Rui Dongliang, project manager of Shanghai Lingang New City Investment and Construction, has participated in the construction of the 54-hectare park since it began in 2019. Lingang was a model for the "sponge city" project in Shanghai, and the park an important part of it, he says.

Besides retaining rainwater from runoffs, another function of the facility is to clean and purify water through eco-engineering.

The sponge park was intersected and divided into four parts by two rivers, and the northeast part of the park is a 9.6-hectare wetland with several ponds and floating islands that forms a demonstration zone for the sponge system.

Xu says the water pumped into the park from the river first goes through a skimmer to remove surface debris before making its way into a pond to sediment. Following that, the water flows through several levels of filtration ponds with aquatic plants such as vallisneria and water lilies.

"The system can purify up to 15,000 cubic meters of water per day, as the water quality rises from Grade V to Grade III when it flows back to the river," Xu says, adding that the system is also connected with the rain drainage so that it can treat the rainwater from the surrounding areas.