Agatsuma River

A river that flows through the central-western part of Gunma Prefecture. It is a tributary of the Tone River, originating near Torii Pass (1,362 meters) on the border with Nagano Prefecture, flows east, and joins the Tone River in Shibukawa City. It is 76 kilometers long. There are gorges in the upper and middle reaches, and the most representative is Agatsuma Gorge (a nationally designated place of scenic beauty), also known as the Kanto Yabakei. Traditionally, the river downstream from Naganohara Town was called a "dead river" because no fish lived there and it was not used for agriculture or power generation. This was caused by the injection of highly acidic rivers such as the Yukawa River from Kusatsu Onsen. In 1963 (Showa 38), a Gunma Prefecture-run neutralization plant was built in Kusatsu Town, and the water quality was improved by constantly injecting lime emulsion into the Yukawa River and other rivers, turning them into "river-reviving rivers." This was the first of its kind in the country, and in 1968 it was transferred to national management. The coast is also part of the Northern Kanto power generation zone, with 15 canal-type power plants generating 160,000 kilowatts of electricity.

[Murakami Sadao]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

群馬県中西部を流れる川。利根川(とねがわ)の支流で、長野県境の鳥居(とりい)峠（1362メートル）付近に源を発して東流し、渋川(しぶかわ)市で利根川に合する。延長76キロメートル。上・中流には峡谷がみられ関東耶馬渓(やばけい)の称がある吾妻峡谷（国指定名勝）が代表的。従来、長野原(ながのはら)町から下流は、魚もすまず、農業や発電にも利用されない「死の川」といわれていた。これは草津温泉からの湯川(ゆかわ)など強酸性河川の注入が原因であった。そこで1963年（昭和38）草津町に群馬県営の中和工場ができ、石灰の乳液を常時恒久的に湯川などに投入する水質改善を行い「よみがえる川」に変えた。これは全国にも例がなく、1968年国営に移管された。また沿岸は北関東電源地帯の一つで、水路式15の発電所で16万キロワットを発電している。

［村木定雄］

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