China's Sponge City programme aims to improve resilience to urban expansion and climate change by enabling cities to save and resupply rainwater. It is crucial for cities such as Beijing and Jinan, which suffer water shortages even after severe flooding. However, several hurdles must be overcome to get it working efficiently.

The programme will involve some 30 pilot cities this year (see www.mohurd.gov.cn). They will create a 'sponge' infrastructure to detain runoff, control flooding, recharge groundwater and reuse storm water. The project still has to recruit enough planners, designers and construction workers to support this colossal initiative. Time is short for completing technical training.

Plans and technology will need to be customized for individual cities, where local weather conditions and the degree of urbanization can vary considerably; a blanket strategy will not work.

Once in place, the sponge infrastructure should be combined with conventional drainage systems, particularly in areas of medium- and high-intensity urbanization.