Editor’s Note: This piece is part of a four-part collaborative series between the University of Denver Water Law Review and the Stanford Environmental Law Journal that studies the public trust doctrine, the stark contrast of its history and development in Colorado and California, and the implications of its extension to groundwater.
The public trust doctrine (“PTD”), moldable to each state’s individual needs, follows the central premise that the state, as trustee, holds natural resources such as water in trust for the benefit of its citizens. The United States Supreme Court has opined that the doctrine’s definition and parameters are a matter of state law and that each state can choose to create a public trust or not. Unlike California and various other states, Colorado has never adopted the doctrine, instead relying on its system of prior appropriation to protect public interests. The Colorado Constitution declares surface water (and tributary groundwater) “to be the property of the public” that is “dedicated to the use of the people of the state.” The right to divert water for beneficial use “shall never be denied,” the state constitution continues. Colorado courts have consistently held that the state’s constitution fails to provide a foundation for the implementation of a public trust for water. Despite the lack of a PTD in Colorado, the state has made efforts to work within the prior appropriation system to preserve the natural environment, fish, and wildlife, and to protect recreational uses.
HOW COLORADO ADDRESSES PUBLIC INTEREST AND ENVIRONMENTAL CONCERNS
Unlike California, where courts have expanded the PTD to encompass environmental protection in the realm of surface water and, recently, some tributary groundwater use, Colorado, in the absence of a state PTD, has created specific statutory programs and beneficial uses for water to address public interests such as recreation and the environment. Specifically, Colorado law permits the state to appropriate or acquire instream flow rights that operate within the prior appropriation system to protect minimum streamflows for fish and other purposes. Colorado has also addressed recreational concerns by expanding the definitions of beneficial use and diversion to permit “recreational in-channel diversion” decrees, which have the byproduct of also simultaneously protecting flows necessary to protect the natural environment. Both of these expanded definitions of beneficial use include a caveat that constrains who can appropriate water for such uses. A brief look into the legislative and legal history of these adaptations to beneficial use highlights how Colorado’s prior appropriation law endeavors to protect public interests as well as the environment in the absence of a robust PTD.
Statewide concern about aquatic habitat spurred legislators to expand the definition of beneficial use in Colorado in 1973. The expanded definition enabled the appropriation of environmentally-protective minimum flows in Colorado lakes and streams. Under Colorado law, beneficial use is
the use of that amount of water that is reasonable and appropriate under reasonably efficient practices to accomplish without waste the purpose for which the appropriation is lawfully made and, without limiting the generality of the foregoing, includes . . . (c) For the benefit and enjoyment of present and future generations, the appropriation by the state of Colorado in the manner prescribed by law of such minimum flows between two specific points or levels for and on natural streams and lakes as required to preserve the natural environment to a reasonable degree.
To limit this expansion of the definition of beneficial use, the Colorado General Assembly granted exclusive authority to appropriate instream flows to the Colorado Water Conservation Board (“CWCB”). For the CWCB to initiate a water appropriation, it must make a determination that preservation of the natural environment will occur to a reasonable degree by the current amount of water available for appropriation. If a reasonable degree of natural environment preservation can occur by CWCB’s instream flow appropriation, the right is created but it must not cause material injury to senior surface water or tributary groundwater rights.
The water rights the CWCB appropriates are junior rights, but they do not require a diversion. In 1979 the Supreme Court in Colorado River Water Conservation District v. Colorado Water Conservation Board confirmed that the CWCB did not need a diversion to appropriate water. The Court outlined that the state constitution only uses the word “divert” once and that it does not mandate that diversion be an essential element of appropriation in Colorado.
This confirmation of the CWCB’s ability to appropriate water without a diversion allowed the CWCB to work to preserve lakes and streams; in its duty to appropriate to protect the natural environment, the CWCB has preserved cold and warm water fisheries, waterfowl habitat, glacial ponds, unique hydrologic and geologic features like Hanging Lake, and critical habitat for threatened or endangered native fish. These types of environmental protections are also at the core of the PTD’s ability to protect the natural environment for the public interest. Colorado’s instream flow program therefore provides for these environmental protections in the absence of a public trust doctrine.
The CWCB has instream flow rights “on more than 1,500 stream segments covering more than 8,500 miles of stream and 477 natural lakes.” In 2002 the Colorado General Assembly authorized the CWCB to acquire existing senior water rights by lease, purchase, or donation in order to enable CWCB to further protect the natural environment. Instead of only appropriating junior rights for minimum stream flows, now the CWCB can obtain decreed, senior rights and put those rights to instream flow use to preserve and improve the natural environment. This expansion of the instream flow program creates more potential for environmental protection in the state: since the 2002 change, the CWCB has completed more than twenty voluntary water acquisition transactions. These legislative enactments exemplify an alternative approach to the PTD and allow for a state without a PTD to protect aquatic life and habitat, and to maintain minimum flows throughout the state, by other means.
RECREATIONAL IN-CHANNEL DIVERSIONS
In 1998 the City of Golden saw an opportunity to develop a recreational niche and filed an application for a decree for one thousand cubic feet per second (“cfs”) of water for the months of May, June, and July for its whitewater sports park. This very large application spurred the water court to address the definition of diversion and beneficial use. The water court stated that structures that control, concentrate, and direct the flow of water constitute a diversion. The water court also confirmed that using water for recreational boating is a beneficial use. On appeal, the Colorado Supreme Court affirmed the decree. This decision confirmed that recreational in-channel diversions (“RICDs”) could be very large and opened up the possibility that RICDs could have negative impacts on upstream transfers, storage, and trans-mountain diversion plans. Following the court’s decision, in 2001 the Colorado General Assembly enacted Senate Bill 216 (“SB 216″) to address similarly large RICD applications.
SB 216 implemented restrictions on RICDs similar to those imposed upon instream flow rights. The bill changed the definition of beneficial use and diversion to specify that only “a county, municipality, city and county, water district, water and sanitation district, water conservation district or water conservancy district” could divert water for the beneficial use of recreational in-channel purposes. The ability to control water for RICDs, therefore, is only for those specified entities. This new bill also defined RICD as “the minimum stream flow as it is diverted, captured, controlled, and placed to beneficial use between specific points defined by physical control structures pursuant to an application filed by a [local government entity] for a reasonable recreation experience in and on the water.” The law mimics the instream flow regulations, requiring a municipality seeking a RICD to first submit an application to the CWCB for review and recommendation, and to then bring the application to the water court for final review. Public policy concerns and the technical expertise needed to analyze RICDs resulted in the selection of the CWCB as the recommending body for RICDs.
The role of the CWCB in the RICD application process caused quite a controversy and led to a Colorado Supreme Court confirming the CWCB’s authority to recommend RICD applications. In 2002 the Upper Gunnison River Water Conservancy District filed a RICD application with the CWCB. The CWCB significantly reduced the amount of water in the application to an amount it considered reasonable and then made a favorable recommendation to the water court. When the application moved to the water court for review, the CWCB had made no factual findings, as statutorily required. The water court made its own findings, based on the statutory factors outlined in SB 216, and granted the decree for the full application amount. The CWCB appealed the decree to the Supreme Court, which held that the CWCB is a “narrowly constrained fact-finding and advising body” when reviewing RICD applications and must act as such. The court agreed with the CWCB’s concern about water waste and held that decreed RICD water rights are only for the minimum amount needed for a reasonable recreational experience.
While the role of the CWCB in approving RICDs and determining the minimum flow needed for recreation has proved tenuous at times, RICDs have provided for the protection of flows that benefit recreational interests, but also the natural environment. RICDs are appropriated for recreational beneficial use, but by leaving the water in the streams for recreational use they provide for minimum instream flows that benefit the natural environment. More than ten cities, counties, and water districts hold decreed RICDs in Colorado. These municipalities may find RICD tourism and economic benefits as the greatest assets, but RICDs also allow for environmental conservation. Demonstrating that recreational interests span from boating to fishing, Trout Unlimited has indicated the potential for RICDs to benefit fish and recreational fishing by protecting flows sufficient to support habitat.
Colorado courts have consistently held that there is no public trust doctrine, but RICDs do consider the public interest to some extent. Similar to legislatively‑enacted minimum instream flow rights, RICDs are a legislative means to address the public interest without impinging on Colorado’s system of prior appropriation. RICDs, while legislatively constrained, address the public interest in providing minimum flows for recreation. This collaterally provides for the preservation of the natural environment. The intention of Colorado legislators may not have been to provide for the aquatic environment directly, but RICDs certainly have that additional benefit.
Colorado courts have consistently held that the public trust doctrine does not apply to appropriative water rights in this state. This steadfastness to a “pure” system of prior appropriation has led instead to highly specific legislative enactments that modify the prior appropriation doctrine to accommodate additional interests. These enactments address developing concerns about the preservation of fisheries, wildlife, and aquatic habitat, as well as the promotion of recreational water use in the state. As public interest needs and values have developed in Colorado, adaptations to the prior appropriation system have effectively addressed these additional public interest concerns. Unlike California, where the courts are responsible for implementing the public trust doctrine, the Colorado judiciary only applies prior appropriation as directed by the state constitution and the Colorado General Assembly. In the ongoing legislative attempt to accommodate environmental and recreational interests under the Colorado Doctrine, collaborative discussions and engagement with multiple parties to creatively address water concerns have flourished. As Justice Hobbs stated, “there are no aspects of the public interest that cannot be protected” within Colorado’s prior appropriation framework. Given the adaptive qualities of Colorado’s prior appropriation system, this will continue to be true.
 Dave Owen, The Mono Lake Case, The Public Trust Doctrine, and the Administrative State, 45 U.C. Davis L. Rev. 1099, 1107 (2012).
 Illinois Cent. R. Co. v. Illinois, 146 U.S. 387, 435 (1892); see also Danielle Spiegel, Can the Public Trust Doctrine Save Western Groundwater?, 18 N.Y.U. Envtl. L.J. 412, 428–29 (2010).
 See Safranek v. Town of Limon, 228 P.2d 975 (Colo. 1951).
 Colo. Const. art. XVI § 5; see also Stephen H. Leonhardt & Jessica J. Spuhler, The Public Trust Doctrine: What It Is, Where It Came From, And Why Colorado Does Not (And Should Not) Have One, 16 U. Denv. Water L. Rev. 47, 48–49 (2012).
 Colo. Const. art. XVI, § 6.
 Leonhardt & Spuhler, supra note 4, at 60.
 Gregory J. Hobbs, Jr. & Bennett W. Raley, Water Rights Protection in Water Quality Law, 60 U. Colo. L. Rev. 841, 879, 881–82 (1989). Justice Hobbs currently sits on the Colorado Supreme Court and is an outspoken critic of movements to adopt the public trust doctrine in Colorado.
 Id.; see also Joshua Mack, The Evolution of Colorado’s Recreational In-Channel Diversions, 10 U. Denv. Water L. Rev. 73, 76 (2006).
 Owen, supra note 1, at 1109–10 (discussing Marks v. Whitney, 491 P.2d 374, 380 (Cal. 1971)); see also Order After Hearing on Cross Motions for Judgment on the Pleadings at 9, Envtl. Law Found. v. State Water Resources Control Bd., No. 34-2010-80000583 (Cal. Super. Ct. Jul. 15, 2014).
 Colo. Rev. Stat. § 37-92-103(4) (2013).
 Mack, supra note 8, at 76, 79, 94.
 Id. at 76.
 Cynthia F. Covell, A Survey of State Instream Flow Programs in the Western United States, 1 U. Denv. Water L. Rev. 177, 184 (1998).
 Mack, supra note 8, at 75–76.
 Colo. Rev. Stat. § 37-92-103(4) (2014).
 Thomas Hicks, An Interpretation of the Internal Revenue Code and Treasury Regulations Supporting the Tax Deductibility of the Voluntary Charitable Contribution in Perpetuity of A Partial Interest in an Appropriative or Riparian Water, 17 Hastings W.-NW. J. Envtl. L. & Pol’y 93, 148–49 (2011) (discussing Colo. Rev. Stat. § 37-92-102(3)–(4)).
 Colo. Rev. Stat. § 37-92-102(3); see Covell, supra note 13, at 185.
 Colo. Rev. Stat. § 37-92-103(4); Colo. River Water Conservation Dist. v. Colo. Water Conservation Bd., 594 P.2d 570, 573 (Colo. 1979); see Hicks, supra note 16, at 148–49.
 Colo. River Water Conservation Dist., 594 P.2d at 574.
 Id. at 573.
 Instream Flow Program, Colorado Water Conservation Board (“CWCB”), http://cwcb.state.co.us/ENVIRONMENT/INSTREAM-FLOW-PROGRAM/Pages/main.aspx (last visited March 7, 2015) [hereinafter Colorado Water Conservation Board].
 Owen, supra note 1, at 1109.
 Colorado Water Conservation Board, supra note 22.
 Colo. Rev. Stat. § 37-92-102(3) (2014); see Hicks, supra note 16, at 148.
 Colorado Water Conservation Board, supra note 22.
 In re Application for Water Rights of Golden, No. 98CW448, 1 (Colo. Water Ct. Div. No. 1 2001), available at http://cdss.state.co.us/onlineTools/Pages/WaterRights.aspx (last visited Mar. 24, 2015).
 Id. at 4-5; see also Mack, supra note 8, at 77.
 In re Application for Water Rights of Golden. at 5; see also Mack, supra note 8, at 77.
 State Eng’r v. City of Golden, 69 P.3d 1027, 1028 (Colo. 2003).
 Mack, supra note 8, at 78–79.
 S.B. 01-216, 63rd Gen. Assemb., 1st Reg. Sess. (Colo. 2001); see also Mack, supra note 8, at 79.
 S.B. 01-216, 63rd Gen. Assemb., 1st Reg. Sess. (Colo. 2001) (current version at Colo. Rev. Stat. § 37-92-103(4)(b) (2014); see also Rebecca Abeln, Instream Flows, Recreation as Beneficial Use, and the Public Interest in Colorado Water Law, 8 U. Denv. Water L. Rev. 517, 523–24 (2005).
 Colo. Rev. Stat. § 37-92-103(10.3).
 Abeln, supra note 34, at 527.
 Mack, supra note 8, at 81.
 Colo. Water Conservation Bd. v. Upper Gunnison River Water Conservancy Dist., 109 P.3d 585, 593 (Colo. 2005); see Mack, supra note 8, at 84–85.
 Upper Gunnison River Water Conservancy Dist., 109 P.3d at 589.
 Mack, supra note 8, at 84.
 Upper Gunnison River Water Conservancy Dist., 109 P.3d at 590.
 Id. at 593; see Mack, supra note 8, at 85.
 Upper Gunnison River Water Conservancy Dist., 109 P.3d at 593.
 Reed D. Benson, “Adequate Progress,” or Rivers Left Behind? Developments in Colorado and Wyoming Instream Flow Laws Since 2000, 36 Envtl. L. 1283, 1301 (2006).
 Pending and Decreed RICDs, Colorado Water Conservation Board, http://cwcb.state.co.us/environment/recreational-in-channel-diversions/Pages/PendingandDecreedRICDs.aspx (last visited March 7, 2015).
 Abeln, supra note 34, at 533.
 Id. at 543.
 Id. at 533.
 Leonhardt & Spuhler, supra note 4, at 65–66.
 Abeln, supra note 34, at 537.
 Id. at 533.
 Leonhardt & Spuhler, supra note 4, at 49–50.
 Id. at 94.
 Abeln, supra note 34, at 541.
 Leonhardt & Spuhler, supra note 4, 95.
 Hobbs & Raley, supra note 7, at 874.