The Sanjiangyuan National Nature Reserve, the source of China's three major rivers, has maintained high water quality, according to an environmental bulletin released on Tuesday in Xining in northwest China's Qinghai province.

The Sanjiangyuan National Nature Reserve. [File photo]?

The quality of water on sections of the Yangtze, Yellow and Lancang rivers in Qinghai has reached or exceeded national standards for surface water quality, according to the 2011 Qinghai Environmental Bulletin.

Remote monitoring data showed that the reserve's water quality was above the national average in 2011, the bulletin said.

The reserve, located on the Qinghai-Tibet Plateau and described as "Asia's water tower," provides the lower reaches of the Yangtze, Yellow and Lancang rivers with 60 billion cubic meters of water annually.

However, Sanjiangyuan has become ecologically vulnerable due to global warming and human activity.

In 2005, China launched a 7.5-billion-yuan (about 1.18 billion U.S. dollars) ecological conservation project in the region to repair the reserve's ecology.