Storing water is not only space consuming but can be quite heavy to transport also. Since a very steady supply of portable water is critical,(in any/all AOs), I would strongly recommend finding ways to replenish your water supply first and concern yourself with storing and carrying second.

Things like learning how to build a Solar Water Ground Still and being able to filter and purify other water sources is far better than having to collect and store and possibly carry the water that you'll need for whatever time you have to.

http://www.desertusa.com/mag98/dec/stories/water.html (Learn This! A couple sheets of plasic are far lighter and easier to carry than gallons and gallons of water, cheaper too.)
Adding/lining fresh vegatation,(such as catus and the like), in the bottom of this type of solar still at least doubles the water yield that can be obtained with it. This type of solar still also purifies your own urine and other, otherwise directly undrinkable water/moisture sources.

http://www.katadyn.com/usen/ (Look seriously into this or something like this, way handier than carrying all the water that you'll need.)
There are still exceptions to relying only on this type of filtration, many water sources may still need to be chemically treated or boiled to render the water truely "Safe" to drink for long periods.

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I use a couple of 5gal water containers,(mostly kept in the vehicles), and I use canteens for carrying the daily water supply that I'll need. These are "Refillable" and "Reuseable". Nothing replaces the "Knowledge of Where and How to Find the Water" to refill them with!

IHTH

Michael