; 137.84667