The area where Rigzin Chophel played with his childhood friends is now at the bottom of a lake, and he is worried that more land will be submerged.

The 45-year-old herdsman lives in Tseten village on the southern bank of Serling Tso Lake, which has expanded over 40 percent between 1976 and 2009.

The village has around 42,000 hectares of land for herdsmen to raise their cattle. Rigzin has been the director of the village Party committee for the last 15 years.

"Over a dozen families have complained to me that their land has been inundated by the lake. Five of them have suffered great losses," he said.

Herdsman Nordey pointed toward a lakeside area, and said that was where he used to live.

"About six years ago, the lake was expanding very fast. There were fences between my house and the lake, and every year I had to move the fences closed to the house," he said. The herdsman said he has now built a new home a few miles back away from the lake.

Ten years ago, the lake was expanding at an even faster pace than it is now, said Rigzin. "We marked the area of the lake. It expanded by 20 to 30 steps a year, especially noticeable low-lying areas," said Rigzin.

According to the latest data, which was obtained in 2014, Serling Tso measured 2,391 square kilometers. It has replaced the Buddhist holy lake Namtso as Tibet's largest lake at about 45.5 kilometers wide and 77.7 kilometers long.

Since 1990, the plateau's 1,000 lakes have seen an increase of 100 billion cubic meters of water, with Serling Tso probably the fastest-growing lake, according to scientists from the Institute of Qinghai-Tibet Plateau Research of Chinese Academy of Sciences (CAS).

Preliminary studies by the CAS found that precipitation contributed 76.5 percent of the increase, thawing glaciers about 9.5 percent and diminishing evaporation contributed about 14 percent.

CAS scientists said they will continue to unravel the mystery behind the lake expansion and attempt to find solutions for its future development.

About 100 scientists recently began a expedition on the Qinghai-Tibet Plateau to study changes in climate, biodiversity, and environment. The expedition, which will last for five to 10 years, is the second of its kind in the last 40 years.

Zhu Liping, a CAS researcher leading the lake observation team, said they will study the whole water system from Serling Tso to the origin of the Yangtze River.

"We will study the existing lake and river resources, obtain samples and compare new data with that obtained 40 years ago," said Zhu.

"We hope our study will provide a base for further studies on the development of the eco-system on the Tibetan Plateau," he said.