Omarugawa Pumped Storage Power Station

The Omarugawa Pumped Storage Power Station (Hepburn: Omarugawa Hatsudensho) is a large pumped-storage hydroelectric power station in Kijo in the Koyu District of Miyazaki Prefecture, Japan. With a total installed capacity of 1,200 megawatts (1, 600, 000 hp), it is one of the largest pumped-storage power stations in Japan. The facility is run by the Kyushu Electric Power Company. The power plant started operation in July 2007 and all four units were commissioned by July 2011. Like most pumped-storage facilities, the power station uses two reservoirs, releasing and pumping as the demand rises and falls. Oseuchi Dam and Kanasumi Dam form the upper artificial reservoir, while Ishikawauchi Dam on the Omaru river (Omarugawa) forms the lower reservoir. Ishikawauchi Dam is a 47.5 m concrete gravity dam, while Oseuchi and Kanasumi dams are rock-fill dams, 65.5 m and 42.5 m high, respectively. The natural influx on water on the upper reservoir is limited, therefore the plant can be considered almost pure pumped-storage. The entire upper pond was made waterproof with asphalt to avoid leakage in the surrounding permeable soil. The two reservoirs are connected through underground penstocks. The power plant is located underground in the middle. The power station employs 4 pump-generators. Unit 1 and 4 were manufactured by Hitachi, while units 2 and 3 are from Mitsubishi. The maximu

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