Lakes in the nature reserve of Hol Xil on the Qinghai-Tibet Plateau, west China, have been swelling over the past decade, due to warmer and wetter climate, scientists have said.

Sitting 4,600 meters above sea level, the 45,000 square km Hol Xil nature reserve is China's largest unpopulated area and is home to wild yak and the endangered Tibetan antelopes.

The Chinese Academy of Sciences Qinghai salt lakes research institute began sampling several salt lakes in the reserve in November 2016.

Initial investigation showed that the areas of these salt lakes have expanded markedly and the water is less saline.

Ma Haizhou, a researcher at the institute, said it might be attributed to the glacial ablation and melting permafrost aquifer around the lakes.

A survey conducted in September 2016 by the water conservancy department of northwest China's Qinghai Province and Changjiang Water Resources Commission (CWRC) showed that from 1989 to 2015, three major lakes in the reserve expended.

The size of Hoh Sai Lake rose to 326 square kilometers in 2015 from 259 square kilometers in 1989; Haiding Nor Lake expanded to 77 square kilometers in 2015 from 38 square kilometers in 1989; and the size of Yanhu Lake expanded from 30 to 147 square kilometers during the same period, said Tan Debao, a research fellow of application of spatial information technology at the CWRC's Changjiang River Scientific Research Institute.

Liu Baokang, senior engineer with Qinghai Provincial Academy of Meteorological Sciences, said the warmer and wetter climate of the Qinghai-Tibet Plateau is the major cause of the swelling lakes in the reserve.

Qinghai Province meteorological data shows that precipitation in Hol Xil increased by 20.7 mm per decade from 1961 to 2014.

The average annual temperature of Hol Xil had risen at a rate of 0.32 degrees Celsius per decade.

Liu said the areas of lakes in Hol Xil have been growing since 2006.