China's Pollution: Post Three Gorges Dam Impact

China's Three Gorges Dam, the world's largest hydropower project, has been the subject of controversy due to its environmental and social impacts. One of the key concerns is pollution, and while there have been some efforts to curb it, it remains a pressing issue. The dam has slowed the flow of the Yangtze River, reducing its ability to flush out polluted areas. This has led to increased water pollution and contributed to the contamination of tributaries and lakes, affecting both the environment and local communities. Despite the Chinese government's acknowledgment of these issues and their plans for improvement, the dam continues to have a significant impact on the region's ecology and the livelihoods of those living in its shadow.

Landslides and flooding

The Three Gorges Dam has been linked to an increase in landslides and flooding in the surrounding areas. The dam's reservoir, which holds a massive 42 billion tonnes of water, has caused fluctuations in water levels, leading to increased pressure on the surrounding land. This has resulted in dozens of landslides along a 20-mile (32-kilometer) stretch of riverbank. In 2003, around 700 million cubic feet of rock slid into the Qinggan River, just two miles from the Yangtze River, creating 65-foot waves that killed 14 people. Since then, there have been numerous landslides, including one in 2020 that killed at least 30 people when the ground gave way near a railway tunnel in Badong County.

The landslides are directly linked to the filling of the reservoir and the subsequent fluctuations in water levels. The weight of the water has also eroded significant portions of the Yangtze River banks, triggering waves as high as 50 meters. The combination of soil saturation and the drawdown of the lake has also been cited as a potential cause of landslides in the area.

The dam's inability to effectively control large amounts of floodwaters during the rainy season has led to questions about its efficiency. In 2020, three flood waves hit the dam, causing it to open its sluice gates, which exacerbated flooding downstream. The Yangtze River has grappled with a surge of floods that have killed hundreds and displaced millions, leading to doubts about the dam's ability to prevent major floods caused by incessant rainfall.

The dam's impact on the surrounding environment and communities has been significant. The displacement of millions of people, the destruction of natural habitats, and the loss of arable land, biodiversity, and valuable topsoil have all contributed to the social and economic strains in the region. The environmental degradation caused by the dam has also affected the reproduction patterns of many species, and the alteration of water flow has endangered fish populations in the Yangtze River.

Water pollution

The dam's construction has also led to the displacement of over a million people, with many receiving inadequate compensation and facing a lack of farmland and job opportunities after relocation. This has resulted in reduced living standards and further environmental degradation as farmers are forced to cultivate steep, unsteady slopes, leading to increased erosion.

The weight of the water behind the dam has also caused frequent fluctuations in water levels, triggering landslides and increasing the risk of earthquakes. The blocking of sediments by the dam has resulted in significant erosion downstream, affecting ecosystems and agricultural productivity.

To address these issues, the Chinese government has invested billions of dollars in water treatment projects and fortifying reservoir banks. However, the dam continues to face criticism from environmentalists and scientists, who warn of potential ecological disasters and the destruction of natural species and historical sites.

Flood control

The dam's reservoir has a flood storage capacity of 22 cubic kilometres, which will reduce the frequency of major downstream flooding from once every 10 years to once every 100 years. The dam is expected to minimise the impact of even a "super flood".

However, the efficacy of the dam in flood control has been frequently questioned. In 2020, China experienced its heaviest floods in more than three decades, and the dam's reservoir neared maximum capacity. While officials claimed that the dam reduced damage and loss of life from the floods, critics asserted that the heavy floods highlighted the limitations of the dam as an effective flood control tool.

In 2024, the dam was on high alert as floods triggered by torrential rains wreaked havoc in southwestern China. The water level in the Three Gorges Dam reservoir rose to its highest ever level in July, and a new round of floods was expected to flow into the reservoir around July 16.

Some geologists argue that the dam has a limited role in flood control. During a "once-in-a-century flood", more than 244 billion cubic metres of water can pass through the Three Gorges in two months, according to Fan Xiao, a Chinese geologist and long-time critic of the dam. The storage capacity of the dam's reservoir can handle only about 9% of that amount, he added.

The dam can only hold back the water for so long as it has to make room for new rains, and in the flood season, torrential downpours can come in quick succession. In 2020, three flood waves hit the Three Gorges, causing the dam to open its sluice gates multiple times and drawing criticism on Chinese social media that this exacerbated the floods downstream.

Despite these criticisms, the dam's operator, China Three Gorges Corporation, has claimed that the dam has played a "crucial role" in intercepting floodwaters. After the 2020 floods, the company told China's state news agency, Xinhua, that the dam had intercepted 18.2 billion cubic metres of potential floodwater. A water resources ministry official told the state-run newspaper *China Youth Daily* that the dam "effectively reduced the speed and extent of water level rises" on the middle and lower reaches of the Yangtze.

Biodiversity loss

The Three Gorges Dam in China has had a significant impact on the biodiversity of the region. The dam's construction has threatened the biodiversity of the area by endangering several plant, insect, fish, and animal species. The dam's reservoir has flooded some habitats and reduced water flow to others, altering weather patterns and ecosystems. This has endangered plant species such as the Chinese dove tree and the dawn redwood, and contributed to the decline of the baiji dolphin, a rare species now considered functionally extinct. The dam has also affected the reproduction patterns of many species, suggesting that even if they are still present in the area, they may soon disappear.

The dam's impact on water flow has also endangered fish populations in the Yangtze River. The river contains some of the densest clusters of human habitation in the world, and overfishing has already put 25 of the river's 177 unique fish species at risk. The dam's reduction of flooding downstream will further fragment the network of lakes and lower the water level, making it difficult for these fish to survive.

The dam has also led to the flooding of farmlands and the destruction of habitats for many species. Two cities, over 100 towns, and 1600 villages along the Yangtze River banks have been submerged by the reservoir. This has resulted in the displacement of over a million people and the loss of arable land, biodiversity, medicinal flora, and valuable topsoil. The weight of the water has also eroded significant portions of the Yangtze River banks, further degrading the environment and threatening ecosystems.

The Three Gorges Dam has also contributed to drought conditions in central and eastern China. The decreased water flow has affected households and contaminated freshwater sources, with saltwater from the East China Sea creeping farther upstream. This has led to a rise in jellyfish, which compete with river fish for food and consume their eggs and larvae, further endangering native fish populations.

Overall, the construction and operation of the Three Gorges Dam have had significant negative consequences for biodiversity in the region. The dam has endangered numerous species, altered ecosystems, and reduced water flow, leading to drought and further threatening fish populations. The displacement of local communities and the loss of arable land have also indirectly contributed to biodiversity loss by removing the ability of people to manage and conserve the environment.

Earthquakes

The Three Gorges Dam in China has been linked to increased seismic activity in the region. The dam, which is the world's largest, is located on two major fault lines: the Jiuwanxi and the Zigui–Badong.

Since the construction of the dam and the subsequent filling of the reservoir began in 2003, tens of thousands of earthquakes have been recorded in the reservoir area. A 2010 study by the China Earthquake Administration found that the dam had triggered about 3,400 earthquakes from mid-2003 to the end of 2009. The frequency and intensity of these earthquakes has gradually increased, with some registering magnitudes of up to 5.1 on the Richter scale.

The earthquakes are believed to be caused by the increased water pressure in the pore spaces of rocks at lower depths, which can trigger faults that are under stress to move. This is known as reservoir-induced seismicity, and has been observed in other dam projects globally. The weight of the water has also been found to erode significant portions of the Yangtze river banks, triggering waves as high as 50 meters.

The potential for the dam to trigger severe earthquakes is a significant concern, as millions of people live downstream and could be at risk if the dam were to fail due to an earthquake. While the dam has not sustained any apparent damage from earthquakes so far, researchers warn that the risks remain and that strengthening the dam to withstand stronger quakes may be necessary to mitigate the risk of disaster.

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