By: Alice Walker
May 16, 2025
Published as part of The Headwaters Report
The Colorado River Basin is home to thirty federally recognized Tribal Nations,[i] each with unique histories, cultures, and relationships to the Colorado River and its tributaries. These Tribal Nations rely on the River for various purposes, including cultural and spiritual activities, domestic use, agriculture and economic development to serve their members and reservations which are their permanent homelands. The Tribal Nations of the Colorado River Basin have varying degrees of recognized water rights, with twenty-two Tribal Nations holding rights to use approximately 3.2 million acre-feet (MAF) of Colorado River water annually, which equates to about 25% of the Basin’s average annual water supply. Additionally, twelve Tribal Nations have unresolved water rights claims,[ii] which, when resolved by adjudication or settlement, will increase the total volume of water that must serve the Tribal Nations’ interests. Given the impact of their claims, the Tribal Nations play a crucial role in the ongoing discussions and negotiations surrounding the management and allocation of the Colorado River’s resources. Their role is especially critical in resolving the challenges posed by drought and climate change, as well as pressure from states and other non-Tribal interests.
Current Issues on Colorado River Management
The Colorado River Basin is divided into two groups of states, pursuant to the 1922 Colorado River Compact, with the dividing line located at Lee’s Ferry, just below Glen Canyon Dam in Northern Arizona. The Upper Basin consists of Colorado, Utah, Wyoming, New Mexico and a small portion of Arizona. The Lower Basin consists of California, Nevada and the majority of Arizona. The Interim Guidelines for Lower Basin Shortages (2007) (Shortage Guidelines) specify how and when deliveries are made to California, Arizona and Nevada, and are triggered by reservoir levels in Lake Mead (specifically when the elevation drops below 1,075 feet). The Shortage Guidelines are set to expire in September 2026. This is forcing the seven basin states to renegotiate how the River’s water is divided amid growing scarcity due to the dual pressures posed by population increase and climate change in the American West. To address these complex issues, the federal government has pressured the seven basin states to reach consensus as to a new River management scheme by August 2026, warning that if they fail, federal authorities will impose a solution that will bind the states without their consent. Efforts to revise the Shortage Guidelines for post-2026 operations are actively underway, led by the U.S. Bureau of Reclamation (USBR) in collaboration with the seven basin states, Tribal Nations, Mexico, and other stakeholders. USBR has initiated a multi-year process under the National Environmental Policy Act (NEPA) to develop new operational strategies for Lake Powell and Lake Mead.
In November of 2024, the Biden administration released new proposals for long-term River management,[iii] but uncertainty remains about how the current Trump administration might alter or halt these plans, especially regarding federal funding for water conservation. Persistent drought, rising temperatures, and reduced snowpack in the Rocky Mountains have significantly diminished the River’s flow, which is down by about 20% since 2000. These reductions in flow worsen water shortages and further complicate the post-2026 River management negotiations. Both Lake Mead and Lake Powell remain at about 35% capacity, and projections for Colorado River inflows to Lake Powell are for 71% to 81% of normal due to dry conditions across much of the Upper Basin, increasing pressure on water supplies.[iv]
In light of what are becoming structural shortages—meaning the amount of water available in the system is permanently reduced going forward—there is substantial tension among the Upper Basin and Lower Basin states over how future water cuts should be shared. The Lower Basin states have historically used more than their compact allocation and are likely to face the deepest cuts. The Upper Basin states are pushing to avoid new curtailments but may be limited by overall river conditions and existing legal constraints. Tensions remain over how to share the pain of water use reductions,[v] with the Lower Basin proposing equal cuts at low storage levels and the Upper Basin resisting new mandatory curtailments. Past voluntary conservation efforts have not been enough. The new framework is expected to include broader, enforceable regulations to ensure water use matches the river’s declining capacity. In addition, the Lower Basin states are pressing for a new federal review of management plans and infrastructure upgrades at Glen Canyon Dam, which in the Lower Basin states’ view are urgently needed to maintain water delivery and reservoir function, adding another layer of complexity to negotiations.
Importantly, Tribal Nations and Mexico, all of whom rely on the Colorado River, are advocating for a fair share in future agreements, increasing the number of stakeholders and interests at the table. Tribes historically have been excluded from Colorado River management, but their presence at the negotiating table now will likely lead to their water rights being more fully quantified and recognized, as described below.
Federal Management Alternatives
In January 2025, USBR published an Alternatives Report outlining several proposed operational strategies. These alternatives are being analyzed in a draft Environmental Impact Statement (EIS), expected to be released in summer 2025. There are four main alternatives being analyzed in the EIS:
- Lower Basin States’ Proposal: Arizona, California, and Nevada have proposed a plan to reduce their collective water usage by 1.5 MAF annually. This proposal aims to address the structural deficit in Lake Mead (where water withdrawals exceed inflows and other reservoir replenishment). The proposal also includes provisions for additional reductions if necessary, with contributions from both Upper and Lower Basin states as well as Mexico. Lake Mead is losing more water each year than it gains, even when there is no drought. The current structural deficit ranges between 1.2 and 1.5 MAF. As of May 4, 2025, Lake Mead was at 1,061.56 feet above mean sea level (MSL).[vi] At 895 feet MSL, or dead pool, Lake Mead can no longer provide water supply or hydropower generation to 40 million people.[vii]
- Cooperative Conservation Alternative: This alternative emphasizes basin-wide conservation efforts, integrating stewardship and mitigation strategies for Lakes Powell and Mead. It proposes flexible water management strategies and incentivizes water conservation across the basin.
- Basin Hybrid Approach: This alternative is aimed at fostering consensus by combining elements from various proposals submitted by Upper and Lower Basin states and Tribal Nations. It includes new delivery and storage mechanisms for the reservoirs and considers both priority-based and pro-rata shortage distributions.
- Federal Authority Alternative: This alternative focuses on protecting critical infrastructure using only the Department of the Interior’s and Bureau of Reclamation’s existing statutory authorities, without new stakeholder agreements.
The draft EIS will analyze these proposed alternatives, as well as the required No Action alternative. Public comment will be taken after the draft EIS is released, and Tribal Nations will likely consider commenting to ensure robust Tribal input in the analysis of the alternatives. Following public review and feedback, a final EIS and Record of Decision are expected before the end of 2026, ensuring new guidelines are in place for implementation in 2027.
Continued Negotiations with Tribal Nation Engagement
So far, USBR has emphasized inclusive stakeholder engagement throughout the post-2026 negotiation process, involving states, Tribal Nations, and non-governmental organizations. In the original 1922 Compact, the only parties to the negotiated allocation of the waters of the Colorado River were the seven basin states and the United States. None of the thirty Tribal Nations who have rights and claims to the River and its tributaries was present at the negotiation table. As a result, Tribal Nations of the Colorado River Basin—both Upper and Lower Basins—demanded to participate in the current shortage guideline negotiations to best represent their own interests. These efforts have been assisted by the work of the Water and Tribes Initiative,[viii] which, among other things, focuses on ensuring Tribal representation in the negotiations.
The current negotiations of water allocations after 2026 and how the Colorado River will be operated in the future are expected to result in lower water allocations for all states, Tribal Nations, Mexico and stakeholders. The original compact overestimated the River’s supply, promising more water than is actually available—an issue now made worse by climate change and a two-decade drought. Any new agreements will undoubtedly embed reduced allocations, potentially as percentages of actual River flow or as set volumes based on the best available science. Proposals also include adaptive management, allowing for more flexible annual releases and water cuts that respond to actual River conditions. This could mean deeper cuts in dry years and efforts to optimize releases to meet environmental, Tribal, and supply goals.
Tribal Nations and Mexico are expected to have more formal roles in future allocations. Tribal Nations hold significant water rights in the Colorado River Basin that have not been fully quantified, and Mexico is entitled to a set share under the 1944 Treaty described below. Several Tribal Nations, such as the Navajo Nation, Hopi Tribe, and San Juan Southern Paiute Tribe, are pursuing legal settlements to secure and clarify their water rights. The outcome of these negotiations could grant them legal certainty and the ability to access, develop, or lease their water, which is crucial for communities where many still lack running water. While many Tribal water rights are senior (dating back before the 1922 Compact), they have often gone unquantified or unused due to legal, funding, and infrastructure barriers. Ongoing negotiations could help resolve these issues, but there are still hurdles, including the need for Congressional approval and concerns from basin states about how Tribal water use will be accounted for and addressed. For example, participation in compensated water conservation programs could provide both revenue and flexibility, but restrictions in some settlement agreements and shifting federal support remain obstacles. With access to funding streams for water infrastructure and conservation programs, Tribal Nations could better fulfill their sustainable water management goals in the arid southwest, but uncertainty created by changing federal funding and staffing priorities threatens to stymie everyone’s attempts to be good neighbors and good stewards of the limited water available.
Regardless, the process to renegotiate what is referred to as the Law of the River (see more below) requires elevating the recognition of Tribal sovereignty in water management. As stated, many Tribes still lack legally quantified water rights, making it difficult to enforce or use their allocations. If post-2026 negotiations prioritize quantifying and securing Tribal rights, Tribal Nations will gain greater control and certainty over their water resources, which is essential for long-term sustainability. As Tribal Nations secure their formal and legally rightful seats at the negotiation table, state authorities, who have long operated in the absence of Tribal representation, must now adapt to a new reality where Tribal interests are finally being recognized as integral to basin-wide planning and decision-making.
In summary, the renegotiated Colorado River Compact will almost certainly mean less water than what stakeholders have been used to receiving, but it will also mean more flexible and science-based management, and a broader set of voices at the table, all underpinned by stricter, federally enforceable rules to address chronic shortages. As Tribal water rights are quantified and exercised, the water available to states for non-Tribal users will most likely decrease, potentially increasing competition and tension—especially in states like Arizona with many Tribal Nations and a significant number of unrecognized claims. This dynamic makes it crucial for States and Tribal Nations to negotiate in good faith and seek mutually beneficial solutions.
Colorado River Legal Overview “Law of the River”
The Law of the River is the complex body of agreements, laws, court decisions, and regulations that govern the allocation and management of the Colorado River. It is not a single document, but a framework developed for Colorado River management and water distribution that has evolved over more than a century. The following discussion provides a breakdown of the Law of the River’s key components:
1. The Colorado River Compact (1922)[ix]
- Divides the Colorado River Basin into the Upper Basin (Colorado, New Mexico, Utah, Wyoming) and Lower Basin (Arizona, California, Nevada).
- Allocates 7.5 MAF per year to each basin—an amount set by choosing a high-water hydrograph for the basin and thereby over-estimating the amount of available water.
- This foundational agreement aimed to avoid conflict over water rights and enabled the development of large infrastructure including the Hoover Dam (creating Lake Mead) in Nevada.
- Art. VII of the 1922 Compact states, “Nothing in this compact shall be construed as affecting the obligations of the United States of America to Indian tribes.”
2. Boulder Canyon Project Act (1928)[x]
- Authorized construction of Hoover Dam in Nevada and All-American Canal in California.
- Officially apportioned 4.4 MAF to California, 2.8 MAF to Arizona, and 0.3 MAF to Nevada within the Lower Basin.
3. Mexican Water Treaty (1944)[xi]
- Guarantees Mexico 1.5 MAF of Colorado River water annually.
- An additional 0.2 MAF may be delivered in surplus years.
4. Upper Colorado River Basin Compact (1948)[xii]
- Divides the Upper Basin’s 7.5 MAF by percentage among Colorado (51.75%), New Mexico (11.25%), Utah (23.00%), and Wyoming (14.00%), with a small portion to Arizona (50,000 acre-feet).
- These percentages apply to the apportionment available to the Upper Basin, which is not necessarily 7.5 MAF each year because the Upper Basin’s supply depends on snowmelt and annual runoff, which can vary significantly.
- These allocations are for consumptive use, meaning water that is permanently removed from the river system for various purposes such as irrigation, municipal, domestic and industrial uses.
- The 1922 Compact obligates the Upper Basin states to deliver an average of 75 MAF every ten years to the Lower Basin, as measured at Lee Ferry, in order to fulfill the delivery obligations to the Lower Basin and Mexico. This is a rolling average that approximates to 7.5 MAF annually. The Upper Basin states must manage their water uses so they can collectively meet this downstream obligation, even during dry years.
5. Arizona v. California (1963 & subsequent decisions)[xiii]
- A series of United States Supreme Court rulings affirming federal authority over water distribution in the Lower Basin.
- Confirmed California’s 4.4 MAF limit and clarified Arizona’s rights.
- Established the Secretary of the Interior’s role as water master to manage water allocations.
- Established important rules of federal Indian law, including the practicably irrigable acreage (PIA) standard for quantification of federal reserved water rights for Indian homelands, and the rights of Tribal Nations to participate in litigation—as opposed to the United States representing their interests as trustee—to assert and protect their water rights.
6. Colorado River Storage Project Act (1956)[xiv]
- Authorized construction of major reservoirs like Glen Canyon Dam (creating Lake Powell) in Arizona to regulate Upper Basin deliveries.
7. Long-Range Operating Criteria (commonly known as LROC) (1970)[xv]
- Established guidelines for coordinated operation of Lake Powell and Lake Mead to ensure water delivery obligations are met.
8. Interim Guidelines for Lower Basin Shortages (2007)[xvi]
- Created rules for reducing water deliveries during shortages.
- Scheduled to expire in 2026 (now under revision, discussed below).
9. Minute 319 and Minute 323 (2012 & 2017)[xvii]
- Binational agreements with Mexico allowing for flexible water deliveries and joint conservation efforts.
10. Drought Contingency Plans (2019)[xviii]
Agreements among Basin states and the federal government to proactively reduce water use during drought conditions.
This legal framework is evolving as new challenges—particularly prolonged drought and climate change—require adaptive management. The post-2026 negotiation process currently underway aims to update and potentially reshape the Law of the River for the future.
ENDNOTES
[i] The Tribal Nations are: Ak-Chin Indian Community; Chemehuevi Indian Tribe; Cocopah Indian Tribe; Colorado River Indian Tribe; Fort McDowell Yavapai Nation; Fort Mojave Indian Tribe; Fort Yuma Quechan Indian Tribe; Gila River Indian Community; Havasupai Tribe; Hopi Tribe; Hualapai Tribe; Jicarilla Apache Nation; Kaibab Band of Paiute Indians; Las Vegas Tribe of Paiute Indians; Moapa Band of Paiute Indians; Navajo Nation; Paiute Indian Tribe of Utah; Pascua Yaqui Tribe; Pueblo of Zuni; Salt River Pima-Maricopa Indian Community; San Carlos Apache Tribe; San Juan Southern Paiute Tribe; Southern Ute Indian Tribe; Tohono O’odham Nation; Tonto Apache Tribe; Ute Indian Tribe; Ute Mountain Ute Indian Tribe; White Mountain Apache Tribe; Yavapai-Apache Nation; Yavapai-Prescott Indian Tribe.
[ii] The Navajo Nation, Pueblo of Zuni, Fort McDowell Yavapai Nation, and San Carlos Apache Tribe have partially resolved water rights claims in the Colorado River Basin.
[iii] See www.DOI.gov/pressreleases/Biden-Harris Administration Puts Colorado River on Path to Success | U.S. Department of the Interior (Nov. 20, 2024).
[iv] See https://lakemead.water-data.com/; https://lakepowell.water-data.com/
[vi] Bureau of Reclamation, Lower Colorado River Operations, “Lake Mead at Hoover Dam, End of Month Elevation (Feet)” https://www.usbr.gov/lc/region/g4000/hourly/mead-elv.html .
[vii] Robyn White, “What Happens if Lake Mead Hits Dead Pool and Hoover Dam Stops Working?”, Newsweek, Sept. 21, 2023 (https://www.newsweek.com/lake-mead-dead-pool-hoover-dam-ramifications-1781704#:~:text=Dead%20pool%20is%20when%20the,no%20water%20passes%20through%20it.%22&text=If%20dead%20pool%20were%20reached,all%20its%20operations%20to%20cease).
[ix] Colorado River Compact, 70 Cong. Rec. (1928), available at www.usbr.gov/lc/region/pao/pdfiles/crcompct.pdf.
[x] Boulder Canyon Project Act, Pub. L. No. 70-642, ch. 42, 45 Stat. 1057 (1928).
[xi] Treaty between the United States of America and Mexico Respecting Utilization of the Waters of the Colorado and Tijuana Rivers and of the Rio Grande, U.S.-Mex., 59 Stat. 1219, T.S. No. 994 (Feb. 3, 1944).
[xii] Upper Basin River Basin Compact, ch. 48, 63 Stat. 31 (Oct. 11, 1948).
[xiii] Arizona v. California, 373 U.S 546 (1963) (establishing specific water allocations for Arizona, California and Nevada); Arizona v. California, 376 U.S. 340 (1964) (decree implementing 1963 decision); Arizona v. California, 383 U.S. 268 (1966) (making amendments to 1964 decree); Arizona v. California, 439 U.S. 419 (1979) (addressing issues related to decree administration); Arizona v. California, 460 U.S. 605 (1983) (considering the rights of Tribal Nations and the role of the Secretary of the Interior); Arizona v. California, 466 U.S. 144 (1984) (further decree modifications clarifying tribal water rights); Arizona v. California, 531 U.S. 1 (2000) (approving consolidated amended decree to address the Quechan Tribe’s water rights); Arizona v. California, 547 U.S. 150 (2006) (technical corrections and updates to decree).
[xiv] Colorado River Storage Project Act, 43 U.S.C. §§ 620-620o.
[xv] Criteria for Long-Range Operation of the Colorado River Reservoirs, 35 Fed. Reg. 8951 (June 10, 1970), referenced in 43 U.S.C. § 1552.
[xvi] Interim Guidelines for Lower Basin Shortages and Coordinated Operations for Lake Powell and Lake Mead, 72 Fed. Reg. 62272 (Nov. 2, 2007).
[xvii] Minute No. 319: Interim Int’l Cooperative Measures in the Colorado River Basin Through 2017 and Extension of Minute 318 Cooperative Measures to Address the Continued Effects of the April 2010 Earthquake in the Mexicali Valley, Baja California (Nov. 20, 2012), available at www.ibwc.gov/wp-content/uploads/2012/11/Minute_319.pdf; Minute No. 323: Extension of Measures and Adoption of Binational Water Scarcity Contingency Plan in the Colorado River Basin (Sept. 21, 2017), available at www.ibwc.gov/wp-content/uploads/2023/03/Min323.pdf .
[xviii] Colorado River Drought Contingency Plans, www.usbr.gov/ColoradoRiverBasin/dcp/index.html.
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