| Minamiaiki Dam | |
| Location: | Minamiaiki, Nagano National Forest |
| Dam Length: | 444 m |
| Dam Height: | 136 m |
| Construction Began: | 1995 |
| Opening: | 2005 |
| Res Capacity Total: | 19,170,000 m3 |
| Res Catchment: | 6.2 km2 |
| Coordinates: | 36.0044°N 138.6536°W |
The Minamiaiki Dam is a rock-fill embankment dam on the Minamiaiki River in Minamiaiki, Nagano Prefecture, Japan. Together with the Ueno Dam, it provides water for the Kannagawa Hydropower Plant owned by the Tokyo Electric Power Company. The Minamiaiki dam is the higher of the two dams. When completed, the station will have the largest power output of any pump-storage power plant in the world at around 2.82 GW.[1] Since 2005, Unit 1, with an installed capacity of 470 MW, is in commercial operation.[2] Commercial operation of Unit 2 is planned in 2012, commercial operation of all six units as late as 2020.[3]