Tone River

Japanese: 利根川 - とねがわ

It is a large river that originates in Higashikozawa on Mt. Ominakami in the Mikuni Mountains on the border between Gunma and Niigata prefectures, flows roughly southeast across the Kanto Plain, and empties into the Pacific Ocean at Choshi, Chiba prefecture. It is a Class A river. With a length of 322 kilometers, it is the second longest river in Japan after the Shinano River, and with a drainage area of 16,840 square kilometers, it is the largest in Japan. It is also known as Bando Taro.

[Yamamura Junji]

Topography and river improvement

Granite is widely distributed in the upper reaches of the river, and erosion of this has created deep valleys where dams are concentrated. At Oana it joins the Yubiso River to form the valley of Minakami Onsenkyo, and then joins the Akaya River to form the Numata Basin. Several large river terraces have formed in the Numata Basin, on which the town of Numata rests. Downstream, the Shibukawa River flows into the Agatsuma River, and flows out into the Kanto Plain, where it meets the Karasu River, Kabura River, and Kanna River that flow out of the Kanto Mountains near Takasaki, where it flows turbulently and forms an alluvial fan plain. In the midstream, the river joins with the south-flowing Watarase River, Kinugawa River, and Kokai River, and then flows slowly eastward through the low-lying marshes of the water towns of Teganuma, Inbanuma, Sawara, and Itako, before reaching a mouth about 1 kilometer wide in Choshi.

In ancient times, the downstream area was a wide bay called Katori Sea, and the Tone River flowed into Tokyo Bay, but in the early modern period, it was changed to flow into the Pacific Ocean at Choshi, and the sediment that flowed into it formed the low-lying marshes and lakes that we see today. The former course of the river flowing into Tokyo Bay became the Old Tone River, and it also led to the diversion of the Edo River at Sekiyado (Noda City), Chiba Prefecture. It is said that the Edo Shogunate's purpose in changing the course of the river was to protect the city of Edo from flooding, to promote the development of new rice fields in the Nakagawa River basin to secure food, and to create a defensive line for Edo against the Tohoku feudal domains. The Tone River was closed off at Kawamata in Hanyu City, Saitama Prefecture, and the Watarase River was renovated and diverted, while the Kinu River and Kogai River were separated and renovated to allow the Tone River to flow eastward. However, construction began in 1594 (Bunroku 3) and was tentatively completed in 1654 (Shoo 3) after two artificial channel excavations. However, the Akabori River, which was the connecting waterway that diverted the Tone River water to the Kinu River system, was narrow, and it was not until 1809 (Bunka 6) that the river's width was four times that of the original width, widened to 95 meters, that it achieved sufficient results. In addition, the confluence of the Watarase River with the Tone River caused the Watarase River to flow backwards around Koga in Ibaraki Prefecture, making the area more susceptible to flooding. For this reason, many houses were built with water mounds and boats kept on hand from the confluence with the Watarase River to Katori City. In 1900 (Meiji 33), the Tone River was designated a direct-controlled river and flood control works were carried out to protect against high water levels. The first phase of construction involved the excavation and construction of a direct waterway from Sawara to Sasagawa. In addition, construction of the Watarase Reservoir (also known as the Watarase Reservoir) was carried out from the end of the Meiji period to the Taisho period, and has since been useful for flood control.

[Yamamura Junji]

Tone River Water Transportation

In the early modern period, when the Tone River was diverted eastward and flowed into the Pacific Ocean at Choshi, goods from the Tohoku region traveled up the Tone River to Sekijuku, and from there were transported to Edo via the Edogawa River. Because the traditional route off the coast of the outer Boso Peninsula, known as the Omi-mawari route, was dangerous, water transport along the Tone River, known as the Uchi-mawari route, flourished, and many river banks developed along the coast. From the downstream, there were river ports such as Choshi, Sasagawa, Omigawa, Sawara, Kanzaki, Namegawa, Ajiki, Kinoshita, Fusa, and Sekijuku, and once in the Edogawa River, Noda, Nagareyama, Matsudo, and Gyotoku became bustling towns. The riverbank was lined with boat wholesalers, boat lodges, restaurants, and other establishments, including the former home of Ino Tadataka, a nationally designated historic site along the Ono River in Katori City. Kinoshita-gashi was also a stopover point where goods brought by Takase boats from Choshi were unloaded and transported overland to Shiroi, Kamagaya, and Gyotoku. After the wholesalers at Kinoshita-gashi began operating tea boats in 1678 (Enpo 6), tea boats bound for the three shrines of Katori, Kashima, and Ikisu began to come and go, and the number of tourists visiting the area also increased. At the end of the 18th century, the number of Takase boats leaving Kinoshita reached 4,000 per year. Until the mid-Edo period, the main goods sent to Edo were rice for the castle and rice stored in the warehouses, but in the later period, more goods were sent to Edo, such as dried sardines from Kujukuri, seafood from Choshi, sake from Sawara, and soy sauce from Choshi and Noda. The shogunate's checkpoint was located in Sekijuku, and the town flourished as a post town. In 1874 (Meiji 7), steamships began operating, connecting Choshi and Tokyo in 18 hours, a time that was incomparably shorter than the two weeks it took by takasebune boats, and water transportation on the Tone River flourished until the Narita Line, which ran parallel to the river, was opened in 1933 (Showa 8). In 1886, at the request of Ibaraki Prefecture, the government shortened the long route connecting the Tone River and Edo River at Sekijuku, and also began excavating the Tone Canal to deal with the dry winter season, which was completed in 1890. As a result, travel time was reduced by six hours, and the number of ships using the canal rose to 38,000 per year. However, during the Taisho period, competition with railways led to a rapid decline in the canal's use.

[Yamamura Junji]

Water Use

In 1951, the upstream area was designated the Tone Special Region under the National Comprehensive Development Act, and multipurpose dams were constructed to take advantage of the abundant water. Examples include Yagisawa Dam, Fujiwara Dam, and Sudagai Dam on the main stream of the Tone River, and Aimata Dam on the tributary Akatani River and Sonohara Dam on the Katashina River. These dams are used for power generation, flood control, irrigation water, and drinking water. In 1970, the Water Resources Development Public Corporation (now the Water Resources Agency) completed the Gunma Irrigation Canal at the southern foot of Mount Akagi and the eastern foot of Mount Haruna, which takes in water discharged from Yagisawa Dam to ensure stable rice paddy management. In the midstream area, the Tone River Ozeki Weir was built in the northern part of Gyoda City, Saitama Prefecture, in 1968, and is used for drinking water and industrial water for Tokyo and Saitama Prefecture, and helps purify the water quality of the Arakawa River. In the downstream area, the Otone Irrigation Canal and the Ryoso Irrigation Canal were completed in 1951 and 1965, respectively, and have water intakes at Sasagawa and Sawara to send agricultural water to the rice paddies of the Kujukuri Plain, making a great contribution to the development of agriculture, which had suffered from drought. However, to deal with the shortage of water for agricultural use and the increasing demand for drinking water and industrial water in the metropolitan area, and to improve the rice paddies that were being adversely affected by the backflow of salt water, the Tone River Estuary Weir was built in Tonosho Town, 18 kilometers from the river mouth, in 1971. The Tone River, which once caused many floods in coastal areas, is now designated as Joshin'etsu Kogen National Park in its upper reaches and Suigo Tsukuba Quasi-National Park in its lower reaches. People visit the river for its beautiful valleys and hot springs in the upper reaches, river fishing and boating in the middle and lower reaches, golf courses on the riverbed, recreation at sports parks, and cycling along the banks.

[Yamamura Junji]

"The Tone River - Nature, Culture and Society" edited by the Nine Academic Societies Union Tone River Basin Research Committee (1971, Kobundo)" ▽ "The Tone River" by Homma Kiyotoshi (1978, Saitama Shimbun)" ▽ "Changes in Tone River Flood Control and Flood Disasters" by Okuma Takashi (1981, University of Tokyo Press)" ▽ "Cultural History of River Water Transport - Edo Culture and the Tone River Cultural Zone" by Kawana Noboru (1993, Yuzankaku Publishing)" ▽ "Tone River Dictionary" edited by Morita Tamotsu (1994, Shinjinbutsu Oraisha)" ▽ "Tone River Research Group edited, "Tone River Floods - Passing on the History of the Basin" (1995, Sankaido)" ▽ "Tone River Culture Research Group edited, "Life and Culture of the Tone and Arakawa River Basins" (1995, Kokusho Kankokai)" ▽ "The History of the Tone River - From the Source to the Mouth" by Kanai Tadao (1997, published by Nihon Tosho Kankokai and Kindai Bungeisha)" ▽ "The New Tone River Atlas, volumes 1 and 2, by Yamamoto Kotaro (1997, 1998, published by Ronshobo Publishing)" ▽ "The Tone River - People and Technological Culture" edited by Kitano Susumu and Korenaga Sadayoshi (1999, published by Yuzankaku Publishing)" ▽ "Archives Tone River, edited by Miyamura Tadashi and compiled by the Archives Tone River Editorial Committee (2001, published by Shinzansha Publishing and published by Daigaku Tosho)" ▽ "A Study of the History of Modern Tone River Water Transport" by Watanabe Hideo (2002, Yoshikawa Kobunkan)" ▽ "The Green Water Veins - The Beautiful Nature of the Tone River Basin in Gunma" by Arai Yukito (2004, published by Shogakukan)" ▽ "Tone River Cultural Research Group, ed., Tone River Arakawa Encyclopedia (2004, Kokusho Kankokai)" ▽ "Tone River Maps by Akamatsu Sotan and Yanagita Kunio (Iwanami Bunko)"

Mouth of the Tone River
A large river that flows southeast through the Kanto Plain and empties into the Pacific Ocean. Its drainage area of 16,840 km is the largest in Japan. The photo shows the river mouth near Choshi City, Chiba Prefecture (left), with Ibaraki Prefecture on the opposite bank. During the Edo period, it was the gateway to the Tone River water transport, transporting goods to Edo by going upstream to the river port of Sekijuku. Choshi City, Chiba Prefecture / Kamisu City, Ibaraki Prefecture ©Shogakukan ">

Mouth of the Tone River

"Tone River Illustrated Guide"
A map of Kinoshita-gashi. Located on the right bank of the Tone River, west of Lake Inban, Kinoshita-gashi was an important place for shipping during the Edo period. It is said that the area was also bustling with tourists, many of whom made pilgrimages to the three shrines of Kashima, Katori, and Ikusu, and sightseeing trips to Choshiura. Volume 3, "A Map of Boats Departing for a Pilgrimage to the Three Shrines," by Akamatsu Sotan, edited by Yanagita Kunio, published in 1938 (Showa 13), Iwanami Bunko, National Diet Library .

"Tone River Illustrated Guide"

Tone River Water Transportation (Meiji Period)
"Geographical Photo Album, Inland Section, Volume 2" (1900, Meiji 33) owned by the National Diet Library ">

Tone River Water Transportation (Meiji Period)

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

群馬県と新潟県の境、三国(みくに)山脈中の大水上(おおみなかみ)山の東小沢に水源を発し、関東平野をほぼ南東流して千葉県銚子(ちょうし)で太平洋に注ぐ大河川。一級河川。延長322キロメートルで長さでは信濃(しなの)川に次いで全国2位、流域面積は1万6840平方キロメートルで日本最大である。坂東太郎(ばんどうたろう)の別称がある。

［山村順次］

地形・河川改修

上流地域は花崗(かこう)岩が広く分布し、これを侵食して深い谷が続いており、ダムが集中する。大穴(おおあな)で湯檜曽(ゆびそ)川と合流して水上温泉郷の渓谷をなし、さらに赤谷(あかや)川と合流して沼田盆地をつくる。沼田盆地には大規模な数段の河岸段丘が形成され、沼田の市街をのせている。その下流の渋川では吾妻(あがつま)川を流入させて関東平野に出て、高崎付近で、関東山地から流れ出た烏川(からすがわ)、鏑川(かぶらがわ)、神流川(かんながわ)を集めて乱流し、扇状地的平野を形成。中流地域では南流する渡良瀬川(わたらせがわ)、鬼怒川(きぬがわ)、小貝川(こかいがわ)とをあわせて、以後、手賀沼(てがぬま)、印旛沼(いんばぬま)や佐原(さわら)、潮来(いたこ)の水郷の低湿地帯をゆっくりと東流、銚子で幅約1キロメートルの河口に至る。

　下流地域は古代には香取海(かとりうみ)という広い湾入になっており、利根川は東京湾へ注いでいたが、近世になって銚子で太平洋に注ぐ流路に変えられ、その流入土砂によって今日みるような低湿地と湖沼群が形成されたのである。かつての東京湾に注ぐ流路は古(ふる)利根川となり、さらに千葉県関宿(せきやど)（野田市）で江戸川を分流させることにもなった。江戸幕府が行った瀬替えの目的は、江戸市街を水害から守るため、食糧確保のために中川流域の新田(しんでん)開発を進めること、また東北諸藩に対する江戸防御線とすることにもあったといわれる。利根川を埼玉県羽生(はにゅう)市川俣(かわまた)で締め切り、渡良瀬川の改修、瀬替えを行う一方、鬼怒川、小貝川の分離、改修によって利根川の東流を図った。しかし、1594年（文禄3）に始まった工事は二度の人工流路開削を経て1654年（承応3）にいちおうの完成をみたが、利根川の水を鬼怒川水系へ流す連絡水路である赤堀川の川幅が狭く、1809年（文化6）になって川幅を4倍の95メートルに広げるまでは十分な効果をあげられなかった。また茨城県古河(こが)付近では、利根川との合流によって渡良瀬川の逆流がおこって洪水を受けやすくなった。そこで、渡良瀬川合流付近から香取(かとり)市へかけて水塚(みつか)を構え、揚舟(あげぶね)を常備している民家が多くみられた。1900年（明治33）、利根川は直轄河川として高水防御の治水工事が展開されることになり、第一期工事として佐原から笹川(ささがわ)まで直流水路の掘削と築堤が行われ、また明治末から大正期にかけて渡良瀬遊水地（渡良瀬遊水池とも）の工事が行われ洪水調節に役だってきた。

［山村順次］

利根川水運

近世期に利根川が東遷されて銚子で太平洋に注ぐようになると、東北の物資が利根川をさかのぼって関宿に至り、ここから江戸川を経由して江戸へ運ばれるようになった。従来の外房(そとぼう)沖を航海するいわゆる外海廻(まわ)りは危険が伴ったため、内廻りとよばれた利根川水運は盛況を呈し、沿岸には多くの河岸(かし)が発達した。下流から銚子、笹川、小見川(おみがわ)、佐原、神崎(こうざき)、滑川(なめがわ)、安食(あじき)、木下(きおろし)、布佐(ふさ)、関宿などの河港があり、江戸川に入って野田、流山(ながれやま)、松戸、行徳(ぎょうとく)などがにぎわった。河岸には船問屋、船宿、料理店などが建ち並んでおり、香取市の小野川沿いにある国指定史跡伊能忠敬(いのうただたか)旧宅も商家の一つであった。木下河岸は銚子から高瀬舟で運ばれた物資を陸揚げし、ここから陸路で白井(しろい)、鎌ヶ谷(かまがや)、行徳へと輸送する中継ぎ基地でもあり、また1678年（延宝6）木下河岸の問屋が茶船の営業を開始して以後、香取、鹿島(かしま)、息栖(いきす)の三社参りの茶船が出入りするようになり、遊覧客の来訪も盛んになった。18世紀末における木下の高瀬舟出船数は年間4000隻にも達した。物資は江戸中期までは城米や蔵米の輸送が主であり、後期になると新たに九十九里の干鰯(ほしか)、銚子の海産物、佐原の酒、銚子・野田のしょうゆなどの江戸送りが多くなった。関宿には幕府の関所が置かれ宿場町としても栄えた。1874年（明治7）に蒸気船が走るようになり、銚子―東京間を18時間で結び、高瀬舟で2週間もかかっていた時代とは比較にならないほどに短縮され、川筋に並行して走る成田線が1933年（昭和8）開通するまで利根川水運は活況を呈した。1886年、政府は茨城県側の要請で、利根川と江戸川を結ぶ大回りのコースを関宿で短縮し、また冬の渇水期に対応するために利根運河の開削に着手し、1890年に完成した。このため所要時間は6時間短縮され、運河を往来する船の数は年間3万8000隻にも上ったが、大正時代になると鉄道との競合で急速に衰退した。

［山村順次］

利水

上流地域は1951年（昭和26）に国土総合開発法に基づき利根特定地域に指定され、豊富な水を利用して多目的ダムが建設された。利根川本流の矢木沢ダム(やぎさわだむ)、藤原(ふじわら)ダム、須田貝(すだがい)ダムや支流の赤谷川の相俣(あいまた)ダム、片品(かたしな)川の薗原(そのはら)ダムなどはその例で、発電、洪水調節、灌漑(かんがい)用水、上水道などに利用されている。1970年には水資源開発公団（現、水資源機構）によって、赤城山南麓(なんろく)や榛名(はるな)山東麓に矢木沢ダムの放水を取水して安定した水田経営を図る群馬用水が完成した。中流地域では1968年埼玉県行田(ぎょうだ)市北部に利根大堰(おおぜき)ができ、東京都、埼玉県の上水道や工業用水に使用されたり、荒川の水質浄化に役だっている。下流地域では、笹川と佐原に取水口を設けて九十九里平野の水田へ農業用水を送る大利根用水と、両総用水(りょうそうようすい)がそれぞれ1951年と1965年に完成し、干害に苦しんできた農業の発展に、多大の貢献をしている。しかし、農業用水の水量不足や首都圏での上水道、工業用水の需要増大に対応するため、さらに塩水の逆流で悪影響の出ている水田を改良するために、1971年に河口から18キロメートルの東庄(とうのしょう)町に利根川河口堰が設けられた。かつて沿岸地域で多くの水害を引き起こしてきた利根川も、現在では上流地域は上信越高原国立公園(じょうしんえつこうげんこくりつこうえん)、下流地域は水郷筑波国定公園(すいごうつくばこくていこうえん)に指定され、上流部での渓谷美、温泉、中・下流部での川釣り、舟遊び、河川敷のゴルフ場、運動公園でのレクリエーションや堤防に沿ってのサイクリングなどに利用されている。

［山村順次］

『九学会連合利根川流域調査委員会編『利根川――自然・文化・社会』（1971・弘文堂）』▽『本間清利著『利根川』（1978・埼玉新聞社）』▽『大熊孝著『利根川治水の変遷と水害』（1981・東京大学出版会）』▽『川名登著『河川水運の文化史――江戸文化と利根川文化圏』（1993・雄山閣出版）』▽『森田保編『利根川事典』（1994・新人物往来社）』▽『利根川研究会編『利根川の洪水――語り継ぐ流域の歴史』（1995・山海堂）』▽『利根川文化研究会編『利根川・荒川流域の生活と文化』（1995・国書刊行会）』▽『金井忠夫著『利根川の歴史――源流から河口まで』（1997・日本図書刊行会、近代文芸社発売）』▽『山本鉱太郎著『新・利根川図志』上下（1997、1998・崙書房出版）』▽『北野進・是永定美編『利根川――人と技術文化』（1999・雄山閣出版）』▽『宮村忠監修、アーカイブス利根川編集委員会編『アーカイブス利根川』（2001・信山社出版、大学図書発売）』▽『渡辺英夫著『近代利根川水運史の研究』（2002・吉川弘文館）』▽『新井幸人著『緑の水脈――群馬・利根川流域の美しい自然』（2004・小学館）』▽『利根川文化研究会編『利根川荒川事典』（2004・国書刊行会）』▽『赤松宗旦・柳田国男著『利根川図志』（岩波文庫）』