Technical resources

About rainwater harvesting

Rainbarrels line the side of a garage.Rainbarrels line the side of a garage.This page includes the main article, web resources, city resources, and links to other water harvesting organizations around the county.

Harvesting rainwater can reduce our need--and demand--for water transport systems that threaten the health of the water cycle and our local environments.

On any house lot, there are three potential sources for harvesting the rain: Direct rainfall, street harvesting, and roof harvesting.

Rainfall data from San Francisco

Some plots of historical rainfall in San Francisco: (uses USGS data, 1960-2007)

Rainfall Data and Calculations

Sample charts and calculations looking at rain potential, frequency, and patterns in San Francisco and Berkeley, California. Sample charts show how large a tank would be needed to store rainfall from this area.

Rainfall data from Berkeley

Sample rainwater harvesting calculations

Sample rainwater harvesting calculations in 3 different document types.

Tucson rainwater harvesting ordinance

Tucson, Arizona is the first municipality in the country to require developers of commercial properties to harvest rainwater for landscaping.All new developments must meet 50 percent of their landscaping water needs by capturing rainwater. The new rule goes into effect June 1, 2010.