Historically, the most common means of long term water storage was the cistern. This is precisely what was done during the 19th century with many Midwest households; a handmade brick cisterns was sized to last months between rainfalls for one household.

Now, for long term planning, cisterns of many different sizes are available, along with pumps and accessories for treating the water while in the tank.

Modern Underground Cisterns

With proper planning, one could easily store enough water in a cistern to last months (depending on your regional annual rainfall and the size of the household), or, you could use the cistern in-line with city water.

Cistern Technology

Planning a cistern in new construction plans might be smart. In rural areas where pump capacity is low, cisterns can add not only volume but pressure to a system. One could retrofit this technology to an older home or, like my place, you may have an abandoned (but still functional) cistern somewhere buried in your yard.

I like the idea of water catchment and the use of cisterns as storage.

Some of the home designs I've been looking at recently include rainwater-harvesting systems. In some of these they use a good portion of the house's roof area to shed and channel rainwater to filters and from there to huge cisterns.

Most of the testimonials from home owners that have catchment systems lead me to believe the plastic ones are preferable to concrete because they can handle environmental stresses better and are low maintenance.

Now, if I could only afford to build a house. <img src="/images/graemlins/grin.gif" alt="" />

I love cisterns, and grew up useing one.
I even have a rain barrel for the greenhouse.

Some things to point out:
Don't use asphalt shingles, or roofs treated with oil based preservatives or insecticides.
Use a flush box and a filter before the water goes into the cistern.

A plastic cistern kept above ground can be surounded with planks and black straps to look like a wood barrel, for appearance and protection from puncture.

Size a cistern for normal water usage for 1 year, with a 30% evaporation cushion, for your family.

Back in the 60's and 70's the Civil Defence suggested plastic sheeting be kept to cover a roof for a temporary emergency rain catch. (the idea being that the radioactive roof/fallout could not contaminate the collected water)

I'm a board member of a large Rural Water District. We have thousands of customers who only have rural water. Our district is very well prepared for the worst, but if we lose even 1 well from our system, or lose electric power for 2 days, we're down, maybe for months on some sections of the grid.
There is probably not a single municipal water system in the country that can go 3 days without power.

Nature stores water in other ways

http://www.earthfiles.com/Images/news/I/IceKilimanjaroContrast.jpg

http://www.earthfiles.com/news/news.cfm?ID=1065&category=Environment

Until it starts to melt. Things are a changin.