Reclamation’s dry case puts Lake Powell at about 3,497 feet by late next September

Lake Powell would sink to 3,497.03 feet on September 30, 2027, if the dry case in the Bureau of Reclamation’s October study plays out, roughly 21 feet below the 3,518.08 feet the same table shows at the end of September 2026. The projection comes from the agency’s Probable Minimum 24-Month Study, dated October 15, and it covers the reservoir that feeds Glen Canyon Dam.

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The number is a stress test rather than a prediction of the most likely outcome. Reclamation built the scenario around a deliberately poor runoff year, and the study itself describes the inflow assumption as one that would be exceeded about nine times in ten. Readers comparing it with other Powell forecasts need to keep that framing in view.

A dry-case run with 4.07 million acre-feet of inflow

The Bureau of Reclamation’s October 2026 Probable Minimum 24-Month Study states that Lake Powell’s elevation is projected to be 3,497.03 feet on September 30, 2027, with end-of-month storage of 4,072 thousand acre-feet. The model run was processed on October 8 and the document is dated October 15. Under this scenario, unregulated inflow into Lake Powell in water year 2027 is 4.07 million acre-feet, or 42 percent of average, a figure that Reclamation labels as statistically exceeded 90 percent of the time.

The study then assumes a release volume from Glen Canyon Dam of 6.00 million acre-feet in each of water years 2027 and 2028. That release figure is a modelling assumption written into the dry case, not an operating decision announced by the agency, and the document says nothing about adjusting it if conditions worsen. With the same 6.00 million acre-feet leaving the dam every year, the reservoir absorbs the whole shortfall in inflow, plus evaporation that the study puts at 154 thousand acre-feet in water year 2027 and 140 thousand in water year 2028.

Regulated inflow, the water that actually arrives after upstream reservoirs are operated, is listed at 4,984 thousand acre-feet in water year 2027 and 6,382 thousand in water year 2028. The second year is far wetter than the first in this run, because unregulated inflow rises to 6,801 thousand acre-feet in water year 2028. That recovery matters for the shape of the curve, because it is the reason the reservoir bottoms out in winter 2028 and then climbs again.

The month-by-month path through 2027 and 2028

The table in the study opens at 3,519.23 feet at the end of October 2026 and 3,519.44 feet in November. From there the dry case slides: 3,518.29 feet in December, 3,515.58 in January 2027, 3,513.27 in February, and 3,511.22 in March. April 2027 is the first local low at 3,511.03 feet, before a modest spring bump lifts the reservoir to 3,512.40 feet in May and 3,517.10 feet in June.

Then the decline resumes. July 2027 closes at 3,511.76 feet, August at 3,503.22 feet, and September at the 3,497.03-foot mark. The drop of roughly 14 feet between June and September 2027 is the steepest stretch in the table, a summer in which releases and evaporation outrun a thin runoff. The study continues past that point: 3,495.61 feet in October 2027, 3,494.43 in November, 3,493.05 in December, and 3,491.39 in January 2028.

The lowest end-of-month value anywhere in the 24 months is 3,490.99 feet in February 2028, with storage of 3,788 thousand acre-feet. After that the second, wetter year takes over. The reservoir rises to 3,492.71 feet in March 2028, 3,496.20 in April, 3,507.95 in May, and 3,519.10 in June 2028, before easing to 3,501.61 feet in September 2028. In other words, the dry case does not show a one-way slide; it shows a trough that reaches within one foot of a critical line before runoff rebuilds the pool.

Why 3,490 feet matters to Glen Canyon Dam’s turbines

That line is the minimum power pool. The Bureau of Reclamation’s Glen Canyon Dam page lists the minimum power pool at 3,490 feet and describes a powerplant of eight generating units with a combined capacity of 1,320 megawatts. The study’s February 2028 low of 3,490.99 feet sits about one foot above that threshold, which is why the scenario draws attention even though it is a low-probability case.

Reporting from earlier this year shows how close the reservoir already is to that territory. In an ABC News report published on July 13, the reservoir stood at 3,524.3 feet, about 34 feet above minimum power pool, according to Reclamation’s figures. Peter Soeth, the agency’s public affairs lead, said at that time that the basin was experiencing its lowest snowpack on record, and that Reclamation and the department were committed to reducing the collective risk of Lake Powell and Lake Mead falling below critical elevations. Jack Schmidt, who directs the Center for Colorado River Studies at Utah State University, said that in dry years the system depletes reservoir storage.

Below the power pool, water would pass the turbine intakes and could allow air into the machines. A 2023 report from KUNC explained that falling below 3,490 feet risks cavitation that can damage turbines, and that Reclamation could be unable to generate hydropower for about five million people across seven states. Eric Balken, executive director of the Glen Canyon Institute, said at the time that decision makers were worried about infrastructure problems at the dam below that level.

Reclamation publishes its studies on a page that archives each month’s Most Probable, Minimum Probable and Maximum Probable reports, and the 24-Month Study archive shows how this dry case compares with its companions as new runs arrive. The November study will replace this one, and the 3,497.03-foot figure should be read as a floor-style scenario from an October model run rather than a standing forecast.

This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.

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