 Although the North Aral Sea is currently rising, the South Aral Sea is still dropping, thus expanding the size of the desert.In the late Pleistocene, the Amu Dar'ya used to flow through the Karakum to the Aral Basin and Sarykamysh Depression, but flooding in the Amu Dar'ya valley during a pluvial period resulted in overflow to the Zeravshan River valley.The Amu Dar-ya merged with the Zeravshan and eventually reached Horezm Lake.