Information about the Pearl River

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

Formerly known as Yuejiang, it is the third longest river in China and the second largest river in China in annual flow. 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.

Night Pearl River-In Ren Minqiao, Guangzhou, its main stream, Xijiang, originates from Maxiong Mountain in Zhanyi County, Qujing City, northeast Yunnan Province, and the main stream flows through Yunnan, Guizhou, Guangxi (autonomous region), Guangdong Province, 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.

Pearl River, the southern river of China. 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 change and uneven spatial and temporal distribution lead to frequent natural disasters such as floods, droughts, salinization and so on.

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. [Edit this paragraph] There are many tributaries of the Pearl River system, with a total of six tributaries, with a drainage area of 1 000 km2, namely Beipanjiang, Liujiang, Yujiang, Gui Jiang, Hejiang and Lianjiang.

2. 1 Xijiang River System

Xijiang River, the main stream of the Pearl River, originates from Nanpanjiang River, originates from the eastern foot of Maxiong Mountain, the residual vein of Wumeng Mountain in Qujing City, Yunnan Province, and meanders from west to east through Yunnan, Guizhou, Guangxi and Guangdong to Modaomen South China Sea in Zhuhai City, Guangdong Province, with a total length of 22 14km, an average gradient of 0.58 ‰ and a catchment area of 353 120km2. Among them, Xijiang River The main stream of Xijiang River from its source to the mouth of Beipanjiang River is called Nanpanjiang River. The confluence of Nanpanjiang and Beipanjiang to Liujiang is called Hongshui River; The junction of Liujiang River and Yujiang River is called Qianjiang River; Yujiang junction to Guijiang junction is called Jiang Xun; The river network area where Gui Jiang meets the delta is called Xijiang River. Nanpanjiang River and Hongshui River are upstream, Qianjiang River and Jiang Xun River are midstream, and Xijiang River is downstream. Among the first-class tributaries of Xijiang River, the basin areas of Beipanjiang, Liujiang, Yujiang, Gui Jiang and Hejiang exceed 10000 km2.

Nanpanjiang River is 9 14km from its source to Shuangjiang estuary in Zhexiang, Wangmo County, Guizhou Province, with a drainage area of 56880km2 and an average river gradient of 1.74 ‰. There are eight first-class tributaries with a drainage area of 1000278km or more, namely Haikou River, Bajiang River (Bapanjiang), Huaxi River (Qujiang River, Jiudian River), Lujiang River, Dianxi River, Qingshui River, Huangni River and Mabie River (also known as Qingshui River, with Chuchang River in the upper reaches), among which Huangni is the largest tributary of Nanpanjiang River in Huiren. Followed by Qingshui River, which originates from Laoyin Mountain in Qiubei County, Yunnan Province, with a river length of 18 1km and a catchment area of 5376km2.

Hongshui River starts from Shuangjiangkou and ends at Sanjiangkou, Shilong, Xiangzhou County, Guangxi, with a total length of 659km and a catchment area of 54870km2, with an average gradient of 0.366 ‰. There are 1 1 of the first-class tributaries with a watershed area exceeding 1000km2, namely Beipanjiang, Lianjiang (Mengjiang), Niuhe (Bailong), Buliu, Qingshuihe (Nandan), Blessing, Liang Qi, Pingzhi, Diaojiang, Qingshuihe and Beizhijiang. Beipanjiang, the largest tributary, originates from the northern foot of Maxiong Mountain in Qujing City, Yunnan Province, with a catchment area of 26590km2 and a river length of 444km, with an average gradient of 2.8 ‰. Followed by Lianjiang, which originated in Zhang Ke Village, Guiyang City, with a drainage area of 8607km2 and a river length of 241km; Thirdly, Niuhe River originated in Jiajiashan, dushan county, Guizhou Province, with a catchment area of 5843km2 and a river length of 235km.

The Qianjiang River of the Pearl River starts from Sanjiangkou and ends at the confluence of Guiping County, with a total length of 122km, an area of 22 10 km2, and an average river slope of 0.0625 ‰. There are 1 of the first-class tributaries with a watershed area exceeding 1000km2, namely Liujiang River. Liujiang River originates from Jiujiutan in the south of dushan county, Guizhou, with a total length of 755km and a catchment area of 58270km2.

Jiang Xun starts from Yujiangkou and ends at Gui Jiang at the confluence of Wuzhou City, with a total length of 172km, an area of 20570km2 with an average river slope of 0.0968 ‰. There are four first-class tributaries with basin area exceeding 1000km2, namely Yujiang River, Baisha River, Mengjiang River and Beiliu River. Yujiang River originates from Jiulong Mountain in Guangnan County, Yunnan Province, with a drainage area of 89870km2 (including 78280km2 in China), a river length of 1 145km, and an average river slope of 0.33 ‰. It is the largest first-class tributary of Xijiang River. Baisha River (Baisha River) originates from Tiandingling, Shapo Township, Guiping County, with a river length of 102km and a catchment area of 1 155km2. Mengjiang River originated in San Shancun, Jinxiu County, with a total length of 189km and a drainage area of 3895km2. Beiliu River originates from the top of Sanshan Mountain in Beiliu County, with a total length of 259 kilometers and a catchment area of 9,359 square kilometers.

The Xijiang section of the main stream of the Xijiang River starts at the mouth of Gui Jiang and ends at Sixianjiao, Sanshui County, Guangdong Province. The section length is 208km, the catchment area is 43860km2, and the average river gradient is 0.086 ‰. The tributaries whose catchment area exceeds 1000km2 are Gui Jiang, Hejiang, Luoding and Xinxing River. Gui Jiang originates from the south side of the border of North Laoshan Mountain in Mao 'er Mountain, Xing 'an, Guangxi, with a total length of 438km, catchment area of 18790 km2 and average river gradient of 0.43 ‰. Hejiang River originates from Man Zi Ridge, fuchuan county, Guangxi, with a total length of 338km and a catchment area of 1 1590km2, with an average gradient of 0.58 ‰. Luoding River originates from Jilong Mountain in Xinyi County, Guangdong Province, with a total length of 20 1km and a catchment area of 4493km2. Xinxing River originates from Dalushan, Enping County, Guangdong Province, with a length of 145km and a drainage area of 2355km2.

There are many plateau lakes in Nanpanjiang River basin in the upper reaches of Xijiang River, the main stream of the Pearl River, including Fuxian Lake, Xingyun Lake, Yangzonghai Lake, Qilu Lake, Yilong Lake, Datunhai Lake and Changqiaohai Lake. These lakes have a total area of 388km2, controlled catchment area of 2742km2, annual average inflow of 6170,000 m3, and total water volume of 019.7 million m3.

2.2 Beijiang River System

Beijiang River is the second largest water system in the Pearl River Basin. Its main source is Mianshui, which originates from Xixiwan, Xinfeng County, Jiangxi Province, with a total length of 468km and a drainage area of 467 10 km2, accounting for 10.3% of the Pearl River Basin area. 92% of its basin area is in Guangdong province, and the rest are in Jiangxi and Hunan provinces. The main source of Beijiang River is Zhenshui, which originated in Xixiwan, Xinfeng County, Jiangxi Province. Its main stream is 468 kilometers long. Originated in Xiwan, Qiaodabang, Xinfeng County, Jiangxi Province, it flows through Nanxiong, Shixing, Qujiang, Shaoguan, Yingde, Qingyuan and other counties and cities in Guangdong Province. At Sixianjiao, Sanshui County, it joins the Xijiang River. Some water flows to the west, others to the east.

The total drop of Beijiang River is about 3 10/0m, with an average gradient of 0.26 ‰. From the source to the end of Shazhou in Shaoguan, it is upstream, from the end of Shazhou to Feilaixia in Qingyuan, and from Feilaixia to Luobei in Sixian County, Sanshui County, it is downstream. The main tributaries of Beijiang River system are Wujiang, Pujiang, Lianjiang and Suijiang.

Wujiang River originates from Sanfengling, Wuxian County, Hunan Province, with a total length of 260km and a catchment area of 7097km2, with an average gradient of 0.9 1 ‰. Pujiang originated in Du Dong, Yuyuan County, Guangdong Province, with a total length of 173km, a drainage area of 4847km2 and an average river gradient of 1.24%. From the source to the southwest, it flows through Yuyuan County and joins Xiaobeijiang River at Shizikou, Yingde County. Lianjiang, the largest tributary of Beijiang River, originates from the ground stone in Xingziwei, Lian County, Guangdong Province, with a total length of 275km, catchment area of 1006 1km2 and an average river slope of 0.77%. . Suijiang River originates from Wuyaling, Jixian County, Guangdong Province, with a total length of 226km, a catchment area of 7 1.84 km2 and an average river gradient of 0.25 ‰.

2.3 Dongjiang River System

Dongjiang River is the third largest water system in the Pearl River Basin, originating from Yajipo, Xunwu County, Jiangxi Province, with a total length of 520km, a catchment area of 27040km2, a total drop of about 440 meters and an average river slope of 0.39 ‰. After Xunwu River joins Dingnan Water, its source is called Dongjiang River. The source of Heheba in Longchuan County is the upper reaches of Dongjiang River, and Heheba to Guanyinge in Boluo County is the middle reaches of Dongjiang River. Below Guanyin Pavilion is the lower reaches of Dongjiang River. The main stream of Dongjiang River flows through Longchuan, Heyuan, Zijin, Huiyang, Boluo, Dongguan and other counties and cities in Guangdong, and flows into the Pearl River Delta in Shilong Town, Dongguan.

The main tributaries of Dongjiang River system are: Beiling Water (also known as Anyuan Water), Xinfeng River and Xizhijiang River.

Beiling Water originates from Daji Village, Anyuan County, Jiangxi Province, flows through Anyuan County, dingnan county County and Longchuan County, Guangdong Province, and flows into the main stream of Dongjiang River at Longchuan River Dam, with a total length of 140km and a catchment area of 2364km2. Xinfeng River originates from Yutian Dianbing (Qixingling) in Xinfeng County, Guangdong Province, and flows into the main stream of Dongjiang River in Yuancheng District of Heyuan City, with a total length of 163km, a catchment area of 58 13 km2 and an average gradient of 1.29‰. Xizhijiang River originates from Zhu 'ao, Huidong County, and flows into the main stream of Dongjiang River in Huicheng District, Huizhou City, with a total length of 190km and a catchment area of 4 103km2, with an average gradient of 0.6 ‰.

2.4 Pearl River Delta Water System

The water system in the Pearl River Delta includes the river network system below Xijiang River, Sixian River in Beijiang River, Shilong River in Dongjiang River and rivers flowing into the Pearl River Delta, with a drainage area of 26820km2, accounting for 5.9 1% of the total drainage area. Total length of waterway in river network area 1600km.

The river network in the Pearl River Delta integrates the lower reaches of Xijiang River, Beijiang River and Dongjiang River, but their main streams are divided into systems after discharge. Xijiang River runs from Sixian West Exit of Sanshui County to Qirenshi reach of Zhuhai City, which is called Xijiang main stream waterway, Xihai waterway and Modaoshi waterway respectively, and finally passes through Modaomen Sea. The Beijiang River starts from the north mouth of Sixian River, which is called Beijiang main channel, Shunde channel and Shawan channel respectively, and finally flows out of Humen and into Lingdingyang via Shiziyang. Dongjiang estuary in the Pearl River Delta is the main stream of Dongjiang River north below Shilong, surrounded by people and lions in Zengcheng Fish Cave.

The rivers flowing from west to east in the Pearl River Delta are Tanjiang River (Jinshui), Gaoming River and Shapingshui River (Xilao River). Delta rivers flowing from north to south include Liuxi River, Zengjiang River, Shahe River, Xifu River, Yayaoshui River and Nangang River. Delta rivers flowing from east to west include cold current and so on. In addition, there are Maozhou River and Shenzhen River, which flow directly into the ocean.

Tanjiang River originates from Wufengfeng, Siping County, Guangdong Province, and flows out of Yamenhai to Yinzhou Lake, Xinhui District, with a total length of 248 kilometers and a catchment area of 5,068 square kilometers, with an average gradient of 0.45 ‰. Gaoming River originates from the top of Tray in Gaoming County, Guangdong Province, and finally flows into the main channel of Xijiang River at the intersection of Gaoming County, with a total length of 86km and a catchment area of 1, 0 10 km2, with an average gradient of 0.45 ‰. Liuxi River originates from Guifeng Peak, Guangdong Province, and flows into the White Swan Pond Zhukang, with a length of 174km, a catchment area of 39 17 km2 and an average river slope of 0.8‰. Shahe River originates from Pangfeng, Boluo County, and flows into the main stream of Dongjiang River in Shilong, Dongguan, with a total length of 89 kilometers, a catchment area of 1.235 square kilometers and an average river slope of 0.64%. Ceng He originated in Qixingling, Longmen County, and belongs to the main stream of Liujiapu Liudong River, with a total length of 203km, catchment area of 3 1 14 km2 and average river slope of 0.74‰.

2.5 seaport

River runoff from the Pearl River system gathers in the delta and flows into the South China Sea through eight rivers. The exit of each waterway is called a "door". The Pearl River has eight exit doors, which are called Eight Doors. Lingdingyang (also known as the Pearl River Estuary) in the east has four entrances, namely Humen, Jiaomen, Hongqimen (Li) and Hengmen from east to west; In the west, there are sharpening gates, crowing gates, tiger jumping gates and cliff gates.

Humen is located in Shajiao, Dongguan. The runoff injected into Lingdingyang through Humen includes all the runoff from Dongjiang River, part of the runoff from Xijiang River and Beijiang River, and part of the runoff from the Pearl River Delta itself. Humen is a gate with strong tidal action, and its tidal throughput ranks first among the eight gates, with the maximum tidal range of 2.59 m and the maximum tidal range of 3.12 m. The annual runoff of Humen is 60.3 billion m2, accounting for 65.438+08.5% of the total runoff of the Pearl River, and the annual sediment discharge is 6.58 million t, accounting for 9.3% of the total sediment discharge of the Pearl River.

Jiaomen is located in Guangxingwei, Panyu County, about 8 kilometers west of Humen River, and is the outlet of Jiaomen Waterway. The annual runoff of Jiaomen is 56.5 billion m3, accounting for 65.438+07.3% of the total runoff of the Pearl River, and the annual sediment discharge is12.89 million t, accounting for 65.438+08. 1% of the sediment discharge of the Pearl River. The maximum tidal range is 2.72m, and the maximum tidal range is 2.81m.

Hongqimen (Li) is located in Likou, Panyu County, which is the estuary of Hongqi Waterway. The annual runoff of Hongqimen (Lishui) is 20.9 billion m3, accounting for 6.4% of the total runoff of the Pearl River, and the annual sediment discharge is 565,438+700,000 t, accounting for 7.3% of the total sediment discharge of the Pearl River. The maximum tidal range is 2.79 m and the maximum ebb range is 2.57m m.

Hengmen is located in Hengmen Mountain, Zhongshan City, 4 kilometers away from Hongqimen, which is the mouth of Hengmen Waterway. The annual runoff at Hengmenkou is 36.5 billion m3, accounting for 1 1.2% of the total runoff in the Pearl River, and the annual sediment transport is 9.25 million t, accounting for 13% of the total sediment transport in the Pearl River.

Modaomen, located in Qirenshi, Hongwan, Zhuhai, is the main outlet of Xijiang River runoff. Modaomen's annual runoff is 92.3 billion m3, accounting for 28.3% of the total runoff of the Pearl River, and its annual sediment transport is 2310.4 million t, accounting for 33% of the total sediment transport from the Pearl River into the sea. The maximum tidal range of the sharpening gate is 1.9m, and the maximum tidal range is 2.29m.

Jitemen is located in Dalin, Doumen County, adjacent to the west side of the sea area in Modaomen, and is the mouth of Jitemen waterway. The annual runoff of Jiti Gate is 65.438+09.7 billion m3, accounting for 6. 1% of the total runoff of the Pearl River, and the annual sediment transport is 4.96 million t, accounting for 7% of the total sediment transport of the Pearl River. The maximum tidal range is 2.44m, and the maximum tidal range is 2.71m. Jiti sluice is a sea gate formed after the plugging project of 1959 Niwan sluice is completed. Prior to this, Niwan Gate was located at the upstream of Jiti Gate 16km, which was one of the eight outlets of the Pearl River.

Hutiaomen, located in Doumen County, is the mouth of Hutiaomen Waterway. The annual runoff of Hutiaomen is 20.2 billion m3, accounting for 6.2% of the total runoff of the Pearl River into the sea, and the annual sediment transport is 5.09 million t, accounting for 7.2% of the total sediment transport of the Pearl River into the sea. The maximum tidal range is 2.5 1m and the maximum tidal range is 2.66m m.

Yamen, located in the south of Yanan, Xinhui County, is the entrance of Yinzhou Lake, and it and Hutiaomen are located on the head of Huangmaowan. Yamen is the westernmost point of the eight gates of the Pearl River, and the runoff in the Tanjiang River basin mainly goes out to sea from Yamen via Yinzhou Lake. The annual runoff of Yamen is 65.438+09.6 billion m3, accounting for 6% of the total runoff of the Pearl River, and the annual sediment transport is 3.63 million t, accounting for 5. 1% of the total sediment transport of the Pearl River. The maximum tidal range is 2.73 meters, and the maximum ebb range is 2.95 meters. Its length and basin area rank second in China. [Edit this paragraph] Natural characteristics of the basin 3. 1 landform

The Pearl River lies between east longitude10214 ′ ~1553 ′ and north latitude 2131′~ 26 49 ′. The basin is surrounded by mountains, bounded by Nanling and Miaoling in the north, Wumeng Mountain in the northwest and Wangliangshan in the west. In the southwest, Ailao Mountain is separated from the Red River Basin. There are 100,000 mountains, 60,000 mountains, Yunkai mountains, cloud mountains and rivers in Guangdong and Guangxi in the south. To the east, Wuyi Mountain Range, Lianhua Mountain Range and Hanjiang River Basin are the boundaries. Zhongshan is the main mountainous area in the Pearl River Basin, with individual peaks as high as 2000 meters, and the highest is Wumeng Mountain, with an altitude of 2866 meters. ..

The topography of the basin is generally high in the west and low in the east, high in the north and low in the south. The former causes the Xijiang River and its largest tributary, the Yukang River, to flow from west to east, while the latter causes the main streams of the East and Beijiang Rivers and the first-class tributaries of Nanpanjiang River, Beipanjiang River and Xijiang River to flow from north to south in the Pearl River Delta and Xikang River respectively.

The Pearl River Basin is mainly composed of three macro geomorphic units, namely Yunnan-Guizhou Plateau, Guangxi Basin and Pearl River Delta Plain. There is a transition or separation of mountains and hills between the three geomorphic units, and Guangxi basin is the main body of the basin.

There are three basic types of landforms in the Pearl River Basin: mountains, hills and plains. Mountainous areas account for more than 60% of the basin area, with Zhongshan (1000 ~ 1500 m) as the main area, and most of the mountains are northeast-northeast. Hills are generally distributed in front of the mountain, or around the basin and on both sides of the valley, accounting for more than 20% of the total area of the basin, mainly distributed in the southeast of the basin. The plain area of Zhukang Basin is small, including small high plains in the middle and upper reaches of mountain basin, valley plain and delta alluvial plain at low altitude.

The strata in the Pearl River Basin are diverse in lithology, and sedimentary rocks, magmatic rocks and metamorphic rocks are all distributed. Sedimentary rocks are exposed from pre-Sinian to Quaternary, among which Devonian, Carboniferous, Permian and Triassic are the most developed. Magmatic rocks are concentrated in eastern Guangxi and Guangdong, and the exposed area accounts for 22% of the basin area, of which granite accounts for the vast majority.

3.2 Climate and Hydrology

The Pearl River Basin has a subtropical climate with an annual average temperature of 14 ~ 22℃. There is little annual change, but there are great regional differences. The highest temperature is 42℃ and the lowest temperature is -9.8℃. The relative humidity for many years is between 7L% and 82%. The annual average wind speed is 0.7 ~ 2.7m/s, and the maximum wind speed is 30m/s. The average sunshine hours for many years 1282 ~ 2243h, including 2243h in Nanpanjiang Luliang and Tiane in Hongshui River 1282h. The sunshine is most distributed in July and August in a year, about180h per month; At least in February and March, about l00h per month. There is abundant rainfall in the basin, with the average precipitation for many years 1470mm. Precipitation decreases from east to west, with more precipitation in mountainous areas and less precipitation in plain valleys. In the upper reaches of Zengjiang River, Shang Ping Station in Longchuan County has the largest precipitation, with an average annual precipitation of 2574mm；; The average annual precipitation at Yupupu Station in Mengzi County, southeast Yunnan is the smallest, which is 720mm. ..

The total water resources of rivers in the Pearl River Basin is 336 billion m3, of which the total human runoff is 326 billion m3. The annual runoff of Xijiang River (above the west exit of Sixianjiao) is 230 billion m3, accounting for 68.5% of the annual runoff of the whole basin. The annual runoff of Beijiang River (above the north exit of Sixianjiao) is 565.438+0 billion m3, accounting for 65.438+05.2% of the annual runoff of the whole basin. The annual runoff of Dongjiang River is 25.7 billion m3, accounting for 7.6% of the total runoff in the whole basin. The annual runoff of delta rivers is 29.3 billion m3, accounting for 8.7% of the total runoff in the whole basin. The change of natural runoff is mainly influenced by climate and underlying surface, and the regional distribution of annual runoff depth is basically consistent with that of areas with large annual precipitation. The annual variation of runoff is mainly precipitation, concentrated in the flood season, and the runoff accounts for 75% ~ 85% of the whole year.

Water surface evaporation in different parts of the basin is related to factors such as temperature, humidity and wind speed. The average annual evaporation in the basin is 900 ~ 1600 mm, with low evaporation in the north and high evaporation in the southeast. The measured maximum evaporation in the basin is 1635.5mm, and the measured minimum evaporation is 808.9mm at Yuguopu Station in Mengzi County, Yunnan Province, and at leye county Station in Guangxi.

The Pearl River has the smallest sediment concentration among the seven rivers in China, with an average sediment concentration of 0.27 kg/m3 for many years. Although the sediment concentration is small, due to the large annual runoff, the average annual sediment transport in the whole basin still reaches 88.72 million t. The sediment concentration varies greatly during the year, ranging from 0.14 to 0.53 kg/m3 in flood season and from 0.02 to 0.07 k8/m3 in non-flood season. Different river systems and different river sections have different sediment concentrations. The upper reaches of Xijiang River system are the largest reach in the whole basin because of its steep ground slope and poor vegetation. The annual average sediment concentration of Dadukou Station in the upper reaches of Beipanjiang River is 2.6 1k8/m3, the annual average sediment discharge is1040,000 t, and the annual sediment concentration of the first tributary in the middle reaches of Xijiang River system is 0.067 ~ 0.34kg/m3. The average sediment concentration in Swan Station of Hongshui River in the main stream of Xijiang River is 0.9 1 kg/m3. The sediment concentration in Beijiang River and Dongjiang River is less than that in Xijiang River, and the average sediment concentration in Shijiao Station of Beijiang River and Boluo Station of Dongjiang River is 0. 13 kg/m3. The lowest sediment concentration is at Zou Wei Station of Qingshuihe River in Guangxi, with an average of 0.067 kg/m3 for many years.

Historically, the floods that caused the great floods in the Pearl River Basin occurred in 1535, 1833, 188 1 902, 19 14 and/kloc-0. There have been 35 major floods, 2 16 minor floods, an average of 16 major floods and 2-3 minor floods in Yunnan province since the Yuan Dynasty. Since the Ming Dynasty, there have been major floods 17 times and minor floods 66 times in Guizhou Province, with an average of one major disaster in 27 years and one minor disaster in 7 years. Since the Han Dynasty, there have been six major floods 16 times and 290 minor floods in Guangxi. Since the Yuan Dynasty, major floods have occurred once every 40 years and minor floods once every two years. Since the Song Dynasty, there have been 33 major floods and 402 minor floods in Guangdong Province, with an average of one major disaster every 30 years and one minor disaster every 2-3 years.

1833 and 19 15 are the most serious floods in the whole basin. 1833, xuanwei county and Fuyuan counties in Yunnan province were affected, and 8 counties in Guizhou province were affected, with countless victims and dead. Many houses and fields in Cangwu, Guiping, Pingnan and Laibin counties in Guangxi were flooded, and Guangzhou, Xinhui, Shunde, Xiangshan, Nanhai, Panyu, Yingde, Lianxian, Qingyuan, Gaoyao, Sihui, Deguang, Fengchuan, Dongguan, Longmen, Boluo, Huiyang and Heping counties in Guangdong Province suffered heavy losses. 19 15 flood is a major historical flood in southern China, including Xijiang River, Beijiang River, Dongjiang River and some tributaries of coastal rivers in western Guangdong, and the upper reaches of Hanjiang River, Xiangjiang River, Ganjiang River and Minjiang River, covering an area of 500,000 km2. The water level of Wuzhou Station in Xijiang River reached 27.07m, and the flood peak discharge was 54,500m3/s. The flood affected 27 counties (cities) in the lower reaches of the Pearl River and the delta region, covering an area of 432,000 hm2, with 3.82 million people affected and more than 65,438+10,000 casualties.