Rainwater Catchment

Rainwater Harvesting

Rainwater Collection to Augment Water Supply

Washington State has two distinct climates.  On the east side of the Cascades typical rainfall averages 10-20 inches, less for central Washington and more for the Cascade foothills and the northeast and southeast corners.  On the west side of the Cascades, typical rainfall averages 30-60 inches in the lowlands and double that for the Cascade foothills and the Olympic Peninsula.  Given the east side’s lack of rainfall, the economics of rainwater collection will likely prevent rainwater collection from catching on, though some areas in the northeast and southeast may offer potential.

On the west side it’s a different story, though with so much rain falling it seems counter-intuitive to imagine a need for more water supply.  However, the need becomes more obvious when you realize that when the rain isn’t falling (summer) we use the most water (irrigation).  Large cisterns can store enough water to enable continued toilet flushing with rainwater through the summer and can augment an existing source for small irrigation needs.