Kanna River

A river that flows through the southwestern part of Gunma Prefecture. It is a first-class river. It originates in the north of Mikuniyama in the Kanto Mountains, flows north, then turns eastward and meanders, passing through Kanna Town in Tano County, flows along the Saitama Prefecture border, joins the Karasu River, and empties into the Tone River. It is 87.4 km long and has a drainage basin of 407 square km. There is a legend that the river got its name from the fact that a hair of a sacred object was washed away when an epidemic broke out in the Noguri settlement (Ueno Village) upstream. The drainage basin is made up of old rocks of the Nagatoro system, the Chichibu Mesozoic and Paleozoic layers, and the Cretaceous system. The Sanchu Graben is located upstream, and the Sanbashiki Gorge is located in the middle of the river. The Jikkokutoge Highway along the river was also difficult in many places, but has now been improved. In 1967, Shimokubo Dam and Lake Kanna were completed, and the area has been attracting attention as one of Tokyo's drinking water sources.

[Murakami Sadao]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

群馬県南西部を流れる川。一級河川。関東山地の三国(みくに)山北方に源を発して北流し、やがて東流に変じ蛇行しつつ多野(たの)郡神流町を過ぎ、埼玉県境を流れて烏川(からすがわ)に合流し、利根川(とねがわ)に注ぐ。延長87.4キロメートル、流域面積407平方キロメートル。昔、上流の野栗(のぐり)集落（上野村）に疫病が流行したとき、御神体の髪を流したことからこの名が出たという伝説がある。流域は古い岩石の長瀞(ながとろ)系、秩父中・古生層および白亜系で、上流に山中(さんちゅう)地溝帯、中流に三波石峡(さんばせききょう)があり、川沿いの十石峠(じっこくとうげ)街道も難所が多かったが現在は改善された。1967年（昭和42）下久保ダム(しもくぼだむ)と神流湖ができ、東京の上水源の一つとして脚光を浴びている。

［村木定雄］

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