BEIJING — The water quality of the Yellow River, China's second-longest river, has seen improvement in the past five years, the environment authority said.

The river's water quality improved from mild pollution to good during the 13th Five-Year Plan period (2016-2020), according to the Ministry of Ecology and Environment.

About 84.7 percent of the surface water in the river was graded Class I to III (good quality) in 2020, up 25.6 percentage points from 2016.

For the tributaries, 80.2 percent of the surface water was graded as good quality in 2020, up 31.2 percentage points from 2016.

Surface water quality in China is divided into five classes, with Class I being the best.

In 2020, China reported improved air and water quality as well as reduced carbon dioxide emissions amid the country's efforts to boost green development, an official report showed in March.