Kaiga

A large river that flows through North China. It is also called the Gu River. The five rivers Chaobai River, Yongding River, Daqing River, Ziya River, and Wei River join near Tianjin and are called the Hai River. It flows east and empties into the Bohai Sea at Dagu Kou. The Wei River, the longest of the five major rivers, has a total length of 1,090 km, is 69 km downstream from the confluence, and the drainage area of ​​the entire system reaches 264,000 square kilometers north of the Yellow River. The five great rivers originate in the Yanshan Mountains, Taihang Mountains, Wutai Mountains, Hengshan Mountains, and the Loess Plateau, respectively, and carry large amounts of sediment downriver. In addition, the rivers flood at the same time, and the gradient of the river in the lower reaches is extremely gentle, so drainage is poor and they often cause major floods. In 1939, Tianjin city was flooded above the river floor for two months. The Yongding River, as its former name Wuding River suggests, was also a dangerous river that frequently changed course.

After the liberation, flood control works were started, and especially after the fall of 1963, when another major flood occurred. In the middle and lower reaches, spillways such as Duliu Genga, Yongding Xinhe, Ziya Xinhe, and Chaobai Xinhe were excavated, and in the upper reaches, large dams such as Miyun, Guangdeng, and Gangnan were constructed to regulate floods, as well as to ensure a stable supply of water for urban areas and generate hydroelectric power. Furthermore, the People's Victory Canal was opened in the upper reaches of the Wei River, and irrigation water is also being taken from the Yellow River. Part of the Chaobai River in the Hai River system is called the North Canal, and the lower reaches of the Wei River are called the South Canal, because they were incorporated into the Grand Canal. The South Canal is still used today as an important waterway in the North China region, and is also scheduled to be incorporated into the eastern route of the South-to-North Water Diversion Project, which is currently being planned to send water from the Yangtze River (Changjiang) to Tianjin and Beijing.

[Kono Michihiro]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

中国、華北地区を流れる大河。沽河(こが／クーホー)ともよばれる。潮白河(ちょうはくが／チャオパイホー)、永定河(えいていが／ヨンティンホー)、大清河(だいせいが／ターチンホー)、子牙河(しがが／ツーヤーホー)、衛河(えいが／ウェイホー)の五つの河川が天津(てんしん／ティエンチン)市付近で合流して以後を海河とよび、東流して大沽(タークー)口で渤海(ぼっかい／ポーハイ)に注ぐ。五大河川中最長の衛河を基準とすると、全長1090キロメートル、合流点より下流は69キロメートル、全水系の流域面積は黄河以北の26.4万平方キロメートルに達する。五大河川はそれぞれ、燕山(えんざん／イエンシャン)山脈、太行(たいこう／タイハン)山脈、五台山(ごだいさん／ウータイシャン)、恒山(こうざん／ホンシャン)山脈および黄土高原上に源を発し、大量の土砂を流下する。そのうえ増水の時期が同時で、しかも下流部の流路勾配(こうばい)がきわめて緩やかなため、排水不良でしばしば大水害を生じ、1939年には天津市で床上浸水2か月に及んだこともあった。また永定河も旧名無定河の名のごとく、流路がしばしば変わる危険な河川であった。

　解放後治水工事が始まり、とくに1963年8月にまたも大水害を生じたので、同年秋以後治水工事が促進された。中・下流部には独流減河(どくりゅうげんが)、永定新河、子牙新河、潮白新河などの放水路が開削され、また上流には密雲(みつうん／ミーユン)、官庁(かんちょう／コワンティン)、崗南(こうなん／カンナン)などの大型ダムが建設され、洪水調節とともに都市用水の安定供給や水力発電が図られている。さらに衛河上流では人民勝利渠(きょ)が開かれ、黄河から灌漑(かんがい)用水の取水も行われている。海河水系の潮白河の一部は北運河とよばれ、また衛河の下流部は南運河とよばれるが、これは大運河の一部に組み込まれていたためである。現在も南運河は華北地区の重要な水上交通路として活用されており、また現在計画中の長江(ちょうこう／チャンチヤン)（揚子江(ようすこう／ヤンツーチヤン)）の水を天津、北京(ペキン)に送る南水北調計画の東ルートにも組み込まれることになっている。

［河野通博］

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