Water Resources Collections and Archives

In drought-prone northern California, homeowners can collect rainwater to irrigate their waterintensive summer vegetable gardens. Rainwater harvesting requires a three-part system: a method of collection (commonly the roof), a form of storage (cistern) and a method of distribution (a pump, filter and soaker hose are proposed here). To optimize and properly size a rainwater harvesting system, homeowners should consider both their rainwater supply and their garden’s water demand. Gardeners can reduce demand by planting early to take advantage of spring rains and by grouping crops according to irrigation needs. The authors analyze the water use of a sample garden, which they adapt to both Berkeley and Sacramento. In both of these cities, one can collect more than enough rainwater to support a small vegetable garden: an individual homeowner’s water supply is more likely to be limited by storage capacity than rainfall. Ultimately, although rainwater harvesting can supply adequate quantities of water to irrigate vegetable gardens, the level of water treatment required to safely irrigate food crops adds dramatically to the cost of a system. For a smaller investment, rainwater harvesting can be used to irrigate landscaping vegetation.