Why rainwater harvesting was once illegal in Colorado
Rainwater harvesting is not illegal in Colorado or Utah today. For years, an ordinary Colorado homeowner who put a barrel under a downspout was breaking state water law. Colorado and Utah both follow a doctrine called prior appropriation, meaning the first person to put water to use holds the senior legal claim across an entire river system. Under that doctrine, the rain that never reaches a stream still counted as water someone else already had a claim to, so an ordinary resident needed a specific numeric exception written into law before catching that rain was legal. Neither state exception hands the resident a water right of their own, both laws say so directly.
What Colorado H.B. 16-1005 changed
Colorado signed H.B. 16-1005 into law on May 12, 2016, and the law took effect on August 10, 2016, the standard 90 day delay for a bill carrying no safety clause. It lets a resident of a single family home, or a building of 4 units or fewer, collect rain in up to 2 barrels holding no more than 110 gallons combined, with no permit required. The water can only be used outdoors, on the same property where it fell, for a lawn or a garden. The Colorado Division of Water Resources and Colorado State University Extension both describe the law the same way.
the capture and use of rainwater using rain barrels does not constitute a water right.
Colorado State University Extension, in a guide describing what Colorado law says about rain barrel collection. Source 5.
The 500 dollar fine that made this a real risk
Before H.B. 16-1005 took effect, an ordinary rain barrel outside the narrow exempt well allowance was not a permitted use in Colorado. Colorado Public Radio reported that the state could have fined Aaron Broderick, a science teacher near Fort Collins, 500 dollars for the rain barrel systems he had already installed on his rental property and his home near Boulder, right up until the week the bill was signed.
Rain barrels were kind of looked at as the red-headed step child in a sense.
Marc Arnusch, a farmer and Colorado Farm Bureau board member. Source 4.
How Utah law differs from Colorado
Utah Code, cited in full as source 3, sets 2 tiers instead of 1. Without registering anything, a resident may keep up to 2 covered containers, neither one larger than 100 gallons, for a combined limit of 200 gallons.
The Utah figure comes from source 3, the Utah rainwater storage law.
Show the numbers
| Colorado, 2 rain barrels, no permit needed | 110 |
| Utah, 2 containers, no registration needed | 200 |
Register with the state engineer, giving a name, an address, the container capacity and the property location, and the combined limit rises to 2,500 gallons, at no stated cost.
Registering costs nothing and requires only a name, an address, the container capacity, and the property location, given to the state engineer.
Show the numbers
| Without registering with the state engineer | 200 |
| After registering with the state engineer | 2,500 |
Utah law also states directly that none of this creates a water right, and the collected water cannot be sold, transferred, or combined with an actual water right. Both totals only cover water used on the same parcel of land where it was collected. The registered ceiling in Utah, 2,500 gallons, is about 22.7 times the unpermitted limit in Colorado, 110 gallons, a comparison this publication calculated by dividing the 2 sourced figures, not a number either state publishes itself.