BEIJING, Jan. 17 (Xinhua) -- The water quality of the Yangtze River, China's longest waterway, continued to improve last year, official sources said Friday.

The proportion of water with good quality rose to 91.7 percent, up 4.2 percentage points year on year, while the proportion of water that is functionally unusable fell to 0.6 percent, down 1.2 percentage points from a year earlier, Zhang Bo, chief engineer with the Ministry of Ecology and Environment, told a press conference.

Of the 12 inferior sections of the Yangtze River that have to be improved according to the Yangtze River Conservation and Restoration Action Plan, the water quality of nine sections is no longer rated below Grade V, the worst in China's water quality grading system, due to unremitting efforts to crack down on pollution. The remaining three sections also saw improvement in water quality.

A survey conducted by the ministry last year found that there were over 60,000 sewage outlets in the Yangtze River basin.

China has pledged greater efforts to restore the environment of the Yangtze River, including cracking down on illegal emissions from ships and punishing offenders polluting the environment.