Lake Inawashiro

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Lake Inawashiro
Lake Inawashiro 1.JPG
Location Fukushima Prefecture
Coordinates 37°28′29″N 140°05′37″E / 37.47472°N 140.09361°E / 37.47472; 140.09361Coordinates: 37°28′29″N 140°05′37″E / 37.47472°N 140.09361°E / 37.47472; 140.09361
Type tectonic lake
Primary outflows Nippashi River
Basin countries Japan
Surface area 103.3 km2 (39.9 sq mi)
Average depth 51.5 m (169 ft)
Max. depth 94.6 m (310 ft)
Water volume 5.40 km3 (4,380,000 acre·ft)
Shore length1 49 km (30 mi)
Surface elevation 514 m (1,686 ft)
Islands Okinajima
1 Shore length is not a well-defined measure.

Lake Inawashiro (猪苗代湖 Inawashiro-ko?) is the fourth-largest lake in Japan,[1] located in central Fukushima Prefecture, south of Mount Bandai. It is also known as the 'Heavenly Mirror Lake' (天鏡湖 Tenkyōko?). The lake is located within the borders of Bandai-Asahi National Park. In winter swans migrate to the beaches of the lake and stay there until spring.

Lake Inawashiro was formed some 30-40,000 years ago when a tectonic depression was dammed by a major eruption and pyroclastic flow from Mount Bandai. The water is acidic with a pH value of approximately 5.0, and has a high degree of transparency. The water level was considerably less during the Jomon period as numerous artifacts and ceramic fragments have been found offshore. The lake water is an important source for irrigation in the Aizu region of western Fukushima Prefecture. An irrigation canal was completed during the Edo period and another in 1882. A third canal completed in 1915 supplies the city of Kōriyama with drinking and industrial water. The water also supplies a number of hydroelectric power plants. The lake is also an important tourist and leisure attraction in Fukushima Prefecture.


  1. ^ Takeda T., page 174.


  • Takeda, Toru; Hishinuma, Tomio; Kamieda, Kinuyo; Dale, Leigh; Oguma, Chiyoichi (August 10, 1988), Hello! Fukushima - International Exchange Guide Book (1988 ed.), Fukushima City: Fukushima Mimpo Press 
  • World Lake Database