“1. Accumulate a large amount of stored water. Secure a very local water source.”
A more practical solution would be a quality water filter. A company called Berkey (www.berkeyfilters.com/) sells a ceramic filter that will purify 3,000 gallons per replaceable element. I have no affiliation with them, but I may buy one.
Water purification is a BIG consideration. Even a Brita pitcher is a help, but having a good system with a reliable source of water is ideal. If electricity goes out, so does any municipal water system. It always helps to plan accordingly. A fast-flowing stream is safer than a lake or pond.