Idaho Falls, ID Landscaping Rules: Rainwater Harvesting (2026)

There is no provision in Idaho Falls City Code prohibiting or permitting residential rainwater harvesting; the city's water rules in Title 8, Chapter 4 govern the municipal supply, not private rooftop collection. The controlling rules are at the state level. Idaho is a prior-appropriation state, and all water is subject to the public water-rights system administered by the Idaho Department of Water Resources. However, a 2008 Idaho Attorney General clarification recognized that a person may collect 'diffused surface waters,' including rainwater that falls on their property, so long as the collection does not injure existing water rights. The widely cited limitation is that you may harvest rainwater that has fallen on the rooftop of your property, but not water that has already entered a natural stream or waterway flowing through the property. Idaho does not cap the volume a homeowner may collect for ordinary domestic and landscape use, and no state permit is required for typical rooftop barrels and cisterns. Because Idaho Falls actively promotes outdoor water conservation and xeriscaping, rain barrels used to irrigate gardens and beds are consistent with city conservation guidance. If a collection system were ever large enough to affect downstream users, a water right could be implicated, so very large cisterns should be checked against state water-rights rules.