What is a sponge city?
Sponge city is to compare the city to a sponge, which can absorb, store, infiltrate and purify the rain, add groundwater and regulate the water cycle during the rainfall, and in the drought period release the stored water and make use of it.
Sponge is the concept of a new generation of urban rainwater management. Through the strengthening of urban planning and construction management, buildings, roads, greenbelts and water systems and other ecosystems are able to fully absorb, store, infiltrate and slowly release rainfall so as to effectively control rainwater runoff and realize the urban development way of natural accumulation, natural infiltration and natural purification. Sponge city construction can help the city have a good "elasticity" in adapting to environmental changes and dealing with the natural disasters caused by rainwater.
The purpose of the sponge city planning and construction is to make the city have a healthy water cycle, a good ecological environment and a beautiful urban landscape system. Sponge city planning and construction should follow the principles of planning guide, ecological priority, safety first, adjusting measures to local conditions and overall construction.
Absorbing The Future
- Urban Rainwater Management
- Green Intrastructure
- Low impact development
Why build sponge cities?
City is the comprehensive product of human’s civilization development, and about half of the world’s population is living in cities. China's urbanization rate is close to 57.35% (based on the 2016 data of National Bureau of Statistics), and by 2020, China's urbanization rate will exceed 60% (based on the 2017 government work report of Premier Li Keqiang), meaning that more than 800 million people will live in cities. The process of rapid urbanization brings high-speed social and economic development, but it also causes many problems, for example, the woodlands, farmlands and water systems and other ecological spaces are occupied, destroyed, fragmented and finally functionally declined, and the city underlying surface turns into stereoplasm, etc. In view of cities' current prominent hydrological security issues like urban waterlogging and water quality degradation, the government has put sponge city construction to the national strategic level. President Xi said at the Central Urbanization Work Conference in 2013:" In order to solve the problem of urban water shortage, we must conform to nature, give priority to staying the limited rainwater and making use of natural forces to drain away water, and thus build a sponge city of natural accumulation, natural infiltration and natural purification." So far this is the first time that the word "sponge city" appears in the central documents.
Half the world's population is living in cities.
In the case of waterlogging, according to the survey data of the Ministry of Housing and Urban-Rural Development, from 2008 to 2010, 62% of the cities in China had waterlogging. 137 cities have endured waterlogging for more than three times, and 57 cities’ longest ponding time exceeded 12 hours. Waterlogging has obviously become a normal city problem faced by nearly half of the cities in China, resulting in a huge loss of property and life casualties.
How to build a sponge city?
The construction of a sponge city involves a large number of concepts and techniques from different areas, such as water industry, planning, construction, landscape architecture, forestry and environmental protection. The essence of it is to use urban natural systems (green infrastructures), including rivers and lakes and other water systems, wetlands, woodlands, and farmlands, to multi-levelly control, scatter and strand water in the source of rainfall and combine with the city's pipe network facilities (gray infrastructures) to reduce the city's water problems.
Experience shows that under normal climatic conditions and complete urban pipe network construction, a typical sponge city can store up more than 80% of the rain. For the city of natural endowment, sponge city construction focuses more on the function recovery of water, wetlands and woodlands. For other cities of higher level of urbanization and inferior natural endowment, especially old cities, the cities’ sponge transformation task rather relies on the "sponge" function of urban garden greening, such as roof greening, urban green parks, and artificial wetlands and so on.
The sponge city construction is a classic case of urban sustainable development in combining green infrastructures and gray infrastructures. On the basis of the city’s complete drainage system, it aims to enhance the additional function of urban natural system components, make the hydrological function of urban complex ecosystem reach a dynamic balance, and ultimately solve the problem of urban waterlogging.
Due to the complex construction, large investment demand and long return cycle, it is necessary for sponge cities to follow the urban development laws and natural laws, respect civilian force, use civilian resources and play the citizens’ principal role. Government investment is certainly an important force for the sponge city, but the social forces also need to be widely mobilized. Take as an example of the foreign advanced urban construction case, the costs of sponge city construction account for 20% of the total cost of urban construction, and the costs may be higher due to the historical problems of domestic urban drainage system. This part of financial deficit requires the civil and government’s joint efforts to introduce social funds, and carry the project out together with the governmental investment. Meanwhile, the projects like urban ecological greenbelts and green roof platforms also need civilian participation in the implementation.
Current sponge city construction
In 2005, the General Office of the State Council issued the Guiding Opinions on Promoting the Construction of Sponge Cities. It points out that through the construction of sponge city, the measures such as "infiltration, stagnation, storage, purification, usage and drainage" and so on need be adopted to minimize the impact of urban development and construction on ecological environment, and absorb and use 70% of the rainfall on the spot. By 2020, more than 20% of the urban built-up area should meet the target requirements. By 2030, more than 80% of the urban built-up area should meet the target requirements.
To this end, the Ministry of Finance, Ministry of Housing and Urban-Rural Development, and Ministry of Water Resources in 2015 and 2016 carried out the pilot work of national sponge city construction. The first batch of 16 pilot cities are Qian'an, Baicheng, Zhenjiang, Jiaxing, Chizhou, Xiamen, Pingxiang, Jinan, Hebi, Wuhan, Changde, Nanning, Chongqing, Suining, Guian New District and Xi Xian New District. The second batch of 14 pilot cities are Beijing, Tianjin, Dalian, Shanghai, Ningbo, Fuzhou, Qingdao, Zhuhai, Shenzhen, Sanya, Yuxi, Qingyang, Xining and Guyuan.
What do we do?
Private institutions in the construction of sponge city can achieve a lot by cooperating with the government. Therefore, the Paradise Foundation established the working group led by the director Ma Huateng, and united with The Nature Conservancy (TNC) to carry out the special work of sponge city. It has also signed a memorandum of cooperation with Shenzhen, using Shenzhen as a window city to carry out a series of work like sponge city policy research, case demonstration and promotion to coordinate with the government to better promote the pilot work of the sponge city.
Our work is mainly carried out from the following four aspects:
1. Training Program for City Governors
We will carry out the training of sponge city construction concept and the best practice for the city's mayor and municipal party secretary so as to get across the concept, methods and practice of sponge city and better promote its construction.
2. Sponge City Policy Research
We will do special research by combining with the planning, construction, financing and other issues in sponge city construction process, and provide the government with rational proposals through appropriate channels.
3. Case Study of Sponge City
We will introduce overseas advanced cases of sponge city construction, operation and maintenance so as to provide reference for domestic sponge cities, and from a civil perspective promote experience exchangement between China and foreign countries.
4. Concept Promotion of Sponge City
We will spread the concept of sponge city through the use of modern media means to help more citizens understand sponge city, promote sponge city, and participate in the construction of sponge city in the flesh. We will also set up the "sponge city award" to reward and publicize the outstanding individuals, planning cases, construction cases, operating management cases and social participation cases during the construction process of sponge cities.
By 2030, 80% of urban built-up area should reach target goal.
Concept of green infrastructures
Green infrastructure is not a new concept. It is linked to the concepts of greenway and ecological network. They interconnect with each other, and their core issue is how to create a harmonious and sustainable environment by planning the open space system of the city. Green infrastructure concept is the extension of urban green space construction theories such as park systems, greenbelts, green roads and ecological infrastructures.
The construction of the sponge city is a better link to the green infrastructures and the gray infrastructures. Compared to gray infrastructures, green infrastructures are able to generate considerable ecological benefits, and the costs of construction and maintenance are relatively low, but this does not mean that all gray infrastructures should be turned into green. What we need to do is to make gray infrastructures and green infrastructures be better connected to play a coordinated role.