New Sponge City

I. Definition of a Sponge City

　　Cities can exhibit remarkable “resilience” by functioning like sponges—absorbing, storing, infiltrating, and purifying water during rainfall, and then releasing and utilizing the stored water when needed. This enhances urban ecosystem functions and reduces the occurrence of urban flooding.

　　II. Background of Sponge City Construction

　　On December 12, 2013, General Secretary Xi Jinping emphasized in his speech at the Central Conference on Urbanization: “When upgrading urban drainage systems, priority should be given to retaining limited rainwater, maximizing the use of natural forces for drainage, and building sponge cities that naturally store, naturally infiltrate, and naturally purify water.”

　　III. Sponge City Design Concept

　　Urban development will prioritize the use of “green” measures such as vegetated swales, rain gardens, and sunken green spaces to manage stormwater runoff, with “slow release and gradual attenuation” and “decentralized source control” serving as the core planning and design principles.

　　IV. Principles Followed by Sponge Cities

　　Sponge city development should adhere to principles such as ecological priority, integrating natural processes with engineered solutions. On the premise of ensuring urban drainage and flood resilience, it aims to maximize the storage, infiltration, and purification of rainwater within urban areas, thereby promoting the sustainable use of rainwater resources and the protection of the ecological environment.

　　The construction of sponge cities should ensure the full utilization of both tap water and rainwater, with water quality purified and reused through various treatment processes. The implementation plan for the comprehensive utilization of rainwater should be tailored to local conditions, aligned with the specific circumstances and level of economic development in each region, and carried out in a phased manner—starting with simple measures and gradually progressing to more complex ones, from easy to difficult.

　　The water systems of sponge cities should be treated as resources for sustainable utilization. Pollution control should begin at the source, with tailored water collection and treatment strategies implemented based on the characteristics of different underlying surfaces and project requirements. This approach enables on-site infiltration and utilization of moderate- and small-scale rainfall events, while large- and extremely large-scale storms are managed through on-site detention followed by delayed release, thereby leveraging temporal staggering to reduce pressure on the urban drainage network.

　　Emphasize end-of-pipe water purification to deliver drinking water that meets international health standards, thereby reducing pipeline infrastructure investment by approximately 80% while also lowering energy and operational costs associated with wastewater treatment, reclaimed water reuse, and sewage diversion. Moreover, treated reclaimed water that meets regulatory standards can be locally integrated into urban water systems, enhancing landscape aesthetics and creating a cohesive water network.

Treatment of Black and Odorous Water Bodies in Rivers and Lakes