A recurring event in my dreams for the past six months or year or so is being in a situation where water is in limited supply. The setting changes—last night, it was in the Redmond area, and it was due to some disaster that contaminated the water supply, so it was shut off. In the past I've been stuck in a college cafeteria due to a blizzard, and probably a dozen other situations with the same theme.
I don't know what the source of these dreams could be, if there is one. I don't wake up thirsty, or really having to go to the bathroom, or soaking in a mess of my own urine. There appears to be no real-world correlation.