Local residents and water experts are concerned that the 735-kilometremile-long) Min River could become permanently altered by dams built on its upper reaches which also threaten one of the world's oldest irrigation systems downstream, Probe International said.

Below the nearly-completed Zipingpu dam, Sichuan's largest water control project, "the Min River reduces to a thin stream that leaves most of its waterbed uncovered," the group, citing online press reports from the region, said.

Further upstream in the Nanxin Town of Mou County, "the Min has completely disappeared and the exposed riverbed almost resembles a desert strewn with huge rocks and pebbles," it added.

Water experts in Sichuan province say hydro development on the upper Min River is responsible and that operators regulate their dams independently of one another without paying attention to the river's water levels.

As many as 15 dams have either been built or are under construction along a 200-kilometer valley following from Sichaun's ancient city of Songpan to the famous Dujiangyan Irrigation System, a water conservancy project built during China's Warring States Period (475-221 BC), it added.

"The situation could jeopardize the Dujiangyan downstream which functions as a comprehensive water web, providing cities and villages along the river with water for domestic use and irrigation for millions of hectares of farmland, as well as power for electricity generation," it said.