Rainwater Harvesting Viable Alternative in Arid Climates

Gone are the days when we could expect to apply endless amounts of municipal water to our West Texas lawns without forfeiting a little capital.  Some estimates place outdoor irrigation as high as sixty percent of total home water use with at least half of that being wasted by poorly timed or inefficient systems.   In the future you can anticipate hearing more about novel methods of providing water for your home and particularly your landscape.

One innovative method to supply supplemental water to your garden or landscape is to catch and store rainwater.  This little trick, called rainwater harvesting, can be simple or complex but all systems share some basic components.   For the simplest system you’ll need a surface to catch the rainwater.  The obvious choice for a catchment surface is the roof of your home.  A gutter system is essential for conveying the rain from the roof to a storage container.  Finally, a reservoir with a hose attached to a spigot at the base is a handy means of delivering the stored water to the location you intend to use it.  More complex systems may incorporate a timer with a pump connected to an irrigation system.  Another consideration is perhaps a treatment method to supply water for in-home use.

Avoid using a storage tank that allows light to penetrate through to the water.  Light will encourage the development of algae and microorganisms that will place a strain on your filtration system. If you must use a clear or opaque tank, paint it entirely with a dark color to deny the penetration of light.  Place a screen over the point where the rain enters the tank from the gutter to ensure that mosquitoes don’t have easy access to the water.

In your calculations, the shape or slope of the roof isn’t important, rather the footprint of the roof is used to determine the size of the catchment area.  If you are fortunate enough to plan the construction of your catchment surface, avoid materials that contain lead such as some wood shingles or flashing.  Standard composite shingles and metal roofs work well.

How much water can you expect to collect?  A 1,000 square foot roof will catch approximately 630 gallons of water from a one inch rain (rainwater harvested = square feet of surface area x inches of rain x 0.63).

Jeff Floyd

Texas A & M Agrilife Extension Agent – Horticulture