Scientists of the Chinese Academy of Sciences studied changes at the wetlands of the Qinghai-Tibet Plateau in western China which is the source of the Yangtze and Yellow rivers.

Using aerial photos and satellite images, they found the wetlands on the plateau have shrunk more than 10 percent over the past four decades. The wetlands at the origin of the Yangtze have suffered the most, contracting by 29 percent.

"The wetlands play a key role in containing water and adjusting the water volume of the rivers," researcher Wang Xugen was quoted as saying. "The shrinking of the wetland on the plateau is closely connected with global warming."

The drop in water flow comes despite an increase in the amount of rain in the region.

"The increased rainfall didn't lead to more water flow in the rivers because the evaporation was so fast as a result of global warming," Li Shijie, a researcher with the Nanjing Institute of Geography and Limnology, was quoted as saying. The institute is connected to the Chinese Academy of Sciences.

The report did not comment on the impact of the reduced water levels in the rivers.

Officials say the country's efforts include energy conservation measures, increasing forest coverage and family planning policies that have slowed population growth.