Water quality in China's largest saltwater lake Qinghai Lake remains good, said local authorities on Saturday.

Results from three monitoring stations of the lake showed that water levels of inflowing rivers were above level III, said Cui Yuxiang from the water environment monitoring center of west China's Qinghai Province.

China classifies water quality in major rivers and lakes into six levels, ranging from level I, which is good for drinking, to level VI, which is too polluted for any purpose.

Cui attributed the good water quality to less population around the lake and less industries.

However, she pointed out that protection of local environment is was still important. In the past several years as the lake saw little rainfall, saltness of the water kept rising, from 14 grams per liter in the 1980s to more than 16 grams.

"Now that we are seeing more rainfall, but the saltness still remains at 15.6 grams per liter," she said.

Some other experts warned that as the lake had just inflowing rivers but no exits, the pollutants could only evaporate on its own or be decompounded by the water. If polluted, the lake will need a longer period to recover. With an increase of tourists, protection of the lake is becoming more difficult.

China is facing an arduous mission to improve water quality as 30 percent of the country's major river drainage areas had not met the state required standard by the end of 2008.

The 13th World Lake Conference is to kick off on Sunday in central China's Hubei Province.