Colorado River System 5-Year Projected Future Conditions

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General Modeling Information

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 August of 2018.

Control Display Icon  Modeling Approach

The August 2018 projections utilize CRSS to simulate the system conditions beginning in January 2019. For this CRSS run, projected December 2018 reservoir conditions were obtained from the most probable August 24-Month Study, and used to initialize CRSS. This modeling approach was selected since the majority of the annual runoff has already occurred and the August 24-Month Study sets the operational tier for the coming year. Because there is little uncertainty in the hydrology and the operations of Lakes Powell and Mead for the remainder of the current year, there is no significant effect on future projections when using a single set of initial conditions instead of a range of initial conditions. This run uses the 1906-2015 natural flow record, resampled using the Index Sequential Method to create 110 future inflow sequences, which results in a total of 110 future projections, i.e., traces, for analysis.

Modeling Approach Flow Chart

Modeling Approach Flow Chart

Control Display Icon  Future Projections

CRSS 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 110 future projections (i.e., traces), however; the percentages shown may not be representative of the full range of future possibilities that could occur with different modeling assumptions. These operational tiers are depicted in the coordinated operations diagram.

Table 1: Percent of Traces with Event or System Condition. Results from August 2018 CRSS
Event or System Condition 2019a 2020 2021 2022 2023
Upper Basin - Lake Powell
Equalization Tier N 11 16 19 23
Equalization - annual release > 8.23 maf 0 11 16 19 21
Equalization - annual release = 8.23 maf 0 0 0 0 2
Upper Elevation Balancing Tier 100 49 52 51 44
Upper Elevation Balancing - annual release > 8.23 maf 75 43 43 43 33
Upper Elevation Balancing - annual release = 8.23 maf 25 5 9 8 10
Upper Elevation Balancing - annual release < 8.23 maf 0 1 0 0 1
Mid-Elevation Release Tier 0 40 22 16 19
Mid-Elevation Balancing - annual release = 8.23 maf 0 0 0 1 3
Mid-Elevation Release Tier - annual release = 7.48 maf 0 40 22 15 16
Lower Elevation Balancing Tier 0 0 10 14 15
Lower Basin - Lake Mead
Shortage Condition - any amount (Mead <= 1,075 ft) 0 57 68 70 65
Shortage - 1st Level (Mead <= 1,075 and >= 1,050 0 57 42 40 28
Shortage - 2nd Level (Mead < 1,050 and >= 1,025 0 0 26 23 24
Shortage - 3rd Level (Mead < 1,025) 0 0 0 7 14
Surplus Condition - any amount (Mead>= 1,145 ft) 0 0 3 5 7
Surplus - Flood Control 0 0 0 1 2
Normal Year or ICS Surplus Condition 100 43 29 25 27
a The chance of a mid-year adjustment to equalization is negligible in water year 2019.

Download Table 1


For additional information or questions, please contact us via email at: ColoradoRiverModeling@usbr.gov.

Last updated: 2018-08-21