Rainwater Harvesting
Rainwater harvesting is the process of collecting, storing, and then putting to beneficial use the runoff from precipitation events. Rainwater is considered “waters of the State” as a portion of the water runoff finds its way to streams and shallow groundwater systems, which then contributes to water supplies that vested water rights rely upon. Since waters of the State are controlled by the Doctrine of Prior Appropriation (LWS blog of CO Water Law Basics #1, 6/6/2020), and rainwater is considered a tributary water source, rainwater harvesting has been - until recently - illegal because it could deprive senior water rights of their rightful allocation of water.
To a limited degree that restriction changed with the passage of Senate Bill 09-080, which only applies to rural residential properties that are provided their potable water supply with an exempt well. Under this bill, rural residents can only harvest rainfall if they first obtain a Precipitation Collection System Permit from the Colorado Division of Water Resources. Any rainwater collected under the permit has to be collected via downspouts from the home’s rooftop and the water may only be used for the permitted uses of the home’s exempt well permit.
The allowance of rainwater harvesting was expanded with the passage of House Bill 16-1005 in 2016. Now, individual single-family homeowners are allowed to install rain barrels and collect and use up to a total of 110 gallons of water per year. Some other restrictions also apply, such as (a) the rainwater has to be collected from roof downspouts and the water has to be used on that property, (b) it can only be used for outdoor landscaping, and (c) cannot be used for any potable purposes.
A more expanded rainwater harvesting program was approved by the Legislature in House Bill 15-1016, amended from House Bill 09-1129. This bill established the procedure for conducting a pilot study in a new planned unit development to better understand the percent of precipitation that is consumed through evapotranspiration of the native vegetation that will be removed based on the new planned unit development. The bill authorized up to 10 pilot studies on a statewide basis.
The criteria for the pilot studies are instrumental in understanding the standards that may be applied if a permanent rainwater harvesting system could be implemented as part of new developments. Under these pilot studies, out-of-priority depletions only have to be augmented to the extent that the runoff from newly impermeable surfaces exceeds what would have been consumed by native vegetation evapotranspiration. The burden of providing evidence of the historical consumption of rainwater in developed areas falls on the applicant, but with this information the applicant can then apply to Water Court for an augmentation plan that would allow rainwater harvesting that will not injure vested downstream water rights.
These criteria are important as they distinguish a rainwater harvesting system from the concept of “salvaging evapotranspiration”, a concept that was rejected by the Supreme Court in the Shelton Farms case. In that case, the applicant owned a property adjacent to the Arkansas River and subsequently cleared the phreatophytes on the property and filled in a marshy area to eliminate evaporation, then claimed the water saved as a right free of call from the river, i.e., not subject to the Doctrine of Prior Appropriation. It was then requested that this salvaged water could be used to augment the out-of-priority use of alluvial wells along the Arkansas River. That argument was rejected by the Colorado Supreme Court, as it ruled that salvaging evapotranspiration does not confer a water right.
As such, rainwater harvesting is based on obtaining a new water right that is subject to the Doctrine of Prior Appropriation, while salvaged evapotranspiration does not, in and of itself, create a water right.
If you have any other questions regarding your water rights, please give LWS a call at 303-350-4090 or send an email.
Bruce Lytle, P.E. bruce@lytlewater.com
Chris Fehn, P.E., P.G. chris@lytlewater.com
Ben Bader ben@lytlewater.com
Anna Elgqvist anna@lytlewater.com
