Wei River

A river in China. It is the largest tributary of the Yellow River. It is also called the Wei River or the Wei River. It originates in the Shanxi Mountains south of Weiyuan County in southern Gansu Province, flows east north of the Qinling Mountains, and flows through eastern Gansu Province and central Shaanxi Province, before joining the Yellow River where it makes a large bend to the east. It forms the Tianshui Basin in Gansu Province and the Wei River Plain in Shaanxi Province, and has a length of 787 km and a drainage area of ​​134,000 square km. The tributaries flowing in from the south are short and rapid, but those from the north have their drainage basins on the Loess Plateau, and many of the rivers, such as the Jing River and the Luo River, have wide catchment areas and slow currents, resulting in the development of a topography unique to loess soil. The plains made up of alluvial loess soil are fertile, but the topography and dry climate mean artificial irrigation is necessary, and in particular in the northern part of the Wei River Plain, artificial waterworks such as the Zhengguo Canal and Baiqu Canal have been constructed since ancient times. Even today, irrigation by the Luohui Canal, Jinghui Canal, and Weihui Canal makes the area one of the country's leading agricultural bases, with the cultivation of cotton, wheat, and other crops thriving. The area centered on Xi'an (Xian) in the river basin (Guanzhong) has been a cultural center since ancient times and is home to many historical ruins.

[Motohide Akiyama]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

中国の河川。黄河(こうが／ホワンホー)の最大の支流。渭水(いすい)、渭川(いせん)ともいう。甘粛(かんしゅく／カンスー)省南部渭源県の南、鳥鼠(ちょうそ)山に源を発し、秦嶺(しんれい／チンリン)山脈の北を東流、甘粛省東部、陝西(せんせい／シャンシー)省中部を貫流して、黄河が大きく東へ湾曲する地点で合流する。甘粛省では天水盆地、陝西省では渭河平原を形成し、延長787キロメートル、流域面積は13万4000平方キロメートルに達する。南から流入する支流は短く急流をなすが、北からの流れは黄土(こうど／ホワントゥー)高原に流域をもち、涇河(けいが／チンホー)や洛河(らくが／ルオホー)のように集水面積も広く緩流のものが多く、黄土特有の地形を発達させる。黄土の沖積土からなる平野は肥沃(ひよく)であるが、地形と乾燥気候のため人工灌漑(かんがい)が必要で、とくに渭河平原北部では古代から鄭国渠(ていこくきょ)、白渠などの人口水道がつくられた。現在も洛恵渠、涇恵渠、渭恵渠などの灌漑で、全国でも有数の農業基地となり、綿花、小麦などの栽培が盛んである。流域の西安(せいあん／シーアン)を中心とした地域（関中(かんちゅう／コワンチョン)）は、古代から文化の中心で多くの歴史的遺跡がある。

［秋山元秀］

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