Yangtze River

 

Factfile

  • Length: 6,300 km

  • Sources: Ulam Moron (Wulanmulun) river, glacial meltwaters of the Tanggula Mountains in Qinghai province near Tibet

  • Key Tributaries: Yuland, Min Jialing, Han rivers (all left bank); Wu, Yuan, Xiang and Gan rivers (right bank)

  • Basin area: 1.808 million km²

  • Countries within: China (Qinghai, Yunnan, Sichuan, Chongqing, Hubei, Hunan, Jiangxi, Anhui, Jiangs), Tibet, Shanghai

  • Basin Population: 400 million

  • Discharge: 30,170 m³/s

 

Physical Geography

The Yangtze River, the longest river in Asia at a length of 6,300 km, finds its source from the Ulam Moron river in Qinghai, China at the border with Tibet. The Yangtze is mainly supplied in this region through the Alpine glacial meltwaters that originate from the Tanggula mountains. The Yangtze is one of the largest rivers in the world, there are large amounts of regional variation across the basin as it flows from its source in the Tanggula mountains through 9 provinces of China before reaching the mouth of the river near Shanghai. As such the overall physical setting of the Yangtze River and its catchment area will be further expanded on below.

Formation/Geology

The building blocks, which would later form the region and conditions for the current Yangtze River and its basin, were formed approximately 140 million years ago when the Qinghai-Tibet region rose and the Tanggula mountains were formed. This process also led to the Tethys sea being pushed further west, between 90 and 100 millions years later the Himalayas were formed in this area removing the Tethys Sea meaning that the waters within the Yangtze Basin would now have a different drainage route. The change in drainage in the area led to a massive rise in the headwaters of the Yangtze, with the region now seeing an influx of meltwater from glaciers on the Qinghai-Tibet plateau and smaller neighbouring tributary systems. This led to the formation of a relatively larger single stream that cut through the steep gorges that were present in this region. The system in the region would remain like this until approximately 3 million years ago when a further rise in the height of the Himalayas as well as fluvial erosion of the Wushan Mountain allowing for the flow of water throughout this region, leading to the formation of the current setting of the Yangtze began as the previously isolated sections of the river combined to form the single Yangtze fluvial system that is still present today.

Geomorphology

The development of large river systems in Asia is closely linked to the evolving topography driven by both near-field and far-field effects of the interplay among Indian, Eurasian and Pacific plates (Zheng, 2015). The geomorphology of the yangtze river basin contains a high level of variation from the upper-course to the mouth of the river. The upper course is punctuated with the Tibetan plateau, with elevations at this point reaching 5000 m above Sea-level, before transitioning into elevations near sea-level in the Sichuan basin. The region is also home to one of the first landmarks along the Yangtze, the First bend of the Yangtze river, where the Yangtze makes a 90° turn from south to east where it begins to flow through China. As well as one of the deepest gorges in the world the Tiger Leaping Gorge. Towards the end of the upper course having travelled 2,600 km of the yangtze’s course, the elevation of the river has descended by 5,200 m from its source.

Moving further along the upper-course of the river, at the transition between the upper- and middle-course of the Yangtze, one of the most recognisable geomorphological features of the Yangtze is found that being the Three Gorges, where anthropogenic activity has led to the damming of this landform. Before the construction of the Three Gorges Dam this section of the middle-course was home to an extremely narrow section of the river that was home to rapids and eddies that were removed by the flooding of the area behind the dams.

Transitioning into the Lower-course of the Yangtze the region becomes much flatter and is home to the lowland plains of east-central China, the Yangtze also transitions into a much more complex system with the presence of interconnected lakes, marshes and river channel developed across the plains. In this region major tributaries such as the Yuan, Xiang and Han rivers join the main course of the river as it flows through the plains. Throughout the lower course of the Yangtze there are many major lake systems that vary greatly in size as a result of the transition in climate for this region between flood and Low-flow seasons, these include the Dongting, Hong and Liangzi Lakes. As the Yangtze continues to flow throughout the lower-course past Lake Liangzi the river begins to widen reaching a width of 800 m across the plain and reaching a depth of approximately 30 m. The natural geomorphology of this region of lakes has however been altered as a result of anthropogenic action with the reduction of lake area in this region being seen as a result of reclamation efforts. Once it has flown through this region, continuing eastwards along its course, the Yangtze moves through areas of valleys and plains where it reaches another tributary where the river is supplied with freshwater from China’s largest freshwater lake, Lake Poyang. The river then begins its transition into one of the largest landforms of the basin, the Yangtze Delta, following the rivers movement across the North China Plain where the river increases in width to between 900 and 1800 m.

The Yangtze Delta is a region at the mouth of the river starting beyond Zhenjiang, the delta is home to many geomorphological landmarks including tributaries, lakes, ancient river systems and marshland. The Yangtze covers a total area of 99,600 km² however as the region is low lying it can be fully submerged as a result of extreme flooding events. The Yangtze river, following past the delta, begins to widen into an estuary before it reaches the mouth of the river flowing into the East China Sea where Shanghai is located.

Climate

The Yangtze basin has many regional climates throughout the course of the Yangtze with differences in the climate from the tibetan plateau and the rest of the upper-course to the middle and lower-course. Across the basin the overall climate is dominated by heavy thunderstorms through July and September while throughout the winter the climate is much colder. On average the temperature is between 20 and 24°C with annual precipitation of 1,067 mm. The upper-course is dominated with a much colder climate along the tibetan plateau transitioning into the middle course the climate is characterised by hot summers and milder winters as a result of the regional protection provided by the high mountains to the west, protecting the region from the cold north and westerly winds . In the lower course the climate changes further with warm springs, hot summers and cool autumns with relatively cold winters, the region is also dominated by a monsoon climate in this section of the river, with the potential for typhoons periodically.

Ecosystems

The Yangtze Basin has some of the highest biodiversity levels in the world, with many different ecosystems and biomes found across the basin, supporting approximately half of China’s total flora and fauna species.

Ecological setting

This is seen as a result of the vast nature of the basin, covering 1.808 million km², with many different settings provided across the basin from regions of mountains, forests, wetlands to interconnected waterways throughout the area. Across this region you can find a wide array of both flora and fauna ranging from the bamboo forests that support the Giant Pandas found in the basin to the fish swimming throughout the region.

Flora

A high level of biodiversity is found across the basin with the most identifiable of these being the bamboo plants that provide sustenance for many species in the basin, closely associated with the panda species of the yangtze basin. Other key flora species include the Chinese willow tree, Lotus blossoms, a species that lives in an aquatic environment submerging to blossom, Dove trees as well as Chrysanthemum that grow along the banks of the Yangtze that are used in traditional medicines.

Fauna

To develop an understanding of the rich fauna found in the Yangtze basin the species will be divided providing an overview of the most synonymous species with the basin.

Mammals

280 species of mammals live within the Yangtze basin.

  • Giant Panda: One of the most identifiable species across the globe, the giant panda is a protective species that is endemic to the Yangtze river basin, calling the bamboo forests that are supported by the fluvial environment their home.

  • Red and White Flying squirrels: A species of smaller tree dwelling mammals that are found throughout the rich forrest using its own anatomy to glide long distances between results using the air currents and wind in the region,

  • Pangolin: A unique scaled mammal species found across the region, the pangolin is a nocturnal mammal that has often been misidentified as a reptile species. This species are known to be active during the night using invertebrates as the main source of sustenance.

  • Chinese Golden Monkey: A species of monkey are found in the dense forests of the yangtze basin, towards the upper course of the yangtze in the regions of the Yunnan -Tibetan area. This species of monkey can be found living in large clusters reaching over 600 individual monkeys per herd and often share their ecosystem with the much larger Giant Panda.

  • Snow leopards: Found in the upper course of the Yangtze basin the snow leopard call the foothills of the himalaya’s home descending further into the yangtze basin in search of prey. This species is extremely rare with an estimate of less than 5,000 left in the wild.

  • Grey Wolves: This species can be found in small clusters across the entirety of china with one of the regions known to support this species being the Yangtze basin with the rich biodiversity of the region providing an adequate source of food and an area large enough for them to range.

  • Yangtze River Dolphin: The most noticeable of aquatic mammals throughout the yangtze basin is that of the Yangtze River Dolphin, this species is extremely rare with only 800 remaining in the river with the number dropping at alarming rates as a result of anthropogenic actions throughout the basin including fishing and river dredging that have severely affected their habitats within the basin. In recent years efforts have been made to protect the species and habitats.

Birds

  • Golden Eagle: One of the most well known avian species throughout the globe, they can often be seen using the Yangtze basin as hunting grounds and have even been known to target the larger species across the basin such as wolves. 

  • Siberian Crane: A migratory species known to call the Poyang lake home when travelling from the harsh tundra of the arctic. In recent years the migratory patterns of this species have been affected by anthropogenic actions, such as the Three Gorges Dam, thousands of this species still migrate to the Yangtze basin during the arctic winter.

Amphibians

145 amphibian species have been identified across the yangtze basin. 

  • Chinese Giant Salamander: The most notable amphibian species throughout the yangtze basin, the Chinese Giant Salamander is supported by the fresh fast running waters of the Yangtze basin. This unique species is situated in the upper course of the Yangtze river preferring the rocky mountain species and darker regions as this species has severely reduced sight. Excessive hunting has led to reductions in population  numbers with links to traditional chinese medicine.

Reptile

166 reptile species have been identified across the basin, below the most notable species will be outlined.

  • Yangtze giant softshell turtle: An extremely rare species with only 4 known to remain in the wild. This species once thrived across the region calling the Yangtze and associated waterways and lakes home, living within the muddy bottoms of rivers and lakes, however, due to anthropogenic actions such as dredging and hunting this species is on the verge of extinction 

  • Chinese Alligator: The only known alligator species that is native to china and exclusively the Yangtze and supporting waterways, the Chinese Alligator is relatively small when compared to its counterparts across the globe. This species is another that is found within the Yangtze basin that is extremely endangered with 200 found within the wild, repopulation and habitat protection efforts have been made in recent history as well as the implementation of strict restrictions on the exportation of the species.

Fish

Within the waters of the Yangtze river basin there are 378 identified species of fish, some of the most populous aquatic species are that of the yellow head catfish and Carp providing a pivotal role in the food chains supporting the ecology in the region. Other more notable fish species in the region are that of the Copper fish, Chinese Shad, Eels, Anchovy and the poisonous Chinese Puffer fish.

Human Geography

The Yangtze basin has been key to the development of China with the Yangtze itself being China’s key waterway. The Yangtze basin contains one third of China’s population with continuous development throughout the basin with many projects reclaiming land in the lower-course of the river for further expansion and agricultural purposes. The population across the basin is not evenly distributed; the upper-course of the Yangtze is sparsely populated with the population in this region mainly being Tibetans continuing to live a traditional lifestyle of raising livestock. The middle course of the river is home to many of china’s most developed and largest cities including Chengdu, the capital of Sichuan, Chongqing and Wuhan. The lower-course of the river basin also contains the most densely populated region of China, the Yangtze delta with 150 million people living in this region. This region is responsible for a large proportion of China, responsible for a third of the imports and exports of china. The yangtze basin also contains the most populated city in China, Shanghai, with over 24 million people living in an area of 6,340 km². Shanghai is a major outlet for China operating as one of the largest financial centres for the country with a GDP of approximately £406 Billion. 

The large population and anthropogenic activity within the basin has however led to many negative impacts to the natural function of the basin with this anthropogenic activity leading to the damage of the natural fluvial system in the region, destruction of habitats and ecosystems, as well as the pollution of the Yangtze.

Climate Change

As a result of anthropogenic climate change there have been losses in the water within the Yangtze basin itself, with clear visible losses in the lakes of the basin situated along the lower-course of the Yangtze. However, the largest threat that is coming as a result of anthropogenic climate change comes at its headwaters, with the yangtze sourcing its water from the alpine glaciers of the Himalayas changes in the melting patterns meaning that there could be a reduced supply of water to the yangtze leading to an increased risk of massive water shortages that will impact the whole fluvial system.

Pollution

One of the largest threats to the fluvial environment of the Yangtze comes as a result of anthropogenic activity throughout the region. The high levels of pollution in the Yangtze come from many sources along the course of the river with Industrial activity, Agriculture, transportation of hazardous materials and the discharge of wastewater. There were The discharge of industrial wastewater into the river system originates from the many factories along the middle- and lower-course of the river with these facilities often discharging untreated wastewater and sewage generated on site directly into the Yangtze affecting the natural chemical balance of the yangtze leading to the potential for habitat loss and eutrophication. It has also been noted that as a result of the industrial discharge the natural environmental quality of the river will never be recoverable with the discharge of 32.04 billion tonnes of wastewater discharged in 2016 alone.

Agricultural activity across the basin is very prevalent in an effort to support the high population of not only the Yangtze basin but the rest of china, in order to meet these demands high levels of chemical pesticides and fertilisers are used, with much of these being discharged into the main waterways and lakes of the yangtze leading to an increase in nutrients such as nitrogen and phosphorus in the river system, which in turn leads eutrophication. A prime example of the impact of agricultural pollution is that of Taihu Lake where there is an annual eutrophication event with the bloom of blue-green algae as a result of the agricultural activity in the region, this led to the removal of thousands of tonnes of the algae on a daily basis in 2007.

The active shipping along the course of the tangtse has led to not only the discharge of chemicals from the ships themselves but also from the people working on these ships throwing waste and litter directly into the river. Ships are used as a major source of transportation for domestic and commercial waste along the course with over 300 million tonnes of sewage discharged from these ships and over 70,000 tonnes of rubbish in 2015 alone.

As such the largest threat to the stability of the fluvial environment in the Yangtze basin is that of pollution and the many sources of pollution across the basin. With regulation of this pollution being an extremely contentious issue with local and national governments making efforts to reduce the impact on the river through increased regulation of chemical producing companies and factories, reducing the connectivity of these sites to the river itself as well as improvements to the sewage systems of the region. However, the ever growing population of the basin and industrial activity with very little environmental awareness of the population means that these environmental issues will not be addressed until education on this issue is provided. These environmental issues will also be addressed with improved supervision throughout the industry of the region, which continue to illegally discharge wastewater into the Yangtze in secret continuing to propagate the environmental damage. 

River dredging

River dredging is an active process throughout the middle- and lower-course of the Yangtze in an effort to improve the transportation along the interconnected waterways of the basin. However, this has led to damage to the fluvial habitats for the diverse ecology of the region with this dredging destroying the muds and sediments along the course of the river that have been home to life for centuries. In recent times efforts have been made to limit the amount of dredging that occurs in the basin, with major crackdowns in the unregulated sand dredging industry, to protect the ecosystems and habitats that are present throughout this system.

Three Gorges Dam

The three gorges dam has been labelled as one of China’s great engineering marvels acting as the world largest hydropower dam as well as protecting the downstream region from flooding, however, the dam has many negative impacts on the region. Many concerns were raised throughout the completion of the dam with the relocation of 1.2 million people as a result of the filling of the dam flooding 13 cities and over 1300 villages. Through the construction of the Three Gorges Dam there were also major losses in terms of archeological locations as well as the potential for major environmental damage with hazardous waste sites being identified in the region prior to the completion of the dam. The construction of the dam has led to major environmental concerns related to the impact of the dam on the natural environment. The impacts include increased seismic activity as a result of the increased loading of the region with the filling of the dam, landslide from unstable cliff sides, salinity changes downstream due to changes in the natural water supply and major ecosystem change due to the loss of the natural area behind the dams. The dams also pose a threat to the human population of the basin with the accumulation of pollution within the reservoirs and an increased chance for the spread of waterborne diseases.

Bibliography

Zheng, H. (2015) ‘Birth of the Yangtze River: age and tectonic-geomorphic implications’, National Science Review, 2(4), pp. 438–453. doi: 10.1093/nsr/nwv063.