Rainwater Harvesting

An important aspect of green building and sustainable design is human interaction with the hydrologic cycle. Urban environments have reduced areas covered by vegetation, and increased impervious surfaces such as pavements, roads, and rooftops. Historically, stormwater runoff has been viewed as a waste product and a nuisance. In sustainable design, stormwater runoff is viewed as an opportunity and a resource.

The use of harvested rainwater for landscape irrigation can significantly reduce domestic potable water consumption. In San Diego, the average water use is 14 hundred cubic feet per month for residential households, which is over 10,000 gallons. About 60% of this water is used outdoors for irrigation. To conserve water, it makes sense to match the water quality level with the application. Potable water is most appropriately used for drinking and cooking. The use of native and drought-tolerant plants along with soil amendments such as compost and mulch that retain water, can reduce irrigation requirements.

Rainwater harvesting also manages building runoff on site, which removes a substantial amount of stormwater from wastewater systems, reducing sewer overflow events. Furthermore, the combined practices of rainwater harvesting and conversion of impervious surfaces to planted ones (green roofs, curbside plantings, parks) and pervious hardscapes can mitigate the degradation of receiving waterways (and associated wildlife) from urbanization.

A Typical Residential Rainwater Harvesting System with an Above-ground Tank

The basic components of rainwater harvesting systems for irrigation include: catchment (rooftops and or paved areas), conveyance (gutters and downspouts), storage (above or below-ground tanks), and distribution (hose or pump and drip irrigation system).

Benefits of Rainwater Harvesting

• Reduces personal water bills
• Provides naturally soft, neutral pH water
• Conserves water
• Conserves energy
• Erosion and flood control
• Protects our beaches and rivers