By Jan Tik (Flickr) [CC BY 2.0 (], via Wikimedia Commons
By Jan Tik (Flickr) [CC BY 2.0 (, via Wikimedia Commons
It’s one of the most common questions and concerns we hear from Coloradans interested in water “Why can’t we capture rainwater? Aren’t rain barrels illegal in Colorado?” (the barrels themselves are legal, and widely sold, it’s the rainwater storage that isn’t in most cases)… But that could change.

On Monday, Colorado’s House of Representatives voted in favor of H.B. 1259, which, if successfully passed by the Colorado Senate, would allow people to collect and store up to 110 gallons of rainwater from residential rooftops. The bill passed the House by a bipartisan vote of 45-20 and was amended to allow rainwater storage in two 55-gallon rain barrels (upped from a proposed combined storage maximum of 100 gallons).

Under Colorado’s prior appropriation system of water law, the water that falls on your roof already belongs to other downstream users. Because someone else already owns the right to that water, rainwater capture is not legal for most Colorado households. From the Citizen’s Guide to Colorado Water Law, on adjudicated water rights:

Adjudication of a water right results in a decree that confirms the priority date of the water right, its source of supply, and the amount, point of diversion or storage, type and place of use.

In times of water scarcity, those with older water rights can claim that water before those with more junior rights. As explained in the Washington Post:

During dry times, someone with a senior claim gets to suck down her full allotment. The people down the line might get nothing.

(In Colorado, she’s even entitled to the rain that falls onto her neighbor’s roofs. That rain, by law, must be allowed to flow unimpeded into the river for her to use.)

Although all precipitation belongs to this system of water rights, some studies estimate that only a small fraction of rain makes it all the way from rooftops to rivers, with most of it lost to evaporation. A 2007 Douglas County study by Leonard Rice Engineers found that a maximum of about 15 percent of precipitation returned to the stream system. Bill sponsors said that an estimated 97 percent of water that falls on residential property never ends up in a river or stream.

After that 2007 study, Colorado’s rain barrel ban was loosened, when in 2009 SB-80 allowed some residents with private wells to begin rainwater harvesting. Through HB 09-1129, Colorado created a pilot program for harvesting projects administered by the Colorado Division of Water Resources, find guidelines for those pilot projects here. But those water catching programs aren’t available to the majority of Coloradans, including municipal residents.

… perhaps small-scale collection and storage of rooftop rainwater runoff wouldn’t have such a large affect on downstream water users. But opponents say that the principle behind rainwater harvesting can lead to much more. From the Durango Herald:

Republican Reps. Don Coram of Montrose and J. Paul Brown of Ignacio both voted against the measure. Coram said the bill serves as a literal slippery slope, suggesting that what starts as roof collection could end in allowing Coloradans to collect rainwater off their entire property.

“We keep nibbling away on the prior appropriation doctrine, and you know you eat an elephant one bite at a time,” Coram said, referring to the system in Colorado in which water rights are granted to the first person to take water from an aquifer or river, despite residential proximity. “I object more to changing the process.”

Others opposed are expressly worried about agriculture. From the Washington Post:

But the bill also signals that as Colorado’s cities grow, and as the political balance shifts, the legal custom of prior appropriation may be slowly renegotiated in favor of the urbanites. At the committee meeting last week, agriculture industry representatives strongly opposed HB 1259.

“It is a small step. And it’ll get bigger, and bigger, and bigger, until you dry up all of agriculture without buying it,” said Jim Yahn, a commercial water manager and farmer.

“At least the other way that we do it, farmers get compensated for the water that’s used. This is a small step in the wrong direction.”

While those in favor see water conservation and education as the major benefits of rainbarrels. From the Denver Post:

Rep. Jessie Danielson, D-Wheat Ridge, countered: “It still goes into the same ground it would if it came down the gutter and straight into the ground.”

And rather than seeing that water be absorbed or evaporate, residents could replace the gardening water that comes from a spigot — saving water for those with downstream water rights, she said.

“While the amount of water saved is modest, having rain barrels in yards around the state will serve as an important tool to increase Coloradans’ knowledge of our limited rainfall and water supply,” said Pete Maysmith, executive director of Conservation Colorado. “This common-sense step should help people understand the need for smart water-conservation policies.”

Drew Beckwith with Western Resource Advocates further explained that concept in a letter calling for support:

We think that someone with a rain barrel begins to pay more attention to how much water it takes to water the lawn; they begin to question where their water really comes from beyond the tap; and that this leads to a greater conservation ethic in our residents. The bill places limits on rain barrel use to the extent that published research suggests there will be no discernable impact on downstream water users.

The legislation is now in the hands of the senate. Where do you stand?


8 thoughts on “Catching Colorado’s Rainwater

  1. So who are the down stream water users and would loose out if folks used the FULL extent of their roofs to catch more than a piss in a pot? Wouldn’t be Nestle would it? Question is, who does it fiscally impact the most, allowing the common citizen to have access to what was rightfully theirs to start.

    But good on them for at least entertaining the illusion of freedom.

    1. Thanks for the comment. The downstream users could have a right to water for myriad purposes. In Colorado the majority of concentrated rooftops are along the Front Range, so theoretically if Denver, Aurora, Fort Collins etc. residents captured their rainwater it could affect water rights on the South Platte. If Colorado Springs or Pueblo residents captured rooftop rainwater it could affect water rights on the Arkansas River. On the South Platte and Arkansas, many of the senior (and downstream) rights are for agricultural purposes on Colorado’s Eastern Plains… but of course there are large (and also senior) municipal rights as well as industrial, environmental etc.
      As you read, most studies show that 110 gallons of rainbarrel storage probably wouldn’t have a major affect on other water rights since most of that water would normally be lost to evaporation or evapotranspiration. But many of those opposed to this legislation worry about the principle that rainwater storage is a step outside of Colorado’s prior appropriation system and could lead to more water stored or set the precedent for other measures that give individuals or municipal water users priority outside of the prior appropriation system over agricultural users and others. Assuming that the priority system was still intact in this example, if the senior downstream water users were affected by rainwater capture and weren’t getting all of the water they’re entitled to, they could issue a “call” for that water, and those with newer more junior upstream water rights wouldn’t be able to use their water. Check out page 18 of the Citizen’s Guide to Colorado Water Law to see how a call works

      1. My question: How much water would be lost to those “down stream?” Are we talking about a 1000’s? 100,000’s? Millions?What measures are they using to make accurate claims about the loss?

        I don’t care about legislation I want numbers.

  2. Check out that Douglas County Study for their numbers:–HolisticApproachtoSustainableWaterManagementinNorthwestDouglasCounty.pdf
    You could also connect with DWR to hear first-hand they’ve learned from the pilot projects:
    Or check with Sterling Ranch, the first of those Pilot Projects to see what numbers they’ve come up with after a few years of studying.

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