Kinugawa

This river originates in Kinunuma, near the border with Gunma Prefecture in northwest Tochigi Prefecture, flows south through the central plains of Tochigi Prefecture and western Ibaraki Prefecture, and empties into the Tone River. It is a first-class river. In ancient times it was called the Kenu River, and was also written as Koromo River or Kinu River. It is about 177 km long, with a drainage area of ​​about 1,760 square kilometers. For about 50 km upstream it flows through a deep valley between the mountains. At Kawaji Onsen, it changes course to the south, joins the Ojika River, and then passes through Kinugawa Onsen and enters the plains, where it joins the Itana River, which originates on the slopes of Mt. Nyoho and Mt. Akanagi. As it flows southeast along the northeastern edge of the Imaichi alluvial fan, it joins the Daiya River, which originates in Lake Chuzenji, flows south from Sakura City, dissects the former alluvial fan, and flows through the lowlands, joining the Tagawa River in Yuki City and joining the Tone River in Moriya City, Ibaraki Prefecture. The main and tributaries in the upper mountain areas have multipurpose dams at Ikari, Kawamata, and Kawaji, which are used for power generation, irrigation, flood control, etc., as well as the Kurobe Dam, which is used exclusively for power generation, and there are many power plants in the upper reaches. The mountainous areas are blessed with tourist spots such as Setoaikyo, Ryuokyo, the fountain tower, a nationally designated natural monument, and the Kinunuma Marsh, as well as fishing spots for char and other fish in the main and tributaries. In addition to the Kinugawa, Kawaji, and Yunishigawa hot springs, there is also the Okukinu hot spring resort, which attracts tourists throughout the year, not to mention during the seasons of new greenery and autumn leaves. Headworks (dams at the head of a waterway) for agricultural water have been constructed in the middle and lower reaches of the river, with the main ones being the Sanuki and Katsuri headworks. Both were directly managed by the Ministry of Agriculture and Forestry (now the Ministry of Agriculture, Forestry and Fisheries), and agricultural water taken from Sanuki is diverted via the Kazami power station to the Ichinohori irrigation canal on the left bank and the Sakasagi irrigation canal on the right bank, irrigating approximately 9,000 hectares. The Kinu Central Waterworks Project, which supplies water to the Kiyohara Industrial Park and farmland in Utsunomiya City, has also been completed. Young sweetfish from Lake Biwa are released into the river, and fish such as iso (dace) can also be caught. In the Middle Ages and early modern times, shipping was common, Mitsukaido flourished as a commercial port, and Akutsugashi in the middle reaches was a transhipment port for rice and charcoal from Aizu and other places. The river once flowed into the Pacific Ocean together with the Kokai River, but in the early Edo period, in 1629 (Kan'ei 6), the Kokai River was separated and, around the same time, several excavations were carried out to change its course so that it flows into the Tone River. The river's water quality is good throughout the entire area, and the environmental standards for water quality are AA upstream of Sanuki and A downstream.

[Mitsue Hirayama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

栃木県北西部、群馬県との県境近くの鬼怒沼に源を発し、栃木県中央平地、茨城県西部を南流して利根川(とねがわ)に注ぐ川。一級河川。古くは毛野(けぬ)川といわれ、衣川、絹川とも書かれた。延長約177キロメートル、流域面積約1760平方キロメートル。上流約50キロメートルは山間を深い渓谷となって流れる。川治温泉(かわじおんせん)において南に流れを変え、男鹿(おじか)川をあわせ、鬼怒川温泉を経て平野に出た所で、女峰(にょほう)山・赤薙(あかなぎ)山斜面に発する板穴(いたあな)川をあわせる。今市(いまいち)扇状地の北東縁を南東に流れる途中で、中禅寺(ちゅうぜんじ)湖に発する大谷川(だいやがわ)をあわせ、さくら市から南流し、かつての扇状地を開析して低地を流れ、結城(ゆうき)市で田川をあわせ、茨城県守谷(もりや)市において利根川に合流する。上流山間の本・支流に五十里(いかり)、川俣(かわまた)、川治の多目的ダムが存し、発電、灌漑(かんがい)、洪水調節などに利用されるほか、発電専用の黒部(くろべ)ダムもあって、上流部は発電所が多い。山間部は、瀬戸合峡(せとあいきょう)、龍王峡(りゅうおうきょう)、国指定天然記念物の噴泉塔、鬼怒沼湿原などの観光ポイントや本・支流のイワナなどの釣り場に恵まれる。また、鬼怒川、川治、湯西川(ゆにしがわ)温泉に加え奥鬼怒温泉郷もあって、新緑、紅葉の時期はいうに及ばず、四季観光客が訪れる。中・下流部に農業用水の頭首工(とうしゅこう)（水路の頭部に設けられたダム）が築造されており、佐貫(さぬき)と勝瓜(かつうり)頭首工がおもなもの。いずれも農林省（現農林水産省）の直轄工事で施行され、佐貫から取水した農業用水は風見(かざみ)発電所を経て左岸の市堀(いちのほり)用水と右岸の逆木(さかさぎ)用水に分水され、約9000ヘクタールを灌漑する。宇都宮市の清原工業団地や耕地に用水を供給する鬼怒中央部用水事業も完了している。琵琶(びわ)湖産の稚アユなどが放流され、アイソ（ウグイ）なども釣れる。中世・近世には舟運が行われ、水海道(みつかいどう)は商港として栄え、中流の阿久津河岸(あくつかし)は会津などからの廻米(かいまい)や木炭などの積換え港であった。かつては小貝川(こかいがわ)をあわせて太平洋に注いでいたが、江戸初期、1629年（寛永6）小貝川を分離し、また同じころ数次にわたる開削によって、利根川に注ぐように流路変更された。川の水質は全水域にわたり良好であり、水質の環境基準は、佐貫の上流はAA、下流はA類型に指定されている。

［平山光衛］

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