Not to be too contrarian, but before we declare this an unmitigated disaster, shouldn't the cost of the destruction of the Aral sea be measured against the benefits of provided by the water that used to flow into it?
The soviet scientists involved with the water diversion were aware that the Aral sea would eventually dry up. In fact, the decline in sea level was observable from the very beginning. It is true the lake drying up was an intended and foreseen consequence.
However, what was unforeseen were the ecological consequences of the lake drying up, that has turned the dry lake bed into a salt desert where dust storms kicking up toxic sediments are a common occurrence. Without a large body of water to moderate the weather, nearby communities now experience hotter summers and colder winters. In effect, one desert has been traded for another.
And while diverting water for agricultural uses might be beneficial, most of the canals used for the diversion are not properly lined, experiencing significant water wastage during transport. And most of this water is being used for water-intensive crops like cotton and rice. Were good irrigation practices used, and if more suitable crops that required less water were used instead, it is likely only a fraction of the water would be needed. It also has to be kept in mind that the economic benefits agricultural irrigation has brought has to be balanced the economic loss resulting from the loss of fishery in the area,loss of tourism (some of the villages were once seaside resorts), and economic hardship resulting from the ecological changes to the landscape