Sponge Cities, China’s Nature-based Solutions for Urban Water Management

Urbanization, land-use changes, and the climate crisis are increasing the risk of flooding in major cities worldwide. In China, where cities have been expanding rapidly, nature-based solutions like sponge cities emerge as a climate-adaptive urban design, especially for sustainable urban water management.

Urban Water Challenges

Urbanization usually calls for the development of the urban built environment to accommodate population growth. Most of the time, this involves gray infrastructures, with concrete, steel, and so on.

However, the spread of impermeable surfaces and inadequate drainage systems makes cities increasingly vulnerable to waterlogging and flood damage. Extreme weather events and rising sea levels due to climate change further exacerbate flood risks. At the same time, cities also face growing clean water demands because of drought and water pollution.

China’s cities are no exception. In Hunan Province, for instance, floods in 2020 submerged more than 21,000 houses, damaged 600,000 hectares of farmland, and affected nearly seven million people. This situation highlights the issues of conventional drainage systems and increasingly reduced soil absorption capacity in dealing with heavy downpours.

China’s Sponge Cities

In response, the Chinese government officially launched the sponge cities initiative in 2015. This model emphasizes the use of green infrastructures, such as urban green spaces, rain gardens, permeable pavements, retention ponds, and green roofs. Unlike conventional drainage systems, sponge cities are designed to facilitate water infiltration, storage, and purification to reduce urban flooding while enhancing water security.

The national target is that by 2030, 80% of China’s urban areas should be able to absorb and reuse at least 70% of rainwater. Some cities and districts have already implemented this model. In Chongqing, a 700 m² sponge garden can hold water from a 2,000 m² impermeable area while also serving as an educational public space on sustainable water management. Nanjing has tested various permeable pavements that reduce runoff volume and velocity, though maintenance remains a challenge. In Quanzhou, a combination of green spaces and permeable pavements has reduced pressure on drainage systems while improving overall urban environmental quality.

Still, the scale of rainwater reuse remains limited. Reviews of sponge cities implementation show that most projects have primarily focused on flood risk reduction and runoff control, with rainwater harvesting and reuse gradually introduced in some pilot sites.

Toward Climate-Adaptive, Resilient Cities

Beyond flood management, sponge cities can bring social and environmental benefits as well. These spaces also serve as recreational areas, improve air quality, and help mitigate the urban heat island effect.

China’s sponge cities are still evolving, with success rates varying across pilot districts and cities. So far, their effectiveness heavily depends on environmental conditions, local design, and regular maintenance.

Still, this model and implementation offer insights into nature-based solutions in urban areas, especially those vulnerable to flood. Ultimately, the key lies in consistent policy support, the selection of technologies adapted to local contexts, long-term investment, and community participation.

Editor: Nazalea Kusuma