Running the Grand this fall or winter and wondering what the water levels might be? So are we. Read on for the latest report from Tom Martin and Grand Canyon Private River Runners…
Grand Canyon Report (by Tom Martin/Grand Canyon Private River Runners )
“Still holding on… sorta. Here’s a look at what might be ahead of us for boating the Colorado River in Grand Canyon this winter.
As of today, July 29, 2026, the reservoir behind Glen Canyon Dam has lost roughly 5,600 acre-feet of water per day in the last 19 days. If this rate of decline continues, then we can expect the reservoir to reach minimum powerpool — 3,500 feet — in about 190 days, or early February, 2027.
The last 19 days show increased inflow to the reservoir due to the arrival of monsoon rains. This is true for the reservoir behind Hoover Dam as well, with increased inflow from the Little Colorado River and other tributaries to the Colorado River in Grand Canyon.
What could happen in early February, 2027.
If the level drops below 3,500 feet, dam operators will no longer be able to release water through the penstocks and hydroelectric turbines, meaning they must rely entirely on the river outlets lower on the dam for all releases. This would not only zero out the dam’s hydropower output, but could also damage the outlet tubes, since they aren’t engineered for long-term, sustained use.
In order not to damage the dam, keep the turbines doing something, and keep some water going to Mead, Reclamation may defend that 3,500-foot level, presumably even if it means going to a run-of-the-river operation.
During a run-of-the-river operation, water is released from the dam at the approximate rate that it is flowing into the reservoir, minus evaporation and seepage around the dam. Today, the evaporation amount is about 397 cubic feet per second (cfs) and the inflow from the Colorado and San Juan is 4,434cfs. Leakage around the dam is about 500cfs. This would allow a run-of-the-river release of about 3,537 cfs, less than half one-half of current releases. This may happen this winter during the motor-free river running season in the Grand Canyon.
This 3,537 cfs figure does not include bank seepage or possible decreases in the upstream releases from Flaming Gorge Dam and Navajo Dam. This means the actual run-of-the-river release from Glen Canyon Dam in February 2027 may be even less if the Flaming Gorge and Navajo releases decrease.
If — or more likely, when — this occurs, it will render Lake Powell useless as a water savings account, and reduce it to a marginal power generator. Meanwhile it will still be a silt collector and large evaporation pool. Boating will still be possible on the reservoir and rafting downstream of the dam in Grand Canyon, but most existing boat ramps on the reservoir will no longer be usable. This will lend strength for calls to drain the reservoir, either by decommissioning the dam altogether, or by building bypass tunnels that can be shut down if climatic conditions change and aridification is reversed.
I appreciate help from Jonathan P Thompson in writing this outlook.”