Dongting Lake - Dongting Lake

Located in the north of Hunan Province, China, it is the second largest freshwater lake in China after Lake Poyang. It is located on the south side of the Yangtze River, has an area of ​​2,860 square kilometers, is 34.1 meters above sea level, and is 30.8 meters deep. In addition to the four major rivers of Hunan Province, the Xiangjiang, Yuanjiang, Lishui, and Zishui, which flow into the lake from the south and west, the Yangtze River flows into the lake during flood seasons through four waterways in the north: Songzi, Taiping, Guchi, and Zhaoxuan. It also drains into the Yangtze River at Chenglingji, Yueyang City, at the northeastern end.

Because it takes in and discharges such a large amount of water, the surface area of ​​the lake differs greatly between high and low water periods. In addition to the sediments from the four rivers, which flow in at 24 million cubic meters per year, the mud from the Yangtze River flows in at an average of 118 million cubic meters per year (82% of the total) through the four northern waterways, causing the lake surface to gradually shrink. In particular, a large inverted delta has developed in the north, and the lake has been reclaimed, so that what was once China's largest freshwater lake, known as "800 Li Dongting," is now smaller than Lake Poyang. The lake surface has also been divided into many large and small lakes, including the three Dongting Lakes in the East, West, and South, and Datong Lake. However, it is still one of China's important freshwater aquaculture bases, and produces a lot of lotus root. In addition, shipping routes have been opened to various parts of Hunan Province, such as Changsha, Changde, Yiyang, and Yueyang, as well as to Wuhan on the Yangtze River, and water transportation is thriving.

[Kono Michihiro]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

中国、湖南省北部にある湖で、鄱陽湖(はようこ)に次ぐ中国第二の大淡水湖。長江(ちょうこう／チャンチヤン)（揚子江(ようすこう)）の南側にあり、面積2860平方キロメートル、湖面の標高34.1メートル、水深は30.8メートルに及ぶ。南方および西方から湘江(しょうこう)、沅江(げんこう)、澧水(れいすい)、資水の湖南省の四大河川が注ぐほか、北方の松滋(しょうじ)、太平、藕池(ぐうち)、調弦(ちょうげん)の四つの水路を通って、増水期には長江の水が流入する。また、北東端の岳陽(がくよう／ユエヤン)市城陵磯(じょうりょうき)で長江に排水している。

　このように大量の水を呑吐(どんと)するため、増水期と減水期とでは湖面の面積に大差がある。しかも年2400万立方メートルも流入する4河川の堆積(たいせき)物のほか、とくに北方の4水路を通じて長江の泥が年平均1億1800万立方メートル（全体の82％）も流入する結果、湖面はしだいに縮小し、ことに北部では大面積の逆デルタが発達、さらに湖面干拓も行われたため、かつて「八百里洞庭」とよばれて中国最大の淡水湖であったものが、いまでは鄱陽湖より小さくなっている。湖面も分割され、東、西、南の三つの洞庭湖や大通(だいつう)湖など大小多数の湖水に分かれている。しかし現在も中国の重要な淡水養殖基地の一つであり、蓮根(れんこん)の産出も多い。また、長沙(ちょうさ／チャンシャー)、常徳、益陽、岳陽など湖南省各地のほか、長江沿岸の武漢(ぶかん／ウーハン)などとの間にも航路が開け、水運が盛んである。

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