5-Year Probabilistic Projections

Overview

Five-Year Probabilistic Projections of future conditions in the Colorado River system currently extend through 2026. They are typically updated every January, April, and August, while probabilistic results for the 2-year period are updated every month. The 5-Year Probabilistic Projections are generated using the Colorado River Mid-term Modeling System (CRMMS) in Ensemble Mode. CRMMS Ensemble Mode is driven by an ensemble of monthly unregulated streamflow forecasts developed by the National Weather Service Colorado Basin River Forecasting Center (CBRFC) using the Ensemble Streamflow Prediction (ESP) method. Results from CRMMS run with ESP are referred to as CRMMS-ESP.

The most recent 5-year projections of future Colorado River system conditions were produced using the following assumptions:

  • Initial Conditions: CRMMS is initialized with previous end-of-month reservoir elevations.
  • Hydrology: Upper Basin inflows are 30 unregulated inflow forecasts traces produced by the CBRFC using the ESP method, which relies on observed temperature and precipitation from 1991-2020. Lower Basin inflows are the historical intervening flows from 1991-2020 that align with the ESP traces.
  • Water Demand: Upper Basin demands are estimated and incorporated in the unregulated inflow forecasts provided by the CBRFC; Lower Basin demands are developed in coordination with the Lower Basin States and Mexico.
  • Policy: 2007 Interim Guidelines, Lower Basin Drought Contingency Plan, and Minute 323 are modeled reflecting Colorado River policies.
  • Drought Response Actions: CRMMS projections contain actions undertaken with the 2022 Drought Response Operations Plan, 2022 Glen Canyon Dam operational adjustment, and the 2023 operations described in the 24-Month Study.
    • The 2022 Drought Response Operations Plan includes an additional release of 500 kaf from Flaming Gorge from May 2022 through April 2023.
    • The reduction of releases from Lake Powell from 7.48 maf to 7.00 maf in water year 2022 will result in a reduced release volume of 0.480 maf that normally would have been released from Glen Canyon Dam to Lake Mead as part of the 7.48 maf annual release volume, consistent with routine operations under the 2007 Interim Guidelines. The reduction of releases from Glen Canyon Dam in water year 2022 (resulting in increased storage in Lake Powell) will not affect future operating determinations and will be accounted for “as if” this volume of water had been delivered to Lake Mead. Lake Powell and Lake Mead operations are modeled as if the 0.480 maf had been delivered to Lake Mead for Lake Powell operating tier and condition determination purposes for the U.S. Lower Basin and for Mexico.
    • Because the 2022 operations were designed to protect critical elevations at Lake Powell, Reclamation will implement Lower Elevation Balancing Tier operations in a way that continues to protect these critical elevations, or preserves the benefits of the 2022 operations to protect Lake Powell, in water year 2023 and 2024. Specifically, Reclamation modeled operations as follows:
      • The Glen Canyon Dam annual release is initially set to 7.00 maf, and in April of the given year Reclamation will evaluate hydrologic conditions to determine if balancing releases may be appropriate under the conditions established in the 2007 Interim Guidelines;
      • Balancing releases will be limited (with a minimum of 7.00 maf) to protect Lake Powell from declining below elevation 3,525 feet at the end of December; and
      • Balancing releases will take into account operational neutrality of the 0.480 maf that was retained in Lake Powell under the May 2022 action. Any Lake Powell balancing release volume will be calculated as if the 0.480 maf had been delivered to Lake Mead in WY 2022.

Additional details are available in CRMMS Ensemble Mode page. All modeling assumptions and projections are subject to varying degrees of uncertainty. Please refer to this discussion of uncertainty for more information.

Projections

5-Year Probabilistic Projections presented in the tables below are reported as the percentage of projected Lake Powell and Lake Mead operations that fall below critically low elevations or are within each operational tier in the next five years.

Chance of Reaching Critically Low Reservoir Elevations1
Comparison of Current (August 2022) and Last Published (May 2022) CRMMS-ESP 5-Year Projections
Run WY 2023 WY 2024 WY 2025 WY 2026 WY 20272
Lake Powell less
than 3,525 feet
May 2022 90% 50% 37% 30% 23%
August 2022 100% 50% 37% 30% 30%
Difference 10% 0% 0% 0% 7%
Lake Powell less
than 3,490 feet
(minimum power pool)
May 2022 3% 23% 17% 23% 13%
August 2022 10% 30% 20% 17% 13%
Difference 7% 7% 3% -6% 0%
Lake Powell less
than 3,375 feet
(dead pool = 3,370 feet)
May 2022 0% 0% 0% 0% 0%
August 2022 0% 0% 0% 0% 0%
Difference 0% 0% 0% 0% 0%
Run 2023 2024 2025 2026 20272
Lake Mead less
than 1,020 feet
May 2022 40% 50% 47% 50% 53%
August 2022 47% 57% 57% 60% 57%
Difference 7% 7% 10% 10% 4%
Lake Mead less
than 1,000 feet
May 2022 0% 13% 20% 20% 13%
August 2022 0% 23% 20% 20% 17%
Difference 0% 10% 0% 0% 4%
Lake Mead less
than 950 feet
(minimum power pool)
May 2022 0% 0% 0% 3% 3%
August 2022 0% 0% 0% 7% 3%
Difference 0% 0% 0% 4% 0%
Lake Mead less
than 900 feet
(dead pool = 895 feet)
May 2022 0% 0% 0% 0% 0%
August 2022 0% 0% 0% 0% 0%
Difference 0% 0% 0% 0% 0%
Notes:
1 All results are computed as the chance of falling below physical elevations in any month in the calendar (water) year for Lake Mead (Lake Powell).
2 For modeling purposes, simulated years beyond 2026 assume a continuation of the 2007 Interim Guidelines, the 2019 Colorado River Basin Drought Contingency Plans, and Minute 323, including the Binational Water Scarcity Contingency Plan. With the exception of certain provisions related to ICS recovery and Upper Basin demand management, operations under these agreements are in effect through 2026. Reclamation anticipates beginning a process in early 2023 to develop operations for post-2026, and the modeling assumptions described here are subject to change for the analysis to be used in that process.
Chance of Reservoir Operating Conditions1
August 2022 CRMMS-ESP Projections
Upper Basin - Lake Powell - Operating Condition 2023 2024 2025 2026 20272
Equalization Tier (Powell >= Equalization [EQ] Elevation) 0 0 3 13 13
Equalization - annual release > 8.23 maf 0 0 3 13 13
Equalization - annual release = 8.23 maf 0 0 0 0 0
Upper Elevation Balancing Tier (Powell < EQ Elevation and >= 3,575 ft) 0 13 27 23 33
Upper Elevation Balancing - annual release > 8.23 maf 0 10 27 23 33
Upper Elevation Balancing - annual release = 8.23 maf 0 0 0 0 0
Upper Elevation Balancing - annual release < 8.23 maf 0 3 0 0 0
Mid-Elevation Release Tier (Powell < 3,575 and >= 3,525 ft) 0 37 37 33 27
Mid-Elevation Release - annual release = 8.23 maf 0 0 7 7 3
Mid-Elevation Release - annual release = 7.48 maf 0 37 30 27 23
Lower Elevation Balancing Tier (Powell < 3,525 ft) 100 50 33 30 27
Lower Elevation Balancing - annual release > 8.23 maf 23 20 13 13 17
Lower Elevation Balancing - annual release < 8.23 maf 77 30 20 17 10
Lower Basin - Lake Mead - Operating Condition 2023 2024 2025 2026 20272
Surplus Condition - any amount (Mead >= 1,145 ft) 0 0 0 0 0
Surplus - Flood Control 0 0 0 0 0
Normal Year or ICS Surplus Condition (Mead < 1,145 and > 1,075 ft) 0 7 0 7 13
Recovery of DCP ICS / Mexico’s Water Savings (Mead >/>= 1,110 ft) 0 0 0 0 0
DCP Contribution / Mexico’s Water Savings (Mead <= 1,090 and > 1,075 ft) 0 7 0 3 3
Shortage Condition - any amount (Mead <= 1,075 ft) 100 93 100 93 87
Shortage / Reduction - 1st Level (Mead <= 1,075 and >= 1,050 ft) 0 17 30 13 10
DCP Contribution / Mexico’s Water Savings (Mead <= 1,075 and >= 1,050 ft) 0 17 30 13 10
Shortage / Reduction - 2nd Level (Mead < 1,050 and >= 1,025 ft) 100 57 30 33 33
DCP Contribution / Mexico’s Water Savings (Mead < 1,050 and > 1,045 ft) 100 0 0 13 3
DCP Contribution / Mexico’s Water Savings (Mead <= 1,045 and > 1,040 ft) 0 10 0 7 3
DCP Contribution / Mexico’s Water Savings (Mead <= 1,040 and > 1,035 ft) 0 7 7 3 10
DCP Contribution / Mexico’s Water Savings (Mead <= 1,035 and > 1,030 ft) 0 13 7 7 7
DCP Contribution / Mexico’s Water Savings (Mead <= 1,030 and >=/> 1,025 ft) 0 27 17 3 10
Shortage / Reduction - 3rd Level (Mead < 1,025 ft) 0 20 40 47 43
DCP Contribution / Mexico’s Water Savings (Mead </<= 1,025 ft) 0 20 40 47 43
Notes:
1 All results computed as the percent of traces with a system condition. Percentages shown in this table may not be representative of the full range of future possibilities that could occur with different modeling assumptions.
2 For modeling purposes, simulated years beyond 2026 assume a continuation of the 2007 Interim Guidelines, the 2019 Colorado River Basin Drought Contingency Plans, and Minute 323, including the Binational Water Scarcity Contingency Plan. With the exception of certain provisions related to ICS recovery and Upper Basin demand management, operations under these agreements are in effect through 2026. Reclamation anticipates beginning a process in early 2023 to develop operations for post-2026, and the modeling assumptions described here are subject to change for the analysis to be used in that process.

Download Tables

Archived Tables

Previous tables (starting in January 2012) are also available. Select the date (a new window will open):

The following two figures show a combination of historical and projected reservoir elevations for Lake Powell and Lake Mead.

Projections of Lake Powell (top) and Lake Mead (bottom) end-of-month physical reservoir elevations. The colored region, or cloud, for the scenario represents the minimum and maximum of the projected reservoir elevations. Solid lines represent historical elevations (black), and median projected elevations for the scenario (yellow). Dashed and dot dashed lines represent the 10th and 90th percentiles, respectively. Horizontal gray lines represent important elevations for operations. These projections rely on future hydrology from the CBRFC’s ESP method and may not be representative of the full range of future possibilities that could occur; other hydrology methods may result in a wider range of future hydrology and elevations.


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Last updated: 2022-09-06