The Largest Lakes in the World are Rapidly Shrinking!

According to a recent study, more than half of the largest lakes and reservoirs in the world have lost substantial amounts of water over the last three decades. The latest academic report places the majority of the blame on climate change and unsustainable water use.

A study by a group of international scientists that was published on Thursday in the journal Science revealed that almost one-quarter of the world’s population resides in the basin of a drying lake.

While lakes only make up around 3% of the earth’s surface, they contain approximately 90% of the planet’s freshwater liquid surface, are important sources of drinking water, irrigation, and power, and serve as key homes for both animals and plants. But they are in apocalyptic decline.

Although rain and snowfall variations in the environment naturally cause changes in lake water levels, human activities are also having an increasing impact. The most important lakes are seeing rapid decreases all throughout the world. In the midst of a megadrought and decades of overuse, Lake Mead on the Colorado River in the Southwest United States has significantly shrunk. The largest inland body of water in the world, the Caspian Sea, which lies between Asia and Europe, has long been in decline as a result of water consumption and climate change.

Though the shrinking of numerous lakes has been well reported, Fangfang Yao, the study’s lead author and a visiting scholar at the Cooperative Institute for Research in Environmental Sciences at the University of Colorado Boulder, stated that the reasons for the change and its breadth have been less thoroughly investigated.

Nearly 2,000 of the greatest lakes and reservoirs on Earth, which collectively hold 95% of all lake water storage on Earth, were measured by satellite by the researchers.

Incorporating climate models and more than 250,000 satellite pictures from 1992 to 2020, scientists were able to retrace the history of the lakes over several decades.

The results were “staggering,” according to the author’s reports. The amount of decline is the relative capacity of 17 Lake Meads. They also discovered that 53% of the lakes and reservoirs had lost large amounts of water, with a net decline of almost 22 billion metric tons annually. The survey concluded that human activities and climate change are to blame for more than half of the net loss of water volume in natural lakes.

Everywhere decreases in lake water storage were detected, including in the chilly Arctic and the humid tropics, according to the paper. As a result, it appears that “drying trends worldwide are more extensive than previously thought,” according to Yao.

Different factors had an impact on certain lakes. The analysis showed that while changes in rainfall and runoff have contributed to the loss of the Great Salt Lake, while unsustainable water consumption is the main cause of the shrinking of the Aral Sea in Uzbekistan and the Salton Sea in California.

Lakes in the Arctic have been getting smaller as a result of a combination of temperature, precipitation, evaporation, and runoff changes. Many of the human and climate change impacts on lake water losses, such the desiccation of Lake Good-e-Zareh in Afghanistan and Lake Mar Chiquita in Argentina, were previously unknown, according to Yao. Lakes may experience a variety of effects from climate change. The most obvious one, according to Yao, is to boost evaporation.

The study discovered that as lakes get smaller, this might also contribute to a “aridification” of the nearby watershed, which in turn raises evaporation and hastens their demise. Winter evaporation is becoming more of a concern for lakes in colder regions of the world as higher temperatures melt the ice that typically covers them, exposing the water to the atmosphere.

A decline in water quality, an increase in harmful algal blooms, and the extinction of aquatic species are just a few of the cascading repercussions that these changes may have. The worsening of the lakes’ water quality brought on by a warmer climate, which strains the water supply for the populations who depend on them, is a significant factor that is not frequently acknowledged, according to Yao.

According to the paper, sedimentation—where silt seeps into the water, clogging it up and diminishing space—is the main cause of reservoirs’ decrease. Yao called it a “creeping disaster” that has been developing over many years and decades. For instance, silt build-up has caused Lake Powell, the second-largest reservoir created by humans in the US, to lose about 7% of its storage capacity.

Climate change can have an impact on sedimentation, he continued. For instance, when the planet heats, wildfires spread through forests and undermine the soil, which contributes to an increase in the flow of sediment into lakes and reservoirs. As a result of sedimentation, reservoirs will be able to hold less water, making them less dependable for the provision of freshwater and hydroelectric generation, especially for us in the US given the age of our country’s reservoirs, said Yao.

Not all lakes are losing water; according to the study, around a third of lake decreases were partially offset by rises elsewhere. 24% of the lakes have seen large increases in water storage as a result of certain lakes expanding. The report discovered that these were typically lakes in less inhabited places, including parts of the inner Tibetan Plateau and the northern Great Plains of North America. Some of these improvements bear the imprint of climate change, as lakes filled by melted glaciers could pose concerns to those who live downstream. Although nearly two thirds of reservoirs saw significant water loss, the survey concluded that overall there was a net increase because of more than 180 newly filled reservoirs.

Untangling the relative importance of the variables causing the loss of lakes is made easier by this new research, according to Illinois State University’s Catherine O’Reilly, a professor of geology who was not involved in the study. “How much water do we have access to, and what are the options to increase water storage?” asks the researcher. “This study really highlights the impact of climate in ways that bring it close to home.” She continued, “It’s a little frightening to realize how many freshwater systems can’t store as much water as they used to.

Lakes need to be properly managed because many regions of the world are getting hotter and drier. Otherwise, human activity and climate change “can lead to drying sooner than we think,” according to Yao.