“It was clear from the proposals that from a practical perspective, no one knew exactly what it meant,” Lam acknowledges. “But the ideological concept had taken hold.”
Stormwater systems that send runoff into sewers are largely inadequate at the scale of major cities. “Until recently, many of the decision-makers and experts in the drainage industry supported a larger, gray-infrastructure, civil engineering approach to water management,” notes Andrew Buck, an urban planner at the Beijing-based design firm
Turenscape (which is led by Yu). “But most of these systems are overloaded, and urban floods happen even in moderate sustained rains.”
Central government wants to change the model from gray to green. Still, not many people know how to design a sponge city. At the same time as the model cities are being funded and rolled out, local officials are attempting to learn how they work in practice.
“I sit on the National Sponge City Technology Committee,” Yu says. “Businesses want to sell us their technology, but technology is not really what we need. Even if you have permeable pavement, it’s not really the central idea.”
Reverse-engineering a city to make it more spongey requires a mental rather than physical shift, he argues. “It’s a whole new philosophy of dealing with water. It is about how we plan and design our cities in an ecological way. Not about piecemeal, manmade engineering projects. So we need to avoid this kind of trap.”
Sponge-city design could also run up against China’s centralized planning system.
“Some aspects of sponge city will not work in northwest China, but will work in southeast China, depending on the localized climate,” says Buck. (For instance, Wuhan deals with regular flooding, while in Xixian, the problem is drought.) “But China’s not used to doing that. Beijing chooses one model and stamps it out to every part of the country.”
Finally, there is the delicate question of financing. While the government has promised to fund 16 sponge cities in the short term, it is looking for public-private partnerships to make a long-term social investment. Still, it’s not clear how sponge cities will make money for investors.
Infrastructure projects are usually lucrative for local governments in China. Thousands of acres of cheap, state-owned land (often reclaimed wetlands) are sold off to developers, while the projects themselves drive economic growth and create thousands of jobs.
But sponge cities are different. They don’t need to consume vast amounts of resources: quite the opposite.
“The question is how to build the relationship between the business interest and the common interest,” says Yu. “The government is trying to find public-private partnership models that can be applied to green sponge construction projects.”
One idea could be for a city to buy ecological services from a private company. “But how you measure such ecological services is a big challenge,” Yu admits.
So far, the central government has been successful in communicating its desire for change. But it’s not clear whether provincial officials have the tools to live up to the rhetoric.
Local administrators need criteria to guide them when commissioning sponge-city services, Lam points out. “In China, there is no existing system for measuring a project’s long-term benefit for society, only tools to measure short-term gains. So how will money be distributed by local government?” he says.
Sponge cities might well turn out to be ecologically sustainable. But from a practical perspective, their future looks far less certain.