Stored water is about 200 gallons in barrels and smaller containers. We put some bleach in the water and try to change it out annually. That capacity is about 3 weeks for my family of 4. Additionally, it means that I would only have to run my generator for about an hour every 3 weeks to fill them.
If the generator fails I have a couple of well buckets that I made. Here is where I got the plans for the bucket:
Build a Well Bucket
It is a bit of a pain because I would have to pull the pump and piping out of the well to use but it is not difficult with a length of pipe to pull your pitless adapter. Our well is about 160 ft deep but the water is within 50 feet of the top. A hand pump would be better but at this point that is not in the budget.
We have a rain catchment system that has a capacity of about 150 gallons. It cost me about 125 to build. It is just a length of gutter running into 3 barrels on my garage. My eventual goal is to have gutters on the whole house with a couple thousand gallon cistern but that is several years away.
There are a couple of ponds within a couple hundred yards of the house and in a worst case scenario we can use the garden cart and wheelbarrow to move water from there.
Treatment is vital to prevent disease. You can use Clorox, boiling or filtering. For filters I have a Berkey as well as a couple of filter kits that can be built out of 5 gallon buckets. Those are both backups for us and hand outs for the neighbors as I don’t want people getting sick around me. The filter kits are here:
http://www.homespunenvironmental.com/product_p/bc-0102.htm
A good source of barrels here in Southern Maine is the Barrel Man in Scarborough. He advertises in craigslist.