They use drought resistant / low water plants, bunch of retainment strategies (membranes, local rainfall water storage). IIRC still need to truck/pipeline/drip irrigate some water when plants initially growing (more water hungry), but the goal is to pick right plants that can survive on local conditions.
Yeah, I have read a lot about the plants, Populus Euphratica, and a lot of others, but it still...
There just isn't enough rainfall. Annual average precipitation in the Taklimakan Desert is less than 100 millimeters. With drip irrigation, they can probably keep at it at reasonable expense, but that place is horrid. Just look at it: https://www.youtube.com/watch?v=KuylRKAK1Tc
IIRC ~40% is in arid regions, rest in semi arid or better regions. I think in arid regions they'd prioritized desert margins with 100-200 mm rain. <100mm is extreme arid zones, i.e. central Takilmakan. I'm not sure if they'd even bother with that.
