The Minamiaiki Dam is a rock-fill

embankment dam An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil or rock. It has a semi-pervious waterproof natural covering for its surface and ...

on the Minamiaiki River in Minamiaiki,

Nagano Prefecture is a landlocked prefecture of Japan located in the Chūbu region of Honshū. Nagano Prefecture has a population of 2,052,493 () and has a geographic area of . Nagano Prefecture borders Niigata Prefecture to the north, Gunma Prefecture to the ...

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

. Together with the Ueno Dam, it provides water for the

Kannagawa Hydropower Plant The Kannagawa Hydropower Plant (神流川発電所) is an under construction pumped-storage hydroelectric power plant near Minamiaiki in Nagano Prefecture and Ueno, Gunma, Ueno in Gunma Prefecture, Japan. The power plant utilizes the Minamiaiki Riv ...

owned by the

Tokyo Electric Power Company , also known as or TEPCO, is a Japanese electric utility holding company servicing Japan's Kantō region, Yamanashi Prefecture, and the eastern portion of Shizuoka Prefecture. This area includes Tokyo. Its headquarters are located in Uchisaiw ...

. 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. Since 2005 Unit 1 with installed capacity of 470 MW is in commercial operation. Commercial operation of Unit 2 is planned in 2012, commercial operation of all six units as late as 2020.TEPCO 2009 Annual Report
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References

Dams in Nagano Prefecture Rock-filled dams Dams completed in 2005 {{Japan-dam-stub