The primary cause behind the shrinking of the Aral Sea is the diversion (for purposes of irrigation) of the main sources of inflowing water, the riverine waters of the Syr Darya (ancient Jaxartes River) in the north and the Amu Darya (ancient Oxus River) in the south, which historically discharged into the Aral Sea.
Why has the Aral Sea been shrinking?
How big was the Aral Sea originally?
In 1960 the surface of the Aral Sea lay 175 feet (53 meters) above sea level and covered an area of some 26,300 square miles (68,000 square km). Its greatest extent from north to south was almost 270 miles (435 km), while from east to west, it was just over 180 miles (290 km).