In Northern Alabama, a poultry farm implemented the use of a 100,000 gallon bladder-style reservoir to store rainwater for its livestock. The system was engineered to harvest the rainwater that comes down on an 82,000 ft2 poultry house roof. Two inches of rain is all that is needed to fill the 100-foot by 36-foot bladder to maximum capacity. The rain is cleaned through various fine-particle and ultraviolet light filters and the result is clean, potable water, pure enough for drinking and to be used in the poultry houses’ cooling systems, an excellent example of rainwater harvesting integration.
An Alabama Cooperative Extension System (ACES) specialist named Dr. Gene Simpson estimates a typical poultry farm with four houses uses between 1.8 and 2 million gallons of water every year. It is estimated that this Alabama poultry farm’s system for harvesting rainwater could pay for itself in 4 to 5 years just with the money saved from no longer purchasing municipal water for its operations.
The Basics of Rainwater Harvesting
Rainwater harvesting is fairly simple in its concept and in its application. The concept: capture, filter, clean, and direct rainwater to a properly-sized storage container for use on demand. At the base of RWH design, a structure called the “catchment area,” most often a roof, is utilized for capturing the rain. From there, instead of normal runoff to the ground, the rainwater is channeled to piping where it will be filtered and cleaned of potential contaminants, to various levels depending on intended use. After initial filtering and cleaning, the harvest will be stored in a rainwater collection tank.
Texas A&M University’s agricultural division gives us the equation for calculating number of gallons collected per inches of rain. This equation can be used to calculate the amount of rainwater potentially collected from a specified rain-catching area and is important when considering a rainwater system:
Harvested Water (gal) = Catchment Area (ft2) x Rainfall Depth (in) x 0.623 Conversion Factor
The Potential for Livestock Use
An equestrian property in Great Britain has successfully used a rainwater harvesting system to supply water for 30 horses year round, specifically by collecting rain from the roofs of stables and hay barns: an approximate 1600 ft2 area. Livestock owners tend to have large, well-suited catchment areas already constructed on their property due to the housing requirements of managing livestock.
Leveraging the surface area of existing structures such as houses, barns, stables, and sheds gives farmers a comparative advantage in rainwater collection. The long-term result saves money and resources by self-sourcing the most inelastic commodity: water. The implementation of rainwater collection should be a top priority for farmers and ranchers world-wide.