The Aral Sea is shrinking because the Soviet Union diverted its two source rivers for cotton irrigation in the 1960s, and the region never reversed course. What was once the world’s fourth-largest inland lake, covering 68,478 square kilometers in 1960, had lost nearly 88% of its surface area by 2018. The total water volume lost over that period was roughly 1,000 cubic kilometers, a staggering disappearance driven almost entirely by human decisions about how to use the rivers that fed it.
The Soviet Decision That Started It All
The Aral Sea sits on the border of Kazakhstan and Uzbekistan, fed by two major rivers: the Amu Darya from the south and the Syr Darya from the northeast. In the 1950s, under Nikita Khrushchev’s leadership, the Soviet government launched a massive program to turn the surrounding desert into farmland, primarily for cotton production. By the 1960s, both rivers were being systematically diverted through a network of canals and irrigation channels to water millions of acres of cropland.
The effect was almost immediate. Less water reached the sea each year, and evaporation in the hot Central Asian climate steadily outpaced inflow. The sea began to drop. What made this particularly devastating is that the Aral Sea is a terminal lake, meaning it has no outlet. It depends entirely on those two rivers to replace the water it loses to evaporation. Once the rivers were redirected, the math was simple and brutal: more water was leaving than arriving, and the sea started to die.
How Fast the Water Disappeared
The pace of the shrinkage is hard to overstate. From 1960 to 1990, the surface area dropped from 67,499 square kilometers to 39,734, nearly cutting the lake in half in just three decades. But the worst was yet to come. By the 2000s, the sea had split into distinct water bodies: the smaller North Aral Sea and the larger South Aral Sea, which itself fractured into eastern and western lobes connected only by narrow channels. In 2014, the eastern lobe of the South Aral Sea completely disappeared, leaving behind a flat expanse of dry, salt-crusted lakebed.
Between 1960 and 2018, the Aral Sea shrank from 68,478 square kilometers to just 8,321 square kilometers, losing area at an average rate of about 1,037 square kilometers per year. That’s roughly the equivalent of losing a mid-sized city’s worth of water surface every twelve months for nearly six decades straight.
Rising Salt Killed Everything in the Water
As the water volume dropped, the salt stayed behind. The original Aral Sea was mildly brackish, with a salinity of about 10.3 grams per kilogram, comparable to some estuaries. That was low enough to support a productive freshwater ecosystem with native fish species and a commercial fishing industry that employed tens of thousands of people in surrounding towns.
As the sea shrank, salinity climbed relentlessly. By the late 1990s, the South Aral Sea had passed 60 grams per liter, killing off even the hardiest introduced fish species. Today, the South Aral’s salinity exceeds 100 grams per liter in the western basin and has reached 210 grams per liter in the eastern basin. For comparison, normal ocean water is about 35 grams per liter. The South Aral is now saltier than the Dead Sea in places, and researchers predict it will ultimately lose all complex animal life.
The ecological collapse unfolded in stages. Native fish populations crashed first, then introduced salt-tolerant species like the flounder-gloss (brought from the Sea of Azov in the 1980s) followed them into extinction as salinity continued to climb. Even small invertebrates and snails that had survived the initial salinity increases vanished from the South Aral by the 2000s. The deep waters of the remaining southern basins have become partially anoxic, meaning they lack oxygen entirely, and now produce methane instead of supporting life.
A Poisoned Landscape Left Behind
The exposed lakebed created a new set of problems. Decades of agricultural runoff had deposited pesticides and fertilizer chemicals in the sea’s sediment. As the water receded, those contaminated sediments dried out and turned to dust, which winds carry across the surrounding region. Salt and chemical-laden dust storms now blow off the dry lakebed regularly, damaging crops and contributing to serious respiratory health problems in nearby communities.
There’s also a more unusual hazard. Vozrozhdeniya Island, once safely isolated in the middle of the Aral Sea, housed a secret Soviet biological weapons testing facility until 1991. Various pathogens were tested and potentially weaponized there. As the water level dropped, the island became a peninsula and eventually connected to the mainland, raising concerns that surviving pathogens could spread beyond the former test site.
One Partial Success Story in the North
The North Aral Sea is the one piece of this story with a hopeful turn. In 2005, Kazakhstan completed the Kok-Aral Dam, a 12-kilometer barrier that separates the North Aral Sea from the South Aral Sea. The dam traps water from the Syr Darya in the northern basin, preventing it from flowing south into the lower-elevation southern basins where it would simply evaporate.
The results have been significant. By 2011, the salinity in the North Aral Sea had dropped back to about 8 grams per liter, essentially matching its 1960s levels. The water level has risen, and fish populations have begun to recover. The surrounding climate has moderated somewhat, and the fishing town of Aralsk, which had been stranded far from the receding shoreline, is slowly seeing water return in its direction.
But this recovery came at a cost. The dam deliberately sacrifices the South Aral Sea, cutting off any shared water and accelerating the southern basins’ decline. Uzbekistan, which borders the South Aral, receives no benefit from this arrangement and continues to rely heavily on Amu Darya water for its cotton fields. The fundamental tension that created the crisis, too many people drawing on too little river water in an arid climate, remains unresolved.
Why It Keeps Shrinking
The Aral Sea’s shrinkage is not a historical event that stopped at some point. The South Aral Sea continues to lose water because the irrigation demands that caused the crisis still exist. Uzbekistan and Turkmenistan still depend on the Amu Darya for agriculture. The canal systems built in the Soviet era are notoriously inefficient, losing enormous volumes of water to seepage and evaporation before it ever reaches crops, but replacing that infrastructure would cost billions and disrupt the livelihoods of millions of farmers.
Glacier melt in the mountains where the Amu Darya and Syr Darya originate has also played a role. Research shows that glacier mass loss in the river basins has been much larger than the lake’s own volume changes, meaning the long-term water supply feeding these rivers is itself diminishing. As glaciers continue to retreat, there will be even less water available to split between agriculture and any future restoration efforts.
What remains of the original Aral Sea is now three separate water bodies with very different futures. The North Aral Sea is stable and recovering behind its dam. The western South Aral Sea persists as a deep, hypersaline basin with salinity above 110 grams per liter and almost no life. The eastern South Aral Sea fluctuates between a shallow, extremely salty puddle and a dry salt flat, depending on the year. Together, they occupy a fraction of the footprint that once made the Aral Sea visible from space as a single, vast blue expanse.