What you use for storage, and how much water you store should be as factors of how much you think you might need, how much room you have to store water and other things, as well as other available sources. The idea of adding plumbing so that you continually refresh barrells or tanks of water is great, if you can do that. With my NYC apartment, that is imply not an option. Storing enough to get a couple of us through a week take up enough room. Storing enough to get a family of four through a few weeks is simply not an option. If we are going to need to haev water for more people for a longer period, we have to either find more sources than storage or hopefully will have bugged out.
As with any need, do not count on only one source. So, you should not count only on stored water. One source of water can and should be the stored water, and another source can and should be something you have stored. Look for more sources.
Perhaps you can collect rainwater, which over the long term should be of some benefit in Minnesota. Obtain some methods of purifying water. You could buy some chemcial purifying tablets, but a small bag of pool chlorine might go a long way. I've got instructions on how to do this at home. You can find other instructions on using bleach, such as chlorox.
As some of the other posters have mentioned, it may also be possible to have storage you normally keep empty. Our BOBs, by the front door, have water storage bags inside them, as well as some water. If there is some event going to hit that will have us buggin in or buggin out with a car, then one option is to fill those as soon as possible.
One comment, think about sources for water that provide for other needs besides drinking. I live not far from one of NYC's rivers, but the water is more salt than fresh, and there is a sewage treatment plants that dump into it. Drinking it would would probably require distilling it, and then one might be drinking something you did not want to drink. However, being able to bring buckets of it inside might give me use of a toilet. Same thought with filling bathtub, it might not be worth drinking, by the time you are thinking about drinking it. Water stored like that, uncovered, static, etc, in a city, is liked to have a layer of dust of unknown origin settle over it in hours. Still, I might be able use it to flush.