There are several ways to clean water.
Water Filters - 1 filter can clean a 55 gallon drum every 2 weeks. That would take a lot of filters to keep a year's supply of water clean. He says that every six months, he dumps the stored water and puts fresh water in the drums. He has 1 drum for every member of his family.
Boiling Water - Here in Utah at our altitude (3,000-5,500 feet above sea level) water needs to boil at a full rolling boil for 17 minutes.. So we can always boil our water to clean it, if we have enough fuel. It might be tough if it is raining or flooding where you are, however.
Clorox - This was the most interesting section. He said that Clorox is a 72 year old technology. One year after the manufacturer's date on the bottle all chlorine has evaporated through the plastic and the compounds that are left, such as detergent and bleach and other fillers which aren't good for the GI tract, won't clean the water and diarrhea is going to be a problem.
SPA is a product on the market that can be purchased at any swimming pool business, has no expiration date, can last indefinitely as long as it doesn't get wet. You can buy a bottle for about 15 dollars and with 1/8 tsp can clean a 55 gallon drum in 24 hours. This can be used in any kind of water. Lakes, rivers, so that water can be available in any kind of situation. He suggested getting a water testing kit to be able to test your water source for free floating chlorine. If you detect Free Floating Chlorine in the water that means there is no bacteria to kill. Obviously a Katrina type disaster demonstrates the need for clean water, but not for just a few weeks. It may take months to get clean water supplies flowing again.
Find a way to store and clean water.
anybody got other ideas? I am planning on making a solar still....for water, of course....