Rain Barrels – A one-inch rain event can generate up to 623 gallons of water on a 1,000 square foot roof

by Aaron Wilson

People have been using rain barrels, or cisterns, for thousands of years to capture and store free water from the sky. Historical records show that rainwater was collected in simple clay containers as far back as 2,000 years ago. In recent years, they have regained popularity as drought conditions have persisted, and local utility companies have raised rates.

A one-inch rain event can generate up to 623 gallons of water on a 1,000 square foot roof, enough to fill over ten 55-gallon rain barrels! In the New River Valley, precipitation is well distributed throughout the year with a maximum in July and the minimum in November. Monthly amounts of rainfall vary from less than ¼ inch to more than 10 inches. The average annual rainfall from the National Weather Service Station in Blacksburg is approximately 41 inches. Assuming it was possible to catch all 41 inches of that rain, almost 30,000 gallons of reusable water could be collected each year from the average roof, which is more than enough for most families’ outdoor water needs.

Realistically, most people who have rain barrels only have one. Let’s say this one barrel holds 55 gallons. One quarter of a 1000 square foot roof would generate about 70 gallons of rain run-off each time it rained 1/2 inch. The challenge would then be to use the 55 gallons of stored water before the next rain event. Let’s look at the flip side. As we all know, rain does not always fall uniformly throughout the year, and our late summer (August and September) tends to get dry. If a family had two or three barrels, they could collect enough water to get them through that ‘dry season’ and into the fall gardening season.
Why let good water go to waste when it can be collected, stored and used later? The overwhelming benefits of using rain barrels include:

• Provides soft water for watering plants, washing cars and filling
birdbaths or fish ponds

• Alleviates demand on municipal treatment systems

• Reduces polluted runoff

• Lowers water and electricity bills and in some cases storm water

• Reduces flooding

• Recharges groundwater

Since 30 to 40 percent of a home’s summer water bill can go for outdoor use, a rain barrel can be part of the solution. Water collected in rain barrels isn’t drinkable (potable), but it is perfect for lawns and gardens, ponds and birdbaths. Rainwater, while it may be slightly acidic, is naturally soft and free of minerals, chlorine, fluoride and other chemicals so plants thrive on it. It can be used for washing cars, decks and windows, as well.
The New River Valley Master Gardeners present rain barrel workshops and demonstrations throughout the New River Valley where participants have the opportunity to assemble a barrel out of a food safe container with hardware included. Then the barrel can be used to collect rain water at their home. The rain barrels can be placed in the yard or connected to a gutter downspout to collect water. The gutter option will generate a great deal more of the stored water vs. an open collection system. A submersible pump can be included inside the barrel to provide a pumping system to a water hose or the barrel can be elevated slightly providing a gravity fed system to irrigate your landscape.

Rain barrels can be decorated or painted to add a lasting piece of garden art to the landscape. If you are interested in learning more about rain barrel workshops in the area, please contact Kelli H. Scott at the Virginia Cooperative Extension-Montgomery County office at 540.382.5790 or kescott1@vt.edu.

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