The correct answer is - discontinue the use of irrigation systems.
There has been multiple suggestions as two how the Aral Sea can be saved because it is in a situation where its waters have retreated significantly, as things go it will be totally dried out very soon in the future.
The stopping of the usage of the irrigation systems is not one of the suggested measures though, even though that is the biggest reason why the Aral Sea is drying out, because lot of water is used for irrigation, and its tributaries bring in less water to it.
The big problem is that the economy is heavily dependent in this region on the agriculture, and the region is naturally very dry. So if the irrigation is stopped, the agriculture will crumble, and millions of people will lose their only income.
