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Water evaporation from lakes is far greater than expected

The Colorado River has been a source of contention for many years, with many states wanting a piece of this precious water source. Now, Lake Mead, the largest reservoir in the United States, is draining – and fast. 

Considering that there has been a rise in temperatures and a decrease in rainfall, researchers at Texas A&M University set out to investigate the amount of water evaporating off the surface of artificial and natural lakes. This knowledge of evaporation loss may provide water managers with more insight and encourage more effective management.

Although water evaporation has been explored as something to consider when talking about climate change, there is not much information on its long-term trends and spatial distribution. The researchers created the global lake evaporation volume (GLEV) dataset to fill these gaps. This dataset utilizes modeling and remote sensing to measure evaporation in 1.42 million lakes and reservoirs worldwide. 

The findings, published in Nature Communications, were not encouraging. The experts determined that from 1985 to 2018 evaporation rate increased by 3.12 cubic kilometers per year. 

Study first author Dr. Gang Zhao, a postdoctoral fellow in the Department of Global Ecology at the Carnegie Institute for Science, further explained the results and their importance. 

“We found that the long-term lake evaporation is 1,500 plus or minus 150 cubic kilometers per year, which is 15.4% larger than previous estimates. This suggests that lake evaporation plays a larger role in the hydrological cycle than previously thought.”

According to GLEV, reservoirs account for only 5% of the storage capacity and 10% of the surface area of lakes. Despite this, they account for 16% of total evaporation volume, meaning that the water lost to evaporation in reservoirs is equivalent to 20% of worldwide water consumption. 

Dr. Huilin Gao, who led the study, pointed out that having this data to make projections is valuable. “This dataset helps the science community better understand the role that these water bodies play in Earth systems, from global weather forecasting, flood and drought modeling to Earth system modeling under climate change.”

Texas A&M researchers, along with the Desert Research Institute and the U.S. Bureau of Reclamation, will be working on a NASA project to continue monitoring reservoir evaporation in the western U.S. In addition, they will expand their work with Texas reservoirs.

By Erin Moody , Staff Writer

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