Clean water is something that we all take for granted. We turn on the faucet and there it is. It is plentiful, it is clean and it is drinkable. Yes, it may have some undesirable chemical additions (fluorides come to mind) but that is a subject for another day. So if a disaster occurred and the supply lines to fresh water were comprised, we would be in a pickle. There is a possibility that safe water would not be available for days and possibly not for weeks.
Click the link below to see the fantastic 101 article on how to store water to finding outdoor sources in an emergency. You wont regret reading this.