China's largest desert freshwater lake has shrunk by one-third in the last 13 years, state media said Thursday, as the country's breakneck modernisation continues to damage the environment.

Northern China's Hongjiannao Lake covers 32.16 square kilometres (12.86 sq miles), less than half its size in 1969 and two-thirds of its area in 2000, Xinhua news agency said.

"Experts said human activities including reservoir construction, mining and agricultural irrigation are the main causes for the sad phenomenon," Xinhua added.

The lake, in Shaanxi province on its border with Inner Mongolia, could vanish completely in a few decades, state media has previously claimed.

China's rapid industrialisation has caused massive environmental damage and is a major source of discontent.