The US Bureau of Reclamation released the Colorado River Basin August 2021 24-Month Study. This month’s study projections are used to set annual operations for Lake Powell and Lake Mead in 2022. Releases from these massive reservoirs are determined by anticipated reservoir elevations.

Most of the flow of the Colorado River originates in the upper portions of the Colorado River Basin in the Rocky Mountains. The Upper Basin experienced an exceptionally dry spring in 2021, with April to July runoff into Lake Powell, the reservoir created by the Glen Canyon Dam, totaling just 26% of average despite near-average snowfall last winter.

The projected water year 2021 unregulated inflow into Lake Powell—the amount that would have flowed to Lake Mead, the reservoir created by Hoover Dam, without the benefit of storage behind Glen Canyon Dam—is approximately 32% of average. Total Colorado River system storage today is 40% of capacity, down from 49% at this time last year.

Given ongoing historic drought and low runoff conditions in the Colorado River Basin, downstream releases from Glen Canyon Dam and Hoover Dam will be reduced in 2022 due to declining reservoir levels. In the Lower Basin the reductions represent the first “shortage” declaration—demonstrating the severity of the drought and low reservoir conditions, the Bureau said.

Map of Colorado Basin reservoir conditions, showing percent average contents, 16 Aug 2021. Source: Colorado River Basin Forecast Center, NOAA.

Plans that have been developed over the past two decades lay out detailed operational rules for these critical Colorado River reservoirs:

• Based on projections in the study, Lake Powell will operate in the Mid-Elevation Release Tier in water year 2022 (1 October 2021 through 30 September 2022), and Lake Mead will operate in its first Level 1 Shortage Condition in calendar year 2022 (1 January 2022 through 31 December 2022).

• Lake Powell Mid-Elevation Release Tier: The study projects Lake Powell’s 1 January 2022 elevation to be 3,535.40 feet—about 165 feet below full and about 45 feet above minimum power pool. Based on this projection, Lake Powell will operate in the Mid-Elevation Release Tier in water year 2022. Under this tier, Lake Powell will release 7.48 million acre-feet in water year 2022 without the potential for a mid-year adjustment in April 2022.

• Lake Mead Level 1 Shortage Condition: The study projects Lake Mead’s 1 January 2022, elevation to be 1,065.85 feet—about 9 feet below the Lower Basin shortage determination trigger of 1,075 feet and about 24 feet below the drought contingency plan trigger of 1,090 feet. Based on this projection, Lake Mead will operate in a Level 1 Shortage Condition for the first time.

Lake Powell water elevation. Source: Bureau of Reclamation

The required shortage reductions and water savings contributions under the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and Coordinated Operations of Lake Powell and Lake Mead, 2019 Lower Basin Drought Contingency Plan and Minute 323 to the 1944 Water Treaty with Mexico are:

• Arizona: 512,000 acre-feet, which is approximately 18% of the state’s annual apportionment

• Nevada: 21,000 acre-feet, which is 7% of the state’s annual apportionment

• Mexico: 80,000 acre-feet, which is approximately 5% of the country’s annual allotment

In July 2021, drought operations to protect Lake Powell were implemented under the Upper Basin Drought Response Operations Agreement which project releasing up to an additional 181,000-acre feet of water from upstream initial units of the Colorado River Storage Project to Lake Powell.

The Colorado River is a critical resource in the US West because seven basin states—Arizona, California, Colorado, Nevada, New Mexico, Utah, and Wyoming—depend on it for water supply, hydropower production, recreation, fish and wildlife habitat, and other benefits.