Tanbara Dam (玉原ダム, which can be mistakenly read Tamahara 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 ...

impounding the headwaters of the Hotchi River, a

Tone River The is a river in the Kantō region of Japan. It is in length (the second longest in Japan after the Shinano) and has a drainage area of (the largest in Japan). It is nicknamed Bandō Tarō (); ''Bandō'' is an obsolete alias of the Kantō ...

tributary in

Gunma Prefecture is a prefecture of Japan located in the Kantō region of Honshu. Gunma Prefecture has a population of 1,937,626 (1 October 2019) and has a geographic area of 6,362 km2 (2,456 sq mi). Gunma Prefecture borders Niigata Prefecture and Fukushima ...

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 ...

. It is located north of

Numata is a city located in Gunma Prefecture, Japan. , the city had an estimated population of 46,908 in 20,589 households, and a population density of 110 persons per km². The total area of the city is , making it the largest city in terms of area w ...

. 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 Pumped-storage hydroelectricity (PSH), or pumped hydroelectric energy storage (PHES), is a type of hydroelectric energy storage used by electric power systems for load balancing. The method stores energy in the form of gravitational potential ...

power station is created by the

Fujiwara Dam is a gravity dam on the Tone River in Gunma Prefecture of Japan. It is located north of Minakami. It was constructed between 1951 and 1957. The dam itself supports a single Francis turbine hydroelectric generator with a 23 MW capacity which ...

, 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 The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The proces ...

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 .

References

{{Dams in Gunma Prefecture Dams completed in 1981 Dams in Gunma Prefecture Rock-filled dams Pumped-storage hydroelectric power stations in Japan

See also

References