The dyke actually cuts the north from the south, allowing the water from the river to be held instead of flowing south and evaporating.

That article is mad. The Kazakhs are back fishing freshwater fish whilst the Uzbeks are reluctant to do anything similar because of their success farming cotton. To stop the continued waste of water, which spills over the top of the dyke, the Kazakhs want to increase the height of the dyke by 4m.