Tamahara Dam

Tanbara Dam (玉原ダム, which can be mistakenly read Tamahara Dam) is a rock-fill embankment dam on a Tone River tributary in Gunma Prefecture of Japan. It is located north of Numata. It creates the upper reservoir for the Tamahara Pumped Storage Power Station (玉原発電所). Construction began in 1973 and the dam was complete in 1981 while the power station was commissioned in 1986. It is tall and withholds a reservoir with a storage capacity of . Of that capacity, is active (or useful) for power generation. The lower reservoir for the pumped-storage power station is created by the Fujiwara Dam, located to the northwest on another Tone River tributary. Power is generated during periods of high energy demand and pumping occurs during times when energy demand is low such as at night. The power station contains four reversible Francis turbine pump-generators which serve to both pump water and generate electricity. The upper Tamahara Reservoir is at an elevation of and the lower Fujiwara Reservoir is at which affords the power station an effective hydraulic head of . When pumping, the pump-generators can move up to of water and when generating, they discharge up to .