Rainwater Harvesting

We don’t get a lot of rain in San Diego, but the rain that falls on your property is a free supply of water, and each gallon you catch and use in the weeks after a storm is a gallon saved from the Colorado and Feather rivers. Each gallon you catch is also one less gallon running down the street, washing litter, fertilizer and pet waste from yards, and gas, oil and coolant from streets into storm drains that empty into the nearest creek, river or bay. This is called stormwater runoff and it is the leading cause of water pollution.  How bad is water pollution in San Diego County? Find the watershed you live in and see.

Which Watershed Do You Live In?

Explore Project Clean Water’s interactive map of San Diego County watersheds. Click on individual watersheds until you find the city or area you live in — that’s your watershed.

What is the Water Quality Level?

San Diego Coastkeeper’s web-based watersheds report compiles and analyzes the water quality data for each of the county’s watersheds. Learn about pollutants and sources in yours.

What You Can Do

Catch the Rain on the Roof

Install a rain barrel under one or more of your rain gutter downspouts.

Where to Get One

The County of San Diego maintains a list of retailers that sell rain barrels and rebates may be available. You can also make your own from a recycled plastic trash can or food container.

Raise It

Place rain barrels on cinder blocks or a platform so that gravity improves the flow of water through the hose when you water plants.

Adapt the Downspout

Cut your downspout a foot or two above your rain barrel and attach an elbow or diverter piece to direct water into the barrel.

A Lot of Rain Falls on a Roof

When a rainstorm rolls through San Diego chances are that more rain will fall on your roof than you can catch in one or two barrels. Use the equation below to calculate what’s possible. Note that larger cisterns are available for storing rainwater, but if a cistern requires a pump it will also require a building permit and a backflow prevention assembly.

Roof Area (square feet) x Rain (inches) x 0.623 = Usable Water


1,500 sf. Roof x 0.25 in. Rain x 0.623 = 234 Gallons of Water

Prevent Runoff

Install one or more basins, called rain gardens, to keep runoff from slopes or downspouts on your property.

Dig the Basin

The basin that your rain garden will sit in is 6-12 inches deep. The length and width of a basin can vary.

Amend the Soil

Assure good drainage in your rain garden by mixing compost and sand into the top 1-2 feet of soil.

Plant It

Plant water efficient shrubs and perennials. Their roots will filter nutrients out of the water.

Learn More

Rainwater Harvesting for Drylands and Beyond
Brad Lancaster

Rain Barrel Information
County of San Diego

Leveraging the Landscape to Manage Water
American Society of Landscape Architects

Low Impact Development

Font Size
Share This