Sponge Cities in Chinaincluding Wuhan, Chongqing and Xiamen, are using green infrastructure to address urban water issues. These cities incorporate rain gardens, wetland restoration and permeable pavements to improve water absorption and reduce flooding. This initiative is part of China’s broader effort to create resilient and sustainable urban environments.

What is the Sponge City concept?

The sponge city concept is an innovative approach to urban planning and design aimed at improving a city’s resilience to climate change and managing urban water challenges. A sponge city absorbs, stores, and releases rainwater, much like a sponge, to reduce flooding, replenish groundwater, and improve water quality. This concept integrates green infrastructure, nature-based solutions, and sustainable urban design to create a more harmonious relationship between urban development and the natural environment.

China is at the forefront of the sponge city movement, with a government-led initiative to transform urban areas into resilient, water-absorbing environments. The country has designated more than 30 cities as sponge cities, including Wuhan, Chongqing and Xiamen. These cities are using advanced technologies and innovative designs to sustainably manage water and enhance urban resilience.

Wuhan

Wuhan, a major city in central China, is a leading example of the sponge city conceptAs one of the pilot cities, Wuhan has implemented numerous projects to address frequent flooding and improve water management.

Key projects and technologies:

1. Green roofs: Wuhan has installed green roofs on residential, commercial and public buildings on a large scale. These roofs absorb rainwater, reduce runoff and improve insulation.
2. Permeable paving:The city uses permeable pavements in public squares, streets and parks to allow rainwater to infiltrate into the ground, reducing surface runoff and replenishing groundwater.
3. Constructed wetlands: Wetlands are created to naturally filter and store rainwater. These wetlands increase biodiversity and provide recreational spaces for residents.
4. Rain gardens:These are being implemented in various neighborhoods to collect and filter rainwater, thereby reducing the burden on the city’s sewer system.

Statistics:

• Wuhan aimed to ensure that 70% of the urban area could absorb and reuse at least 70% of rainwater by 2020.
• More than 389 projects were launched, covering an area of ​​approximately 20.9 square kilometers.

Chongqing

Chongqing, a mountainous city in southwest China, faces significant challenges due to its topography and heavy rainfall. The sponge city initiative here aims to reduce flood risks and improve water quality.

Key projects and technologies:

1. Green infrastructure:Chongqing has developed green areas and parks with permeable surfaces to manage rainwater and create urban green spaces.
2. Rainwater harvesting systemsBuildings are equipped with systems to collect and store rainwater for non-potable uses such as irrigation and toilet flushing.
3. Bioswales:These landscape features are designed to concentrate and drain stormwater while removing debris and pollution.
4. Underground water storage:Large underground tanks are used to store excess rainwater, which can be used during dry periods.

Statistics:

• Chongqing’s sponge city area covers about 20 square kilometers, and more than 250 projects had been completed by 2020.
• Surface water runoff in the city has decreased by about 25%, significantly reducing the risk of flooding.

View more at Sponge City Tampa

Xiamen

Overview: Xiamen, a coastal city in southeastern China, focuses on balancing urban development with natural water cycles. Its sponge city projects aim to reduce flood risks and protect the coastal environment.

Key projects and technologies:

1. Green roofs and walls:These installations on buildings help absorb rainwater, reduce heat island effects and improve urban aesthetics.
2. Permeable paving:These pavements are widely used in public spaces. They reduce water runoff and allow water to seep into the ground.
3. Urban wetlands and lakes:Xiamen has restored and created wetlands and lakes to manage rainwater, enhance biodiversity and create recreational areas.
4. Desalination of seawater:As part of integrated water management, Xiamen uses desalination technologies to replenish freshwater supplies.

Statistics:

• In 2020, Xiamen’s sponge city projects covered an area of ​​about 19 square kilometers.
• The city has reduced flood risk by 30% and improved coastal water quality through better stormwater management.

Economic and ecological impact of Chinese sponge cities

Economic impact

1. Reducing water damage:
   • Cost savings: By mitigating flood risk, sponge cities significantly reduce economic losses associated with flood damage. This includes savings on infrastructure repairs, health care costs from waterborne diseases, and losses from business interruption.
   • Insurance:A lower flood risk can lead to lower insurance premiums for both municipalities and homeowners.
2. Higher real estate values:
   • Real estate market: Improved urban environments with green spaces and better water management can increase property values. Residents are willing to pay a premium for properties in areas with improved livability and reduced flood risks.
   • Investment attraction:Sponge City’s features make areas more attractive to investors and developers, which promotes economic growth.
3. Creating employment:
   • Construction and maintenance:The development and maintenance of green infrastructure, such as green roofs, permeable pavement, and wetlands, creates jobs in construction, landscape architecture, and environmental engineering.
   • Research and development:Continued innovation in sustainable urban design and water management technologies boosts employment in R&D sectors.
4. Cost efficiency:
   • Long term saving:While the initial investment in Sponge City projects may be high, the long-term savings in reduced flood damage, lower water treatment costs, and improved public health can more than offset these costs.
   • Public services:Efficient water management reduces the pressure on public water and sewer systems, potentially reducing municipal operating costs.

Environmental impact

1. Flood control:
   • Stormwater management: Sponge cities absorb and store rainwater, reducing surface runoff and preventing urban flooding. This helps protect natural waterways and reduces erosion.
   • Groundwater recharge:By allowing water to infiltrate into the ground, sponge cities help replenish groundwater levels, supporting a sustainable water supply.
2. Improving water quality:
   • Filtration of pollutants:Green infrastructure such as wetlands and bioswales naturally filter pollutants from stormwater, improving the quality of water that flows into rivers, lakes and oceans.
   • Less sewer flooding:By managing rainwater at the source, sponge cities reduce the frequency and volume of combined sewer overflows, reducing the amount of raw sewage entering natural water bodies.
3. Biodiversity and habitat creation:
   • Urban green spaces:Green roofs, parks and wetlands provide habitats for various plant and animal species, thus increasing biodiversity in the city.
   • Ecosystem services:These green spaces provide ecosystem services such as carbon sequestration, air purification and temperature regulation.
4. Climate resilience:
   • Heat island reduction: Vegetation and water features in sponge cities provide cooling in urban areas, reducing the heat island effect and improving thermal comfort.
   • Climate adaptation:Sponge cities increase resilience to climate change by better managing extreme weather events, such as heavy rainfall and drought.
5. Sustainable urban development:
   • Integrated planning:Sponge city initiatives promote holistic and integrated urban planning and ensure that development projects consider environmental impact and sustainability.
   • Community Involvement:These projects often involve local communities in planning and implementation, creating a sense of ownership and stewardship for the environment.