Why Are So Many Lakes Around the World Drying Up?

More than half of the world’s large lakes have been losing water for decades. A satellite-based study of the 1,972 largest lakes on Earth found that 53% experienced statistically significant declines in water storage between 1992 and 2020, driven mainly by rising temperatures, increased evaporation, and human water consumption.¹ The causes are rarely simple, and the consequences reach well beyond the shoreline.

The Scale of the Loss

That roughly one-in-two figure deserves a closer look. The same global analysis separated natural lakes from reservoirs and found different stories for each. Natural lakes are losing water primarily because the climate is warming, evaporation is ramping up, and people are drawing water out faster than it comes back in. Reservoirs, by contrast, are losing storage mainly to sedimentation: rivers carry dirt and silt behind the dam wall, gradually filling in the space that was supposed to hold water.¹ In both cases, the net effect is less usable freshwater, but the solutions look quite different depending on which force is doing the most damage.

The declines are spread across every populated continent. Some of the most dramatic losses have been in Central Asia, the Middle East, and parts of Africa, but lakes in North America, Europe, and East Asia are affected too. The trend is broad enough that it cannot be chalked up to any single drought or any single dam project.

How a Warmer Climate Drains Lakes

Warmer air holds more moisture, and warmer surfaces push more water vapor into the atmosphere. For lakes, this translates directly into higher evaporation. Modeling work projects that global lake evaporation will increase by about 16% by the end of this century, even though the amount of sunlight reaching the surface barely changes.² Two mechanisms account for roughly half of that jump. First, lakes that used to freeze over for part of the year will have shorter ice seasons, leaving more open water exposed to the atmosphere for longer. Second, as the climate warms, a larger share of the available energy at the lake surface goes into evaporation rather than directly heating the air above it. Both effects accelerate water loss without requiring any additional sunshine.

Regional patterns matter, too. In areas expected to dry further, such as tropical South America, the Mediterranean, and southeastern China, relative humidity drops while incoming solar radiation rises. Both changes push evaporation higher, creating a feedback loop where the lake surface loses water faster just as the atmosphere becomes less willing to return it as rain.³

Lakes that have no outlet to the sea, known as endorheic or terminal lakes, are at an outsized risk. They lose water only through evaporation, so anything that tips the balance between inflow and evaporation pushes them toward decline. Modeling of Shortandy Lake in Central Asia showed that its volume is highly responsive to swings in precipitation: even a modest drop in rainfall can trigger a sharp contraction.⁴ Utah’s Great Salt Lake, Iran’s Lake Urmia, and central Africa’s Lake Chad are all endorheic, and all have been shrinking.

Agriculture, Dams, and Groundwater Pumping

Climate is only part of the story. In many basins, the single biggest draw on water is irrigated farming. Lake Urmia in northwestern Iran lost most of its water not because of a massive climate shift but because rivers and streams feeding it were diverted to irrigate crops. Drought in the early 2000s made things worse, but the underlying cause was the water itself being rerouted before it ever reached the lake.⁵ A strikingly similar pattern played out with the Hamun Lakes on the Iran–Afghanistan border, where rapid expansion of irrigated farmland in upstream Afghanistan consumed water that would have sustained the lakes. A modeling study estimated that without the increase in human water use, the lakes’ surface area from 2010 to 2019 would have been roughly two and a half times larger.⁶

Dams reshape lake hydrology in subtler ways. China’s Three Gorges Dam, for instance, altered the discharge patterns of the Yangtze River downstream, leading to measurable drops in the water level of Poyang Lake, the country’s largest freshwater lake, especially during the dry season from late summer through autumn.⁷ A dam hundreds of kilometers away can dictate when and how much water a lake receives.

Groundwater pumping adds another layer. When aquifers are drawn down, the underground flow that normally feeds streams and rivers slows, reverses direction, or stops entirely, starving downstream lakes of baseflow.⁸ This process can be invisible for years because groundwater moves slowly, but by the time a lake begins shrinking, the aquifer may have been overdrawn for a long time.

Toxic Dust from Exposed Lake Beds

When lake water recedes, it leaves behind vast stretches of dried sediment. That sediment becomes a source of airborne dust, and the dust often carries heavy metals, arsite, and other pollutants that settled on the lake bottom over decades or centuries. Field sampling and laboratory work on drought-exposed lake beds found that dust from these surfaces could contribute daily peak particulate concentrations far above safe thresholds and exceed regional benchmarks for non-carcinogenic health risk.⁹

Utah’s Great Salt Lake is one of the best-studied examples. As the lake level drops, fine particulate matter concentrations in surrounding communities rise. Researchers estimated that falling water levels could push dust-related fine particulate exposure from roughly 24 micrograms per cubic meter to about 32 micrograms per cubic meter, well above the levels considered safe for long-term breathing. The exposure also falls unevenly: communities of color and lower-income populations near the lake face disproportionately higher dust burdens.¹⁰ The health threat from drying lakes, in other words, is not just environmental. It is an environmental justice issue.

Ecological Collapse and Migration Bottlenecks

When a lake shrinks, the water that remains often becomes saltier as dissolved minerals concentrate in a smaller volume. For the invertebrates that form the base of many lake food webs, this rising salinity exacts a steep biological cost. Experiments with alkali flies, a crucial food source for shorebirds at saline lakes, showed that higher salinity slowed larval growth, shrank the size of pupae at maturity, reduced the number of adults that successfully emerged, and lowered the number of eggs females produced.¹¹ Fewer flies means less food for birds, and the decline cascades upward through the food chain.

The damage extends far beyond any single lake. Migratory waterbirds that cross arid continental interiors depend on a limited network of endorheic lakes and wetlands as refueling stops. As those water bodies dry, the network thins out, creating bottlenecks that may force birds onto longer, more dangerous routes or leave them without adequate stopover habitat altogether.¹² A flyway is only as strong as its weakest link, and drying lakes are removing links across multiple continents simultaneously.

Dried Lake Beds Release Greenhouse Gases

A less intuitive consequence of lake drying is that the exposed sediment becomes a significant source of carbon dioxide and methane. When a lake is full, water acts as a lid, slowing the release of gases from bottom sediments. Once those sediments are exposed to air, oxygen penetrates more freely, revving up microbial activity and allowing gas to escape directly into the atmosphere.¹³

Measurements from the exposed lake bed of Great Salt Lake in 2020 put those emissions at roughly 4.1 million tons of carbon dioxide equivalent, primarily as CO₂. That single lake bed’s output represented about a 7% addition to Utah’s total human-caused greenhouse gas emissions for the year.¹⁴ Multiply that effect across the world’s drying lakes and the contribution is not trivial, yet it rarely appears in national emissions inventories. Shrinking lakes create a feedback loop: warming dries the lakes, and the dried lake beds release more carbon, which accelerates warming.

Livelihoods and Geopolitical Tension

Drying lakes destabilize the communities around them. Lake Chad, which straddles Nigeria, Niger, Chad, and Cameroon, has shrunk dramatically since the 1960s. Research into the livelihood impacts found that the communities most affected had few economic options outside agriculture, and the influx of displaced people and rising violence compounded the hardship. People adapted by timing their activities to seasonal flood pulses and drawing on lessons from past droughts, but the responses remained largely reactive rather than planned.¹⁵

When a shrinking lake or its feeder rivers cross national borders, the pressure can become geopolitical. As water availability declines, disputes between countries sharing a watershed grow more frequent and more serious. The challenge is especially acute in arid and semi-arid regions, where dividing a dwindling resource means someone gets less. International frameworks exist to manage these conflicts, but familiarity with those rules varies widely, and enforcement is often weak.¹⁶ The Hamun Lakes basin, shared by Iran and Afghanistan, is a textbook example of how upstream irrigation decisions can hollow out a downstream lake and strain relations between neighbors.

Not Every Lake Is Shrinking

The global trend is clearly downward, but there are exceptions worth understanding. On the Tibetan Plateau, many lakes have actually expanded in recent decades, even as precipitation patterns show little net change. The reason is glacial melt: as glaciers retreat, they release stored water that flows into nearby basins. On the Tibetan Plateau, glacier area shrank at rates approaching a square kilometer per year in some catchments, and the resulting meltwater inflated downstream lakes. This is not a sign of health. It is a sign that a different kind of water savings account, ice stored over millennia, is being liquidated. Once the glaciers are gone, those lakes will lose their bonus inflow and face the same drying pressures as everywhere else.

A few lakes have also benefited from deliberate human intervention. China’s Baiyangdian Lake, which had been shrinking in a water-scarce region, was the subject of an ecological water replenishment program that optimized when, how much, and through which channels water was delivered to the lake. Modeling showed that selecting the right combination of inflow channels and timing significantly improved both water levels and water quality.¹⁷ The approach is resource-intensive and only works where there is surplus water to redirect, but it demonstrates that managed restoration is possible.

What the Deep Past Tells Us

Lakes have dried before, catastrophically, long before industrial agriculture or fossil fuels existed. Sediment cores from Lake Malawi in East Africa reveal that between about 135,000 and 90,000 years ago, tropical Africa endured a series of extreme droughts. Lake Malawi, which today is 706 meters deep, was reduced to a saline, well-mixed pond roughly 125 meters deep. Pollen production plummeted so low that the surrounding landscape could not sustain enough vegetation to maintain fires.¹⁸ When the rains finally returned, thousands of years of accumulated weathered material washed into the lake in a burst before the ecosystem stabilized again.¹⁹

Closer in time, sediment records from Lake Chichancanab in Mexico’s Yucatán Peninsula preserve a detailed record of the Terminal Classic Drought that coincided with the decline of Classic Maya civilization between roughly 750 and 1050 AD. The drought was not a single two-century dry spell but a series of arid episodes separated by somewhat wetter interludes.²⁰ The lesson from both episodes is sobering: natural droughts alone have been severe enough to reshape civilizations and ecosystems. Today’s lake losses are being driven by those same natural forces compounded by industrial-scale water extraction and a warming climate. The combination is historically unusual, and the pace of decline in many basins has no close precedent in the sedimentary record.

Why the Problem Is Hard to Fix

The difficulty with drying lakes is that they sit at the intersection of multiple pressures, and fixing one rarely solves the problem. Reducing irrigation withdrawals in a basin might stabilize a lake, but it threatens the livelihoods of farmers who depend on that water. Building a dam to store wet-season flows for a downstream lake can help in the short term but introduces sedimentation and alters seasonal flooding patterns for years to come. Ecological water replenishment programs like the one at Baiyangdian Lake work only where surplus water exists and where governments are willing to prioritize lake restoration over competing demands.¹⁷

Transboundary lakes add political complexity. When the countries sharing a basin cannot agree on how to allocate shrinking flows, unilateral action upstream can devastate the lake and the communities around it downstream.¹⁶ And even where domestic policy could make a difference, the incentive structures often work against lakes. Agriculture is typically the largest water user in a basin and frequently enjoys subsidized or underpriced water rights, making conservation the least appealing economic option for the people who control the taps.

Meanwhile, the climate signal keeps strengthening. Even aggressive emissions cuts today will not reverse the warming already baked into the system, meaning evaporation will continue rising for decades. For endorheic lakes in particular, where every drop that enters the basin must leave through evaporation, that trend is a ratchet. The lakes most vulnerable are the ones that were already in precarious balance: warm basins with heavy irrigation, arid regions with dwindling precipitation, and terminal lakes with no outlet to buffer short-term losses. For these systems, the window for intervention is narrowing, and the cascading consequences, from toxic dust to greenhouse gas emissions to collapsing food webs, grow steeper with every year of delay.