- Federal water managers released a new Colorado River forecast on October 15, 2026.
- The wet-weather scenario projects inflows into Lake Powell at 157% of the average in water year 2027.
- Lake Powell could rise to 3,606.39 feet by September 30, 2027.
- Lake Mead is projected to remain near 1,033 feet in September 2027 before rising in 2028.
- The projections represent a wetter-than-normal scenario, not the most likely outcome.
Friday, October 23, 2026 — A new federal study offers a look at what could happen to the Colorado River’s major reservoirs if the basin receives substantially more water than normal over the next two years.
The Bureau of Reclamation released its October 2026 Probable Maximum 24-Month Study
on October 15. The report examines how reservoirs throughout the Colorado River system might respond to unusually wet conditions through September 2028.
Under this scenario, Lake Powell could gain more than 88 feet in elevation by September 2027, compared with its September 2026 level.
Lake Mead’s recovery would take longer. The study projects that its water level would remain relatively low through 2027 before rising sharply during 2028.
These are not predictions of what will happen. They are estimates based on one possible set of weather and river conditions.
Understanding the Wet-Weather Forecast.
The Bureau of Reclamation uses computer models to estimate how much water may enter the Colorado River system and how reservoirs might respond.
Its 24-month studies examine three different possibilities.
The probable minimum scenario represents unusually dry conditions. The most probable scenario represents middle-of-the-road conditions. The probable maximum scenario represents unusually wet conditions.
The October 2026 probable maximum study uses a wet-weather scenario that would be exceeded statistically only 10% of the time.
In other words, it describes conditions much wetter than those expected in an average year.
Reclamation reports that approximately 80% of future reservoir elevations are expected to fall between its probable minimum and probable maximum scenarios.
Actual water levels could still fall outside that range.
Lake Powell Could See a Major Increase.
Lake Powell, behind Glen Canyon Dam, shows a substantial increase in the wet-weather projections.
The study estimates that 15.10 million acre-feet of water could flow into Lake Powell during water year 2027 under natural river conditions, without accounting for upstream reservoir operations and other changes.
That represents 157% of average inflow.
An acre-foot is the amount of water needed to cover one acre of land to a depth of one foot.
The federal projections show Lake Powell at 3,518.08 feet on September 30, 2026.
Under the wet scenario, the reservoir would rise to 3,606.39 feet by September 30, 2027.
That would be an increase of approximately 88 feet in one year.
The study also projects that Glen Canyon Dam would release 7 million acre-feet of water during water year 2027.
For water year 2028, the report’s introductory summary identifies a release of approximately 11.50 million acre-feet.
Those releases are important because water passing through Glen Canyon Dam continues downstream toward Lake Mead.
Lake Mead’s Recovery Would Come Later.
The forecast presents a different picture for Lake Mead, the reservoir behind Hoover Dam.
Even with unusually wet conditions across the Colorado River Basin, the study does not show an immediate, dramatic recovery at Lake Mead.
Instead, the reservoir is projected to reach 1,035.36 feet on December 31, 2026.
By September 30, 2027, its elevation would be approximately 1,032.71 feet.
The larger increase would come during the following water year.
By September 30, 2028, Lake Mead is projected to reach 1,081.03 feet.
That represents an increase of more than 48 feet between September 2027 and September 2028.
The projections reflect the modeled movement of water through the river system, including releases from Lake Powell and water entering the river between the two reservoirs.
Other Reservoirs Could Also Gain Water.
The October study includes more than Lake Powell and Lake Mead.
Federal water managers also examined reservoirs throughout the Upper Colorado River Basin, including Flaming Gorge, Blue Mesa, Navajo and Fontenelle.
The projections show different responses depending on how much water enters each reservoir and how much is released downstream.
At Blue Mesa Reservoir, the projected elevation rises from 7,413.10 feet in September 2026 to 7,490.93 feet in September 2027.
Navajo Reservoir is projected to rise from 6,015.22 feet to 6,053.61 feet during the same period.
Flaming Gorge follows a different pattern. Its projected elevation falls from 6,007.21 feet in September 2026 to 6,002.88 feet in September 2027, even under the wet-weather scenario.
The study accounts for water entering and leaving each reservoir rather than assuming that wetter conditions will raise every reservoir by the same amount.
What the Forecast Does and Does Not Say.
The October 2026 study provides one possible picture of Colorado River conditions through September 2028.
It is not a guarantee of future water supplies.
The Bureau of Reclamation developed the projections using its 24-Month Study RiverWare computer model and inflow estimates from the National Weather Service’s Colorado Basin River Forecast Center.
The agency cautions that the results depend on the assumptions and limitations of its computer modeling.
The probable maximum scenario is also not the agency’s middle-range forecast. It represents a wetter possibility used to help describe the range of future reservoir conditions.
Reclamation conducts probable minimum and probable maximum studies in January, April, August and October, or when changing conditions require additional analysis.
The October report provides projected reservoir elevations, water releases and power generation under the wet-weather scenario. The figures are estimates, not measurements of water already in storage.
Source:
U.S. Department of the Interior, Bureau of Reclamation, October 2026 Probable Maximum 24-Month Study, published October 15, 2026, updated October 19, 2026. Colorado River Basin 24-Month Study, 20 pages. Catalog Item 134217.
