Study finds water loss through evaporation increases for lakes and reservoirs

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Texas A&M researchers have created a new dataset that quantifies trends in evaporative water loss from 1.4 million lakes and man-made reservoirs around the world

Led by Dr. Huilin Gao, an associate professor in the Zachry Department of Civil and Environmental Engineering at Texas A&M University, the researchers created the Global Lake Evaporation Volume (GLEV) dataset. It relies on modeling and remote sensing to provide the first long-term monthly time series for 1.42 million individual natural lakes and man-made reservoirs around the world.

The researchers published their findings in Nature Communication.

About 87% of surface freshwater in liquid form is stored in natural and artificial lakes (i.e. reservoirs). Although the volume of evaporation from these global lakes is substantial, little is known about its spatial distribution and long-term trend.

From 1985 to 2018, researchers found that the lake’s long-term average evaporation volume increased at a rate of 3.12 cubic kilometers per year. Trend attributions include an increase in evaporation rate of 58%, a decrease in lake ice cover of 23%, and an increase in lake area of ​​19%.

The results of the study highlight the importance of using evaporation volume (rather than evaporation rate) as the primary index for assessing climate impacts on lake systems.

“We found that the long-term evaporation from the lake is 1,500 plus or minus 150 cubic kilometers per year, or 15.4% higher than previous estimates,” said first author Dr. Gang Zhao, a former Texas A&M student who is now a postdoctoral fellow. in the Department of Global Ecology at the Carnegie Institute for Science. “This suggests that lake evaporation plays a larger role in the hydrological cycle than previously thought.”

According to GLEV, 6,715 reservoirs represent only 5% of the water storage capacity and 10% of the area of ​​all lakes (natural and artificial). However, the reservoirs contribute 16% to the volume of evaporation. This amount of evaporative loss from the reservoir is equivalent to 20% of the world’s annual water consumption. Over the past 33 years, evaporative water loss from reservoirs has increased at a rate of 5.4% per year, exceeding the global trend of 2.1% for all lakes.

“As far as evaporative loss is concerned, this study will be an invaluable place to serve water resources researchers and policy makers,” Gao said. “Our findings have important environmental, societal and economic implications as global evaporative loss will be accelerated and further exacerbated in the future with global warming.

Without precisely quantifying the magnitude and trend of volumetric evaporation loss individually for the world’s millions of lakes, the researchers say it is impossible to make reliable projections of water and energy resources. This freely available data set can benefit policy makers and the wider scientific community.

For future work, researchers from Texas A&M, the Desert Research Institute, and the U.S. Bureau of Reclamation recently launched a nearly $1 million NASA Applied Science Project that focuses on the development of daily, operational, satellite-assisted reservoir evaporation monitoring and forecasting for the western United States. . The team will also develop an ongoing daily reservoir monitoring project for Texas.

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