Similarities and differences in geographical environment between the Yellow River Delta and the Yangtze River Delta

The Yangtze River Delta starts from Toarey Yang Canal in the north, Hangzhou Bay in the south, Zhenjiang in the west and the seaside in the east, including Shanghai, southern Jiangsu Province, northern Zhejiang Province and its adjacent waters. With an area of about 99,600 square kilometers and a population of about 75 million, it is a vast plain. Here, the coastline is straight, the sea water is muddy with yellow sand, and there are shoals in the intertidal zone with a width of several kilometers to dozens of kilometers. This metropolis group has gathered strong strength in industry, finance, trade, education, science and technology, culture and so on. It plays an important role in promoting the economic development of the Yangtze River basin, connecting domestic and foreign markets, attracting overseas investment, promoting industrial and technological transfer, participating in international competition and regional structural adjustment.

The Yangtze River Delta is the largest estuary delta in China, which generally refers to the alluvial plain of Yangtze River sediment deposition east of Zhenjiang and Yangzhou, and is located in the southeast of Jiangsu Province, Shanghai City and Hangjiahu District of Zhejiang Province. The apex of the Yangtze River Delta is near Zhou Zhen Town, Yizheng City, with Yangzhou, Jiangdu, Taizhou, Hai 'an and Bencha as the northern boundary, Zhenjiang, Ningzhen Mountain Range, the eastern foot of Maoshan Mountain and the northern foot of Tianmu Mountain to the northern shore of Hangzhou Bay as the western boundary and the southern boundary, and the Yellow Sea and the East China Sea as the eastern boundary.

form

The delta basement is a part of the Yangtze paraplatform, and the Himalayan tectonic movement interrupted the subsidence. During the Quaternary neotectonic movement, the crust and sea level frequently rose and fell. After the last transgression, the sediment carried by the Yangtze River continued to deposit and began to develop deltas in the estuary.

Because of the Coriolis force, the main river keeps turning right, which makes the estuary sand group merge into the north bank in turn. The sandbars and sandbars formed in Hongqiao period, Huangqiao period, Jinsha period, Haimen period and Beisha period formed the Hanjiang, Taixing, Jingjiang, Rugao, Nantong, Haimen and Qidong counties on the north bank of the Yangtze River today. Now Chongming, Changxing, Hengsha and other sand islands near the estuary will also be merged into the north shore according to this law. The estuary sand mouth also extends synchronously.

The sand mouth on the north bank extends to the northern boundary of the current delta, with a ground elevation of 6-8 meters.

The sand mouth on the south bank extends eastward through Jiangyin, Taicang, Waigang and Maqiao, with a ground elevation of about 4.5 ~ 6 meters, and reaches Hangzhou Bay after connecting with the north bank of Qiantang River. The repulse bay in Shazui silted up and became the predecessor of the ancient Taihu Lake. Since then, the shallow bay has silted up and gradually evolved into a low plain crisscrossed by lakes and rivers. The coastal areas outside the south bank of Shazui are continuously silted into coastal plains.

A series of residual hills with an altitude of 100 ~ 300 meters are scattered on the delta, most of which are composed of Devonian sandstone and Carboniferous and Permian limestone, and a few are composed of Yanshanian granite and trachyte.

history

In the early days of the delta, humans engaged in fishing, hunting and farming here.

After two great migrations in the Eastern Jin Dynasty, the Southern and Northern Dynasties and the Southern Song Dynasty in the 4th-6th century A.D. and the river network construction since13rd century, the delta has gradually developed into a famous "land of plenty" and "land of silk" in China.

Modern industry rose earlier, inland river shipping was developed, Shanghai-Nanjing and Shanghai-Hangzhou railways were built one after another, and Shanghai, Suzhou, Wuxi, Changzhou, Zhenjiang, Nantong and Yangzhou in Jiangsu, Hangzhou and Jiaxing in Zhejiang developed into industrial towns one after another.

In order to promote and strengthen the economic union and cooperation in the Yangtze River Delta region and promote the sustainable economic development in the Yangtze River Delta region, the 14th municipal economic commissions (offices) were initiated and organized by Shanghai, Wuxi, Ningbo, Zhoushan, Suzhou, Yangzhou, Hangzhou, Shaoxing, Nanjing, Nantong, Changzhou, Huzhou, Jiaxing and Zhenjiang 1992, 14.

1997, the municipal government of the above-mentioned 14 city and the municipal government of the newly established 15 city in Taizhou voluntarily formed a new economic coordination organization-Yangtze River Delta Urban Economic Coordination Committee through equal consultation. The coordination meeting shall have a standing chairman and an executive chairman. The executive chairman is held by Shanghai, and the executive chairman is held by other member cities except Shanghai in turn. The Coordinating Committee holds a formal meeting every two years. The coordination meeting set up a liaison office as a permanent office around the executive chairman, responsible for daily work. The member city cooperation offices (commissions) serve as the specific liaison and service departments of the coordination meeting.

A part of the plain in the middle and lower reaches of the Yangtze River. Located in the east of Zhenjiang City, Jiangsu Province, north of Hangzhou Bay and south of Toarey Yang Canal. It covers an area of about 50,000 square kilometers. The terrain here is low and flat, and the altitude is below 10 meter. However, there are some scattered isolated hills, such as Huishan in Wuxi, Tianpingshan in Suzhou, Yushan in Changshu, Sheshan in Songjiang and tianmashan. They either stand in the plain or in Taihu Lake, some become tourist areas, and some become Huaguoshan. The apex of the Yangtze River Delta is near Zhenjiang. About six or seven thousand years ago, it was a triangular harbor. The mouth of the Yangtze River is like a trumpet that opens eastward. The water surface is vast and the tidal effect is remarkable. With the support of seawater, most of the 470 million tons of sediment brought by the Yangtze River every year are deposited into sand dikes on the north and south banks. The sandbars on the north bank extend eastward from Yangzhou to Rudong, and the He Lixia Plain to the north of the sandbars is mainly alluvial by the Yellow River and Huaihe River. The sandbar on the south bank extends from Jiangyin to Caojing, Jinshan County, Shanghai, and connects with the sandbar on the north bank of Qiantang River, forming the Taihu Plain. He Lixia Plain is located on the north bank of the Yangtze River, covering an area of about 6.5438+0.4 million square kilometers, and it is a dish-shaped depression. The central lake of the depression swings continuously, mainly including Sheyang Lake and Dazong Lake. Due to the low terrain, historically, floods have been extremely serious. In order to change this situation, the state invested in building water conservancy projects, blocking the Huaihe River in the west, diverting tides from the east, digging canals, and enhancing irrigation and drainage capacity, making this severely flooded area for nine years an important grain production base in the Jianghuai Basin. Taihu Plain is located in the south of the Yangtze River and is the main body of the Yangtze River Delta. With Taihu Lake as the center, the plain looks like a big plate, and the terrain is high one week and low one week. This topographical feature makes the upper reaches of the Yangtze River and Taihu Lake flooded and flooded. In summer and autumn, it is often hit by typhoons and heavy rains, and floods are very frequent. In order to resist natural disasters, the local people made great efforts to dig canals, remove stagnant water, repair dikes and build gates, and gradually formed a dense water network connected by ditches. This is the area with the highest river network density in China, with an average river network length of 4.8-6.7 kilometers per square kilometer. There are more than 200 lakes on the plain. The Yangtze River Delta is criss-crossed with rivers and lakes, developed agriculture, dense population and numerous cities. It occupies an important position in the national economy and is known as the "Golden Triangle" of China.

■ Yangtze River Delta

China Yangtze River and Qiantang River are alluvial deltas where they enter the sea. Include Jiangsu province, southeastern Shanghai and northeastern Zhejiang. 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.

There is a tidal flat wetland of 153000 hectares where the ancient Yellow River enters the sea in northern Shandong Province. The raging river roared through it and merged into the sea. This is the Yellow River Delta Nature Reserve, established by 1987 to protect wetland ecosystems and rare and endangered birds.

The Yellow River Delta, with Ninghai in Kenli County as the axis, starts from the mouth of Taoer River in the north, reaches the mouth of Zimai River in the south and spreads eastward. Its elevation is below 15m, and its area is 5450km2, which is the youngest land in China. Modern Yellow River Delta is an alluvial fan formed by Yellow River alluvial action since 1855.

The Yellow River Delta Nature Reserve is only 60 kilometers away from Dongying City, which belongs to temperate monsoon continental climate, with four distinct seasons, abundant sunshine and the same period of rain and heat, with an average annual precipitation of 5565438 0.6 mm. This delta is a marine sedimentary plain filled with a large amount of sediment by the Yellow River in Bohai Depression. The landform of the modern Yellow River Delta includes floodplain highlands, sloping fields and large depressions. The newly formed swing tail land zone of the Yellow River is wide and low-lying, with its area expanding year by year and unique ecological type. A large area of shallow sea beaches and wetlands has been formed at the intersection of Haihe River, which has become an important "transit station" and wintering breeding ground in the inland of Northeast Asia and bird migration around the western Pacific Ocean. This area is rich in aquatic biological resources. According to preliminary investigation, there are more than 800 species, among which amphioxus, finless porpoise and Songjiang perch are under national key protection. There are hundreds of kinds of wild plants, and the endangered plant wild soybean under state protection is widely distributed. There are about 187 species of birds, and 108 species are included in the Sino-Japanese migratory bird protection agreement, among which red-crowned crane, white stork, golden eagle, great bustard, swan, cygnet, crane and bee are the national key protected wild animals.

The modern Yellow River Delta has unique landscape, young and vast land, novel natural landscapes such as trees, grasslands and wild animals, and strong wild interest. The wonderful "Tao Jin" pierced the blue sea and formed a rare spectacle in the world. There are abundant oil and gas resources here. There are many derricks in Shengli Oilfield, Dongying Bridge, dampproof dike and other magnificent modernization projects. Dongying, a new oil industrial city, is rich in natural resources. It is a treasure of the motherland and has broad development prospects.

The Yellow River is a river with good siltation, determination and migration ability, which carries about 65.438+0.6 billion tons of sediment southward every year, and about 65.438+0.2 billion tons of sediment is deposited in the estuary delta and coastal areas. On average, it pushes1.5-3km into the Bohai Sea every year, and newly reclaims 23-28km2 every year, which makes 30,000-40,000 mu of sea area silted up into new land resources. "Yesterday's sea, today's mulberry field" can be realized here. This advantage has injected new vitality into conservation. Whether it is used as a resting place and wintering habitat for rare birds or as a unique estuary ecosystem, it has important scientific value and ecological significance.