The rate at which China's largest desert freshwater lake is shrinking has accelerated dramatically in the past four years, figures show.

Hongjiannao Lake, several hundred kilometres to the west of Beijing, has been disappearing since the 1970s, due to a combination of coal mining and climate change. But the speed at which it is losing area has increased rapidly since 2009, when it measured 46 square kilometres (sq km), down from 67 sq km in 1969.

Data released by local meteorological agencies on Thursday and reported by Chinese state media, shows the lake has now shrunk by almost one-third since 2009, to 31.16 sq km.

He Fenqi, a researcher with the Chinese Academy of Sciences, has said previously that even at the end of the 1990s, "one couldn't see the other bank of the Hongjiannao even through a telescope. Today, it's visible with the naked eye."

Ordos, a city north of the lake, has been at the centre of a mining boom for coal and other minerals in recent years. Researchers for the US-based Center for Climate and Security, who have visited the region, have reported: "insatiable demand for the end product means that those who control the land, the communist party and the government (at times a blurry distinction) focus on income while the environment and water are bent to accommodate mining demand."

The center also notes that climate records for the area show rainfall decreasing and temperatures increasing, a prospect that will exacerbate water problems. "In some instances the reduction in runoff to lakes and high withdrawal rates mean lakes may disappear," they write.

The lake is in a transition area between the desert and a region of windblown dust.