Rain Water Harvesting
In many parts of the world, water tables are dropping, and clean sources of drinking water are getting hard to find. The price of bottled water is increasing, and leaves you less self sufficient. One source of water in many climates is rain water harvesting. Catching the rain from roof runoff, and purifying it can be less energy intensive than pumping from hundreds of feet deep in the earth, and cleaner than surface water.
A good source of info on this subject can be found at http://www.rainwaterharvesting.net/