A Disturbing Process Has Been Accelerating in Freshwater Lakes Worldwide

In addition to growing algae blooms and reducing oxygen levels, a recent study shows that freshwater bodies on Earth are also losing water at a faster rate than previously thought.

Ecologist Gang Zhao, who conducted the study at Texas A&M University, adds that "lake evaporation plays a larger role in the hydrological cycle than previously thought". Thus, this process significantly affects how we model the climate and weather.

Lakes, both natural and man-made, beautify around 5 million square kilometers of the planet's surface with their glistening waters. Nearly 90% of the fresh liquid surface water on our globe is found in them, and they are teeming with diverse and frequently rare life.

However, due to changes in cloud cover and rising temperatures, the sky is now more parched than ever. Greater access for the sky to suck up those water molecules has also been made possible by larger regions of uncovered water as a result of a drop in ice cover. These elements all help to speed up the process by which water moves from ponding on ground to being dispersed into the sky.

The evaporation rates used in earlier estimations of this water transfer are insufficient to capture the sheer volume of lake water being lost because of other dynamics including freeze and thaw cycles. This reliance on regional environmental factors necessitates the separate calculation of an accurate evaporation metric for each lake.

Therefore, Zhao and associates performed precisely that for an astounding 1.42 million lakes globally. They took into account variations in each of these lakes' evaporation rate, surface area, ice duration, and heat storage using monthly data on water loss from satellites between 1985 and 2018.

"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," accordnig to Zhao.

And each year, the sky consumes more than 3 trillion liters more than it did before. The researchers also discovered that manmade reservoirs contribute to this evaporation at a proportionately higher rate (16%) than their 5 percent storage capacity would imply.

"From a global perspective, the total reservoir evaporation can be larger than the combined use of domestic and industrial water," explains environmental engineer Huilin Gao.

"However, even in the United States, very few lakes/reservoirs have reliable evaporation data."

Zhao and his team encourage the scientific community as a whole and decision-makers in the water management industry to adopt the global lake evaporation volume (GLEV) information they developed.

"With results for individual water bodies, GLEV can really help improve reservoir management decision-making all over the world, especially under increasing drought events and population growth," accordnig to Gao.

"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."

This research was published in Nature Communications.