Comparison between the Yangtze River and the Yellow River

Yellow River: Geographical Environment

The mountainous and grassland plateaus from Heyuan to Guide belong to the Qinghai-Tibet Plateau. The peaks are all above 3000 meters above sea level; The upper valley is over 4200 meters above sea level. The terrain on both sides of the upper valley is gentle and the drainage is not smooth; Causing large areas of swamps and many lakes. Guide's reach from Jinmeng River is the Loess Plateau, with Xibe and Weihe valleys in Lvliang in the south, Ordos Plateau in the north and Lanzhou Valley in the west. The elevation of the Loess Plateau is generally 65,438+0,000 ~ 65,438+0,300 m, and the terrain is undulating, with steep slope and deep gully. The gully ground slope is 65,438+0.5 ~ 20 degrees, the gully area accounts for 40 ~ 50%, and the gully density is 3 ~ 5km/km2. Below Jin Meng, it enters the low-lying North China Plain, with an altitude of no more than 50 meters. After entering the downstream, the river channel is flat, and the average gradient is only 0. 12%. The water flow slows down and a lot of sediment is deposited, which is 4 ~ 5 meters above the ground. Due to the repeated diversions of the Yellow River, fan-shaped ancient riverbeds and ancient natural dikes are alluvial on the ground, becoming an inclined plain with alternating gentle hills and depressions, and the depressions are relatively open and flat.

River basin survey

The Yellow River reaches Hekou Town, Tuoketuo County, Inner Mongolia Autonomous Region, with a total length of 3,472 kilometers. The middle reaches are from Hekou Town to Taohuayu, Zhengzhou, Henan Province, with a river length of 1206 km. Below Taohuayu is the downstream, with a river length of 786 kilometers. There are many opinions on the division of the upper, middle and lower reaches of the Yellow River, and the division scheme of the Yellow River Water Resources Commission is adopted here. The Yellow River runs across China from east to west, with a length of 1.900 km from east to west and a width of1.654,38+0.000 km from north to south, with a total area of 752,443 square kilometers.

The Yellow River, like a lion with his head held high, crosses the mountains of Qinghai and Gansu provinces from the Qinghai-Tibet Plateau. Hetao Plain across Ningxia and Inner Mongolia; Pentium in the ravine between Shanxi and Shaanxi; Break through the "Longmen", turn around at the foot of Huashan Mountain in Xiyue, cross the North China Plain, and head for the coast of Bohai Sea. It flows through 9 provinces and autonomous regions and gathers more than 40 main tributaries and 1000 streams and rivers, with a journey of 5,464 kilometers and a drainage area of more than 750,000 square kilometers, making it the second longest river in China. The average annual precipitation in the whole basin is about 400 mm, while the average annual runoff of the Yellow River is only 57.4 billion cubic meters, ranking eighth among Chinese rivers. There are more than 200 million mu of cultivated land in the basin, and the population is about 654.38+0 billion along the Yulu River downstream.

The average natural runoff of the whole Yellow River for many years is 58 billion cubic meters, the average annual runoff depth of the basin is 77 mm, the per capita water volume of the basin is 593 cubic meters, and the cultivated land is 324 cubic meters.

The middle reaches of the Yellow River flow through the Loess Plateau. Due to soil erosion, tributaries bring a lot of sediment, making the Yellow River the largest river with sediment concentration in the world. The annual maximum sediment discharge is 3965438+ 1 100 million tons (1933), and the maximum sediment concentration is 920kg/m3( 1977). The average sediment discharge of Sanmenxia Station for many years is about 65.438+0.6 billion tons, and the average sediment concentration is 35 kg/m3.

branch

The main tributaries of the Yellow River are Baihe, Heihe, Huangshui, Zuli, Qingshui, Dahei, Kuye, Wuding, Fenhe, Weihe, Luohe, Qinhe and Dawenhe.

Weihe River is the largest tributary of the Yellow River.

Major lakes

There are Zhaling Lake, Eling Lake, Wuliangsuhai Lake and Dongping Lake.

Mainstream canyon

There are 30 canyons in the main stream of the Yellow River, 28 in the upper reaches and 2 in the middle reaches. The lower reaches flow through the North China Plain without canyons. The canyon section of the main stream is 1707 km long, accounting for 3 1.2% of the total length of the main stream.

Yangtze River: [Edit this section] Overview of the main stream

The names of the main stream of the Yangtze River are different: the name from the source to Dangqukou (called "Qu" in Tibetan) is the main source of the Yangtze River, with a total length of 358 kilometers; From Dangqukou to Batang Estuary in Yushu County, Qinghai Province, it is called Tongtianhe, with a length of 8 13 km; Batangkou to Minjiang Estuary in Yibin, Sichuan, known as Jinsha River in ancient times, is 2308 kilometers long; Yibin's Minjiang River estuary is about 2800 kilometers away from the Yangtze River estuary, commonly known as the Yangtze River. Yibin and Yichang in Hubei Province are called "Chuanjiang" (the Three Gorges section from Fengjie to Yichang is also called "Xiajiang"), Zhicheng in Hubei Province is called Jingjiang, and Yangzhou and Zhenjiang in Jiangsu Province are also called Yangtze River below. Plateau and mountainous areas account for 65.6% of the basin area; Hills account for 24%; Plains and lowlands account for 10.4%.

There are 48 tributaries of the Yangtze River, covering an area of 6.5438+0 million square kilometers; More than 50,000 square kilometers are Yalong River and Minjiang River and their tributaries, including Dadu River, Jialing River, Wujiang River, Yuanjiang River, Xiangjiang River, Hanjiang River and Ganjiang River. Among them, the Yalong River, Minjiang River, Jialing River and Hanjiang River are more than 65,438+10,000 square kilometers, and the Jialing River basin has the largest area, about160,000 square kilometers.

Most of the freshwater lakes in China are distributed in the middle and lower reaches of the Yangtze River, with Poyang Lake, Dongting Lake, Taihu Lake, Hongze Lake and Chaohu Lake in larger areas.

The Yangtze River originates in Tanggula Mountain, southwest of Gladin, the main peak of Tanggula Mountain. Glaciers are widely distributed here, and the melting water of ice and snow of Jiang and Diru Glaciers is the source of the Yangtze River. From Jiangyuan to Hekou, it can be divided into three sections.

Yibin City, Sichuan Province, hereinafter referred to as the Yangtze River; Above Yichang, Hubei is the upper reaches of the Yangtze River; From Yichang to Hukou, Jiangxi is the middle reaches of the Yangtze River; From the mouth of the lake to the mouth of the sea (Chongming Island) is downstream. The upper reaches are about 3,500 kilometers long, and the Chumar River is the northern source of the Yangtze River. Muluwusu River is the southern source of the Yangtze River, with long water flow and large water volume. According to the principle that the source of the Yangtze River is only far away, Tuotuo River, its longest tributary, should be the positive source of the Yangtze River. The section from Dangqu estuary to Yushu in Qinghai is called Tongtianhe, which is 8 13 kilometers long. The river is wide and the water is slow. From Yushu to Yibin, it is called Jinsha River, which was called Lishui in ancient times. From north to south, it crosses the Hengduan Mountains, turns northeast near Shigu in Yunnan, enters the Sichuan Basin, and joins the Minjiang River in Yibin, with a total length of 2,300 kilometers. Known as the Yangtze River after Yibin. The middle reaches are about 1000 km long, and are commonly known as Chuanjiang because they flow through the Sichuan Basin. From Yibin to Chongqing, the river is quite tortuous. This river runs from Baiti Mountain in Fengjie to Nanjinguan in Yichang, passing through the Grand Canyon in the mountainous area at the junction of Sichuan and Hubei. From west to east, there are Qutang Gorge, Wuxia Gorge and Xiling Gorge, collectively known as the Three Gorges, with a total length of 204 kilometers. There are rapids everywhere on the beach, and the river gap is very large. It has been called the natural barrier of the Yangtze River since ancient times. The downstream reach is about1850km long, with small river drop, slow water flow and wide river surface, generally more than 2km, with the narrowest point of 650m.

The river course is very tortuous, especially from Zhijiang, Hubei Province to Chenglingji, Hunan Province, which is called Jingjiang in ancient times and is known as the "nine-bend ileum". Due to the slow flow rate and more sediment deposition, whenever the flood season comes, it is easy to cause floods. Since ancient times, there has been a saying that "a long river travels a thousand miles, and the danger lies in Jingjiang". From Yichang to Wuhu, there are many lakes on both sides of the strait, among which Dongting Lake and Poyang Lake are the largest. Dongting Lake is the natural reservoir of the Yangtze River. After the river entered Jiangsu, it bypassed Ningzhen Mountain to the northeast because of mountain resistance. Turn from Zhenjiang below to southern Sichuan and enter the delta region. The terrain is flat, the lakes are dotted, and the waterways are intertwined like a net, which is a scene of water towns and villages. The mouth of the river is 80 kilometers wide, showing a spectacular view of the river and the sea. There are many famous osawa on both sides of the Yangtze River, with beautiful scenery and many tourist attractions. Because of the long process, wide river basin, fertile land and convenient irrigation, there is a "land of abundance" in the middle reaches and a "land of plenty" in the lower reaches, which is rich in products. Although the cradle of the Chinese nation is in the Yellow River basin, according to historical records, after the destruction of Yin, its territory reached the Yangtze River basin in the south. Since then, the Yellow River and Yangtze River basins have become the focus of China's historical and cultural development.

There are many famous cities along the river, such as Chongqing, Yichang, Wuhan, Nanjing and Shanghai. Shanghai is the largest industrial and commercial city in China. There are many places of interest on both sides of the Taiwan Strait, which are valuable materials for understanding the history of China, and there are also many myths and legends, which are valuable heritages of China literature. Since ancient times, the trunk and tributaries of the Yangtze River have been the main artery of water traffic in southern China, crossing east and west, running through north and south, with a total length of more than 80 thousand kilometers. Ten thousand tons of ships can reach Nanjing, and eight thousand tons of ships can reach Luzhou (wet season).

From the source of the Yangtze River to the estuary, it crosses three huge steps in China's topography, passes through different geological structures and strata, and receives tributaries along the way, which has different influences on the valley shape and flow characteristics of the Yangtze River. According to the hydrological and geomorphological characteristics, the main stream is divided into three sections: the upper reaches from Heyuan to Yichang, the middle reaches from Yichang to Hukou, and the lower reaches below Hukou.

① Upstream part. The upper reaches of the river span two topographical steps. The total length is 4529 kilometers, accounting for 72.0% of the length of the Yangtze River. The basin area is 6.5438+0.006 million square kilometers, accounting for 55.6% of the basin area. Tuotuo River and the upper reaches of Tongtian River (from Nangji Balong to Batang Estuary) are the hot spots in the hinterland of Qinghai-Tibet Plateau, the first step. Because at the top of the plateau, the river valley is wide and shallow, generally the river width is 300 ~ 1700 meters, the river is winding, the water is slow and scattered, and there are many tributaries. From Batang estuary to Yibin, it is called Jinsha River, which is the transition section from the first step to the second step. The terrain here is steep, with high mountains and deep valleys. Except for the wide river valley in some areas, the river runs through the canyon with a large slope and the river is swift. Below the stone drum in Yunnan, it suddenly turns to the northeast, and the famous Tiger Leaping Gorge is 35 kilometers below the stone drum. The canyon is 16 km long, and the narrowest part is only 30 meters. Leave the Tiger Leaping Gorge, cross the northern Yunnan-Guizhou Plateau, enter the second step below the new town of Sichuan Province, and gather the Minjiang River near Yibin, which is called the Yangtze River. Yibin to Yichang is 1030 km long, which is customarily called Chuanjiang. The river twists and turns in the Sichuan Basin, and its riverbed is gentle. Along the way, many tributaries such as Tuojiang River, Jialing River and Wujiang River are accepted, and the water volume is greatly increased and the river surface is widened. The Yangtze River passes through Baidicheng in Fengjie, the transition section from the second step to the third step, and three anticlines and two synclines in July, Wushan and Huangling, forming the world-famous Three Gorges of the Yangtze River (Qutang Gorge, Wuxia Gorge and Xiling Gorge), with a total length of about 200 kilometers, with canyons and wide valleys alternately arranged.

② Middle reaches. The Yangtze River leaves the Three Gorges below Yichang and enters the middle and lower reaches of the Yangtze River at the third level. The river widens, the water flows slowly and the river bends. It is 927 kilometers long, accounting for 14.7% of the length of the Yangtze River. The basin covers an area of 679,000 square kilometers, accounting for 37.6% of the basin area. Among them, the section from Zhicheng in Hubei to Chenglingji in Hunan is about 420 kilometers long. Because it was Jingzhou area in ancient times, it was named Jingjiang. Jingjiang River is divided into upper Jingjiang River (from Zhicheng to Ouchikou) and lower Jingjiang River (from Ouchikou to Chenglingji). The bend of the lower Jingjiang River is developed, and it is known as the "nine-bend ileum". There are many lakes on both sides of the middle reaches, which are connected by rivers and lakes, forming two huge water systems, Dongting Lake and Poyang Lake. After the Yangtze River accepted the water directly from two major river systems and tributaries, the water volume more than doubled. Enter the downstream section below hukou.

③ downstream section. The water depth is wide, from the mouth of the lake to the mouth of the sea, 844 kilometers long, accounting for 13.3% of the length of the Yangtze River. The basin area is 6.5438+0.23 million square kilometers, accounting for 6.8% of the basin area. The main stream of the Yangtze River is also called the Yangtze River in Yangzhou and Zhenjiang, Jiangsu Province. In ancient times, it was named after Yangtze Tianjin and Yangzi County. Now foreigners often use the name Yangtze River to refer to the whole Yangtze River. Affected by the tides below Datong, the average tidal current entering the Yangtze River estuary reaches 266,000 cubic meters per second, which is 8.8 times of the annual flow into the sea of the Yangtze River. Under normal circumstances, the total amount of water coming from a tidal wave is about 3.25 billion cubic meters, and it can reach 4.5 billion cubic meters during the spring tide. Due to the backward flow of seawater, the flow speed of the river slows down, and the sediment carried by it is deposited in the downstream reach, especially near the estuary. So dozens of sandbars of different sizes have been formed in the middle of the river, the largest of which is Chongming Island.

Plains of the Middle and Lower Reaches of the Yangtze River

The banded plain in the middle and lower reaches east of the Three Gorges of the Yangtze River in China. Huaiyang Mountain and Huanghuai Plain are in the north, and Jiangnan hills and Zhejiang and Fujian hills are in the south. It is alluvial from the Yangtze River and its tributaries. It covers an area of about 200,000 square kilometers. The terrain is low and flat, and the altitude is mostly about 50 meters. The middle reaches include Jianghan Plain in Hubei, Dongting Lake Plain in Hunan and Poyang Lake Plain in Jiangxi. The downstream plains include the plain along the Yangtze River and Chaohu Lake in Anhui Province (the central plain of Anhui Province), and the Yangtze River Delta between Jiangsu, Zhejiang and Shanghai. Most of the climate belongs to the north subtropical zone, and a small part belongs to the northern edge of the middle subtropical zone. The annual average temperature is 14 ~ 18℃, the most Leng Yue average temperature is 0 ~ 5.5℃, the absolute minimum temperature is-10 ~-20℃, the hottest month average temperature is 27 ~ 28℃, and the frost-free period is 2 10 ~ 270 days. For agricultural crops, the annual precipitation is 1000 ~ 1400 mm, which is concentrated in spring and summer. Zonal soil is only found in low hills and gentle hills, mainly yellow brown soil or yellow cinnamon soil. The southern margin is red soil, and most of the plains are paddy soil. With developed agriculture and high land reclamation index (62. 1% in Shanghai and 45.6% in Jiangsu), it is an important grain, cotton and oil production base. Rich in rice, wheat, cotton, rape, silkworm, ramie, jute and so on. Rivers and branches crisscross, and lakes are dotted. The lake covers an area of 20,000 square kilometers, equivalent to 10% of the plain area. Large lakes, including small lakes, have an area of10.3 million square kilometers, accounting for more than 20% of the plain area of the two lakes, which is the place with the largest number of lakes in China. There are many freshwater lakes such as Poyang Lake, Dongting Lake, Taihu Lake, Hongze Lake and Chaohu Lake, which are connected with the Yangtze River and have the functions of regulating water volume and reducing flood peak. They produce fish, shrimp, crab, lotus, water chestnut and reed, as well as world treasures such as Chinese sturgeon, Chinese alligator and baiji. Aquatic products occupy an important position in China and are known as the land of plenty. It is one of the most economically developed areas, including Shanghai, Nanjing, Wuhan, Nanchang, Suzhou, Wuxi, Changzhou, Nantong, Wuhu and Changsha. The main industries are steel, machinery, electricity, textiles and chemistry, and it is an important industrial base. The plain is located in the hub of China's north-south and east-west transportation networks, with developed land and water transportation. The Yangtze River runs through the middle and becomes an east-west waterway artery, and its many tributaries form a huge waterway network.

■ Yangtze River Delta

China Yangtze River and Qiantang River are alluvial deltas where they enter the sea. Including the southeast of Jiangsu Province, Shanghai and the northeast of Zhejiang Province. It is a part of the middle and lower reaches of the Yangtze River. It covers an area of about 50,000 square kilometers. The apex of the delta is in Zhenjiang and Yangzhou, and the north reaches Xiaoyangkou. South bank of Hangzhou Bay. The elevation is mostly below10m, and the low hills (such as Huishan, Tianpingshan, Yushan and Langshan) are scattered, with an elevation of 200-300m. The annual sediment discharge of the Yangtze River is 400-900 million tons. In general, 28% of the sediment is deposited in the Yangtze River, and in some years it is as high as 78%. The delta continues to extend to the sea. The ancient sand mouths in Changzhou, Changshu, Taicang, Jinshan and other counties south of the Yangtze River are mostly 4 ~ 6 meters above sea level; The ancient sand mouth in Yangzhou, Taizhou, Taixing and Rugao, north of the Yangtze River, is 7-8 meters above sea level. The ancient sand mouths in Jiangnan and Jiangbei developed gradually after the highest sea level stabilized in the late glacial period. By about 2000, the north bank sand mouth extended to Liaojiaozui, and the south bank sand mouth extended to the southeast with the mainstream of the Yangtze River and connected with the mouth sand mouth of Qiantang River. Sediment continues to accumulate, advancing annually 1958 ~ 1973. It belongs to the northern subtropical monsoon climate, with abundant rainfall, criss-crossing waterways and dotted lakes, and is known as a water town and a country. The land is fertile, and agriculture mainly produces rice, cotton, wheat, rape, peanuts, silk, fish and shrimp. It is one of the most densely populated areas in China. There are many important towns in the lower reaches of the Yangtze River and on both sides of the Shanghai-Nanjing line, such as Shanghai, Suzhou, Changzhou, Wuxi, Zhenjiang, Yangzhou, Taizhou and Nantong. Among them, Shanghai is the largest industrial and commercial city in China and a world-famous foreign trade port, while Suzhou and Wuxi are scenic spots and emerging industrial cities.