The US military at these locations has always had backup generator capacity for emergencies. So communications and emergency lighting, etc, will be available.
**************
What happens if they cut off the water?
Apparently the water to Incirlik has indeed been cut off. There should be at least short term emergency supplies of potable water. Too what extent these are there and how potable they are is another question. Generators and their fuel supplies are regularly tested and easily monitored by Civil Engineering, etc. Emergency water? Who knows? I’m sure there is bottled water at the Exchange and the Commissary. It can be rationed for a few days.