Current week through September 1, 2026

Data through USBR daily data through September 1; weekly hydrologic update through August 30

Powell and Mead start September still drawing down

Weekly Colorado River Basin report: Powell and Mead start September still drawing down. Data through USBR daily data through September 1; weekly hydrologic update through August 30; includes Lake Powell, Lake Mead, operations, storage, and weather context.

Powell and Mead started September still moving lower. USBR RISE data show Powell at 3,517.86 feet and 5.143 million acre-feet on September 1, down 0.80 feet and 44,260 acre-feet from August 25. That leaves Powell 7.86 feet above the 3,510-foot Glen Canyon operating-reliability line Reclamation is using in the 2027-2028 guidelines. [1] [3] [4]

Mead was at 1,038.82 feet and 6.897 million acre-feet on September 1, down 0.34 feet and 23,300 acre-feet over the same seven days. Together, Powell and Mead held 12.040 million acre-feet on September 1, down about 67,560 acre-feet from August 25. The daily values are provisional, but the direction is still down. [1]

The August 31 USBR weekly hydrologic update, using conditions as of August 30, put total Colorado River system contents at 18.315 million acre-feet, or 31% of capacity. Last year at the same point, system contents were 22.177 million acre-feet, or 38%. Upstream support storage also kept slipping: Flaming Gorge was down 17,290 acre-feet over seven days, and Lake Granby was down 7,409 acre-feet through September 2. [1] [2]

Weather is a short-term helper, not a storage fix. NOAA CPC's September 2 outlook favors above-normal precipitation for much of the West during September 8-12 and September 10-16, while Utah, Arizona, Colorado, New Mexico, and Wyoming lean warmer than normal. CPC rates both periods below-average confidence, so the weather signal stays secondary to measured reservoir movement. [6] [7] [8]

Why the new rules matter now

The important shift is not just that Powell and Mead are low. The new operating rules are arriving while both reservoirs are already near stressed operating bands.

The rules now match the reservoir chart
Reclamation set 2027-2028 operations around protecting Glen Canyon reliability near 3,510 feet. Powell ended September 1 at 3,517.86 feet, so that line is close enough to affect how readers should interpret the daily lake chart. [1] [3] [4]
The main reservoirs kept slipping
Powell and Mead lost about 67,560 acre-feet combined from August 25 to September 1, leaving the two reservoirs near 12.040 million acre-feet together. [1]
System storage is lower than last year
The August 31 weekly update put total Colorado River system contents at 18.315 million acre-feet, or 31% of capacity. Last year at the same point, the system held 22.177 million acre-feet, or 38%. [2]

What would change my view: sustained Powell inflow above release, Mead and Powell combined storage flattening for more than a few days, or a new operations update that changes the 2027 implementation path. [1] [3] [6]

Powell remains just above the 3,510-foot operating line

Powell ended September 1 at 3,517.86 feet, below the post-initial-fill operating low set in April 2023 and only 7.86 feet above Reclamation's 3,510-foot operating-protection level.

7-day elevation change

Lake Powell: Down 0.80 ft
Lake Mead: Down 0.34 ft
Flaming Gorge: Down 0.55 ft

What changed since last week

Metric	Prior week	Current week	Change	Why it matters
Lake Powell elevation	3,518.66 ft	3,517.86 ft	-0.80 ft	Only 7.86 ft above Reclamation's 3,510-ft operating-protection level.
Lake Mead elevation	1,039.16 ft	1,038.82 ft	-0.34 ft	Still below 1,040 ft and 3.82 ft above the 1,035-ft Hoover power-capacity reference line.
Mead + Powell storage	12.107 MAF	12.040 MAF	-0.068 MAF	The two main reservoirs lost about 67,560 acre-feet from August 25 to September 1.
Total system contents	22.177 MAF last year	18.315 MAF	31% full	The August 31 weekly update shows the system seven percentage points lower than last year.

Recent basin updates

September 1, 2026: Powell and Mead start September still drawing down
USBR RISE data put Powell at 3,517.86 feet and 5.143 million acre-feet, while Mead was at 1,038.82 feet and 6.897 million acre-feet. Together, the two main reservoirs lost about 67,560 acre-feet from August 25 to September 1.
Bureau of Reclamation
August 31, 2026: Weekly update puts Colorado River system storage at 31%
Reclamation listed total Colorado River system contents at 18.315 million acre-feet, or 31% of capacity, as of August 30. Last year at the same point, the system held 22.177 million acre-feet, or 38%.
Bureau of Reclamation
September 2, 2026: Warm and wetter odds show up in the next two outlook windows
NOAA CPC favors above-normal temperatures and precipitation for Utah, Arizona, Colorado, New Mexico, and Wyoming in the September 8-12 and September 10-16 outlook tables. Forecast confidence is below average in both periods.
NOAA CPC

Weather outlook

Sources checked September 3, 2026.

Storage impact: Low
Early-September storms can help local demand and soils, but they do not change the main reservoir balance by themselves.
Heat pressure: High
CPC favors above-normal temperatures for Utah, Arizona, Colorado, New Mexico, and Wyoming in both outlook tables.
Storm help: Mixed
Above-normal precipitation is favored for many basin states, but week-two confidence is low.

Warm and wetter odds lead the 6-10 day outlook CPC favors above-normal temperatures and precipitation for Utah, Arizona, Colorado, New Mexico, and Wyoming in the 6-10 day table. Nevada leans near-normal on temperature and above-normal on precipitation. Short storms can help local demand and soils, but they do not erase the current Powell and Mead storage losses.

September 10-16, 2026: Warmth and wetter odds continue, with below-average confidence.

West Water Watch read

The practical takeaway: the system is still losing water at the start of September, and Powell is close enough to the 3,510-foot protection line that small daily moves matter.

News review completed September 8, 2026.