Evaporative water loss increasing across lakes, reservoirs globally
Evaporative water loss across the world’s lakes, reservoirs and large water bodies in the wake of climate change has been largely a much neglected research topic so far. Now, a team of researchers in the United States has created a new dataset that quantifies trends of evaporative water loss from 1.4 million global lakes and artificial reservoirs.
The evaporative loss from global lakes (natural and artificial) is a critical component of the terrestrial water and energy balance. However, the evaporation volume of these water bodies—from the spatial distribution to the long-term trend—is as of yet unknown, said the researchers from Texas A&M University.
Using satellite observations and modeling tools, the team quantified the evaporation volume from 1.42 million global lakes between 1985 and 2018. he Our results underline the importance of using evaporation volume, rather than evaporation rate, as the primary index for assessing climatic impacts on lake systems, the team said in a recently published research study in Nature.
Led by Dr Huilin Gao, associate professor in the Zachry Department of Civil and Environmental Engineering at Texas A&M University, the team created the global lake evaporation volume (GLEV) dataset that leverages modeling and remote sensing to provide the first long-term monthly time series for 1.42 million individual natural lakes and artificial reservoirs worldwide.
About 87 per cent of fresh surface water in liquid form is stored in natural and artificial lakes (i.e., reservoirs). While the evaporation volume from these global lakes is substantial, little is known about its spatial distribution and its long-term trend.
From 1985 to 2018, researchers discovered that long-term average lake evaporation volume has increased at a rate of 3.12 cubic kilometers per year. The trend attributions include an increased evaporation rate of 58 per cent, decreased lake ice coverage of 23 per cent and increased lake surface area of 19 per cent.
“We found that the long-term lake evaporation is 1,500 plus or minus 150 cubic kilometers per year, which is 15.4 percent larger than previous estimates,” said first author Dr Gang Zhao, a Texas A&M former 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 only account for five per cent of the water storage capacity and 10 per cent of the surface area of all lakes (both natural and artificial). However, reservoirs contribute 16 per cent to the evaporation volume. This quantity of reservoir evaporative loss is equivalent to 20 per cent of the global annual consumption of water use. In the last 33 years, evaporative water loss from reservoirs has been increasing at a rate of 5.4 per cent per year, outpacing the global trend of 2.1 per cent for all lakes.
“With regard to evaporation loss, this study will be an invaluable venue to serve water resources researchers and decision-makers,” Gao said.
“Our findings have significant environmental, societal and economic implications as the global evaporative loss will be accelerated and further exacerbated in the future under global warming.
Without accurately quantifying the magnitude and trend of volumetric evaporation loss individually for the millions of global lakes, researchers say reliable water and energy resources projections can’t be made. This freely available dataset can benefit decision-makers and the wider science community.
