Historical changes of the Pearl River

The Pearl River, or Pearl River, formerly known as Yuejiang, is the third largest river in China and the second largest river in China. The total length is 2400 kilometers. At first, it refers to a river from Guangzhou to the estuary, and later it gradually became the general name of Xijiang, Beijiang, Dongjiang and Pearl River Delta rivers. Its main stream, Xijiang River, originates from Maxiong Mountain in Zhanyi County, northeast Yunnan, and flows through Yunnan, Guizhou, Guangxi and Guangdong provinces (autonomous regions) and Hong Kong and Macao Special Administrative Regions. In Sanshui, Guangdong, it joins the Beijiang River and flows into the South China Sea from eight estuaries in the Pearl River Delta region. Almost all the Beijiang River and Dongjiang River systems are in Guangdong. The Pearl River Basin covers an area of 442,654,38+0,000 square kilometers in China and 65,438+0.654,38+0,000 square kilometers in Viet Nam.

The Pearl River is the largest water system in southern China (mainly in Guangdong Province), and it is also known as the seven major rivers in China along with the Yangtze River, Yellow River, Huaihe River, Haihe River, Songhua River and Liaohe River.

Night view of the Pearl River-rivers in the south of China, Pearl River, Ren Minqiao and Guangzhou. Formerly known as crossing the river. It used to refer to the waterway from Guangzhou to Humen, but now it is the floorboard of Xijiang, Beijiang and Dongjiang. The basin spans Yunnan, Guizhou, Guangxi, Guangdong, Hunan and Jiangxi provinces, covering an area of more than 452,000 square kilometers (including the area flowing through Vietnam 1 1,000 square kilometers). There are many tributaries of the water system, and the waterways are criss-crossed. Xijiang River is the mainstream of water system, which originated from Maxiong Mountain in Zhanyi County, Yunnan Province. The upper and middle reaches of the main stream are called Nanpanjiang River, Hongshui River, Qianjiang River and Jiang Xun respectively, hereinafter referred to as Wuzhou Xijiang River. The total length of the main stream is 2 129 kilometers, and the drainage area is 355,000 square kilometers. The main tributaries are Beipanjiang, Liujiang, Yujiang and Gui Jiang. The total drop is 2 130m. Huangguoshu Waterfall on Beipanjiang River falls as high as 70 meters. The positive source of Beijiang River is Mianshui, which originated in Xinfeng County, Jiangxi Province. I met Wushui near Shaoguan, called Beijiang. The water above Shaoguan is very urgent, and the river below Shaoguan is very straight, with Jiangge River and Lianjiang River flowing in. After crossing Yuzai Gorge and Feilai Gorge, it enters the plain. The river is wide and shallow, and flows into the Pearl River Delta at Sixian Corner. The main stream is 582 kilometers long. Dongjiang River originated in Dazhuling, Xunwu County, Jiangxi Province. The upstream source is called Xunwu Water, and the southwest flows into Guangdong Province. The upper reaches of the river are narrow and shallow, surrounded by mountains on both sides, and the main stream is 523 kilometers long.

The three rivers in the east, west and north alluvial into a small delta at the estuary, which is connected to form the Pearl River Delta, with an area of 1. 1.3 million square kilometers. At present, the front of each small delta is still developing into the sea at the speed of 100 meters per year. The delta river network is densely covered, with more than 0/00 large and small rivers/kloc, which communicate with each other and interweave into a network. Finally, it flows into the South China Sea through Humen, Jiaomen, Li Hongqi, Hengmen, Modaomen, Jiti, Hutiaomen and Yamen respectively. The Pearl River is rich in water resources, second only to the Yangtze River, and its shipping is also very developed. There are 10,000-ton seagoing ships under Huangpu Port in Guangzhou. The 1000-ton ships can go back to Xijiang to Wuzhou, and small ships can go to Liuzhou and Nanning. The waterway for ships and barges is nearly 5000 kilometers, and its shipping value is second only to that of the Yangtze River. The source of the Lijiang River in Gui Jiang is the Xiangjiang River in the Yangtze River valley through Lingqu. Pearl River Delta is one of the important producing areas of grain, sucrose, sericulture and freshwater fish in China.

The Pearl River runs through six provinces (autonomous regions) in southern China and northern Vietnam, including Yunnan, Guizhou, Guangxi, Guangdong, Hunan and Jiangxi, with a total length of 22 14km and a total drainage area of 453690km2, including 442 100km2 in China and1590km2 in Vietnam.

The Pearl River Basin is bordered by Wuling in the north, Nanhai in the south, Yunnan-Guizhou Plateau in the west, hilly basin in the middle and delta alluvial plain in the southeast, with high terrain in the northwest and low terrain in the southeast. The land resources in the whole basin are * * * 663 million mu, including 72 million mu of cultivated land and 0/89 million mu of woodland. The cultivated land rate is lower than the national average, and the per capita land in the basin is only 9.3 1 mu, which is about three-fifths of the national per capita land.

The Pearl River Basin is located in the subtropical zone, and the Tropic of Cancer runs through the middle of the basin, with a mild and rainy climate. The annual average temperature 14 ~ 22℃ and the annual average rainfall 1200 ~ 2200mm. The rainfall distribution obviously decreases gradually from east to west, and the rainfall distribution is uneven during the year, with great regional differences and great interannual changes.

The average annual runoff of the Pearl River is 336 billion cubic meters, including 238 billion cubic meters in Xijiang, 39.4 billion cubic meters in Beijiang, 23.8 billion cubic meters in Dongjiang and 34.8 billion cubic meters in Delta. The distribution of annual runoff is extremely uneven. The flood season from April to September accounts for about 80% of the total annual runoff, and it accounts for more than 50% in June, July and August. The Pearl River is rich in water resources, with a per capita water resource of 4,700 cubic meters, which is equivalent to 1.7 times of the national average. However, the interannual variation and uneven spatial and temporal distribution have caused frequent natural disasters such as floods, droughts and salinization in the basin.

The flood in the Pearl River basin has the characteristics of high peak, large volume and long duration. The main weather systems causing floods in this basin are flood peak or static peak and southwest trough, followed by tropical depression and typhoon. Rainstorms and floods often occur in June, July and August every year.

The dry season of the Pearl River Basin is generally from June 10 to March of the following year, and the average dry runoff for many years is 80.3 billion cubic meters, accounting for only about 24% of the annual runoff of the whole basin. The minimum flow rate of Wuzhou Station in Xijiang River in dry season is 720 cubic meters per second, Beijiang Cornerstone 130 cubic meters per second, and Boluo Station in Dongjiang River is 3 1.4 cubic meters per second.

The Pearl River is a river with little sediment, with an average sediment concentration of 0.249 kg per cubic meter for many years and an annual average sediment concentration of 88.72 million tons. According to statistical analysis, about 20% of the sediment is deposited in the net river area of the Pearl River Delta every year, and the remaining 80% is exported to the South China Sea through eight gates.

Tides in the Pearl River Estuary belong to an irregular semidiurnal tidal cycle. The Pearl River Estuary is a weak tidal estuary with a small tidal range, with an average tidal range of 0.86 ~ 1.6m and a maximum tidal range of 2.29 ~ 3.36m The annual average of total high tide in Bamen is 376.2 billion cubic meters, and the annual average of low tide is 702.2 billion cubic meters, with a net decrease of 326 billion cubic meters.