It won't be worth much unless you have enough clean water stored up to be able to use it...
(during a disaster where water is cut off, obviously! I once made the mistake of buying too much of this kind of thing and not thinking about the water until much later.)
Sounds like you're on the right track to me! I don't have a nearby creek/river but I do have about 40 gallons of water in 5 gallon containers. It's tapwater which should be fine since it's been treated, but I can always filter or whatever if needed. Otherwise I just swap it out a couple times a year for "fresh" tapwater.