A lake at the lower reaches of the Tarim River, China's longest inland river, has been forced to move 30 to 40 kilometers westward over the past 40 years by a sprawling desert on its northeast.

A satellite picture taken in August 2002 showed the center of Taitema Lake, where the Tarim River empties, has shifted to the western side of a trunk highway in the region, said Yuan Guoying, a research fellow with the Environmental Protection Institute of northwestern Xinjiang Uygur Autonomous Region.

On the 1965 edition of the regional map, however, the lake had been about 20 km east of the place where the highway was later built, Yuan said yesterday.

Taitema Lake is located in Ruoqiang County of the Mongolian Autonomous Prefecture of Bayingolin, in the central eastern part of Xinjiang. The 1,321km Tarim River, known as the mother river for people in southern Xinjiang, flows into Taitema Lake.

Yuan said he first proposed the hypothesis about the lake's moving westward in August 2003, when he accompanied a group of Chinese and German experts on a field survey on the ecosystem at the lower reaches of the Tarim River, which is sandwiched between the Taklimakan and Kuruktag deserts.

Yuan visited the lake again this summer to prove his hypothesis. "Even in the rainy season, water from the swelling Tarim River refused to flow eastward to where the lake had been in the past," he said.