Glen Canyon TWG 

Basin Hydrology, Operations, and 

Water Quality 

June 14, 2023 

Rick Clayton & Robert Radtke 

rclayton@usbr.gov & rradtke@usbr.gov 

1 
 

 

 

 

 

 

 

 

 

 

Background 

This briefing is being provided consistent with the 

provision in Attachment B - Section 1.1 of the LTEMP ROD 

which states: 

“Annually, Reclamation will develop a hydrograph based on the characteristics 

above. Reclamation will seek consensus on the annual hydrograph through 

monthly operational coordination calls with governmental entities, and regular 

meetings of the GCDAMP Technical Working Group (TWG) and AMWG. 

Reclamation will conduct monthly Glen Canyon Dam operational coordination 

meetings or calls with the DOI bureaus (USGS, NPS, FWS, and BIA), WAPA, and 

representatives from the Basin States and UCRC. The purpose of these meetings or 

calls is for the participants to share and seek information on Glen Canyon Dam 

operations. One liaison from each Basin State and from the UCRC may participate 

in the monthly operational coordination meetings or calls.” 

2 
Upper Basin Storage (as of June 12, 2023) 

3 

Reservoir 

Percent 

Current 

Live 

Storage 

Current 

Live 

Storage 

(maf) 

Live 

Storage 

Capacity 

(maf) 

Elevation 

(feet) 

Fontenelle 90 0.30 0.33 6,501.65 

Flaming 

Gorge 82 3.01 3.67 6,022.81 

Blue Mesa 84 0.69 0.83 7,504.21 

Navajo 79 1.31 1.65 6,061.06 

Lake Powell 37 8.72 23.31 3,572.61 

UC System 

Storage 47 14.15 29.93 

Total System 

Storage 42 24.46 58.48 
June Month and May WY Precipitation 

4 

Month to Date Precipitation WY Precipitation 
Climate Prediction Center Short-Term 

Precipitation Forecast 

5 
Upper Colorado SWE and Observed Inflows 

Available online at: https://waterwatch.usgs.gov/index.php?id=wwdur_cumrunoff 

6 
 

 

Most Probable May Forecast

Water Year 2023 

April – July 2023 Water Year 2023 

Forecasted Unregulated Inflow Unregulated Inflow Forecast 

as of June 6, 2023 as of June 6, 2023 

Reservoir Inflow 

(kaf) 

Percent 

of Avg1 

Fontenelle 830 113 

Flaming Gorge 1,280 132 

Blue Mesa 845 133 

Navajo 1,010 160 

Powell 10,700 167 

Reservoir Inflow 

(kaf) 

Percent 

of Avg1 

Fontenelle 1,125 105 

Flaming Gorge 1,628 115 

Blue Mesa 1,095 121 

Navajo 1,251 137 

Powell 13,845 144 

1

Averages are based on the 1991 through 2020 period of record. 

7 
8 
Upper Colorado Basin 

Hydrology and Operations 

Projections Based on April 

and May 2023 24-Month 

Study 

9 
 

 

 

 

 

 

 

 

 

Upper Basin Reservoir Operations 

in Water Year 2023 

• Lake Powell will be operated consistent with the 2007 Interim Guidelines, the Upper Basin Drought Response 

Operations Agreement and Upper Basin Records of Decision 

• Lake Powell’s projected end of calendar year (CY) 2022 “tier determination” elevation in the August 2022 24-

Month Study determined Lake Powell’s operating tier in water year (WY) 2023 

• Lake Powell will operate in the Lower Elevation Balancing Tier where Lake Powell and Lake Mead will balance contents with Glen 

Canyon Dam release volumes no less than 7.0 maf and no more than 9.5 maf 

• Consistent with the provisions of the 2007 Interim Guidelines, and to preserve the benefits to Glen Canyon Dam 

facilities from 2022 Operations into 2023 and 2024, Reclamation will consult with the Basin States on monthly and 

annual operations. Reclamation will also ensure all appropriate consultation with Basin Tribes, the Republic of 

Mexico, other federal agencies, water users and non-governmental organizations with respect to implementation 

of these monthly and annual operations. 

• The Glen Canyon Dam annual release was initially set to 7.00 maf 

• In April 2023, Reclamation evaluated hydrologic conditions and determined balancing releases are appropriate under the conditions 

established in the 2007 Interim Guidelines 

• Balancing releases will be limited (with a minimum of 7.00 maf) to protect Lake Powell from declining below elevation 3,525 feet at 

the end of December 2023. Lake Powell will release between 7.0 MAF and 9.5 MAF in WY 2023 

• Reclamation has removed the operational neutrality of the 0.480 maf that was retained in Lake Powell under the May 2022 action, 

10 such that balancing releases are based on the physical storage of Lake Powell and Lake Mead 
 

 

Most Probable May Forecast

Water Year 2023 

April – July 2023 Water Year 2023 

Forecasted Unregulated Inflow Unregulated Inflow Forecast 

as of May 4, 2023 as of May 4, 2023 

Reservoir Inflow 

(kaf) 

Percent 

of Avg1 

Fontenelle 830 113 

Flaming Gorge 1,300 135 

Blue Mesa 830 131 

Navajo 1,010 160 

Powell 11,000 172 

Reservoir Inflow 

(kaf) 

Percent 

of Avg1 

Fontenelle 1,135 106 

Flaming Gorge 1,658 118 

Blue Mesa 1,083 120 

Navajo 1,260 138 

Powell 14,170 148 

1

Averages are based on the 1991 through 2020 period of record. 

11 
12 
13 
 

 

 

 

 

 

Reclamation Operational Modeling

Model Comparison 

Colorado River Mid-term Modeling System (CRMMS) 

24 CRSS -Month Study Mode 

(Manual Mode) 

Ensemble Mode 

(Rule-based Mode) 

Primary Use 

AOP tier determinations and 

projections of current 

conditions 

Risk-based operational planning 

and analysis 

Long-term planning, comparison of 

alternatives 

Simulated Reservoir 

Operations Operations input manually Rule-driven operations 

Probabilistic or 

Deterministic 

Deterministic – single 

hydrologic trace 

Deterministic OR 

Probabilistic 30 (or more) 

hydrologic traces 

Probabilistic – 100+ traces 

Time Horizon (years) 1 - 2 1 - 5 1 - 50 

Upper Basin Inflow Unregulated forecast, 1 trace Unregulated ESP forecast, 30 traces Natural flow; historical, paleo, or 

climate change hydrology 

Upper Basin Demands Implicit, in unregulated inflow forecast Explicit, 2016 UCRC assumptions 

Lower Basin Demands Official approved or operational Developed with LB users 

14 
Most Probable End of CY 2023 Projection: 

3,573.20 feet (36% full) 

Min/Max Range: 3,565.83 to 3,602.99 feet 

Most Probable End of CY 2024 Projection: 

3,585.98 feet (40% full) 

Min/Max Range: 3,552.33 to 3,627.09 feet 

15 
 

 

Most Probable End of CY 2023 Projection: 

1,067.32 feet (25% full) 

Min/Max Range: 1,061.32 to 1,075.31 feet 

Most Probable End of CY 2024 Projection: 

1,057.25 feet (21% full) 

Min/Max Range: 1042.80 to 1,077.74 feet 

16 
Water Quality 

17 



Questions? 

21