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The fluvial lake system across China’s Yangtze River Plain, which serves nearly half a billion people and is a World Wildlife Fund ecoregion, lost about 10 percent of its water area from 2000-2011, according to Jida Wang, assistant professor of geography. Wang and colleagues published their findings for the lake system’s decline in the American Geophysical Union’s journal Water Resources Research.

“Many people’s first intuition is that the culprit must be the Three Gorges Dam because it impounds so much water in the Yangtze River, but our fingerprinting study undeniably shows that the dam is not the decline’s primary cause,” Wang said. “Climate variability is the predominant driver of this decadal dynamic.”

Wang collaborated with Yongwei Sheng, of the University of California, Los Angeles, and Yoshihide Wada, of Austria’s International Institute for Applied Systems Analysis. They found that roughly 80 percent of the observed lake decline is the result of simultaneous climate variability closely related to the El Niño-Southern Oscillation, which has caused droughts and flooding in the region…….

Wang and his colleagues also quantified the negative impacts of human water consumption from agricultural, industrial and domestic sectors across the downstream Yangtze River Basin. These impacts are surprisingly comparable to the Three Gorges Dam’s impact, Wang said. The dam and human water consumption together comprise 10-20 percent — or less — of the decline’s factors, while up to another 10 percent of the decline may be caused by a variety of other factors, possibly including other dams, sand mining, soil conservation and urbanization, he said.

“It also is important to recognize that anthropogenic impacts have strengthened in the past couple of decades,” Wang said. “Although the Three Gorges Dam already reached its maximal storage capacity in 2010, its induced Yangtze River erosion will continue. This also may come along with increasing human water consumption and trans-basin diversions. We hope our study not only provides an overdue explanation of the past decadal lake decline but also offers scientific guidance for future conservation of this critical fresh water resource.”

For their study, Wang and his colleagues used thousands of satellite images from NASA, an advanced hydrological model from the Netherlands, statistical data from the United Nations, and measurements and censuses from several Chinese organizations.

This research was funded by the U.S. Geological Survey’s Landsat Science Team and a Kansas State University faculty start-up fund.  https://www.sciencedaily.com/releases/2017/08/170803103146.htm