Water can be taken for granted if it is conveniently available. That is a huge mistake. Without water, a person cannot survive much longer than 4 or 5 days at the very best. Lots of things can happen that will interrupt access to water. One such situation nearly happened in 2012, but it was not a catastrophe thanks to a near miss. Quote from the NASA website: “Two years ago, Earth experienced a close shave . . .” “but most newspapers didn’t mention it. The “impactor” was an extreme solar storm, the most powerful in as much as 150+ years.”
Read that article closely. Then read this: http://en.wikipedia.org/wiki/Solar_storm_of_1859
Now, what on earth does this have to do with water. If you read both articles carefully, you will find that a geomagnetic solar storm (sometimes referred to as a coronal mass ejection) of significant strength is capable of shutting down electrical power to nearly everyone on earth. This means no gps, no electricity, no internet, no electric heat . . . . The one in 1859 caused arcing on telegraph lines, and caused fires in the telegraph offices. In this day and age, a storm as strong as that one (like the one that missed us by about a week in 2012) would shut down the internet, and the electrical power that brings water to most people everywhere. There would be no usual public water anywhere, at the worst, at best it would be very difficult to find.
Please, don’t take my word for it, read what the scientists say. At the wikipedia site, there are referenced 41 (some scholarly) articles on this type of occurrence.
This does not mean panic, and get paranoid. Things would be back to normal all over within several years or less, and there should be disaster plans in effect all over that would be able to handle this type of event in a few weeks or so. But, in the mean time, finding water will be a real pain, to say the least.
Set up a couple (maybe more than a couple) of rain barrels and a water filter; you may be really glad you did.