Colorado River System 5-Year Projected Future Conditions

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Colorado River System Mid- to Long-term Projections
    General Modeling Information
    Colorado River System 5-Year Projected Future Conditions
    Colorado River System Projected Future Conditions - Alternative Future Hydrology Scenarios

Control Display Icon  Overview

Projections of future conditions of the Colorado River system are updated at least twice annually in January and August. The modeling approach and assumptions are included below along with the results of the most recent projection.

The most recent projection of future Colorado River system conditions was produced in April of 2021.

Control Display Icon  Modeling Approach

The April 2021 projections are developed using a combination of Reclamation reservoir operations models, the Colorado River Mid-term Modeling System (CRMMS) in MTOM mode and the Colorado River Simulation System (CRSS) (see General Modeling Information for details). The system conditions for April 2021 through December 2021 are simulated in CRMMS using MTOM mode and then the end-of-year conditions are imported into CRSS to continue simulating from January 2022 onward. This process utilizes the current Colorado Basin River Forecasting Center (CBRFC) forecast for the potential near-term inflows, and methods to incorporate hydrologic uncertainty resulting in a wide range of plausible future inflows for the mid- to long-term.

CRMMS in MTOM mode uses 35 potential inflow sequences forecast by the CBRFC that incorporates hydrologic uncertainty by considering current conditions and historical temperature and precipitation patterns.

Each CRMMS simulation results in a set of December 2021 system conditions that are used as initial conditions in CRSS. This means initializing CRSS 35 times- once for each set of initial system conditions. CRSS is run using two different assumptions for future hydrology: the “Full” hydrology and the “Stress Test” hydrology. The Full hydrology resamples the 1906-2019 natural flow record using the Index Sequential Method to create 114 future inflow sequences, while the Stress Test hydrology resamples the 1988-2019 natural flow record to create 32 future inflow sequences. Both the Full hydrology and Stress Test hydrology are combined with all 35 MTOM initializations resulting in 3,990 and 1,120 future projections, i.e., traces, for analysis.

Modeling Approach Flow Chart

Control Display Icon  Future Projections

CRSS and CRMMS in MTOM mode model results are reported as the percentage of future projected Lake Powell and Lake Mead operations that are within each operational tier in the next five years. The percentages are computed out of the total 3,990 future projections (i.e., traces) in the Full hydrology and out of the total 1,120 traces in the Stress Test hydrology; however, the percentages shown may not be representative of the full range of future possibilities that could occur with different modeling assumptions. Reclamation also generates additional projections under different future hydrology scenarios, available at Colorado River System Projected Future Conditions - Alternative Future Hydrology Scenarios. The 2007 Interim Guideline tiers are depicted in the coordinated operations diagram.

Table 1: Percent of Traces with Event or System Condition. Results from April 2021 CRMMS MTOM Mode/CRSS using the Full Hydrology (resampling the 1906-2019 natural flow record).
Event or System Condition 2021 2022 2023 2024 2025
Upper Basin - Lake Powell
Equalization Tier (Powell >= Equalization [EQ] Elevation) 0 0 6 12 17
Equalization - annual release > 8.23 maf 0 0 6 12 17
Equalization - annual release = 8.23 maf 0 0 0 0 0
Upper Elevation Balancing Tier (Powell < EQ Elevation and >= 3,575 ft) 100 3 36 49 50
Upper Elevation Balancing - annual release > 8.23 maf 0 2 35 45 44
Upper Elevation Balancing - annual release = 8.23 maf 100 <1 1 4 5
Upper Elevation Balancing - annual release < 8.23 maf 0 0 <1 <1 <1
Mid-Elevation Release Tier (Powell < 3,575 and >= 3,525 ft) 0 91 51 31 23
Mid-Elevation Release - annual release = 8.23 maf 0 0 0 <1 2
Mid-Elevation Release - annual release = 7.48 maf 0 91 51 30 21
Lower Elevation Balancing Tier (Powell < 3,525 ft) 0 6 7 8 10
Below Minimum Power Pool (Powell < 3,490 ft) 0 0 1 4 6
Lower Basin - Lake Mead
Surplus Condition - any amount (Mead >= 1,145 ft) 0 0 0 1 4
Surplus - Flood Control 0 0 0 0 <1
Normal Year or ICS Surplus Condition (Mead < 1,145 and > 1,075 ft) 100 3 6 17 19
Recovery of DCP ICS / Mexico’s Water Savings (Mead >/>= 1,110 ft) 0 0 0 4 9
DCP Contribution / Mexico’s Water Savings (Mead <= 1,090 and > 1,075 ft) 100 3 5 11 10
Shortage Condition - any amount (Mead <= 1,075 ft) 0 97 94 82 77
Shortage / Reduction - 1st Level (Mead <= 1,075 and >= 1,050 ft) 0 97 81 37 34
DCP Contribution / Mexico’s Water Savings (Mead <= 1,075 and >= 1,050 ft) 0 97 81 37 34
Shortage / Reduction - 2nd Level (Mead < 1,050 and >= 1,025 ft) 0 0 13 44 32
DCP Contribution / Mexico’s Water Savings (Mead < 1,050 and > 1,045 ft) 0 0 11 9 6
DCP Contribution / Mexico’s Water Savings (Mead <= 1,045 and > 1,040 ft) 0 0 2 9 6
DCP Contribution / Mexico’s Water Savings (Mead <= 1,040 and > 1,035 ft) 0 0 <1 11 8
DCP Contribution / Mexico’s Water Savings (Mead <= 1,035 and > 1,030 ft) 0 0 0 10 7
DCP Contribution / Mexico’s Water Savings (Mead <= 1,030 and >=/> 1,025 ft) 0 0 0 5 6
Shortage / Reduction - 3rd Level (Mead < 1,025 ft) 0 0 0 1 11
DCP Contribution / Mexico’s Water Savings (Mead </<= 1,025 ft) 0 0 0 1 11
Table 2: Percent of Traces with Event or System Condition. Results from April 2021 CRMMS MTOM Mode/CRSS using the Stress Test Hydrology (resampling the 1988-2019 natural flow record).
Event or System Condition 2021 2022 2023 2024 2025
Upper Basin - Lake Powell
Equalization Tier (Powell >= Equalization [EQ] Elevation) 0 0 0 3 7
Equalization - annual release > 8.23 maf 0 0 0 3 7
Equalization - annual release = 8.23 maf 0 0 0 0 0
Upper Elevation Balancing Tier (Powell < EQ Elevation and >= 3,575 ft) 100 3 31 41 39
Upper Elevation Balancing - annual release > 8.23 maf 0 2 30 39 36
Upper Elevation Balancing - annual release = 8.23 maf 100 <1 <1 2 3
Upper Elevation Balancing - annual release < 8.23 maf 0 0 0 <1 0
Mid-Elevation Release Tier (Powell < 3,575 and >= 3,525 ft) 0 91 65 45 35
Mid-Elevation Release - annual release = 8.23 maf 0 0 0 0 5
Mid-Elevation Release - annual release = 7.48 maf 0 91 65 45 30
Lower Elevation Balancing Tier (Powell < 3,525 ft) 0 6 4 11 18
Below Minimum Power Pool (Powell < 3,490 ft) 0 0 <1 9 12
Lower Basin - Lake Mead
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) 100 3 8 9 6
Recovery of DCP ICS / Mexico’s Water Savings (Mead >/>= 1,110 ft) 0 0 0 0 <1
DCP Contribution / Mexico’s Water Savings (Mead <= 1,090 and > 1,075 ft) 100 3 7 9 3
Shortage Condition - any amount (Mead <= 1,075 ft) 0 97 92 91 94
Shortage / Reduction - 1st Level (Mead <= 1,075 and >= 1,050 ft) 0 97 71 31 33
DCP Contribution / Mexico’s Water Savings (Mead <= 1,075 and >= 1,050 ft) 0 97 71 31 33
Shortage / Reduction - 2nd Level (Mead < 1,050 and >= 1,025 ft) 0 0 21 60 36
DCP Contribution / Mexico’s Water Savings (Mead < 1,050 and > 1,045 ft) 0 0 17 6 7
DCP Contribution / Mexico’s Water Savings (Mead <= 1,045 and > 1,040 ft) 0 0 4 11 6
DCP Contribution / Mexico’s Water Savings (Mead <= 1,040 and > 1,035 ft) 0 0 0 16 6
DCP Contribution / Mexico’s Water Savings (Mead <= 1,035 and > 1,030 ft) 0 0 0 17 6
DCP Contribution / Mexico’s Water Savings (Mead <= 1,030 and >=/> 1,025 ft) 0 0 0 9 10
Shortage / Reduction - 3rd Level (Mead < 1,025 ft) 0 0 0 <1 25
DCP Contribution / Mexico’s Water Savings (Mead </<= 1,025 ft) 0 0 0 <1 25

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Last updated: 2021-05-05