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China launches “sponge cities” project to tackle flooding


The public authority responsible for water regulation in China has recently highlighted the damage caused by flooding in the country. In 2014, there was flooding in 125 cities. The combination of rapid urbanisation and climate change have made cities more vulnerable to these natural disasters. Since conventional solutions, such as extending sewage systems, are no longer enough to contain the problem, in late September 2015 the Chinese government launched the “sponge cities” programme. This scheme applies a new approach to integrating rainfall into the water cycle.

City of Shenzhen – Credit: Thinkstock – Zhudifeng

16 pilot cities to become “sponge cities”

Over a period of three years, the “Sponge Cities” programme will receive EUR 85 million in funding for each of its 16 pilot cities, including Wuhan, Chongqing, Xiamen and Shenzhen. The scheme primarily involves the construction of new infrastructure that is adapted for heavy rainfall, as experienced by Chinese cities during monsoon season, as well as the redevelopment of urban areas. As such, the pilot cities will feature new green spaces, green roofs, absorbent ground surfaces, such as permeable concrete, and wetlands, with a view to optimising the absorption and runoff of rainwater. Alongside this, campaigns will be broadcast to residents through traditional media and social networks in order to raise awareness. The Chinese government is also encouraging private stakeholders to invest heavily in the programme.

A programme that relies on a circular economy

Could rainwater be an opportunity, rather than a problem? The aim of the programme is to increase the resilience of cities that are prone to flooding, and to develop a recycling system for the water collected through the new infrastructure. The water could thus be used to replenish groundwater reserves, to irrigate green areas, and to replace tap water for some domestic uses. Populating green spaces with plants known for their filtering properties could act as a first step in filtering the rainwater. Furthermore, the new installations will consume less energy than traditional solutions, such as imported water, pumping systems and so on, thus enabling cities to reduce their energy bills.

The city of Shenzhen: a textbook case

Situated in southern China, which accounts for eighty percent of the country’s water resources, the city of Shenzhen (in the Guangdong province) is facing a major water shortage, in spite of heavy rainfall and flooding. Due primarily to the pollution of reserves and inadequate infrastructure, Shenzhen had just 160 m3 of water per resident in 2010 (the absolute scarcity threshold set by the UN is 500 m3/resident per year). . The city currently imports the water it needs from the north-eastern city of Huizhou, and it is forecast that demand will exceed supply by 2020, due to population growth. This situation justifies the implementation of the “sponge cities” programme, which should make the city autonomous. The Mass Sports Centre already boasts a permeable ground surface on its main square. This surface recovers around 10,000 m3 of water per year, which is then used for sprinkling and cleaning. In parallel with this programme, the city has improved its wastewater recycling system and put in place measures to reduce water consumption. These measures include closing down industries that consume large volumes of water, introducing progressive water pricing, and installing water-saving systems in public buildings.

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