Can I Harvest Rainwater?

State law defines water resources as “all water above, upon, or beneath the surface of the earth, located within the state.” (RCW 43.27A.020). Rainwater harvesting is not specifically regulated by the Washington Department of Ecology (Ecology). Ecology does have a policy which indicates that beneficial use of rainwater does not require a water right. However this policy also indicates that local restrictions may be set to govern new rainwater collection systems. Under the policy it is understood that Ecology will step in if the rainwater system negatively affects instream values or existing water rights.

Ecology’s Rooftop/Guzzler Collected Rainwater Policy is as follows:

The on-site storage and/or beneficial use of rooftop or guzzler collected rainwater is not subject to the permit process of RCW 90.03. If and when the department determines that rooftop or guzzler rainwater harvesting systems are likely to negatively affect instream values or existing water rights, local restrictions may be set in place to govern subsequent new systems. To qualify as rooftop collected rainwater, the roof collecting the rainwater must be part of a fixed structure above the ground with a primary purpose other than the collection of rainwater for beneficial use. A guzzler is a device used to catch and store rainwater to provide drinking water for wildlife, livestock or birds.

Ecology indicates on its website, “Once you have collected the rainwater there are no limitations on its use. If and when the department determines that rooftop or guzzler rainwater harvesting systems are likely to negatively affect instream values or existing water rights, local restrictions may be set in place to govern subsequent new systems (there are currently no restrictions).

The cost and expense of a rain water harvesting system is one parameter to consider before moving forward with reliance on rain water harvesting for residential uses. Ecology has created a rainwater harvesting calculator to help homeowners size their rain water harvesting system. This could help engineers determine the costs involved with such a system. Finally, homeowners that seek to rely on rain water harvesting for permitting purposes should first determine if their jurisdiction permits reliance on said harvesting to obtain land use approval. For instance, San Juan County residents have relied upon rain water harvesting for obtaining land use approvals and Whatcom County also allows reliance on rainwater harvesting for demonstration of water availability as a last resort for one or two single family dwelling units or two single family dwelling units. However, the County does not permit reliance on rainwater harvesting for short or long subdivisions.

For now, harvesting rainwater is not regulated by Ecology and at least some local jurisdictions will permit certain homeowners to rely on rainwater as their water source.

Simi Jain, Attorney