Chongqing commits to 'sponge city' concept

Colorful display boards are used to decorate the garden and explain the concept of a "sponge city" to the public. [Photo provided to China Daily]

In October 2015, the State Council, China's Cabinet, launched the sponge city pilot project, in which 30 metropolises are taking part. The project's aim is to ensure that by 2030, around 80 percent of urban areas should be able to capture and reuse at least 70 percent of their rainwater.

The southwestern metropolis of Chongqing has developed its sponge city capabilities particularly rapidly, and is looking for ways to solve the water problems afflicting urban areas of West China.

Situated in the Chongqing Liangjiang New Area, Yuelai New City, which covers 18.67 sq km, was one of 16 sponge cities on a national pilot list of climate-resilient urban designs released in 2016. More sponge city projects are also underway.

In December 2020, research conducted by the local housing and urban-rural development department in partnership with CMCU Engineering Co, a state-owned sci-tech engineering company based in Chongqing, discovered that the soil in Chongqing has insufficient storage capacity for rainwater.

"This means we have to use larger diameter storm sewers, which are more expensive, and we face a greater risk of urban floods," said Mo Tianzhu, an employee of the Chongqing Comprehensive Management Center of Urban Pipeline, which is affiliated with the Chongqing Municipal Department of Housing and Urban-Rural Development.

"The garden acts like a sponge as a result of its various underlayers of different permeability that control leakage, slowing down rainwater runoff and mitigating the effect of peak torrential rains. Additionally, the rainwater storage process filters out pollutants and the resultant water evaporation helps alleviate the urban heat island effect on the local microclimate," Mo said.