The city water was accidentally contaminated, so the city ordered us to stop using it. Overnight, hundreds of thousands of water bottles was trucked in. Very impressive.
We used these gallons for everything:

I learned this trick in Boy Scouts. Heat a bowl of warm water and you can do all of your dishes with almost no water at all. I use gloves so I can do more scrubbing instead of using more soap.

I learned this trick from a crazy survivalist website. At first sign of water problems, fill your tub. There might be uncontaminated water still in the pipes that you can use and you never know when the situation will get suddenly much worse. Having an extra 50 gallons around could keep your family alive for weeks. We ended up using this to flush toilets because the safety was questionable.