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Lake Chuzenji ASI-05

Riparian Nation(s) Japan
Lat. 36°45' N Lng. 139°28' E Alt. 1269 m
Surface Area 12 km2 Mean Depth 94.6 m Volume 1.2 km3
Shoreline 24 km Catchment Area 121 km2 Residence Time 6.1 yr
Frozen Period None   Mixing Type Monomictic   Morphogenesis/Dam volcanic (damming) 
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Lake Chuzenji is located close to Nikkou, one of the most familiar sightseeing places in Japan, about 120 km north of Tokyo. The lake is a natural dammed lake produced by the eruption of the volcano Mt. Nantai, now rising on the northeastern side of the lake. Its forest-covered drainage basin is designated as a national park. The area is blessed with abundant natural beauty, such as the Kegon Falls and the Hakuun Falls, formed by the underground flow of the lake water, as well as fine stands of white birch and rich flora. The famous Toushougu Shrine is also near the lake. Thus about four million tourists visit the area annually both from interior and abroad.

The trophic level of the lake is oligotrophic and a few kinds of trout can be caught. The transparency is generally around 9 m, but is becoming lower as compared with the values in the 1930's.

In these several years, Uroglena americana often blooms during June, and causes a foul smell of tap water from the lake. To reduce the nutrient loading on the lake, municipal wastewater treatment systems have been provided in the area of Lake Chuzenji and water quality improvement countermeasures are also being promoted in Yu-no-ko, a small lake in the upstream of its drainage basin. The Tochigi Prefectural Government enacted in May 1986 the Lake Water Quality Management Plan and the Water duality Protection Countermeasure Ordinance for Lakes Chuzenji and Yu-no-ko (Q).

Photo of Lake Chuzenji
Photo: A. Kurata