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Rain barrels are easy, low-cost ways to collect and use rain water to irrigate a garden. Rain runs from roof gutters to a pipe that empties into a barrel. A screen keeps leaves, debris, and mosquitoes out of the barrel, which should be dark, to prevent algae from growing. A hose is attached near the bottom for irrigation.
Roofs are an amazing source of water. The roof of a 1,000 square foot house can collect around 600 gallons per inch of rain. In an average rainfall year, a 1,000 square-foot roof in San Francisco can collect more than 13,000 gallons of water. Rain barrels typically hold 50 to 100 gallons; you can install more than one. Larger storage tanks, called cisterns, can be installed above or below ground.
San Francisco Public Utilities Commission
Information and instructions on harvesting rainwater with rain barrels and cisterns.
Oakland Discount Rain Barrel Program
Rain barrels at a discount for Oakland residents.
A demonstration home and garden in North Berkeley with a rainwater cistern, plus many more ecological features; offers regular classes and tours.
Urban Farmer Store
Rainwater harvesting equipment and training workshops at stores in San Francisco, Richmond, and Mill Valley.
Rain gardens are landscaped areas planted with wild flowers and other native vegetation. They soak up rain that flows off a roof, driveway, sidewalk, or other impermeable surface. In a storm, the rain garden fills with a few inches of water that slowly filters into the ground. Rain gardens absorb 30% more water than the same area of lawn.
How to Build a Rain Garden
Pamphlet from Sonoma County Master Gardeners with information that applies to many parts of the Bay Area.
Rain Garden Network
Comprehensive information on rain gardens.
PlantSF: Sidewalk Rain Gardens in San Francisco
San Francisco residents, businesses, and neighborhood groups can replace part of their sidewalks with rain-absorbing landscaping. PlantsSF has examples, instructions, and permit information.
The State Water Resources Control Board's Slow the Flow videos have information on rain gardens, permeable paving and more.
When rainwater falls on paved surfaces, it flows directly to streams and storm drains in huge volumes, carrying with it pollutants which eventually reach San Francisco Bay. Permeable pavement systems let water seep through the surface, allowing rain to pass through to the soil, where beneficial microorganisms break down pollutants. Sidewalks, patios, and driveways can be paved with new permeable paving materials that dramatically reduce the volume of storm water runoff.
- A special kind of concrete called pervious concrete soaks up rainwater and allows it to percolate into the soil. For more information and searchable databases to locate contractors who can install this type of paving, go to National Pervious Concrete Association.
- Another option is permeable interlocking concrete pavement, a layer of concrete pavers separated by joints filled with small stones. Water enters the stone-filled joints and flows downward through a layer of crushed stones. The stone layer filters out some pollutants as the water percolates into the soil below, where more pollutants are filtered. For more information and a searchable database of contractors who can install permeable pavers, go to Interlocking Concrete Pavement Institute.
- Additional options include pervious bricks and pervious asphalt.