Daiya River

This river flows through Nikko city in western Tochigi prefecture. It originates from Lake Chuzenji and falls as Kegon Falls. It then joins the Hidarizawa River in the Kiyotaki area, and joins the Arasawa River on the slopes of Mt. Nantai, the Inari River and the Narusawa River on the slopes of Mt. Nyoho Akanagi, before flowing through both Nikko and Imaichi before emptying into the Kinugawa River. Its length is 29.9 km. Its water quality is classified as Type A. River terraces form on the coast downstream from Kiyotaki, and the Imaichi alluvial fan is a composite alluvial fan formed by the sedimentation of this river. It is characterized by its stable flow conditions and low water temperatures in summer. It is also used for hydroelectric power generation, with 10 hydroelectric power plants operating up to Imaichi in the Taniguchi settlement, and it provides power for the electrochemical plant in Kiyotaki, etc. It is important as a water source for the water supply in Utsunomiya and Nikko, and for agricultural water in the river basin.

[Mitsue Hirayama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

栃木県西部、日光市を流れる川。中禅寺湖(ちゅうぜんじこ)に発し、華厳滝(けごんのたき)となって落下したあと、清滝(きよたき)地区で左沢(ひだりさわ)川をあわせ、男体(なんたい)山腹の荒沢、女峰赤薙(あかなぎ)山腹に発する稲荷(いなり)川、鳴沢(なるさわ)川をあわせつつ日光、今市の両市街地を貫流して鬼怒川(きぬがわ)に注ぐ。流路延長29.9キロメートル。水質の環境基準はA類型。清滝から下流の沿岸に河岸段丘を形成し、今市扇状地はこの川の堆積(たいせき)作用などによって生成した複成扇状地。流況が安定し、夏の水温が低いのに特徴がある。水力発電にも利用され、谷口集落の今市まで10か所の水力発電所が稼動し、清滝の電気化学工場などの電源となっている。宇都宮市、日光市の上水道水源や流域の農業用水として重要。

［平山光衛］

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