Urgent fight against subsidence; major cities are sinking
In China, the ongoing construction boom combined with excessive groundwater extraction is leading to a serious problem: many large cities, including Shanghai and Beijing, are increasingly sinking. This development could have dramatic consequences, particularly for the densely populated coastal regions.
China has experienced an unprecedented construction boom in recent decades, which is now having serious consequences. Together with the sharp increase in groundwater use, this is causing the country’s cities, particularly the metropolises of Shanghai and Beijing, to sink noticeably. Experts warn that without appropriate measures, the situation could take on catastrophic proportions, similar to what has already been observed in Tokyo, where countermeasures were successfully taken.
The phenomenon of sinking cities can be observed globally and affects metropolises such as Venice, Jakarta, Bangkok and New Orleans. These cities are particularly at risk due to rising sea levels and simultaneously sinking soil. Without intervention, there is a risk of serious flooding. The cost of damage to infrastructure such as buildings, roads and supply lines is immense. In China alone, the annual damage costs amount to an estimated 1.5 billion dollars.
The causes of subsidence are manifold and include excessive groundwater abstraction, heavy construction and the draining of wet soils. A Chinese research team has analysed the effects of these developments in detail and presented alarming data: Almost half of China’s urban areas are sinking by more than three millimetres a year, and 16 per cent by more than ten millimetres. The problem is particularly acute in the megacity of Beijing.
The research carried out by Zurui Ao and his team at South China Normal University in Foshan is based on satellite measurements of 82 major Chinese cities. These show that around 29 per cent of China’s urban population lives on increasingly sinking ground, which equated to around 270 million people in 2020.
Massive groundwater extraction is a global problem. When water is replaced by air between sediment particles, these particles become more compacted, causing the ground to sink. This phenomenon is particularly pronounced in Jakarta, where the ground is sinking by up to 25 centimetres a year in some parts of the city. The consequences are serious: saltwater intrusion, destroyed infrastructure and considerable water losses are forcing the city to continuously pump affected areas dry.
This example shows the urgent need to develop and implement effective strategies to tackle this global problem in order to minimise long-term damage and risks.