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WARTIME DESTRUCTION OF UKRAINE DAM HAS SET OFF A ‘TIME BOMB’  
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Richard Stone
March 13, 2025
Science
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_ Breach of Kakhovka Dam now threatens seasonal floods thick with
toxic heavy metals, other pollutants _

A view of the former Kakhovka reservoir bottom “No swimming!
Careful mines!” warns a sign posted in the Kakhovka Reservoir’s
dessicated bed., Ivan Antipenko

 

In the Soviet Union, the Zaporozhets automobile was legend. Mass
produced in the 1960s in the Ukrainian city of Zaporizhzhia, early
models were known for steel frames as flimsy as cardboard and a gas
tank under the front hood that could turn a fender bender into a
carbecue. But the plebeian car did have a classy touch: nickel-plated
bumpers, which had consequences that reverberate today. For decades,
factories making Zaporozhets components, along with other industry and
agriculture, poured effluents laden with nickel, cadmium, lead, and
other heavy metals into the huge Kakhovka Reservoir nearby, where the
toxicants settled into the lake-bottom sludge.

On 6 June 2023, those sediments triggered what Alexander Sukhodolov, a
hydrodynamicist at the Leibniz Institute of Freshwater Ecology and
Inland Fisheries, calls “a toxic time bomb.” A 400-meter-wide
section of the Kakhovka Dam collapsed, perhaps as a result of
sabotage, sending 16.4 cubic kilometers of water—and tons of
contaminated silt—surging down the Dnipro River in southern Ukraine.
Scores of people died in the flood, up to 1 million lost access to
drinking water, and irrigation canals for an important agricultural
region turned into trickles. The deluge laid waste to ecosystems
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leaving billions of mussels rotting in the desiccated lakebed and
scrambling estuaries where the river empties into the Black Sea.

In the months since the disaster, “ecosystems have shown a
remarkable resiliency,” says Yuriy Kvach, a biologist at the
National Academy of Sciences of Ukraine’s Institute of Marine
Biology. Habitats and species are reviving, he and
colleagues reported in Ecological Processes
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February. Now that the Dnipro is flowing freely, endangered sturgeon
have reappeared, and meadows dotted with willows are taking hold on
the dry lakebed.

But behind the vibrancy lurks a potent pollution threat
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colleagues detail in a paper this week in Science. Before the dam
breach, Kakhovka’s reservoir accumulated a layer of loess silt up to
1.5 meters thick, amounting to as much as 1.7 cubic kilometers. The
now exposed sediments contain about 83,000 tons of heavy metals, the
researchers estimate. YouTube videos showing a brownish black crust on
the lakebed are evidence of “the really huge accumulations of heavy
metals,” says ecologist Oleksandra Shumilova, lead author on
the Science paper who’s also at the Leibniz Institute.

The emerging danger is that those toxicants won’t stay put,
Shumilova says. Less than 1% of the sediment has been swept downstream
so far, but seasonal floods from heavy rains or snowmelts will
continue to wash the pollutants down the Dnipro and into the watershed
around the former reservoir. In spring 2024, for instance,
contaminated floodwaters inundated nearly 900 square kilometers,
the Science authors report.

The war in Ukraine has stymied efforts to understand the scope of the
threat. Much of the lower Dnipro wends along the front line, leaving
scientists who venture there vulnerable to shelling or drone attacks.
And the Ukrainian military forbids research cruises in the Black Sea,
forcing scientists to rely mainly on remote sensing data to monitor
water conditions. But some upstream areas, near Zaporizhzhia city, are
safer to access. In 2023, Czech and Ukrainian nongovernmental
organizations sampled the river at several sites, finding a witch’s
brew
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heavy metals, polyaromatic hydrocarbons, and the insecticide DDT.

The “real danger” lies in the pollutants building up, or
bioaccumulating, in the food web, Shumilova says. So far, however,
scientists have little data on that. To fill the gap, Shumilova and
Ukrainian colleagues are meeting next month to develop a research plan
for tracking bioaccumulation, for instance by probing for heavy metals
in the scat of local deer populations.

In the meantime, researchers and others are debating whether the
Kakhovka Dam should be rebuilt. Some ecologists think that’s a bad
idea, noting that the willow meadows now thriving in the former
lakebed are stabilizing sediments and sopping up heavy metals from the
soil. Others argue rebuilding is necessary to restore irrigation
networks and ensure drinking water supplies.

Sukhodolov cautions that the willows’ powers of remediation won’t
eliminate the threat of heavy metals borne on seasonal floods. He
expects Ukraine to rebuild the dam, and until the river is impounded
again he and his co-authors propose building two 15-kilometer-long
barriers along the Dnipro to curtail pollution releases.

As long as the war continues, such plans are pipe dreams. In the
meantime, the specter of another threat haunts Ukraine: possible
attacks on the Dnipro’s five remaining dams or on the Dniester River
cascade, a series of hydropower and flood control structures. “If
more dams are targeted, the human toll and environmental damage could
be cataclysmic,” the Science authors warn.

“Water has been a weapon of war throughout history,” says
ecologist Carol Stepien of the Smithsonian Institution’s National
Museum of Natural History, who has worked in the Lower Dnipro Basin.
Until the war ends, she says, “Ukraine will be in a rather
precarious situation.”

_RICHARD STONE contributes to Science as its senior international
correspondent with a focus on Asia. His writing has featured datelines
from challenging reporting environments such as Cuba, Iran, and North
Korea. Stone also serves as a special adviser, science diplomacy and
engagement, for the Human Frontier Science Program organization. He
has contributed to Discover, Smithsonian, and National
Geographic magazines, and is the author of the nonfiction
book Mammoth: The Resurrection of an Ice Age Giant. His overseas
experience includes stints as a Fulbright Scholar at Rostov State
University in Rostov-on-Don, Russia in 1995–96 and at Kazakh
National University in Almaty, Kazakhstan in 2004–05._

_SCIENCE has been at the center of important scientific discovery
since its founding in 1880—with seed money from Thomas Edison.
Today, Science continues to publish the very best in research across
the sciences, with articles that consistently rank among the most
cited in the world. In the last half century
alone, Science published:_

* _The entire human genome for the first time_
* _Never-before seen images of the Martian surface_
* _The first studies tying AIDS to human immunodeficiency virus_

_A trailblazer in online publishing as well, the Science family of
publications has grown to include online journals Science
Translational Medicine, Science Signaling, Science
Immunology, Science Robotics and the open access journal Science
Advances._

__

Did LIGO Just See its Most Important Gravitational Wave Ever?
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Ethan Siegel
The ultimate multi-messenger astronomy event would have gravitational
waves, particles, and light arriving all at once. Did that just occur?
Starts With A Bang — February 11, 2025

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