The correct answer is - Cotton farming.
The cotton farming in Central Asia is the agricultural activity that primarily contributes for the rapid drying out of one of the biggest lakes in the world, the Aral Lake, or as it is often referred to, the Aral Sea. The Aral Sea is located on the border between the countries of Kazakhstan and Uzbekistan, and this is a region that has a long tradition of cotton farming. Since the lake's waters had started to be used for the growth of this highly water demanding plant, the drying out of it has been very quick, and as it goes the lake will probably disappear in the near future.
The problem that makes the drying our so intense, is that the water that is taken out of the lake is in too big of an amount, and the main tributary, the Amu Darya River, can not compensate the loss. Also, the region is very dry, and in summer very hot, so the evaporation contributes even more for the loss of water, so the lake is on the verge of existence at the moment.