For more than a century, since Winters v. United States, 207 U.S. 564 (1908), the Supreme Court has recognized that when the United States establishes a Native reservation, it impliedly reserves sufficient water rights to support that reservation. But many of these Winters rights, like those held by the Navajo Nation, remain unadjudicated and unquantified, creating uncertainty for junior right holders. A recent decision from the Ninth Circuit Court of Appeals confirms that the United States cannot ignore Winters rights held by tribes just because they have not been adjudicated.

The recent decision in Nation v. U.S. Dep’t of Interior (Navajo II), No. 19-17088 (9th Cir. filed Feb. 17, 2022), impacts Navajo Nation most directly. But, its holding is likely to ripple through Native water law. It may hold particular interest for tribes considering whether to sue the United States for failing to quantify, consider, or defend their water rights.  


The Navajo Nation’s Reservation, established in 1868, “sprawls across Arizona, New Mexico, and Utah, and lies almost entirely within the drainage basin of the Colorado River [, which] flows along and defines much of the Reservation’s western border,” according to Navajo II, slip op. at 9. Since colonial contact, the Nation has competed with other tribes, non-tribal governments, and non-native people for this desert water.

The allocation of water from Colorado River among the states that it flows through is governed by a patchwork of compacts, statutes, decrees, and contracts, which together constitute a legal regime generally known as the Law of the River. The Law of the River’s origin traces to 1922, when states throughout the Colorado River Basin signed a compact to apportion the River’s water equally between the “Upper Basin” states (Colorado, New Mexico, Utah, and Wyoming) and “Lower Basin” states (California, Arizona, and Nevada), with each group receiving 7.5 million acre-feet per year (“mafy”).

The United States conditionally approved that interstate compact in 1928 through the Boulder Canyon Project Act, which became effective by presidential decree on June 25, 1929, and was adjudicated in Arizona v. California, 373 U.S. 546 (1963). The BCPA apportioned Colorado River water between the Upper Basin and Lower Basin states, but it did not allocate water within each group. The BCPA authorized the Lower Basin states to negotiate an apportionment between themselves. Arizona was not satisfied with the apportionment’s terms, so, in 1954, it invoked the Supreme Court’s original jurisdiction by filing suit against California to apportion the water among the Lower Basin states. Nevada, the other Lower Basin state, and the United States intervened, and Utah and New Mexico were joined on California’s motion.  

As Arizona proceeded before a special master, the United States asserted claims on behalf of 25 tribes, including the Nation, according to Navajo II, slip op. at 10. However, the claims the United States asserted on behalf of the Nation were limited to a tributary of the Colorado River, the Little Colorado River. The Nation moved to intervene in these proceedings, but that motion was denied at the United States’ urging.

After a decade of litigation, the Supreme Court entered the 1964 Decree, [1] which apportioned the 7.5 mafy available to the Lower Basin states. The 1964 Decree enjoins the United States from managing the river for purposes other than navigation, flood control, and supplying water for domestic, agricultural, and hydroelectric purposes. 1964 Decree, 376 U.S. at 341.

Under the decree, the Secretary of the Interior has the authority to determine water surpluses or shortages in a given year, and to adjust the delivery of Colorado River mainstem waters based on those determinations. Id. at 342. Critically, the Supreme Court held that the apportionment effectuated under the BCPA did not include tributary waters. [2] The 1964 Decree specifically disclaimed any effect as to the “rights or priorities, except as specific provision is made herein, of any Indian Reservation.” 1664 Decree, 376 U.S. at 353. Therefore, the 1964 Decree did not adjudicate the Nation’s rights to the Colorado mainstem or its tributaries.


In 2001 and 2007, the U.S. Department of the Interior (DOI) adopted guidelines for how it would determine whether there is a surplus or shortage of water in any given year. In 2003, the Navajo Nation sued DOI and several other federal agencies under the Administrative Procedure Act, 5 U.S.C. §§ 701-706, alleging that, in developing the 2001 shortage guidelines, they had breached their fiduciary duty to consider the Nation’s Winters rights and had violated the National Environmental Policy Act (NEPA). Various states and non-native groups intervened.

The district court dismissed both claims, holding that the Nation lacked standing to sue under NEPA and that sovereignty immunity barred the breach of trust claim.

In Navajo I, the Ninth Circuit affirmed dismissal of the NEPA claim but reinstated the breach of trust claim, remanding the case and granting the Nation leave to amend its complaint and add detail to its surviving claim. Accordingly, the Nation moved to amend its complaint, alleging that the United States had specifically breached its fiduciary duties by (1) failing to determine the quantity and sources of water necessary to make the Navajo reservation a permanent homeland and (2) failing to secure sufficient water to support it.

After the Nation amended its complaint, the district court dismissed the Nation’s breach of trust claim again, holding that any further amendment would be futile. The district court ruled that the breach of trust claim could not proceed because the Nation had “failed to identify a specific trust-creating statute, regulation, or other form of positive law that the federal government violated.” Navajo II, slip op. at 17. Moreover, the district court held that the Supreme Court’s reservation of jurisdiction over the 1964 Decree precluded the district court’s jurisdiction over the Nation’s claims. Finally, the district court reasoned that “Winters rights alone do not give rise to specific and enforceable trust duties on the federal government.” Id.

[1] State of Arizona v. State of California, 376 U.S. 340, 341 (1964), amended sub nom. Arizona v. California, 383 U.S. 268 (1966), and amended sub nom. Arizona v. California, 466 U.S. 144 (1984)

[2] Arizona v. California, 373 U.S. 546, 567 (1963), judgment entered sub nom. State of Arizona v. State of California, 376 U.S. 340 (1964), amended sub nom. Arizona v. California, 383 U.S. 268 (1966), and amended sub nom. Arizona v. California, 466 U.S. 144 (1984).


The Ninth Circuit disagreed with each basis the district court offered to justify that dismissal. It also rejected the intervenor/respondents’ res judicata argument, which had not been reached below. The Navajo II court first rejected the district court’s conclusion that only the U.S. Supreme Court had jurisdiction to hear the Nation’s claim because it had retained jurisdiction to amend its decree in Arizona v. California concerning the Colorado mainstem’s water. The court reasoned that the Nation was not asking the district court to adjudicate any claims to water on the Colorado River mainstem, but was instead seeking an injunction requiring the United States to investigate the Nation’s water needs, plan for those needs, and manage the Colorado River consistently with that plan. Granting that relief would neither adjudicate the Nation’s actual water rights nor alter the Arizona decree. The Court went further to suggest that it was by no means clear that the Supreme Court retained exclusive jurisdiction over the 1964 Decree, perhaps opening a door to future litigation outside the Supreme Court’s original jurisdiction docket.

The circuit court then turned to an argument raised by non-native interveners, that res judicata barred the Nation’s claim because the United States, as its trustee, could have raised the same claim in Arizona and had not. As with the issue of jurisdiction, the Ninth Circuit rejected this argument by distinguishing a claim to adjudicate water rights on the Colorado River mainstem from the Nation’s claim that the United States breached its trust obligation to consider those water rights in developing its surplus and shortage guidance documents. Prior adjudication of the former could not bar the Nation from raising the latter.

In the most significant section of the opinion, the Ninth Circuit turned to the district court’s conclusion that any amendment to the Nation’s complaint was futile because the Nation could not identify an enforceable trust duty founded in treaty, statute, or other positive law. The Ninth Circuit again disagreed. It reiterated the long-established law set forth in Winters that when the United States sets aside a tribal reservation, it impliedly reserves enough water to make the reservation a proper homeland. And so, the Nation could sue the United States for failing to consider its Winters rights. The court held specifically that “those provisions of the Nation’s various treaties and related statutes and executive orders that establish the Navajo Reservation and, under the long-established Winters doctrine, give rise to implied water rights to make the reservation viable.” Navajo II, slip op. at 27–28.

This conclusion, the Ninth Circuit explained, found further support in the United States’ treaties with the Nation, which had repeatedly recognized the Navajo right to farm their homeland. That promised recognition would have lost its purpose without an implied reservation of water. The court found this to be especially compelling in light of the fact that

[m]ost of the land in [the reservations appurtenant to the Colorado River] is and always has been arid. If the water necessary to sustain life is to be had, it must come from the Colorado River or its tributaries. It can be said without overstatement that when the Indians were put on these reservations they were not considered to be located in the most desirable area of the Nation. It is impossible to believe that when Congress created the great Colorado River Indian Reservation and when the Executive Department of this Nation created the other reservations they were unaware that most of the lands were of the desert kind—hot, scorching sands—and that water from the river would be essential to the life of the Indian people and to the animals they hunted and the crops they raised.

Navajo II, slip op. at 28-29 (quoting Arizona v. California, 373 U.S. at 598-99).

The court also recognized that the federal government’s failure to honor that promise was brought into stark relief by the pervasive control that DOI exercised over the Colorado River’s water. With such control, DOI had the power and thus the responsibility to manage that water as trustee for its tribal beneficiaries, including the Nation.

Accordingly, the court held that the Nation’s motion to amend its complaint was not futile, dismissal was improper, and remanded so the case could proceed.


The Ninth Circuit’s opinion is obviously significant to the Nation and its struggle for the federal government to adequately consider its reservation water rights. It also has reaffirmed the vitality of tribal rights secured under the Winters doctrine, regardless of whether they have been quantified by a judicial adjudication.

The opinion makes plain that the federal government, in its capacity as the trustee for tribal interests, cannot ignore its obligations to assure that tribal reservations have adequate water supplies just because there is no explicit statutory or regulatory provision imposing such a requirement; Winters itself creates such an obligation. Not only did the Ninth Circuit cast doubt on whether the Supreme Court’s jurisdiction over the allocation of water rights on the Colorado River is exclusive, but it also has allowed tribes to enforce their Winters water rights outside of the narrow context of quantifying and adjudicating those rights.

Uncertainty surrounding unadjudicated tribal water rights looms large in Western water law. This case illustrates that states and water right holders throughout the West must take tribal rights seriously regardless of whether they have been formally quantified because courts will not shy away from enforcing them.

This article summarizes aspects of the law and does not constitute legal advice. For legal advice for your situation, you should contact an attorney.

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