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INSIGHTi

Responding to Drought in the Colorado River
Basin: Federal and State Efforts
Updated May 23, 2023
The Colorado River Basin (Figure 1) covers more than 246,000 square miles in seven U.S. states and
Mexico. Basin waters are managed and governed by multiple laws, court decisions, and other documents
known collectively as the Law of the River. The Colorado River Compact of 1922 established a
framework to apportion water supplies between the river’s Upper and Lower Basins (divided at Lee Ferry,
AZ). Each basin was allocated 7.5 million acre-feet (MAF) annually under the compact; an additional 1.5
MAF in annual flows was made available to Mexico under a 1944 treaty. The Bureau of Reclamation
(Reclamation) and the Department of the Interior (DOI) play a prominent role in basin water management
due to the many federally authorized projects in the basin. This Insight discusses the hydrological status
of the basin, as well as recent agreements and proposals to address the basin’s long-term water supply
issues.
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Figure 1. Colorado River Basin Allocations
(Upper Basin allocations in percentages of overall allocation, Lower Basin allocations in million acre-feet [MAF])

Source: Figure by the Congressional Research Service, using data from U.S. Geological Survey ESRI Data & Maps, 2017,
Central Arizona Project, and ESRI World Shaded Relief Map.
Notes: 7.5 MAF in Upper Basin allocations assumes ful allocations under the Colorado River Compact. Due to
uncertainty about how much water would remain after meeting obligations to the Lower Basin and Mexico, most Upper
Basin Compact apportionments are in terms of percentage of the overall Upper Basin allocation.
When federal and state governments originally approved the Colorado River Compact, it was assumed
that river flows would average 16.4 MAF per year. Actual annual flows from 1906 to 2022 were
approximately 14.6 MAF, and have dropped to 12.1 MAF per year since the basin’s drought began in
2000. Some studies have projected that these conditions will continue.

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The structural deficit between basin water supplies and demand has depleted storage in the basin’s two
largest reservoirs—Lake Powell in the Upper Basin and Lake Mead in the Lower Basin—and threatens
urban and agricultural water supplies for millions in the Southwest. Reclamation makes operational
decisions for basin reservoirs in monthly 24-month studies, which project operational conditions for
upcoming years (Figure 2, Figure 3).
Figure 2. Lake Powell Storage Elevations and Projections
April/May 2023 24-Month Study Inflow Scenarios

Source: Bureau of Reclamation, 24-Month Study Projections, https://www.usbr.gov/lc/region/g4000/riverops/24ms-
projections.html.
Note: WY = water year (the 12-month period from October through September).


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Figure 3. Lake Mead Storage Elevations and Projections
April/May 2023 24-Month Study Inflow Scenarios

Source: Bureau of Reclamation, 24-Month Study Projections, https://www.usbr.gov/lc/region/g4000/riverops/24ms-
projections.html.
Note: DROA = Drought Response Operations Agreement
Mitigating Drought in the Colorado River Basin
Previous efforts to improve the basin’s water supply outlook included agreements in 2003, 2007, and
2019 (approved by Congress in P.L. 116-14). These agreements reduced Lower Basin deliveries based on
Lake Mead storage levels, authorized additional water conservation efforts, and implemented a
framework to coordinate Upper Basin operations to prevent losing hydropower generation at Glen
Canyon Dam, among other things.
Despite these efforts, storage levels at both reservoirs have continued to fall, with Reclamation instituting
Lower Basin delivery curtailments for Arizona and Nevada in 2021 and 2022. In the Upper Basin, Lake
Powell fell below 3,525 feet in March 2022 for the first time since the late 1960s. To alleviate the
potential for lost hydropower generation at Glen Canyon Dam at lower storage volumes, Reclamation
made operational changes on Upper Basin reservoirs in 2021 and 2022. In 2023, Reclamation has
upgraded its projected elevations for both reservoirs based on improved hydrology, but there remain
widespread concerns about the basin’s long-term water supplies.
At a June 14, 2022, congressional hearing, Reclamation announced that states needed to conserve an
additional 2 MAF to 4 MAF in 2023 and 2024 to protect storage volumes. Reclamation noted that if the
target was not met with voluntary commitments, it was prepared to act unilaterally. No major
commitments were announced in response to the June request, and Reclamation did not implement new
unilateral delivery curtailments. Instead, in October 2022 Reclamation announced its intent to study
revised operational guidelines for 2023 and 2024. In response to a request for comments on these
revisions, separate proposals were submitted to the federal government by California and the six other
basin states.

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On April 11, 2023, Reclamation released its draft modeling for two action alternatives under this process.
Both alternatives would impose equal amounts of new Lower Basin delivery reductions (0.020-2.900
MAF per year in water years 2024-2026, depending on Lake Mead elevations and the year). The primary
difference between the two alternatives is the approach for apportioning reductions among contractors.
One alternative would apportion reductions based on water rights priority, whereas the other would use
existing federal authorities to impose the same percentage-based delivery reductions on all Lower Basin
users.
On May 22, 2023, DOI announced a consensus-based proposal in which Lower Basin states will conserve
a total of 3 MAF prior to 2026, with 2.3 MAF of these cuts compensated by the federal government via
$4.0 billion in previously appropriated funds in P.L. 117-169 (popularly known as the Inflation Reduction
Act). DOI stated that it will temporarily withdraw its analysis of the other alternatives so it can focus on
analyzing the new proposal, with a goal of finalizing a plan by the end of the year.
Major questions for Congress associated with this plan include how it will affect long-term basin water
supplies, how state-level commitments will be met if contractors with senior water rights are unwilling to
participate in voluntary actions, and whether any needed future delivery curtailments will continue to
require ongoing federal funding commitments similar to the level expected to be provided with IRA
funds.


Author Information

Charles V. Stern

Specialist in Natural Resources Policy




Disclaimer
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to congressional committees and Members of Congress. It operates solely at the behest of and under the direction of
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