Echigo Plain - Echigo Heiya

Occupying the central part of Niigata Prefecture, this is the second largest alluvial plain in Japan. It is also called the Niigata Plain or the Kambara Plain. It is a spindle-shaped plain surrounded by the Asahi-Budou Mountains and Gozu Mountains to the north, and the Tertiary hills of the Yahiko, Nishiyama, Michiyama, and Higashiyama Mountains to the south, stretching 100 km north to south and 10 to 25 km east to west, with an area of ​​2,070 square kilometers. The southern half of the plain, the Nagaoka Depression Area, which forms a geosynclinal valley, was filled in by the Shinano River and its tributaries, and the area up to around Sanjo is called the Chuetsu Plain. The northern half of the area north of the Agano River is the Shibata depression, which has been filled in by the Kaji River, Tainai River, Arakawa River, and Miomote River, which flow from the prefectural border, and the front is blocked by several rows of old and new sand dunes. Behind the sand dunes are a series of lagoons, and the 1645 (Shoho 2) map of Echigo Province shows more than 20 marshes of various sizes, including Yoroigata, Sakata, Ogata, Tagata, Byakurengata, Toyanogata, Shimami-Jusangata, Fukushimagata, Shiunjigata, and Yuwafunegata.

In the early modern period, the various feudal domains of Echigo put all their efforts into flood control projects to reclaim this low-lying lagoon by diverting water, and built the foundation for Echigo's rice production, the largest in the country. The Matsuzakihama Canal on the Agano River and the Shinshinano River Diversion put an end to the struggle with water. Around the time of World War II, large drainage pumping stations were completed on each river, and the groundwater level was lowered by powered drainage. Furthermore, land improvement projects and national lagoon reclamation projects were promoted, and the former wetland areas were transformed into dry fields where double cropping is possible, and now account for 65% of the prefecture's rice production. After World War II, the industrialization of shallow water-soluble natural gas, which had long been used for household purposes in this low-lying lagoon, progressed rapidly, and the pumping of large amounts of groundwater caused land subsidence, which became a major problem, and was completely halted around 1960. Most of the 20 cities in the prefecture, centered on Niigata City, are concentrated on this plain, forming industrial areas for machinery, metals, chemicals, textiles, etc. In addition, fruit farming is thriving on the sand dunes and natural levees, and the area is a nationally-known producer of bulbs such as tulips and hyacinths, as well as bonsai.

[Hisao Yamazaki]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

新潟県の中央部を占める日本第二の沖積平野。新潟平野(にいがたへいや)あるいは蒲原平野(かんばらへいや)ともよばれる。北は朝日・葡萄(ぶどう)山地や五頭(ごず)山脈、南半は弥彦(やひこ)・西山・道山(みちやま)・東山山地の第三紀丘陵列に抱かれた紡錘状の平野で、南北100キロメートル、東西10～25キロメートル、面積2070平方キロメートルに及ぶ。南半は地向斜谷をなす長岡窪地帯(ながおかくぼちたい)を信濃川(しなのがわ)とその支流によって埋積され、三条辺りまでを中越平野(ちゅうえつへいや)とよぶ。阿賀野(あがの)川以北の北半は新発田(しばた)窪地帯を、県境から流れ出す加治川、胎内(たいない)川、荒川、三面(みおもて)川で埋め立てられ、前面は新旧数列の砂丘でふさがれている。砂丘裏には多くの潟湖(せきこ)群が連なり、1645年（正保2）の越後国絵図に、鎧潟(よろいがた)、佐潟(さかた)、大潟、田潟、白蓮(びゃくれん)潟、鳥屋野(とやの)潟、島見(しまみ)十三潟、福島潟、紫雲寺(しうんじ)潟、岩船(ゆわふね)潟など大小20余の沼沢地が描かれている。

　近世越後諸藩は、この低湿なラグーンを分水によって干拓する治水事業に全力を注ぎ、全国一の越後米産地の基盤を築いた。その水との闘いに終止符を打ったのが阿賀野川の松崎浜堀割と、新信濃川分水であった。第二次世界大戦前後からは各河川で大排水機場が完備され、動力排水による地下水面の低下が計られ、さらに土地改良事業や国営潟湖干拓事業が進められて、かつての湿田地帯も二毛作の可能な干田に変わり、現在は本県米産額の65％を占めている。第二次世界大戦後は、古くからこの低湿地帯で家庭用に利用されていた浅い水溶性天然ガスの工業化が急激に進捗(しんちょく)し、多量の地下水のくみ上げで地盤沈下現象をおこし、大問題となり、1960年ころから全面中止された。新潟市を中心とする県下20市の大半はこの平野に集中し、機械、金属、化学、繊維などの工業地帯を形成している。また、砂丘や自然堤防上では果樹園芸農が盛んで、チューリップ、ヒヤシンスなどの球根栽培や盆栽類の全国的産地になっている。

［山崎久雄］

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