#ColoradoRiver System 5-Year Probabilistic Projections — USBR #COriver #aridification

From Reclamation:

Overview

Five-year projections of future conditions, currently through 2026, in the Colorado River system are typically updated every January, April, and August, while probabilistic results for the 2-year period are updated every month. The “mid- to long-term projections” are generated using a combination of Colorado River Mid-term Modeling System (CRMMS) for the current year’s projections along with the Colorado River Simulation System (CRSS) for projections in year 2 and beyond.

The most recent 5-year projections of future Colorado River system conditions were produced in January of 2022 using the following assumptions:

  • Initial Conditions: CRSS was initialized in January 2023 with the January 2022 CRMMS-ESP projected end-of-year reservoir conditions.
  • Hydrology: Index sequential method applied to the 1988-2019 historical record, i.e., Stress Test hydrology; a total of 960 future projections (i.e., traces) in the Stress Test hydrology (30 set of initial conditions from the January 2022 CRMMS-ESP x 32 hydrologic inflow sequences).
  • Water Demand: Upper Basin demands per the 2016 UCRC depletion demand schedules; Lower Basin demands 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.
  • Additional details are available in 5-Year Projections Modeling Approach. 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 results 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.

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

    Projections of Lake Powell (top) and Lake Mead (bottom) end-of-December reservoir elevations. The colored region, or cloud, for the hydrology scenario represents the minimum, 10th percentile, 90th percentile, and maximum of the projected reservoir elevations. Solid lines represent historical elevations (black), and median projected elevations for the scenario (yellow). Horizontal gray lines represent important elevations for operations.

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

    To be notified when updated projections are available, please email ColoradoRiverModeling@usbr.gov with “Add Me” as the subject.

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