Huai River - Wai

A river that flows east between the Yellow River and the Yangtze River (Yangtze River) in China. It is also called the Huai River. It originates in the Tongbai Mountains in southwestern Henan Province, flows east north of the Dabie Mountains, passes through southern Henan Province and northern Anhui Province, enters Jiangsu Province, and flows into Lake Hongze. It is 845 km long upstream of Lake Hongze, and has a drainage area of ​​164,000 square km. Its main tributaries are the Hong River, Ying River, Xifei River, Yu River, Hou River, and Tuo River, which flow in from the north, and the Shi River and Higa River, which flow in from the south. The water of the Huai River that flows into Hongze Lake mainly flows out from Sanhe, passes through Gaoyou Lake, and flows into the Yangtze River at Sanjiangying in Jiangdu City, but some flows through the Subei Irrigation Main Canal and enters the Yellow Sea at the port of Biantan.

The Huai River was originally an independent river that flowed from Xuyi (the present-day entrance to Hongze Lake) through Huaiyin and Lianshui before entering the Yellow Sea at Yunti Pass. The Yi River and Shu River, which now flow into the sea separately, as well as the Si River, which flowed through the present-day Grand Canal, were also tributaries of the Huai River. When it was an independent river, the Huai River was about 1,000 km long and had a drainage area of ​​about 261,500 square km. The northern limit of the basin was the great dike on the south bank of the Yellow River from Zhengzhou to Liangshan and the Yimeng Mountains, and the southern limit was the Tongbai and Dayie mountain ranges and the Bei Wan Hills. At that time, the Huai River was a clear river, there were no floods, and there were no large lakes such as Hongze Lake in the downstream. However, as a result of the flood in 1194, part of the Yellow River, which mainly flowed north of Mount Tai, began to flow into the Huai River through the Si River channel, and then the course changed again, and this time the entire flow flowed southeast from Kaifeng, passed through Xuzhou, flowed into the Huai River, and entered the sea through Huaiyin. Thus, for more than 600 years until 1855, the situation of the "Yellow River taking over the Huai" was observed. During that time, the riverbed in the downstream area rose rapidly due to the large amount of sediment brought by the Yellow River, and the water of the Huai River had no outlet, so it flowed into the depression upstream from the confluence with the Yellow River, forming lakes such as Hongze Lake and Wabu Lake. Over time, the lake's area expanded in response to the rise in the riverbed, creating the large lake we see today. In 1855, the Yellow River moved north, and the large amount of sediment was no longer brought in, but the Huai River lost its original outlet, and even today, during periods of flooding, it is unable to discharge all the water that collects from the upper reaches, causing frequent flooding. After liberation, the excavation of the Subei Irrigation Canal made it possible to drain some of the water into the sea, but most of the water still had to be discharged into the Yangtze. To address this issue, more than 30 large dams were built in the upper reaches of each tributary, including at Foziling, Meishan, Xianghongdian, Tengyoshan, Nanwan, Boshan, Banqiao, and Baisha, and about 10 flood storage facilities were built in the midstream, making it possible to store more than 28 billion tons of water. They also expanded the waterways leading to the Yangtze, built spillways on the Yi and Shu rivers, and tried to straighten the rivers at the confluences of their tributaries in order to improve their flow. In the Shihe River basin south of the Huai River, they developed irrigation facilities in the hills (Shihang Irrigation District) using water stored in dams upstream. East of the Grand Canal, they worked to improve land productivity by drawing water from the Huai River to remove salt from the soil, and they also developed waterways.

Along with the Qinling River, the Huai River has been considered the border between the wet rice farming region in the south and the field crop farming region in the north, but recently, with the development of irrigation facilities in North China and other areas, wet rice cultivation has begun to appear in various places north of the Huai River.

[Kono Michihiro]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

中国、黄河と長江(ちょうこう／チャンチヤン)（揚子江(ようすこう)）の中間を東流する川。淮水ともいう。源を河南省南西部の桐柏(とうはく)山脈に発し、大別山脈の北方を東流、河南省南部、安徽(あんき／アンホイ)省北部を経て江蘇(こうそ／チヤンスー)省に入り、洪沢(こうたく)湖に流入する。洪沢湖より上流の長さ845キロメートル、流域面積16万4000平方キロメートル。主要な支流は、北方から流入する洪河(こうが)、潁河(えいが)、西淝河(せいひが)、渦河(かが)、澮河(かいが)、沱河(だが)などと、南方から流入する史河(しが)、河(ひが)などである。洪沢湖に流入した淮河の水は主として三河から流出し、高郵(こうゆう)湖を経て、江都(こうと／チヤントゥー)市三江営で長江に流入するが、一部は蘇北灌漑総渠(そほくかんがいそうきょ)を流れ、扁担(へんたん)港口で黄海に入る。

　淮河はもとは盱眙(くい)（現在の洪沢湖への流入口）から淮陰、漣水(れんすい)を経て雲梯(うんてい)関で黄海に入る独立河川であった。現在別々に海に入っている沂河(ぎが)、沭河(じゅつが)ならびに現在の大運河の流路を流れていた泗水(しすい)も淮河の支流であった。独立河川であった時代の淮河は長さ約1000キロメートル、流域面積は約26万1500平方キロメートルに達した。流域の北限は鄭州(ていしゅう／チョンチョウ)から梁山(りょうざん)までの黄河南岸の大堤防と沂蒙(ぎもう)山塊で、南限は桐柏、大別の両山脈と皖北(かんぼく)丘陵であった。当時は淮河は清流で、水害もなく、また下流部には洪沢湖などの大きな湖は存在しなかった。ところが1194年の洪水の結果、主として泰山(たいざん)以北を流れていた黄河の一部が泗水の河道を通って淮河に流れ込むようになり、その後また流路がかわり、今度は全流量が開封(かいほう／カイフォン)から南東に流れ、徐州(じょしゅう／シュイチョウ)を経て淮河に流れ込み、淮陰を経て海に入るようになった。こうして1855年まで、600年以上の長い間「黄河奪淮」の情況がみられた。その間黄河がもたらした大量の土砂のため下流部の河床が急速に高まり、淮河の水の出口がなくなったので、黄河との合流点から上流の窪地(くぼち)に流れ込み、洪沢湖、瓦埠(がふ)湖などの湖沼が形成された。湖の面積は、時代が下るにつれ、河床の上昇に対応して拡大し、現在のような大湖が生まれた。1855年黄河が北に移ったため大量の土砂はもたらされなくなったが、淮河はもとの出口を失い、いまもなお増水期には上流から集まる水を排出しきれず、しばしば水害をおこしている。解放後、蘇北灌漑総渠の開削により、一部の水は海に排水できるようになったが、大部分の水はなお長江に排出せざるをえない状況である。そこで各支流の上流部に仏子嶺(ぶっしれい)、梅山、響洪甸(きょうこうでん)、鮎魚(てんぎょ)山、南湾(なんわん)、薄山(はくさん)、板橋(ばんきょう)、白沙(はくさ)など30余の大型ダムを建設するとともに、中流部に10か所ほどの遊水施設を設けて、280億トン余の水の貯留を可能にした。また長江に通じる水路を拡大し、沂河、沭河には放水路を設け、各支流の合流点でも河道の直線化を図って流れをよくすることに努めている。また淮河南方の史河、河流域では上流のダムに蓄えた水を利用して丘陵地の灌漑(かんがい)施設を整備（史杭灌漑区）している。大運河以東では淮河の水を引いて土壌中の塩分を除くなど、土地生産性の向上に努め、また水上交通路の整備も行われている。

　淮河は秦嶺(しんれい)とともに南の水稲農業地域と北の畑作農業地域の境界とされてきたが、最近は華北などの水利の整備により水稲作が淮河以北でも各地にみられるようになった。

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