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Column: Capturing and harvesting water

Posted: June 28, 2018 1:25 p.m.
Updated: June 29, 2018 1:00 a.m.

(A few years ago I came across an article and saved some of the information because the content is relevant and useful. Unfortuanately, I did not save the source, but I do know that it originated in the Lowcountry and wanted to provide full disclosure that even though I have edited and revised the information a good bit, it is based on the work of someone else.)

Rain barrels, cisterns, water catchments, rainwater harvesting. It is known by many names, but the concept is the same in all cases; capturing Mother Nature’s bounty in a container. If you want to go green and make a difference, capturing rain water can be an invaluable contribution to the environment and to your own home water usage. Rain is free, it’s good for your plants and trees and it helps improve the soil. No matter how you slice it, capturing rain water can translate to lower water bills and less storm water runoff.

The practice of harvesting rainwater is not new; water catchment systems have been in use for millennium around the world. One of the most effective ways to make a difference in personal water usage is via a landscape irrigation system. Irrigation systems are generally the biggest users of water for residential properties. Though consumers are led to believe that a 50 gallon rain barrel is the answer, think bigger! If you have an opportunity to upgrade your irrigation system or if building a new home, think water harvesting. An irrigation system that utilizes a rain cistern is ideal and harvested rainwater can easily be used.

A system can be as simple or complex as one prefers. The basic components of a system are gutters or pipes that direct the water from the roof of a house into a cistern. The water is stored until needed and then sent by a pump through a filter to the irrigation system. Most rain collection systems have a method to refill the cistern with potable water for periods of low rainfall. Water catchment systems that have the most positive impact would be those with a large water capacity, ideally 10,000 gallons or more. So, out of curiosity, I calculated the potential rain harvesting capacity for my house using the formula on the Water Innovations website ( Based on the average annual rainfall for our area and the square foot dimensions of my roof, a cistern could capture up to 28,500 gallons of rain water in a year!

Water cisterns can be underground or above ground. They can be made of plastic, cement, fiberglass or any suitable material that will hold water. While it is most feasible to build a system during new home construction, one can also be retro-fitted for an existing home. What kind of front end investment does this require? A larger system may range from $5,000 to $10,000 depending on the size and features selected.

A random computer sampling of four residential irrigation meter records here in town yielded a total usage of 40,686 gallons, 73,578 gallons, 117,840 gallons and 246,857 gallons of water over a 12-month period. However, if we assume watering only occurs during the growing season (March through August) then these homeowners are using 6,700 gallons/month, 12,200 gallons/month, 19,600 gallons/month and 41,100 gallons/month, respectively.

A homeowner who employs the use of a 15,000 to 20,000 gallon cistern could stock their irrigation system and make a substantial difference in water bills. If we look at the sampling above, the irrigation cost equates to a minimum of $283 and maximum of $800 per year. Over time, a rain harvesting system could pay for itself and then afterwards be a yearly savings.

Other than cost, why consider rain harvesting? Well, water is not a renewable resource, so if we can capture, conserve and use it wisely, it allows others in the future to utilize it. For grins and giggles let’s look at a possible city-wide water conservation scenario. If we look at one of the homeowners above using 73,578 gallons per year for their irrigation system and assume that they are able to reduce their water usage in half to 36,789 gallons by using a rain harvesting system and, if all of the 5,000 households within the city limits were to do the same, we would gain a savings of 1.8 million gallons per year of water not going into the storm drains, streams and Wateree River.

I know this scenario is not probable, but why is it significant? Storm water runoff. In populated areas storm water runoff and the pollutants it carries off of roads, driveways and parking lots have been a hot topic of discussion for years. Rain harvesting can lessen the concern of non-point source pollution tremendously. If you take those same 1.8 million gallons of water per year, instead of ending up as storm water they would be filtered through the earth after irrigating home landscapes and recharge the ground water table.

The use of water catchment systems is just as relevant today as millennia ago and perhaps even more advantageous and important because of stormwater runoff pollutants. Capturing and using rain water wisely not only benefits our plants and trees, but can also help save money and conserve a precious natural resource.

For more information, an internet search using the words “rain harvesting” will provide you a wide variety of publications, illustrations and how-to’s, etc.


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