CHENGDU, Oct. 6 (Xinhua) -- Every late autumn, groups of black-headed gulls arrive "as scheduled" in Luzhou City on the upper reaches of the Yangtze River. Circling over the water, the red-billed oceanic birds always attract a crowd of bird-watchers.

"The time for meeting the birds this year is coming soon," said Li Tian, a resident in Luzhou in southwest China's Sichuan Province.

Besides Luzhou, the migratory birds are also frequent visitors to Sichuan's Deyang, Neijiang and other cities where the Tuojiang River flows. Local enthusiasts have all set up bird-watching and bird-love associations.

The black-headed gull, a rare bird species with white feathers and red beak and claws, is regarded as the "barometer" of the ecological environment in watersheds. The spotting of more such birds reflects the promising results produced by Sichuan's green efforts in recent years.

Known as "a province of thousands of rivers," Sichuan is an important water conservation area and a core area for ecological construction along the upper reaches of the Yangtze River.

Among Sichuan's many water systems, Tuojiang River shares a pivotal position, not only because it is an essential tributary of the Yangtze River, but also due to the fact that the 25,500 square km it flows through covers the most concentrated, densely populated and economically powerful areas in the province.

Since the 1990s, the continuous acceleration of industrialization and urbanization exerted huge environmental burdens on the Tuojiang River, making it once the most severely polluted river in Sichuan.

A treating-water pollution campaign was consequently launched in 2018. After years of efforts, the water quality of the Tuojiang River flowing into the estuary of the Yangtze River has now reached its best level in 20 years.

Building a solid ecological barrier in the upper reaches of the Yangtze River not only ensures the ecological safety of the downstream waters but also enables local residents to experience the beauty of life in a good ecological environment.

Chengdu City, capital of Sichuan Province, has embraced more blue skies in recent years thanks to the promotion of air pollution prevention and control work. Watching the snowy scenery of distant mountains has become a new hobby for local residents.

According to the Chengdu Mountain View Data Report released annually on social media platforms by a large group of photography enthusiasts, the number of days when people were able to see snow mountains from downtown Chengdu increased from 50 days in 2017 to 63 days in 2021.