Tribal Water Rights Overview

This information has been prepared in order to understand the complexity of Tribal Water Rights, including its legislative (compacts, treaties, statutes) and hydrological context. The Colorado River Basin covers portions of seven states and Mexico with over 40 million water users.


Federal reserved Tribal water rights are defined and governed by a body of federal law that recognizes that Tribes have unique property and sovereignty rights over water on their reservations. Because Native Americans have occupied land since time immemorial, Tribes often hold the highest priority water rights. Tribal water rights, although created and vested as of the date of the reservation, are not determined unless litigation or congressional action has quantified the amount of the right.[1]

The United States Supreme Court has recognized that to achieve the important goal of finality in water adjudications, Tribal water rights must be quantified for historic, present and future uses. Tribal and non-Tribal stakeholders share mutual goals that motivate efforts to resolve conflicts over water.[2] Tribes resolve conflicts through litigation or settlement agreements.


~325,850 US Gallons

Water rights are usually quantified in terms of acre-feet allocated per year (AFY). An acre-foot (af) is a unit of volume equal to the volume of a layer of water one acre in area and one foot in depth.


What is the law of the colorado river?

The Law of the River is a compilation of compacts, acts, guidelines, minutes, and records of decisions. The main laws are listed below.

Colorado River Compact: In 1922, the Compact was negotiated by the seven basin states (WY, UT, CO, NM, NV, CA, & AZ) and the federal government (Tribes and Mexico were not involved in negotiations). Under the Compact, the states established a framework for apportionment of the water supplies between the Upper Basin and the Lower Basin. The dividing line between the two basins is at Lees Ferry, AZ. The Upper Basin and Lower Basin were each apportioned 7.5 million acre-feet (MAF) annually for beneficial consumptive use. Read More.

Boulder Canyon Act: In 1928, Congress approved this Act which allocated the Lower Basin States’ water rights. The Act states that a fair division of the first 7.5 MAF of such mainstream waters would give 4.4 MAF annually to California, 2.8 MAF annually to Arizona, and 300,000 AFY to Nevada. However, Congress intended to apportion only the mainstream, leaving to each State their own tributaries. Read More.

Upper Colorado River Basin Compact: In 1948, this Compact was adopted to provide equitable division and apportionment of the Upper Basin. Unlike the Lower Basin, Upper Basin water allocations are based on hydrology and percentages: NM (11.25%), WY (14%), CO (51.75%), and UT (23%). The only state in the Upper Basin with a fixed amount is Arizona (50,000 AFY). Tribal water rights were recognized in the Compact; Article XIX states “(a) Nothing in this compact shall be construed as affecting the obligations of the United States of America to Indian Tribes.” Read More.

Additional Information on Key Court Decisions Regarding Tribal Water Rights:
Winters v. United States
Most federal reserved Tribal water rights are based on Winters v. United States, 207 U.S. 564 (1908). In the “Winters” decision, the U.S. Supreme Court held that when the reservations were established, sufficient water to fulfill the purposes of the reservations was implicitly reserved. However, while clearly recognizing Tribes’ federally reserved water rights, the Winters decision does not specify either the method for quantifying or any standards for administering these rights. Reserved Tribal water rights are not quantified unless litigation or congressional action has determined the size of the right.[1]
McCarren Amendment 43 u.s.c § 666
In 1952, Congress passed the McCarren Amendment that waived federal sovereign immunity and allowed states to bring the federal government into states’ courts’ general stream adjudications. Later, the U.S. Supreme Court ruled that the amendment also applied to state adjudications of reserved Tribal water rights held in trust by the United States.
Arizona v. California
In 1963, the U.S. Supreme Court ruled that Tribes were entitled to a major share of the Colorado River that would come out of the shares allocable to the states. It reaffirmed Winters doctrine and established the standard of practicably irrigable acreage (PIA) to quantify reserved water rights on a reservation set aside for agricultural purposes. It quantifies the amount of water needed for irrigable land on a reservation.
General Adjudication of All Rights to Use Water in the Gila River System and Source

In 2001, Arizona Supreme Court held that PIA is not the exclusive quantification measure for determining water rights on Tribal lands, and the quantity of water reserved must satisfy both present and future needs of the reservation as a livable homeland.


Doctrine of Prior Appropriation vs. Federal Reserved Water Rights

"First in time, first in right"

Courts must recognize two sets of legal principles: the states’ doctrine of prior appropriation and the federal reserved water rights doctrine. The concept of Prior Appropriation is that the first people using water should have first right to the water. In the American West, a right to use water is regulated by state laws founded on the principle of “first in time, first in right.” In times of water shortage, the oldest water right is satisfied in full before junior water rights are satisfied.[1] These water rights require an application of beneficial use for ownership. The requirement of continuous beneficial use is enforced by forfeiture and abandonment law.[3] Whereas, reserved Tribal water rights are not subject to loss or forfeiture and do not require actual use to be maintained.[3]

Quantifying Tribal Water Rights

As stated above, in order to achieve the important goal of finality in water adjudications, Tribal water rights must be quantified for both present and future uses.[1] Quantification methods, such as the practicably irrigable acreage (PIA) method, are a basis for quantifying but not restricting the use of the Winters rights. Importantly, once quantified on the basis of particular purposes, tribes can dedicate the use of their reserved water for uses other than the purpose upon which the right was quantified.


Litigation Vs. Settlement

Since the Winters decision, Tribes have filed hundreds of cases claiming reserved water rights and won many of these court battles, but this did not mean they could actually gain control over water resources. Tribes were awarded rights to water, but not the financial means to develop and use that water.

Continued lawsuits kept water users apprehensive of unsettled water rights. To mitigate this, the federal government began exploring the possibility of negotiating, rather than litigating, disputes over water between Tribes and other water users.

Tribal and non-Tribal stakeholders share similar motivations to resolve water conflicts, including reliable access to water, effective management of water resources, economic development, and ability to plan for the future. Federal monies often form a substantial part of many settlement packages, providing for economic development programs on reservations.[2]

Despite the problems with settlement implementation, funding cuts, and environmental conflicts, Tribes continue to be interested in negotiating because the courts are much less receptive to Tribal water claims than they were in the past. Today, it is very risky to take a reserved water rights claim to court, either at the state level or to the U.S. Supreme Court.[4]


The impacts of drought & climate change on tribal water rights claims

The aridity of the western U.S., combined with rapid population growth, and increasing demand for water resources, makes the West highly vulnerable to climate variability and increased fluctuations in water availability. The hydrology of arid and semi-arid areas is particularly sensitive to climate variations. Small variations in temperature and precipitation in these areas can result in larger percentages of changes in runoff, increasing the likelihood and severity of droughts and floods. Climate changes that reduce overall water availability will reduce the productivity of hydroelectric dams, causing greater fluctuations in power generation. Climate variability exacerbates already intense competition for water, adding to the complexity of achieving stable water settlements between Tribes and other water users.[2] The most important implication of climate variability for Tribal settlements is that settlement agreements must be very specific regarding water allocation and management in wet versus dry years. The parties need to spell out priority of deliveries in dry years and access to storage in wet years. Moreover, flexibility and mechanisms to address unanticipated problems and conflicts become even more essential in the face of climate change and increased water supply uncertainty.



[1] Williams, Susan (1997). Volume 107, Issue 1 (1997) Native Indian Water Rights: Overview of Indian Water Rights
[2] Colby, et. al. (2005). Negotiating Tribal Water Rights-Fulfilling Promises in the Arid West. The University of Arizona Press
[3] Jay F. Stein, Volume 107, Issue 1 (1997) Native Indian Water Rights. The McCarren Amendment and the Administration of Tribal Reserved Water Rights
[4] Daniel McCool, Volume 107, Issue 1 (1997) Native Indian Water Rights. Indian Water Settlements: Negotiating Tribal Claims to Water 

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