The Aral Sea in its original form was located in the Northern desert part of Central Asia, within Uzbekistan and Kazakhstan and covered an area of 68 km2 with a volume of 1053 km3. In these dimensions, the Aral Sea ranked as a fourth after Lake Superior (Canada, USA), Lake Victoria (Tanzania, Kenya, Uganda), and the Caspian Sea, which is why people call it the sea. The level of the water surface of the Aral Sea in natural conditions was 53 m above the level of the world ocean, which is almost 80m higher than the level of the Caspian Sea. It was 428 km long and 234 km wide, with a maximum depth of 69m and a volume of 1064 km3. The water temperature on the surface in summer was 26-30°C and in winter-below 0°C. The average salinity was 10-11%, water transparency – up to 25 m. The average salinity fluctuated within a rather narrow range of 9-10%.
However, in the last third of the XX century, the Aral Sea began to dry up. It began to dry up due to excessive water intake for irrigation of newly developed virgin lands in its basin. From 1960 to 1990, the area of irrigated land almost doubled (from 4.3 million hectares to 8.2 million hectares), which doubled the water intake for irrigation. As a result, by 1990, the water level in the Aral Sea dropped by more than 20 m, the sea retreated from its former shores in some places by more than 100-150 km in the lower reaches of the Amu Darya and Syr Darya rivers.
When the Aral Sea dried up, the islands of the Akpetka archipelago joined the land, and the bays that separated them turned into salt marshes. In 1990, the island of Kokaral disappeared. It closed with the land, and the Saryshiganak Bay ceased to exist. Also, along with them disappeared and the Bay of Berg separating the Big Sea from the Small. The area of other islands began to increase. After a decade (10 years), the islands closed with each other and with the land, as a result of which the Great Sea was divided into two seas: the western and eastern.