by Betsy Herbert
published in the Santa Cruz Sentinel on 3/28/2012
“People are amazed when they find out how much rainwater they can capture from their roof tops,” said Landscape Architect Bobby Markowitz at a March 15 presentation at the Museum of Art and History in Santa Cruz. A house with a 2,000 square-foot roof can capture 29,900 gallons of water during an average rain year (24 inches). That’s more than a third of the annual water consumed by a typical household (average 226 gallons per day), according to the City of Santa Cruz Water Department website.
Rainwater harvesting, the ancient practice of capturing and storing rainwater for later use, is experiencing a revival, in light of dwindling global water supplies. In many countries, such as drought-plagued Australia, rainwater captured from rooftops is increasingly supplementing municipal water supplies. It’s also catching on in the American southwest, especially Texas, which is experiencing the longest drought in its history. Water agencies throughout California, including Santa Cruz and Soquel Creek Water District, offer rebates and discounts on rainbarrels and/or cisterns.
Markowitz, owner of Earthcraft Landscape Design (www.earthcraftdesign.com), has been designing rainwater harvesting systems since 1992. He tells the story of his first client in Santa Cruz County. “After losing his well, he tried seven times to drill another one, and then gave up. He was trucking in 30,000 gallons of water to supply his extensive gardens.” To solve the problem, Markowitz designed a rainwater harvesting system with a series of storage tanks to irrigate the 1.5 acre plot throughout the dry season. His client, James Bowen, said, “The only thing I would have done differently is to have done it sooner.”
While finding space for storage tanks on a large property may be easy, it can present a real problem on smaller suburban lots. Markowitz advises all potential clients to “Quantify, quantify, quantify” to understand how to size a rainwater harvesting system. First, calculate how much water your rooftop can capture. Then calculate how much water your garden requires. Finally, calculate how much storage you’ll need.
On-line resources are available to walk you through these calculations. One of the most popular is the “Texas Manual on Rainwater Harvesting.”
For smaller lots, Markowitz advises using multiple smaller tanks or an underground tank. He also recommends using drought tolerant plants to reduce irrigation needs and having qualified professionals design and install the system.
For even more water efficiency, Markowitz recommends installing a greywater system to be used in tandem with rainwater capture. Rainwater could then augment supply to non-potable uses in the house year-round. Greywater from washing machines and showers could be used to irrigate the garden in the dry season. (Do-it-yourself installers should check permitting requirements.)
The main issue for most people considering rainwater harvesting is the cost. Full-blown systems can be expensive. For a complete system, sized for a typical suburban residence, Markowitz estimates a cost of $5,000 for materials alone (tanks, filters, pumps, pipes and accessories). The cost of including an integrated greywater system is roughly double.
Smaller, less costly systems are also effective, according to Ebin Lee Warner, a UCSC electrical engineering student. Warner’s “The Rainharvest Project” aims to increase community awareness of the practice in Santa Cruz. His engineering class has a prototype rainwater-to-toilet system, which is being evaluated for testing by Soquel Creek Water District and Ecology Action. The system is designed to use captured rainwater to flush toilets.
“All you need is a simple, inexpensive 200 gallon system to make a difference. If enough people use them, it’s possible to make a dent,” Warner said.