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INSIGHTi

Responding to Drought in the Colorado River
Basin: Federal and State Efforts
Updated February 1, 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) plays a prominent role in basin water management due to the many federally authorized
projects in the basin.
The basin is in the midst of a long-term drought, during which consumptive use has significantly
exceeded natural flows. 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
January 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
January 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.
Studies project that storage in both reservoirs may decrease further in the coming years. 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. The alternatives under consideration
include new “consensus-based” actions by the states to reduce demand, as well as unilateral delivery
curtailments by the federal government.

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In response to Reclamation’s announcement, on January 31, 2023, all basin states but California
submitted to Reclamation a combined “Consensus Based Modeling Alternative” (CBMA). The CBMA
assumes an additional 1.543 MAF per year in delivery reductions on Lower Basin contractors (largely
through assessing evaporative losses on Lower Basin states). On the same day, California submitted its
own proposal that would, among other things, reduce deliveries for Lower Basin contractors by 1.0 MAF
per year. A primary difference between the two proposals is that the CBMA would distribute reductions
based on consumptive use, whereas the California alternative would institute proportionally greater
reductions on Arizona and Nevada to reflect California’s senior water rights under the Law of the River.
To date, the Upper Basin states have declined to contribute a specific volume of cutbacks, instead laying
out a five-point plan as the basis for their water conservation efforts. Reclamation’s analysis of short-term
operational alternatives for river management is expected later this spring. Parallel to this process,
Reclamation and stakeholders are also developing long-term (post-2026) basin operations.
Congress influences basin water management through authorizations and appropriations for Reclamation
projects and activities. In addition to the 2019 authorization of the Drought Conservation Plans, Congress
reauthorized “system conservation” efforts in the basin. Furthermore, recent regular and supplemental
appropriations included funding for Colorado River water conservation efforts. In Section 50233 of P.L.
117-169, Congress provided $4.0 billion for drought mitigation in the West, with priority given to
Colorado River Basin activities. Reclamation is using this funding to establish a Lower Basin
Conservation and Efficiency Program to pay contractors to forgo deliveries of Colorado River Basin
waters.

Author Information

Charles V. Stern

Specialist in Natural Resources Policy




Disclaimer
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