Agano River

It is a river that runs through the center of Niigata Prefecture, passing through the Tsugawa Basin from the border with Fukushima Prefecture, and empties into the Sea of ​​Japan at Matsuhama in Kita-ku, Niigata City, dividing the Echigo Plain into east and west. It is a first-class river. The Nippashi River, which originates in Lake Inawashiro in the Aizu Basin, and the Tadami River, which originates in Lake Ozenuma, join together in the upper reaches to form the Agano River, and when it enters Niigata Prefecture (Aga Town, Higashikanbara District), it becomes the Agano River. It is 210 km long and has a drainage area of ​​7,710 square km. The upstream prefectural border is famous for its beautiful gorge caused by antecedent meandering, and it combines tributaries such as the Sanekawa, Tokonami, and Araya rivers, and joins the Haide river at the mouth of the valley, creating a vast alluvial fan with a distinctive meandering topography. The river mouth is blocked by the Kambara Sand Dunes, and once shared a mouth with the Shinano River. The current mouth of the river is the Matsugasaki Diversion Channel, which was dug by the Shibata Domain in 1730 (Kyoho 15). During the Edo period, boat transport was opened from Tsugawa Port to Niigata Port, and the road was called the "Tsugawa Shipway" and served as an artery for transporting goods to the Aizu Domain. The Oagano River, which flows into the Shinano River, is an artificial river dug in 1738 (Genbun 3) for the purpose of facilitating boat transport. From the end of the Taisho period, power development became popular, and two large dams, Kanose and Tsunogami, were built in the upper gorge. After World War II, Agekawa Dam was constructed downstream, resulting in a series of artificial lakes, including Lake Tsugawa. The beauty of the gorge and many tourist attractions have led to the area being designated a prefectural natural park, making it a major tourist destination known as the Agano River Line. The coast is well-equipped with modern transportation routes, including the JR Ban'etsu West Line, which passes through the gorge via tunnels and iron bridges, National Route 49, and the Ban'etsu Expressway, and there are many famous historical sites, such as the hot springs of Sakihana, Kirinzan, and Tsunogami, the remains of Kirinzan Castle, the Yakushido Hall of Byodo-ji Temple, and the Kannon Hall of Gotoku-ji Temple. In the spring when the new greenery is coming up and in the autumn when the leaves are changing, the area is bustling with hikers, and you can also take a boat trip down the Agano River Line. The three major power plants, Toyomi, Tsunogami, and Agegawa, have an annual generating capacity of 160,000 kilowatt-hours, and Kanose once housed a large chemical fertilizer factory of Showa Denko, but it fell into decline after losing the Niigata Minamata disease lawsuit in 1971. The Shin'e irrigation canal, which takes in water from Komatsu in the valley, irrigates 30,000 hectares of rice paddies in the Kambara Plain.

[Hisao Yamazaki]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

新潟県中央部、福島県境から津川盆地(つがわぼんち)を通って、新潟市北区松浜で日本海に注ぎ、越後平野を東西に二分する川。一級河川。上流は会津盆地の猪苗代湖(いなわしろこ)に源を発する日橋川(にっぱしがわ)と、尾瀬沼(おぜぬま)に発する只見川(ただみがわ)が合流し、阿賀川とよばれ、新潟県（東蒲原(ひがしかんばら)郡阿賀町）に入ると阿賀野川とよぶ。延長210キロメートル、流域面積7710平方キロメートル。上流県境は先行性蛇行による峡谷美が名物で、実川(さねかわ)、常浪(とこなみ)川、新谷(あらや)川などの支流をあわせ、谷口では早出(はいで)川が合流して蛇行地形を特色とする広大な谷口扇状地が広がる。河口は蒲原砂丘に阻まれて、かつては信濃(しなの)川と河口をともにしていた。現在の河口は1730年（享保15）に新発田藩(しばたはん)によって掘られた松ヶ崎分水である。江戸時代は津川湊(みなと)から新潟湊まで舟運の便が開け、「津川船道(ふなどう)」とよばれ、会津藩への物資輸送の動脈をなしていた。なお、信濃川に通ずる小阿賀野川は、1738年（元文3）舟運の便のために掘られた人工河川である。大正末期から電源開発が盛んとなり、上流峡谷部に鹿瀬(かのせ)、角神(つのがみ)の二大ダムができ、さらに第二次世界大戦後はその下流に揚川(あげかわ)ダムが建設されて、津川湖などの人造湖が連続する。峡谷美と、多くの観光名所をもち県立自然公園に指定され、阿賀野川ラインとよばれる大観光地になっている。沿岸は、峡谷をトンネルと鉄橋で抜けるJR磐越西線(ばんえつさいせん)と国道49号、磐越自動車道の近代交通路が完備し、咲花(さきはな)、麒麟山(きりんざん)、角神の温泉場や、麒麟山城跡、平等(びょうどう)寺薬師堂、護徳(ごとく)寺観音堂などの名所旧跡も多く、春の新緑、秋の紅葉期にはハイキング客でにぎわい、阿賀野川ライン下りの船旅もできる。豊実(とよみ)、角神、揚川の三大発電所では年間16万キロワット時の発電力があり、かつては鹿瀬に昭和電工の大化学肥料工場があったが、新潟水俣病(みなまたびょう)裁判で敗訴し（1971）衰微した。谷口の小松で取水される新江(しんえ)用水は蒲原(かんばら)平野の3万ヘクタールの水田を灌漑(かんがい)している。

［山崎久雄］

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