Suigou

A low-lying, humid delta region in the middle and lower reaches of a large river, with a well-developed waterway network and a large amount of boat traffic. It can be found in the middle and lower reaches of the Tone River, Shinano River, Kiso River, Chikugo River, etc., the creeks in the lower reaches of the Yangtze River in China, and the lowlands known as polders in the Netherlands.

In particular, the lake and marsh area centered on the lower reaches of the Tone River and Lake Kasumigaura presents a typical water town landscape, and its area corresponds to the southern end of Lake Kasumigaura and Lake Kitaura. The Tone River flows eastward and forms a low-lying, swampy delta in the Kawanakajima area, sandwiched between the Yokotone River and the Kitatone River. In the early modern period, the Tone River, which flowed into Edo Bay, was diverted to Choshi, and sediment accumulated in the Katori Sea, creating a low-lying marshland.

The Edo Shogunate had samurai who had returned to agriculture develop 16 new rice fields, with the intention of defending against the Hitachi Satake Domain on the opposite bank. Many of the settlements are named after islands or provinces, because they are located on slightly elevated land on natural levees of 1 to 2 meters, and as a result they have been subject to constant flooding, but after the Meiji period construction was changed from low-water level construction to high-water level construction, the levees were strengthened, and the river was widened. Before World War II, countless waterways ran through the area, and these were the only transportation routes, and farmers went out to work in their rice boats and planted rice up to their waists in water.

In 1957, land improvement and reclamation were carried out in the waterway area as part of the Tone River Specific Area Comprehensive Development Project. Work began to widen the Kita Tone River and Hitachi Tone River to secure industrial water for the Kashima coastal industrial area, and the resulting soil was used to fill in creeks, develop farmland, and promote the prefectural farm project to turn wet rice fields into dry fields. Today, the beautiful rice paddies and paved farm roads that have been reclaimed from the land are a good indication of the transformation of the waterway rural area. Part of Yodaura has been reclaimed and an aquatic botanical garden has been created there. During the iris season in June, farmers operate tourist boats to travel around the area, and the area has become a tourist hub for the Suigo Tsukuba Quasi-National Park, which links the Kato Island Twelve Bridges and Itako.

[Yamamura Junji]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

大河川の中・下流の低湿な三角州地域で、水路網が発達し、舟による交通が発達している地域。利根(とね)川、信濃(しなの)川、木曽(きそ)川、筑後(ちくご)川などの中・下流地方、中国の長江（揚子江(ようすこう)）下流のクリーク、オランダのポルダーとよばれる低地などにみられる。

　とくに利根川下流と霞ヶ浦(かすみがうら)を中心とする湖沼地帯は典型的な水郷景観を呈し、その範囲は霞ヶ浦と北浦の南端にあたる。利根川が東流して横利根川と北利根川に挟まれた川中島の地域で、低湿なデルタを形成する。近世初期江戸湾へ注いでいた利根川が銚子(ちょうし)へと流路を変えられ、香取(かとり)海へ土砂が堆積(たいせき)して低湿地をつくった。

　江戸幕府は対岸の常陸(ひたち)佐竹藩に対する防衛上の意図から帰農武士に16の新田を開発させた。集落は島や州の地名がつくものが多いが、これは1～2メートルの自然堤防上の微高地上に立地しているからであり、ために絶えず水害を受けてきたが、明治以後は低水位工事から高水位工事にかえられて堤防が強化され、川幅も広げられた。第二次世界大戦前においては無数の水路が走り、これが唯一の交通路であって農民は田舟で農作業に出るとともに腰までつかって田植をした。

　1957年（昭和32）に利根川特定地域総合開発事業として水郷地帯の土地改良と干拓が行われた。鹿島(かしま)臨海工業地域の工業用水を確保するために北利根川と常陸利根川の川幅拡張工事が始まり、その土砂を利用してクリークを埋め、圃場(ほじょう)を整備して湿田の乾田化を図る県営圃場事業を推進した。現在、耕地整理されたみごとな水田と舗装された農道とが、水郷農村の変容をよく示している。与田(よだ)浦の一部は干拓され、そこに水生植物園が造成されたので、6月のアヤメのシーズンには農民の操る観光田舟が行き交い、加藤洲(かとうず)十二橋巡りや潮来(いたこ)とを結ぶ水郷筑波(つくば)国定公園の観光拠点となっている。

［山村順次］

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