Lake Inban

Japanese: 印旛沼 - いんばぬま

A swamp formed in the lowlands downstream of the Tone River in northern Chiba Prefecture. The Kashima River and Nagato River flow into the swamp, which drains into Tokyo Bay via the Shinkawa (Hanamigawa) River. It spans the cities of Narita, Sakura, and Inzai, as well as Sakae Town. The swamp once covered an area of 20.5 square kilometers. Reclamation has been underway since the early modern period, and in 1968 (Showa 43), the center of the swamp was reclaimed, dividing it into North Inbanuma, 5.1 square kilometers, and West Inbanuma, 5.6 square kilometers. With a circumference of 26.4 kilometers and a shallow depth of 1.8 meters at its deepest point, the two swamps are connected by the Inban Canal. In ancient times, the Hitachi River flowed through this area, and the eroded valley of the Shimousa Plateau was dammed up, forming an inlet-like topography called the Katori Sea. However, after the Edo Shogunate changed the course of the Tone River to Choshi, a low-lying alluvial plain was formed, and Lake Inban was established. Lake Inban, into which the Kashima River, Kanzaki River, and Takasaki River flow, was once connected to the Tone River by the Nagato River, and served as a flood reservoir when floods occurred due to backflow. As a result, an inverted delta was formed in Lake Inban, and damage was caused by flooding of rice paddies. For this reason, reclamation was carried out several times, and important figures of the Shogunate, especially Tanuma Okitsugu and Mizuno Tadakuni, made efforts to create a canal to Edo Bay with the intention of developing new rice fields, but they were unable to achieve sufficient results.

In order to increase food production after World War II and to subsequently secure industrial water for the Keiyo Industrial Area, as well as water for urban and agricultural use, the Ministry of Agriculture, Forestry and Fisheries and the Water Resources Development Public Corporation (now the Water Resources Agency) took over the reclamation and water diversion work in 1963. 1,400 hectares of rice paddies were created in the center of the swamp, and the work was completed in 1969.

The area is part of the Inba-Tega Natural Park, and the lakeside is covered with aquatic plants such as reeds and wild grasses. There are also many waterfowl such as ducks and little grebes, so a wild bird forest has been established in Sakura City, and many hikers come here. It is also a great fishing spot for carp, crucian carp, and tanago. Get off at Shimousa Manzaki Station on the JR Narita Line, Keisei Usui Station on the Keisei Electric Railway, Keisei Sakura Station on the Keisei Railway, or Inba-Nihon-idai Station on the Hokuso Railway.

[Yamamura Junji]

Reclamation of Lake Inban

There were four plans to reclaim Lake Inban during the Edo period, but all failed. The first attempt was made in 1663 (Kanbun 3), when the Tone River was excavated under the guidance of the shogunate and magistrates, and the reclamation of the Shimo Tone River, Lake Inban, Lake Teganuma, and other areas was promoted through contracts with townspeople and villages. Although some of the plans saw the creation of 24 new fields in Fukama and 14 new fields in Yawara, most of the plans were failures. The second attempt was made in 1724 (Kyoho 9), when Gen'emon (Someya) and others from Hirado Village, Chiba County (Yachiyo City) submitted a petition to the shogunate and received guidance from Izawa Yasobei Tamenaga, the maker of new fields. The plan was to dig a canal over 17 km long leading to Kemigawa River in the same county (Chiba city), but it was thwarted due to lack of funds. The third plan was proposed by Miyamura Magozaemon Takatoyo, a shogunate magistrate, and planned in 1780 (An'ei 9) by Nitta Heizaemon (Katori) of Soufuke in Inba county and Shimadamura Jirobei (Shinoda) of Chiba county. Townspeople in Edo and Osaka contributed funds, and in 1785 (Tenmei 5), buckwheat and barnyard millet were cultivated in some areas, but the facilities were washed away in a flood in June the following year. When the promoter of the project, Elder Tanuma Okitsugu, fell from power in August, construction was halted. The fourth time was in 1843 (Tenpo 14), when Tadakuni Mizuno, a senior councilor, ordered the lords of five domains, including Tottori, Shonai, Numazu, Akizuki, and Kaibuchi, to assist in construction as part of the Tenpo Reforms. The focus was on digging diversion channels for the transport of goods and drainage of the Tone River, rather than on the development of new fields. However, Tadakuni soon fell from power, and the construction was halted.

[Sadao Otani]

"The Development History of Lake Inban, Parts 1 and 2, by Kurihara Toyo (1972, 1976, Lake Inban Development History Publishing Society)" ▽ "Lake Inban and Lake Teganuma - Proposals for the Water Environment, edited by Yamada Yasuhiko, Shiratori Koji, and Tachimoto Hideki (1993, Kokin Shoin)" ▽ "The Culture and Regeneration of Wetlands - From Lake Inban, by Shiratori Koji (2000, Nashi no Kisha)" ▽ "The Tenpo Reforms and the Construction of Lake Inban, by Kaburagi Yukihiro (2001, Doseisha)"

Lake Inban
A dammed lake formed by sediment from the main stream of the Tone River. In 1968 (Showa 43), the center of the swamp was reclaimed, and it was divided into North Inbanuma and West Inbanuma. The photo shows West Inbanuma as seen from the southwest. There is a wide variety of fish and wild birds, and many people visit the lake, including families who enjoy hiking and anglers. Sakura City, Inba Village, Inba District, Chiba Prefecture ©Shogakukan ">

Lake Inban

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

Japanese:

千葉県北部、利根川(とねがわ)下流の低地に形成された沼。鹿島(かしま)川と長門(ながと)川が流入し、新川（花見川）を通じて東京湾に排水される。成田市、佐倉市、印西(いんざい)市と、栄町にまたがる。かつては面積20.5平方キロメートルの沼であった。近世以来干拓が進められてきたが、1968年（昭和43）に沼の中央が干拓され、北印旛沼5.1平方キロメートルと西印旛沼5.6平方キロメートルに二分された。周囲26.4キロメートル、最深部は1.8メートルで浅く、二つの沼は印旛捷水路(しょうすいろ)で連絡している。この地域は、古くは常陸(ひたち)川が流れ、下総(しもうさ)台地の侵食谷がせき止められて香取海(かとりうみ)とよばれる入り江状地形をなしていた。しかし、江戸幕府によって利根川の流路が銚子(ちょうし)へ改修されて以後、低湿な沖積地が形成されて印旛沼が成立した。鹿島川、神崎(かんざき)川、高崎川などが流入する印旛沼は、かつて長門川で利根川とつながっていたので、逆流によって洪水を受けた際に遊水池の役割を果たした。そこで印旛沼には逆デルタの形成をみ、水田冠水の害も出た。そのため数次にわたって干拓が進められ、とくに田沼意次(たぬまおきつぐ)、水野忠邦(ただくに)ら幕府の要人が新田開発を意図して江戸湾への堀割をつくるために尽力をしたが、十分な成果をあげられなかった。

　第二次世界大戦後の食糧増産と、その後の京葉工業地域への工業用水や、都市・農業用水確保のために、農林水産省、水資源開発公団（現、水資源機構）が干拓事業と引水工事を引き継ぎ（1963）、沼の中央部に1400ヘクタールの水田が生まれ、1969年工事は完了した。

　一帯は県立印旛手賀自然公園(いんばてがしぜんこうえん)に属し、湖畔にはヨシ、マコモの水生植物が茂り、カモ、カイツブリなどの水鳥も多いので、佐倉市には野鳥の森が設けられ、ハイキング客も多い。コイ、フナ、タナゴなどの絶好の釣り場ともなっている。JR成田線下総松崎(しもうさまんざき)、京成電鉄京成臼井(うすい)、京成佐倉、北総鉄道印旛日本医大駅下車。

［山村順次］

印旛沼干拓

印旛沼は江戸時代に4回干拓が計画され、すべて失敗した。第1回は1663年（寛文3）に幕府・代官の指導により新利根(しんとね)川を開鑿(かいさく)し、下利根川や印旛沼、手賀沼などの干拓を町人、村の請負で推進したもの。一部、布鎌(ふかま)二十四新田や埜原(やわら)十四新田などの成立をみたものの、ほとんど失敗に帰した。第2回は1724年（享保9）に千葉郡平戸村（八千代市）の源右衛門(げんえもん)（染谷(そめや)）らが幕府に上申し、新田方井沢弥惣兵衛為永(いざわやそべえためなが)の指導を受けたもの。同郡検見川(けみがわ)（千葉市）に至る17キロメートル余の堀割を開く計画であったが、資金難のため挫折(ざせつ)。第3回は幕府代官宮村孫左衛門高豊(たかとよ)の提唱で、印旛郡惣深(そうふけ)新田平左衛門（香取(かとり)）、千葉郡島田村治郎兵衛（信田(しのだ)）が1780年（安永9）に計画したもの。江戸、大坂の町人が出資し、1785年（天明5）には一部にソバやヒエが作付けされたが、翌年6月の洪水で諸施設が流失した。8月、推進者の老中田沼意次(おきつぐ)が失脚するに及び、工事は中止。第4回は1843年（天保14）老中水野忠邦(ただくに)が天保(てんぽう)の改革の一環として、鳥取、庄内(しょうない)、沼津、秋月、貝淵(かいぶち)など5藩の藩主に手伝普請(てつだいぶしん)を命じたもの。新田開発よりも物資輸送と利根川の排水を主目的にした分水路の掘鑿に重点があった。しかしまもなく忠邦が失脚したため、工事は中止となった。

［大谷貞夫］

『栗原東洋著『印旛沼開発史』1部・2部（1972、1976・印旛沼開発史刊行会）』▽『山田安彦・白鳥孝治・立本英機編『印旛沼・手賀沼――水環境への提言』（1993・古今書院）』▽『白鳥孝治著『湿地の文化、再生――印旛沼から』（2000・梨の木舎）』▽『鏑木行広著『天保改革と印旛沼普請』（2001・同成社）』

印旛沼
利根川本流の堆積物によって生じた堰止湖。1968年（昭和43）に沼の中央が干拓され、北印旛沼と西印旛沼に二分された。写真は南西上空から見た西印旛沼。魚や野鳥の種類も豊富で、ハイキングを楽しむ家族連れや釣り客など、訪れる人も多い。千葉県佐倉市・印旛郡印旛村©Shogakukan">

印旛沼

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