Rainwater Harvesting

Learn the best methods of collecting, storing and using rainwater.

| September 2016


Cisterns can be attractive sign of a commitment to water conservation. The Lady Bird Johnson National Wildflower Research Center in Austin collects rainwater in a series of cisterns. Rainwater from the central rooftop of nearly 17,000 square feet feeds two 20,000-gallon cisterns and the 5,000-gallon tower cistern. Several other cisterns ass to the total capacity of 65,000 gallons. With an average rainfall of 30 inches annually, these systems can collect more than 300,000 gallons of rainwater every year.

© Barbara Harper

Gardening with Less Water (Storey Publishing, 2015), by David A. Bainbridge, offers simple, inexpensive, low-tech techniques for watering your garden much more efficiently — using up to 90 percent less water for the same results.

You can purchase this book from the GRIT store: Gardening with Less Water.

Rainwater Harvesting

Rainwater harvesting is a great complement to the super-efficient irrigation systems described in this book and can help provide critically needed water for growing crops, landscaping, and other uses around the home, farm, school, or office. Even in very arid areas, gardens and orchards can benefit from captured rainwater used in the most efficient, demand responsive ways possible.

Ancient civilizations developed very sophisticated rainwater harvesting systems. The Nabatean people of the Negev Desert were the masters of this practice. They developed finely tuned, site-adapted catchment, runoff, dam, and channel systems that harnessed rains and flash floods to irrigate crops and fill the cisterns needed to support farms and a city in the harsh desert. Long ignored, these practices have been rediscovered as rainwater harvesting becomes a key component of more sustainable living, gardening, and farming.

Rainwater harvesting requires a catchment area, a collection system, and storage. The most common catchments are roofs, patios, and walkways, but other impermeable surfaces such as roads and even compacted soil can also work. Keep in mind, however, that road runoff is often contaminated with antifreeze, oil, and other materials. This can be fine for landscape plants but not so good for the garden. Water is usually harvested from relatively clean impervious surfaces where an inch of rain will deliver more than a half gallon per square foot of surface. Ten inches of rain on a 1,000-square-foot roof will provide about 6,000 gallons of water. An intense thunderstorm can deliver 1,000 gallons in less than an hour.

Many cities and states now encourage rainwater harvesting in development regulations or offer incentives for people or firms installing rainwater harvesting systems. Texas was the first state in the US to embrace rainwater harvesting, but Hawaii, North Carolina, and other states are now catching up. North Carolina and the Florida Keys have rainwater harvesting rebate programs.

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