Lake Powell water level

Glen Canyon Dam holds Lake Powell on the Colorado River, the keystone of the Colorado River Storage Project and the upper basin's counterpart to Lake Mead. Second in size only to Mead among US reservoirs, it stores most of the upper basin's capacity and generates the bulk of the project's hydropower. Reclamation times releases to meet the basin's downstream delivery obligations. The reservoir backs about 186 miles up the canyon across the Utah-Arizona line, and it did not reach full pool until 1980, seventeen years after the dam closed the river.

Total capacity is 24.32M af, over the past five years storage has ranged from 5.26M af to 9.88M af.

Those figures describe the reservoir at full pool, not today. The chart at the top of this page tracks storage in acre-feet rather than water depth, so read the current figure against total capacity for how full the reservoir is, and against the full pool elevation and maximum depth for the size of the water column behind the dam. The two do not move together one for one: a reservoir narrows as it deepens, so one holding half its capacity still stands more than half as deep.

Sources: full pool elevation and maximum depth from the Bureau of Reclamation; surface area from the Army Corps' National Inventory of Dams; total capacity from the Bureau of Reclamation.

Reclamation reports Lake Powell two ways, by volume in acre-feet and by surface elevation in feet above sea level. Full pool is 3,700 feet. Minimum power pool, the level below which water no longer reaches the penstocks that drive Glen Canyon Dam's generators, is 3,490 feet. Dead pool, where the river outlet works sit and water can no longer be released downstream by gravity, is 3,370 feet. In the spring of 2023 the surface fell to about 3,520 feet, the lowest reading since the 1960s, when the reservoir was still filling behind the new dam. That left roughly 30 feet of margin above the point where the dam stops making power.

The lake runs on an annual cycle. Snowmelt off the Rockies in Colorado, Wyoming and Utah arrives down the Colorado, Green and San Juan rivers from about April into July, and that runoff is when Lake Powell gains nearly all of what it will hold for the year. Through late summer, fall and winter the inflow drops away while Reclamation keeps releasing water downstream to Lake Mead, so the surface falls until the next melt. A dry winter in the mountains shows up here a season later.

Releases are a policy decision, not weather. Reclamation sets a target annual release volume for Glen Canyon Dam at the start of each water year under the Colorado River operating guidelines. The long-standing figure is 8.23 million acre-feet, and in dry years Reclamation has cut the release below it to hold more water in Powell.

The storage number itself starts as an elevation reading at the dam, converted to volume through an area-capacity table built from periodic sediment surveys. The canyon narrows with depth, so a foot of elevation near full pool holds far more water than a foot near the bottom, which is why a falling reservoir appears to drop faster the lower it goes. Sediment carried in by the Colorado and the San Juan has taken close to 7 percent of the original capacity since the dam closed the canyon in 1963. Reclamation posts a new reading every day, and that daily series is what the chart above tracks.