Exempts the owners of rainwater harvesting systems designed to capture, store, and use rainwater runoff from roofs, paved areas, or other artificial surfaces from certain permitting requirements if the water is put to use on the same property where it was harvested and the harvesting, storage, and use complies with all applicable rules adopted by the department of ecology.

Requires the department of ecology to issue general permits that may address specific geographic areas to specify conditions under which rainwater harvesting systems may be constructed and operated in order to protect existing water rights or to prevent harm, such as reduced instream flows or significant reductions in flow levels to existing streams or water bodies.