Fresh water supplies are becoming increasingly scarce, especially in arid regions where increasing populations are depleting aquifers that took millennia to charge. Harvesting rain not only decreases the demand on the ground water supply, it also consumes significantly less energy to utilize.
Rainwater Collection: We built this cistern under a greenhouse. The cistern is made out of reinforced concrete with a waterproof coating. There is an access door in the floor. Rainwater is collected on the glass roof, a small area 8×10′ but the cistern fills up fast. We installed a valve to ensure that only clean water is collected. The first few gallons run out a drain pipe, then the valve switches on and directs water into the tank. The water is used on landscaping, pumped directly out of the tank with a garden hose. A generous supply of water is also useful in emergencies when electricity is out, for instance, and the well pump is not working, as a source of water for flushing the toilet.
Livestock need a lot of water, and plumbing a barn may not be cost-effective, particularly when you consider the amount of energy it takes to run a well-pump. We installed a underground tank behind our sheep barn. The metal roof collects clean water. (Rainwater harvesting off an asphalt roof is not recommended.)
The water runs into gutters and through a series of gradually finer filters before going into the tank. The tank has an electric unit for ozone filtration.