In a semi-arid city where every thunderstorm feels like a gift, rainwater harvesting is one of the simplest ways to conserve water and lower your bill. As Treehugger explains, “Rainwater harvesting is the practice of collecting and storing rain for reuse, rather than letting the water run off and be absorbed into the ground or channeled into drains, streams, or rivers.” It’s an easy way to conserve water at home.

At its most basic, the system is refreshingly simple: roof → gutter → downspout → barrel. A sealable rain barrel captures runoff for later use in your yard. More complex systems can include filtration, pumps, and large cisterns, but the easiest path is using rain barrels for outdoor irrigation.

To get started, you’ll need a roof that can serve as your catchment surface. From there, gutters and downspouts channel rainfall into your storage system. Those storage barrels must have sealable lids under state law, as per Colorado Division of Water Resources. 

Just as important as capturing the water is managing the excess: your setup should include an overflow plan that directs water several feet away from your home’s foundation. That precaution is especially critical along the Front Range, where clay-heavy soils can expand and create drainage issues if water pools too close to the house. 

Now, the legal part (and this is key). Under Colorado law, single-family homes and multi-family residences with four or fewer units may collect rainwater in two rain barrels with a combined capacity of up to 110 gallons with no permit required. Colorado Division of Water resources notes that the water must be collected from a residential rooftop, stored in barrels with sealable lids, and used only for outdoor purposes on the same property. It cannot be used for drinking or indoor household use.

(Homes with certain exempt or small-capacity well permits may qualify to collect more than 110 gallons, but that requires a rooftop precipitation collection permit through the Division of Water Resources.)

Why bother? Treehugger notes that beyond conserving treated municipal water, harvesting rain reduces stormwater runoff, which can otherwise carry pollutants like fertilizers and metals into streams. It’s softer water, too, meaning it’s free of the dissolved salts commonly found in tap water—a bonus for gardens!

In a place where sunshine steals the spotlight, catching rain might just be Denver’s most underrated sustainability move.