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If you live in the Colorado Front Range region, your treated water supply may have or currently include groundwater from the Denver Basin aquifer system.  If you are one of the many communities, businesses or individuals who rely on it for drinking water and much more, you should be aware that for the first time since the regulations were originally adopted in 1986, the Colorado Office of the State Engineer (SEO) will be updating its Statewide Nontributary Groundwater Rules (“Nontributary Rules”).  The SEO published the proposed revisions to the Nontributary Rules in December 2020, and will hold a rulemaking hearing on March 3, 2021.  Several Front Range municipalities are participating as parties to the rulemaking, and while the opportunity to join the proceeding has passed, interested stakeholders still have until February 22 to file comments or written testimony to be considered at the hearing and included as part of the public record for the rulemaking.

The regulations are especially pertinent to the Denver Basin, the sequence of layered bedrock aquifers underlying the Front Range from approximately Limon on the east, to the Hogsback on the west, and Colorado Springs on the south to Fort Collins on the north.  However, as statewide rules, the rules apply to all groundwater in the state that meets the statutory definition of “nontributary”:

groundwater located outside the boundaries of any designated groundwater basins in existence on January 1, 1985, the withdrawal of which will not, within one hundred years of continuous withdrawal deplete the flow of a natural stream, including a natural stream as defined in Co. Rev. Stat. §37-82-101(2) and Co. Rev. Stat. §37-92-102(1)(b), at an annual rate greater than one-tenth of one percent of the annual rate of withdrawal.

C.R.S. 37-90-103(10.5).  This convoluted definition simply means that while nontributary groundwater may be physically connected to surface streams, its connection is remote and the General Assembly has made the political decision to treat it as physically disconnected for purposes of regulation.  Unlike tributary groundwater, which is subject to appropriation, the right to withdraw nontributary groundwater is allocated based on ownership of overlying land.  The Water Court has jurisdiction to issue a decree confirming the rights to nontributary groundwater, but a decree is not required to obtain a well permit to withdraw nontributary groundwater.  However, these permits are the same as all others:  revocable.  The advantage of a water court decree is it provides a permanent legal determination of the total volume available to the landowner, and allows annual withdrawals based on decree terms.  In the absence of a decree, the State Engineer makes an administrative determination of allowable withdrawal under the method set out in the Statewide Nontributary Rules—which can be subject to change as seen in the proposed revisions.

The Nontributary Rules were last revised 35 years ago, so some of the revisions are routine with little effect on actual regulation.  However, some of the revision proposals do contain important changes:

• The new rules would limit groundwater diversions to account for grandfathered “pre-213 wells.” “Pre-213” wells are those constructed prior to adoption of the nontributary permitting requirement in 1973 (under Senate Bill 213, hence the name).  Pre-213 wells are not subject to the same pumping restrictions as wells constructed after 1973, and if an applicant for a new permit owns land overlapping the pumping impact radius from a pre-213 well [the overlap itself also being a determination made under the revisions], the new rules would require a corresponding reduction in total acreage to be used in calculating the total allowable withdrawal.
• Other significant changes involve Rule 8, which governs the determination of allowable annual withdrawals.
  • Under the Nontributary Rules, the State Engineer proposes to modify the method for calculating “specific yield,” (essentially a measure of how much can be extracted by a well based on how easily water can move through the aquifer).

• The second change to Rule 8 involves a post-calculation reduction for certain wells’ annual withdrawal determinations to account for past/present withdrawals from pre-existing wells on the property or from future withdrawals of water reserved for existing subdivisions.

Issues raised by parties to the hearing include insuring that the rules do not improperly impact or otherwise interfere with decreed water rights to nontributary groundwater and adequate agency process to determine whether or not a new well site in an aquifer outside of the Denver Basin contains tributary or nontributary groundwater.  However, for individual landowners the changes proposed to Rule 8 would likely lead to the most impacts, because of the increased cost associated with determinations of specific yield and the potential for limitations to be imposed on diversion of what is today considered to be available nontributary groundwater beneath a parcel.

For additional information please contact Dan Condren at dcondren@somachlaw.com.

Somach Simmons & Dunn provides the information in its Environmental Law & Policy Alerts and on its website for informational purposes only.  This general information is not a substitute for legal advice, and users should consult with legal counsel for specific advice.  In addition, using this information or sending electronic mail to Somach Simmons & Dunn or its attorneys does not create an attorney-client relationship with Somach Simmons & Dunn.