Lake Powell is a storage reservoir. Its level is primarily determined by inflows from the Upper Colorado River Basin and releases through Glen Canyon Dam. This chart uses current reservoir conditions and Colorado Basin River Forecast Center (CBRFC) water-supply forecasts to project storage forward under fixed release assumptions.
In other words, it asks what Lake Powell storage would look like if the rest of this runoff season follows the April-July volumes in the CBRFC ESP or official forecast guidance.
How to use this chart
The white line shows the current WATER YEAR to date. The colored lines extend storage forward using CBRFC April-July forecast volumes, anchored at today’s storage level on April 1.
Controls
CBRFC mode
The CBRFC mode control switches between forecast sets with GEFS off and on.
Forecast source
The forecast source control switches between ESP percentiles and the CBRFC official forecast percentiles. Only one forecast family is shown at a time.
Benchmark overlays
The benchmark controls add 2002 and 2018 as reference April-July inflow scenarios, regardless of whether ESP or Official is selected.
Annual Release
The release control sets a fixed annual release target. These options span the most important operating levels in the current Lake Powell framework, from 8.25 million acre-feet down to 4.0 million acre-feet.123
Forecast distribution
The CBRFC April-July forecast volumes are distributed through the season using the historical mean daily unregulated inflow shape. This is a storage translation of the forecast volume guidance, not a day-by-day operational forecast.
Lake Powell Storage Projections
Data Sources
- CBRFC GLDA3 water-supply forecast guidance and the derived local JSON used by this chart for ESP, official, and GEFS forecast volumes.45
- CBRFC backend forecast endpoints used to build the local forecast JSON: one call for GEFS off and one call for GEFS on.67
- USBR Lake Powell Hydrodata used for current storage and elevation, with a derived local water-year JSON used for observed storage history, inflow shape, and release context.89
- Lake Powell elevation-area-capacity data used to translate storage into reservoir elevation.101112
- 1
United States Bureau of Reclamation - Colorado River Compact, November 24, 1922. ↩︎
- 2
United States Bureau of Reclamation - 24-Month Study, March 2026. ↩︎
- 3
United States Bureau of Reclamation - Supplement to the 2007 Colorado River Interim Guidelines for Lower Basin Shortages and the Coordinated Operations for Lake Powell and Lake Mead - Record of Decision, May 2024. ↩︎
- 4
Colorado Basin River Forecast Center - GLDA3 water-supply forecast page. ↩︎
- 5
Derived local dataset used by this chart - glda3-2026.json. It was built from two CBRFC API calls to the same backend endpoint, one with GEFS off and one with GEFS on. ↩︎
- 6
CBRFC backend endpoint used for the GEFS-off forecast payload - GEFS-off API endpoint. ↩︎
- 7
CBRFC backend endpoint used for the GEFS-on forecast payload - GEFS-on API endpoint. ↩︎
- 8
United States Bureau of Reclamation - Lake Powell Hydrodata Dashboard, used here as the source for current storage and elevation, the current storage and elevation series to date, and the 2002 and 2018 April-July inflows. ↩︎
- 9
Derived local dataset used by this chart - lake-powell-water-year.json. ↩︎
- 10
Derived local elevation-area-capacity dataset used by this chart - lake-powell-2018-elev-area-capacity.json. ↩︎
- 11
Jones, D.K., and Root, J.C., 2022, Elevation-area-capacity tables for Lake Powell, 2018, U.S. Geological Survey data release. ↩︎
- 12
Root, J.C., and Jones, D.K., 2022, Elevation-area-capacity relationships of Lake Powell in 2018 and estimated loss of storage capacity since 1963, U.S. Geological Survey Scientific Investigations Report 2022-5017. ↩︎