YINCHUAN, Sept. 1 (Xinhua) -- Gu Jincheng takes a daily stroll with his grandson at the Yellow River Wetland Park in Hetan Village, Yinchuan, capital of northwest China's Ningxia Hui Autonomous Region, gratified by the drastic change of the place from a smelly quagmire to a natural oxygen bar over the past few years.

The park now also serves as a natural shelter for migratory birds. But few could imagine that just less than one decade ago, the park was a saline-alkali land on the river flat, with hardly any grass grown and raw sewage poured by nearby drains.

"The water stank, full of dirty bubbles. Even animals wouldn't drink from it. Crops withered away after being irrigated by the water," Gu recalled, adding that the river had even made Hetan Village, where he hailed from, smelly.

Starting in 2018, a wetland purification project was launched by Yinchuan to curb the sewage and other pollutants from harming the Yellow River while preserving the ecological environment along the river by building wetlands and modernizing the local drain system, said Cao Jing, head of the water ecology and environment branch, the city's ecology and environment bureau.

"The city has set up eight protected wetlands, including five man-made ones, covering a total area of 733 hectares," said Cao.

"The 15 wastewater disposal factories in Yinchuan have also been upgraded while their drain systems have been renovated," she added.

Thanks to the municipal government's eco-friendly efforts, the quagmire in Hetan Village has now turned into an environmental filter to absorb and control the pollution from the city, while functioning as a natural park for local people and visitors.

Moreover, the park and many other wetlands in Ningxia along the Yellow River have become a nationwide famous site for photographers to take pictures of migratory birds.

"With the growing area of wetlands and the improving environment, suitable habitats for migratory birds are on the rise," said Li Zhijun, secretary general of Ningxia's bird observation association.

"Many migratory birds have changed their course and visited Ningxia, which expanded the migratory bird varieties in the region," Li added.

Yinchuan's wetlands have become a true paradise for wild birds, as some 240 different kinds of birds have come to build nests during spring and fall, a sharp increase compared with the initial 169 kinds of birds recorded before the project.