we are simply banned from watering our lawns, or gardens (or filling pools). A major water main that feeds our area broke, and the fear is that if everyone watered (i.e. wasted) water outside the way they normally do we would either:

Cause a pressure drop which would then cause us to have to boil our water, for a good period of time until pressure is returned and the water is safe again.
The water pressure drops during a sudden crisis demand time like fighting fires or such.