Document Type

Report

Publisher

Utah State University

Publication Date

6-8-2026

First Page

1

Last Page

6

Abstract

Summary - Colorado River precipitation and flows have been volatile. There is consensus across Reclamation’s hydrologic ensembles that volatility will continue, including annual drops of 6 million acre-feet of natural flow above Lake Powell. At historically low Lake Powell and Lake Mead elevations, a 1-year drop can draw down reservoirs to catastrophic levels where the system can no longer fulfill its Congressionally mandated purposes: deliver water, generate hydropower, protect native fish, or sustain infrastructure. In this post we suggest four reservoir strategies to reduce all those risks: (1) Identify Catastrophic Elevations where we lose the ability to operate the system for one or more intended purposes, (2) Communicate Minimum Drawdown Elevations as storage buffers to mitigate catastrophic risks, (3) Sustain minimum drawdown elevations, such as by adapting releases to monitored changes in physical reservoir inflow and reservoir evaporation, (4) Increase the frequency of decisions to respond sooner and more flexibly to volatile flow. Water held in Lake Powell and Lake Mead between their minimum drawdown and catastrophic elevations generates continuing benefits for hydropower, native fish, infrastructure, and capacity to deliver water, whereas if released, buffer water can only be consumed once by downstream users. Moving to monthly or weekly decisions provides earlier, smaller, smoother, and more predictable changes in reservoir releases compared to delayed, larger, and more sudden shocks from the current practice of setting annual releases in Fall and possibly updating them in the Spring. We do not recommend specific minimum drawdown elevations. Rather, we emphasize the importance to communicate methods that maintain public trust that the Colorado River system will not collapse.

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