When I was six my dad decided he wanted to be a farmer. So he rented forty acres of rich river bottom land in northeast Missouri, very good soil but prone to flooding. Mom, dad and the three of us boys moved into a small farmhouse on the land.
The five hundred square foot house had a good producing well but you couldn't use it because pesticides from continued farming had leached into the ground water. Water for household use was pumped from a two thousand gallon cistern located under the house. The cistern was stocked by rain water and snow melt, and was only used for dish washing, showers and laundry. We got drinking water from my grand parents who lived in the nearest town. We never ran out of water.
Jump forward thirty some years. I wanted a soaking tub under the stars at the cabin. There is no well yet and it seemed wasteful to haul water for a hot tub. One summer evening, on a whim, I put one of the downspouts from the gutter into the one hundred gallon tub I had for soaking.
The cabin is located in the desert southwest and during the summer we get these huge monsoon rainstorms. Anyway, this big thunderstorm rolled in and within about fifteen minutes not only was the one hundred gallon tub full, it was overflowing!
Here is the math, there are 7.48 gallons of water per cubic foot. This breaks down to .62 gallons of water per inch per square foot. For the sake of ease and to take evaporation into account let's round it down to .50 gallons per inch per square foot. The roof is a little over six hundred square foot, so I can collect three hundred gallons of water per inch of rain. So even in the deep desert where you see maybe ten inches of rain a year you are still able to collect three thousand gallons.
One inch of rain on one square foot of roof yields 1/2 gallon of waterIn a survival situation it would make sense to have some tarps that could be rigged to collect rain. A ten by ten foot tarp would deliver fifty gallons of water for every inch of rain, that's a lot of water that does not need to be transported to your retreat site, you just take the tarp. If you are hunkered down in your house you could divert your down spouts into a large trashcan or barrel to collect relatively clean water. If the water is roof runoff it should be boiled or at least filtered with a few drops of bleach added.
Keep at least one gallon of drinking water per person per day. I use plastic five gallon "water cooler" containers with screw on tops. The ones I picked up at Wal-Mart have a really nice carrying handle and screw on caps. I found a couple of old non electric freestanding water dispensers for a couple of bucks at the local ARC (just like Good Will). I keep one at the cabin and one at the house, they work great.
You need to keep enough drinking water for a couple of weeks on hand but for a long term crisis it would be prudent to gather rainwater. If nothing else your clean water supply could be kept for consumption, using the rainwater for cleaning and showers.
Next week I will talk about a really inexpensive way to heat water.