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August 29, 2012

How to conserve water and prevent dangerous rainwater runoff

by Claudia Harmon Worthen, EcoPlanners LLC
Water Carry

Forty-six percent of people in underdeveloped countries walk an average of 3.7 miles for access to drinkable water. Think about that the next time you turn on the tap and let it run down the drain. We don’t have to walk for miles, but potable water is becoming less plentiful and continually more expensive.

As our water table drops due to diminished rainfall, we try to avoid using drinking water to wash our cars or water the garden. We take 3 minute showers to conserve this precious commodity. Then we allow billions of gallons to run down gutters to storm drains that flow directly into the ocean. Along the way, it collects all kinds of nasty stuff – road dirt, dog poop, disease and pesticides.

Rather than encourage runaway polluted water we need to “Slow it, Spread it, and Sink it”.  Allowing rainwater to soak into the ground will recharge both shallow and deep aquifers, reduce pressure on sewage systems, lower water bills and protect our steams and oceans.

Permeable Paving

One way to encourage low-impact development is to use permeable paving rather than high impact asphalt and concrete. Our driveway in Cambria is covered in turf-pavers filled with thyme, which smells good when we drive over it, tastes good in soup, and once established needs very little water.


Capture runoff

Another way to prevent storm water runoff is to capture it as it falls off your roof. In the summer, when we use about 30 percent more water and up to 70 percent more for landscaping, and water sources have dwindled, we can use captured water from the rainy season.

One inch of rain falling on 1 square foot of surface captures 623 gallons of water. That means a 1,000 square foot roof can capture a whopping 24,000 gallons of water in a year with 20″ of rainfall.  The average yearly rainfall in the Central Coast is 15-20 inches.

Above ground tanks can be aesthetically pleasing, like this tank in Santa Fe, New Mexico that holds 400 gallons of water.

Underground tanks are more expensive, but they don’t take up space in your garden. Contact an expert or have fun doing it yourself.

It’s best to start with a steel or clay roof and avoid composition roofing, which sluffs gravel and can leach tar. Drain pipes and other parts of the system need to be constructed of inert materials, such as reinforced concrete, aluminum, recycled plastic and fiberglass.   Analyze your property for natural water runoff and type of soil, then inventory the types of plantings in your garden and location.

Rain barrel systems require a debris filter and a down spout diverter to prevent overflow. Special solar panels are available to provide electricity for pumping the water into your garden or other uses.

These are three excellent resources:

  • Rainwater Management for Low Impact Development  (Available at the SLO Green Build office, your local building department or as a free downloadable PDF on the
  • American Rainwater Catchment Systems Association (ARCSA)
  • Loomis Tank Centers in AG and Paso Robles, members of ARCSA

Next month’s topic: Amazing non-toxic alternatives to toxic chemicals


Claudia Harmon Worthen is the principal designer at EcoPlanners LLC, a network of sustainability experts in building and interior design on the Central Coast of California. You can reach her by email: [email protected]

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