Rainwater Harvesting

Rainfall is a tremendous resource that is too often wasted. Streets, roofs, driveways and paths collect a great deal of water (.623 galllons per square foot, per inch of rain) during a storm. A modest 1500 squeare foot roof generates over 900 gallons per inch of rain. But, our communities are engineered to funnel that runoff into storm drains, ultimately dumping it into our creeks and the ocean. By harvesting rainwater and storing it in the soil or within cisterns, it is possible to control erosion, reduce flooding and minimize water pollution.

A large rainwater collection tank is included in the garden to demonstrate their installation and use, and as an opportunity to discuss the factors that influence the decision to invest in them. Rainwater tanks can be expensive while municipal water is still relatively cheap – locally costing only about 1 cent per gallon. Water use is billed in hundred cubic foot (hcf) – or 748 gallon - increments. An average four-person household in Santa Barbara consumes about 21 hcf of water per month. Because the cost rises sharply the more you use, the bill for that water at current tiered rates in Santa Barbara would total $220, with over half the cost generated by the last 25% used.

Our 530 gal tank would need to be filled and drained 90 times a year to offset the most expensive 25% of water used by an average family. An even relatively large rain tank goes dry quickly at the onset of our dry summers when water demand is highest. However, the high quality of rain water and the threat of water rationing are factors that mitigate the high cost of rainwater tank installation.


The Santa Barbara Botanic Garden conserves California native plants and habitats for the health and well-being of people and the planet.

Santa Barbara Botanic Garden, Inc. is a nonprofit 501(c)(3) organization.
Our Tax ID number is 95-1644628.