'Sponge cities' absorb urban flooding woes

Dalian benefits

In 2016, approval was given for Zhuanghe, a county-level city in Dalian, Liaoning province, to be included in the second group of pilot cities receiving central government financing for sponge city construction.

Covering 21.8 sq km, the Zhuanghe pilot area lies in the south of the city on the lower reaches of a three-river estuary.

Zhu Qinghui, director of the Zhuanghe Sponge City Construction Office, said 143 demonstration projects involving investment of about 3.35 billion yuan have been completed in pilot areas.

"The construction of a sponge city has brought real benefits, with the rivers becoming cleaner and the environment improving," Zhu said.

In 2018, nearly 1,000 relict gulls, a rare and little-known species, were attracted to and spent the winter in Zhuanghe for the first time.

Zhu said that in summer last year, the population of black-faced spoonbills, one of the world's most endangered species, reached a record 165 in Zhuanghe.

In late August, under the influence of Typhoon Bavi, the eighth of the year, rainfall in Zhuanghe reached 131 millimeters in a single day. However, there were hardly any problems, such as flooding, in the sponge city construction area.

"The source emission reduction system, the pipe network terminal regulatory and storage system, as well as the large drainage system play vital roles," Zhu said.

In constructing a sponge city, Zhuanghe, a typical county-level city in Northeast China, faced difficulties such as weak management and a shortage of capital and human resources.

As a result, Zhu said a long-term sponge city management and control mechanism was set up, innovative operation teams introduced, along with new management and control methods. Construction was also accelerated.

Zhuanghe learned from the first group of sponge city pilot projects how to set up new systems, bid for projects, and construct and design infrastructure, thus avoiding many problems, Zhu added.

The city also launched an innovative sponge city planning system, top-level design framework and put forward the concept of building an "energy-saving sponge city", which has been widely promoted among small and medium-sized cities in Northeast China and those in coastal areas.

Seeing the huge potential of the Chinese market as more areas began constructing sponge cities, Japanese entrepreneur Daisuke Itazawa introduced technology from his country to manufacture water-retaining bricks in China.

In 2017, Itazawa took part in setting up a joint venture in Dalian.

President of the Dalian Deta-Shinwa Environmental Science and Technology Development Co, located in the Dalian section of the China (Liaoning) Pilot Free Trade Zone, Itazawa said that in many parts of China there is a shortage of water resources and that control and drainage problems persist during the flood season.

Bricks that retain and filter rainwater have been particularly effective in resolving such issues, he said.

Itazawa added that such bricks produced by his company for use on roads have been a highly popular element of sponge city construction.

He said this construction should involve long-term preparation and technical resources, adding that as it took Japan 50 years to control its water system, this illustrates just how hard and long-term such work is.