You have to sort of have a baseline emergency to be prep for. What you need varies on where you are, what conditions you expect. My old Alaska stuff was quite different than my current Seattle stuff which is very different than what I would have in Arizona. I'd feel pretty comfortable with your choice with fast running water, but not personally with lake water. My personal preparedness means having supplies/resources near by. I'm in no shape to bug anywhere, if it's that bad well here I am. I do need to set up a better long-term/earthquake/out of the house system.
In terms of available space for a pack, bleach or chlorine tablets might be better. Knowing how to start a fire so you can boil is better yet, as is having something big enough to be worth boiling yet small/light enough to be worth carrying. Keep in mind, nothing needs to be packed empty. But learn how much you can actually carry. When I was young, it wasn't much of an effort to go for a week long remote hike with a 40 pound pack. These days... I think maybe I could pick it up and walk it to the car.