As recently as the 1960s, the Aral Sea, on the border of what are now Kazakhstan and Uzbekistan, was the fourth-largest lake on Earth by surface area — larger than the country of Ireland. Today it's a small fraction of that size, split into disconnected remnants, with vast stretches of its former lakebed now an exposed, salt-crusted desert. Almost none of that loss was natural.
Diverting two rivers to grow cotton in a desert
Soviet planners, starting in the 1960s, diverted the two major rivers feeding the Aral Sea — the Amu Darya and the Syr Darya — into a massive irrigation network to grow cotton and other crops across the surrounding arid Central Asian plains, a deliberate, large-scale engineering project intended to turn desert into farmland. It worked, for cotton production. Starved of its two main water sources, the lake itself began shrinking almost immediately, and the shrinkage accelerated for decades.
What losing 90% of a sea actually looks like
By the 2000s, the Aral Sea had lost more than 90 percent of its original volume, splitting into separate northern and southern remnants as the water retreated. The exposed seabed, laced with agricultural pesticide and fertiliser residue that had washed into the lake for decades, became a source of toxic dust storms affecting the health of surrounding populations, while the regional fishing industry that once supported tens of thousands of jobs collapsed entirely as the water receded from what had been thriving port towns.
What we're still unsure about
The two halves of the former sea have diverged sharply since the 1990s. A dam completed in 2005 with World Bank support helped the smaller North Aral Sea partially recover, restoring some fishing activity — a genuine, documented partial success. The much larger South Aral Sea, split between Uzbekistan and shared river resources with several upstream neighbours, has continued shrinking, and restoring it at scale would require Central Asian states to renegotiate water rights over the same rivers that agriculture across the region still depends on — a political and economic problem regional governments haven't resolved, not a technical one.
This sits inside Water Scarcity & Management, one of seven topics in Environmental Geography, one of five domains in Geography, one of seventeen subjects the app can quiz you on.