[helterskelter]

Probably the lack of water. I don't know why they need to continually pump it instead of doing a closed loop and cooling it through a few miles of pipe underground which is practically free, after you install the plumbing. Sure evaporative cooling is good, but certainly there are workable alternatives.

[SoftTalker]

That or latent heat cooling, the other end of the phase-state spectrum: Instead of evaporating water during the day, make ice all night when ambient air temps drop and then use it to cool a closed-loop system during the day.