Former ‘Stinky Ditch’ Turned into Chongqing’s Largest Bypass Wetland Park

Chongqing- Fish swimming around in the crystal-clear pond, with the immense greenery and beautiful flowers, including silene pendula, thalia dealbata, sage, rhododendron, golden chrysanthemum and yellow iris... This is what can be seen at the Liangtan River Wetland in Hangu Town of Chongqing Hi-Tech Industrial Development Zone recently.

Who would have thought that once the river here was sludgy and overgrown with weeds?

Improving the water environment

In fact, the Liangtan River serves as an important ecological water system in the Western (Chongqing) Science City.

Over the past three years, the Science City has carried out water pollution control of the Liangtan River and implemented source control, pollution interception, pollution treatment, and other remediation measures in accordance with the principle of regulating the main streams and tributaries collaboratively, and treating pollution before restoration.

The water quality of the Liangtan River has continued to improve as a result of the River Chief System, an institutional innovation by the government to deal with the ecological environmental crisis in the river basin, which promotes the treatment of the river in a long run.

Specifically for the system, members of the Communist Party of China and government officials at all levels in China act as river chiefs. They are responsible for organizing and leading the management and protection of the corresponding rivers and lakes, with the main task of protecting water resources, preventing and controlling water pollution, improving the water environment, and restoring the water ecology.

In the first quarter of 2022, the water quality of the Laijiaqiao section of the Liangtan River met the Class III surface water quality standard in all surface water sections monitored by the state. Class III is mainly applicable to the second class of protected areas for centralized sources of drinking water, protected areas for the common fish and swimming areas.

Now, in the section of the Liangtan River Hangu, the riverbank becomes green and the river water becomes clear. Additionally, a river wetland was built, which covers an area of about 120,000 square meters, attracting many people to visit and academics to study.

Wetland purification

According to the project designer Chen Jie, also general manager of the Eco-Environment Division of the T.Y.Lin International Engineering Consulting (China) Co., Ltd., the wetland was built by artificial enhancement and simulation of natural ecology by making use of the space of the river beach, combined with the sewage collection pipeline system, the sewage treatment plant and other treatment measures.

This is to enhance the river water quality by way of a bypass wetland and promote water quality improvement, said Chen.

Chen also introduced that the core process of the wetland is "sand pond + surface flow wetland + submerged wetland + sedimentation pond".

In simple terms, the water in the mainstream of the Liangtan River, which is lifted, pre-treated by the sand sedimentation ponds and biological rotary system, enters the surface flow wetland. Then it is evenly distributed to the submerged wetland through the water distribution ponds, and the water from the wetland flows into the Liangtan River again through the sedimentation ponds and outlet ponds.

"The wetland water distribution system, wetland fillers, and plants have been carefully designed," said Chen. "The canna is the major plants, which not only purify the water but also become a scenery in summer when they are in full bloom."

"The wetland fillers are mainly made up of different sizes of gravel and ceramics, about four-five layers and one meter high, which can play a good role in adsorption," he added.

The Liangtan River river water wetland has been in stable operation for about three years since its completion. After the river water has been purified by the wetland, the river's pollution load has been greatly reduced, and its effluent is better than surface water Class V.

This can be mainly used in agricultural water areas and general landscape waters, which effectively promotes the river water quality overall.

According to the person in charge of the Chongqing Ecology and Environment Bureau of Hi-Tech Industrial Development Zone, this wetland not only promotes the overall improvement of the river's water quality, but also improves the river's landscape and expands the city's functions through artificial enhancement and near-natural design, resulting in great environmental, ecological and social benefits.

(Shi Jiaqi, as an intern, also contributed to this report.)