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July 24-Month Study

Date: July 17th 2023

From: Water Resources Group, Salt Lake City

To: All Colorado River Annual Operating Plan (AOP) Recipients

Current Reservoir Status

June Inflow

(unregulated)

(acre-feet)

% (percent) July 16 Midnight

Elevation (feet)

July 16, Midnight

Reservoir Storage

(acre-feet)

Fontenelle 412,200 134 6,501.88 302,300

Flaming Gorge 573,900 147 6,031.49 3,322,900

Blue Mesa 312,300 125 7,511.34 755,200

Navajo 248,800 131 6,059.28 1,283,400

Powell 3,646,000 149 3,584.02 9,619,100

Expected Operations

The operation of Lake Powell and Lake Mead in the July 2023 24-Month Study is pursuant to the 

December 2007 Record of Decision on Colorado River Interim Guidelines for Lower Basin Shortages and 

the Coordinated Operations of Lake Powell and Lake Mead (Interim Guidelines) and reflects the 2023 

Annual Operating Plan (AOP). Pursuant to the Interim Guidelines, the August 2022 24-Month Study 

projections of the January 1, 2023, system storage and reservoir water surface elevations set the 

operational tier for the coordinated operation of Lake Powell and Lake Mead during 2023. 

The August 2022 24-Month Study projected the January 1, 2023 Lake Powell elevation to be less than 

3,525 feet. Consistent with Section 6.D.1 of the Interim Guidelines, Lake Powell’s operation in Water Year 

(WY) 2023 is governed by the Lower Elevation Balancing Tier with an initial projected water year release 

volume of 7.00 million acre-feet (maf). Based on hydrologic conditions in April 2023, in which the most 

probable inflow into Lake Powell was projected to be 11.30 maf (177%) during the 2023 April-July runoff 

period, Reclamation determined that conditions are sufficient to release up to 9.50 maf from Lake Powell 

in WY 2023 consistent with Section 6.D.1 of the Interim Guidelines, but could be as low as 7.00 maf 

consistent with the Interim Guidelines and to protect Lake Powell from declining below elevation 3,525 

feet at the end of December 2023. In addition, Reclamation has removed the operational neutrality of the 

0.480 maf that was retained in Lake Powell under the May 2022 action, such that balancing releases are 

based on the projected end of water year physical contents of Lake Powell and Lake Mead. Further, Lower 

Basin projections for Lake Mead take into consideration updated water orders to reflect additional 

conservation efforts and new completed system conservation agreements under the Lower Colorado River 

Basin System Conservation and Efficiency Program (LC Conservation Program). 

Consistent with this operating approach and based on the most probable inflow forecast, the July 2023 

24-Month Study projects a balancing release of 9.04 maf from Lake Powell in WY 2023; however, the 

actual release in WY 2023 will range between 7.00 and 9.50 maf and will depend on actual hydrology and 

reservoir conditions at Lake Powell and Lake Mead during the remainder of the water year. The projected 

release from Lake Powell in WY 2023 will be updated each month throughout the remainder of the water 
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year. The modeling approach for 2024 and beyond will be consistent with the Interim Guidelines, based 

on projected physical elevations at Lake Powell and Lake Mead, and assume the 0.480 maf retained in 

Lake Powell under the May 2022 action was released as part of the WY 2023 balancing release only if the 

release volume is 7.48 maf or greater. 

The 2022 Drought Response Operations Agreement (DROA) Plan for May 2022 through April 2023 was 

amended to suspend 2022 DROA Plan releases as of March 7, 2023. A total DROA release of 

approximately 463 thousand acre-feet (kaf) occurred under the 2022 DROA Plan. Reclamation will attempt 

to maximize DROA recovery in the Upper Initial Units in WY 2023 and through April 2024. Reclamation 

will provide monthly DROA accounting, including DROA releases and recovery, which can be found online 

at: https://www.usbr.gov/dcp/DROSummarySheet.pdf.

In May of 2023, the DROA Parties agreed to the 2023 DROA Plan. The 2023 DROA Plan does not include 

any DROA releases, but rather provides for recovery of prior DROA releases from the units upstream of 

Powell. 

Reclamation will continue to carefully monitor hydrologic and operational conditions and assess the need 

for additional responsive actions and/or changes to operations. Reclamation will continue to consult with 

the Basin States, Basin Tribes, Mexico, and other partners on Colorado River operations to consider and 

determine whether additional measures should be taken to further enhance the preservation of these 

benefits, as well as recovery protocols, including those of future protective measures for both Lakes 

Powell and Mead. 

The August 2022 24-Month Study projected the January 1, 2023 Lake Mead elevation, determined as if 

the 0.480 maf had been delivered to Lake Mead in WY 2022, to be below 1,050 feet and above 1,045 feet. 

Consistent with Section 2.D.1 of the Interim Guidelines, a Shortage Condition consistent with Section 

2.D.1.b will govern the operation of Lake Mead for Calendar Year (CY) 2023. In addition, Section III.B of 

Exhibit 1 to the Lower Basin Drought Contingency Plan (DCP) Agreement will govern the operation of 

Lake Mead for CY 2023. Efforts to conserve additional water in Lake Mead under a 2021 Lower Basin 

Memorandum of Understanding (MOU) to facilitate near-term actions to maintain the water surface 

elevation of Lake Mead and the LC Conservation Program will also take place in CY 2023.

Current runoff projections into Lake Powell are provided by the National Weather Service’s Colorado Basin 

River Forecast Center. The observed unregulated inflow into Lake Powell for the month of June was 3.65

maf or 149% of the 30-year average from 1991 to 2020. The July 2023 unregulated inflow forecast for 

Lake Powell is 1.24 maf or 128% of the 30-year average. The 2023 April through July unregulated inflow 

forecast is 10.80 maf or 169% of average.

The 2023 AOP is available online at:

https://www.usbr.gov/uc/water/rsvrs/ops/aop/AOP23.pdf.

The Interim Guidelines are available online at:

https://www.usbr.gov/lc/region/programs/strategies/RecordofDecision.pdf. 

The Colorado River DCPs are available online at:

https://www.usbr.gov/dcp/finaldocs.html.

The 2021 Lower Basin MOU is available online at: 

https://www.usbr.gov/lc/region/g4000/2021_MOU.pdf.

The Upper Basin DROA is online at:

https://www.usbr.gov/dcp/droa.html.
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The Upper Basin Hydrology Summary is available online at:

https://www.usbr.gov/uc/water/crsp/studies/24Month_07_ucb.pdf. 

Information on the LC Conservation Program is available online at: 

https://www.usbr.gov/lc/LCBConservation.html.

Fontenelle Reservoir

As of July 07, 2023, the Fontenelle Reservoir pool elevation is 6499.92 feet, which amounts to 86 percent 

of live storage capacity. Inflows for the month of June totaled approximately 412,157 acre-feet (af) or 

134%.

June inflow to Fontenelle was significantly higher than forecasted. The spring runoff has been 

unpredictable due to unsettled weather in the region throughout much of May and June. Release rates 

will ramp down during the beginning of July to approximately 1,400 cfs, pending hydrology. Release rates

may need to increase after the ramp down if unpredictable weather patterns persist in July. 

The July final forecast for unregulated inflows into Fontenelle for the next three months projects near 

average conditions. July, August, and September Most Probable inflow volumes amount to 155,000 af 

(92%), 60,000 af (92%), and 45,000 af (112%), respectively.

The next Fontenelle Working Group meeting is scheduled for August 24, 2023 at 10:00 a.m at Seedskadee 

National Wildlife Refuge, WY. Details on the meeting will be provided as we get closer to the meeting 

date. Prior Fontenelle Working Group meeting minutes are available online on USBR’s website at 

https://www.usbr.gov/uc/water/crsp/wg/ft/ftcurrnt.html. The Fontenelle Working Group is an open public 

forum for information exchange between Reclamation and other parties associated with the operation of 

Fontenelle Reservoir.

Flaming Gorge

As of July 11, 2023 (end of day), Flaming Gorge Reservoir pool elevation is 6031.37 feet, which amounts to 

90 percent of live storage capacity. Unregulated inflow volume for the month of June is approximately 

574,000 acre-feet (af), which is 147% June unregulated inflow volume. Current average daily releases are 

approximately 900 cfs. The Colorado pikeminnow experiment is anticipated to be initiated in mid-July 

and releases will be made, pending the Yampa flow, to achieve greater than 2,200 cfs in Reach 2. 

After much consideration, the Flaming Gorge Technical Working Group representatives, Colorado River 

Recovery Program, and subject matter experts agreed that the smallmouth bass spike flow experiment will 

not be recommended this operational year. This is due to potential negative impacts to the endangered 

Colorado pikeminnow.

The July unregulated inflows into Flaming Gorge for the next three months projects near average. July, 

August, and September forecasted unregulated inflow volumes amount to 181,000 af (89%), 70,000 af 

(98%), and 50,000 af (109%), respectively. 

Reclamation is planning to hold Flaming Gorge Working Group meetings on August 23, 2023, at 10:00 am 

in Vernal (and Teams virtual meeting) at the Utah Division of Wildlife Resources Northeastern Region 318 

N. Vernal Ave., Vernal, Utah. The Flaming Gorge Working Group is an open public forum for information 

exchange between Reclamation and the stakeholders of Flaming Gorge Dam. The public is encouraged to 
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attend and comment on the operations and plans presented by Reclamation at these meetings. Meeting 

notes from past Working Group meetings are posted on the Working Group webpage. For more 

information on this group and these meetings please contact Alex Pivarnik at (385) 475 – 8329.

Aspinall Unit Reservoirs

As of July 9, 2023, releases from Crystal Dam are approximately 1,875 cfs. Flows of the Gunnison River in 

the Black Canyon are being maintained at about 1,040 cfs while the Gunnison Tunnel is diverting 850 cfs. 

Flows in the Whitewater Reach of the Gunnison River are about 2,500 cfs.

The unregulated inflow volume in June to Blue Mesa was 312,300 af (125%). Unregulated Inflow volumes 

forecasted for Blue Mesa for the next three months (July, August and September) are projected to be: 

129,000 af (119%), 63,000 af (111%) and 40,000 af (114%), respectively. The July 24-Month Study will be 

reflective of these new forecasted inflows.

The forecasted 2023 water year unregulated inflow volume to Blue Mesa is projected to be 1,099,000 af 

(122%). The water supply period (April-July) for 2023, which is now coming close to the end, is projected 

to be 845,000 af of unregulated inflow (133%).

Blue Mesa elevation has increased dramatically over the past 3 months. On April 9, 2023 the elevation of 

Blue Mesa was 7444.46 feet above sea level and Blue Mesa was 36.3% full. Now, on July 9, 2023, the 

elevation of Blue Mesa is 7510.97 feet above sea level and Blue Mesa is now 98% full. By the end of water 

year 2023 (September 30, 2023) Blue Mesa elevation is projected to be approximately 7,503.6 feet above 

sea level with about 688,500 acre-feet of storage which will be 83 percent of capacity.

The Aspinall Unit Operations Group is an open public forum for information exchange between 

Reclamation and the stakeholders of the Aspinall Unit. The public is encouraged to attend and comments 

on the operations and plans presented by Reclamation at these meetings. Meeting notes from past 

working Group meetings are posted on the Operations Group webpage. For more information on this 

group and these meetings please contact Erik Knight in the Grand Junction Area Office at (970) 248-0629.

The next Operations Group meeting will be held August 24, 2023 at 1:00 p.m., in person at the Elk Creek 

Visitor Center at Blue Mesa Reservoir. This will be an in-person meeting with an option for remote 

participation. Contact Erik Knight in the Grand Junction Area Office at (970) 248-0629 to get more 

information regarding this Operation Group meeting.
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Navajo Reservoir

On July 5th, the daily average release rate from Navajo Dam was 500 cfs while reservoir inflow was 

averaging 1,200 cfs. The water surface elevation was 6060.01 feet above sea level. At this elevation the live 

storage is 1.29 maf (78 percent of live storage capacity) and the active storage is 670 maf (65 percent of 

active storage capacity). An average of 755 cfs is currently being diverted to Cutter Reservoir for the 

Navajo Indian Irrigation Project (NIIP). Approximately 360 cfs is being diverted to the San Juan-Chama 

Project (SJC) above Navajo Reservoir.

Releases from Navajo Dam are made for authorized purposes of the Navajo Unit and are pursuant to the 

Record of Decision for the Navajo Reservoir Operations. Releases target the San Juan River Recovery 

Implementation Program's (SJRIP) recommended downstream baseflow range of 500 cfs to 1,000 cfs 

through the critical habitat reach of the San Juan River (Farmington, NM to Lake Powell).

Preliminary modified unregulated inflow (MUI) into Navajo in June was 249 kaf, which was 131%for the 

month. The release averaged 2,820 cfs and totaled 168 kaf, which was 138%for the month. The total 

April-July modified unregulated inflow observed so far through July 5th is 998 kaf

The most probable MUI forecast for July, August, and September, is 553 kaf (110%), 25 kaf (76%), and 25 

kaf (72%), respectively.

The official April-July forecasts are as follows:

MIN: 1025 kaf (163%, an increase of 80 kaf since the June Forecast)

MOST: 1,035 kaf (165%, an increase of 25 kaf since the May Forecast)

MAX: 1,060 kaf (169%, a decrease of 50 kaf since the June Forecast)

As per the Reclamation Record of Decision for Navajo Dam (2006), a spring peak release was conducted in 

May and June of 2023. The release peaked at 4,600 cfs and achieved three of the four SJRIP flow goals.

Reclamation conducts Public Operations Meetings three times per year to gather input for determining 

upcoming operations for Navajo Reservoir. Input from individuals, organizations, and agencies along with 

other factors such as weather, water rights, endangered species requirements, flood control, hydro power, 

recreation, fish and wildlife management, and reservoir levels, will be considered in the development of 

these reservoir operation plans. In addition, the meetings are used to coordinate activities and exchange 

information among agencies, water users, and other interested parties concerning the San Juan River and 

Navajo Reservoir. The next meeting will be held on Tuesday, August 22nd at 1:00 PM. This meeting is 

open to the public, and will be held at the Farmington Civic Center, 200 West Arrington, in Farmington, 

New Mexico (subject to change based on guidance at the time). The meeting will also have a virtual 

option.

Glen Canyon Dam / Lake Powell

Current Status

The August 2022 24-Month Study projected the January 1, 2023 Lake Powell elevation to be less than 

3,525 feet. Consistent with Section 6.D.1 of the Interim Guidelines, Lake Powell’s operation in WY 2023 is 

governed by the Lower Elevation Balancing Tier with an initial projected WY release volume of 7.00 million 
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acre-feet (maf). Based on hydrologic conditions as of April 2023, in which the most probable inflow into 

Lake Powell is projected to be 11.30 maf (177 percent of average) during the 2023 April-July runoff 

period, Reclamation determined that conditions are sufficient to release up to 9.50 maf from Lake Powell 

in WY 2023 consistent with Section 6.D.1 of the Interim Guidelines, but could be as low as 7.00 maf 

consistent with the Interim Guidelines and to protect Lake Powell from declining below elevation 3,525 

feet at the end of December 2023. In addition, Reclamation has removed the operational neutrality of the 

0.480 maf that was retained in Lake Powell under the May 2022 action, such that balancing releases are 

based on physical elevations of Lake Powell and Lake Mead. 

Consistent with this operating approach and based on the most probable inflow forecast, the July 2023 

24-Month Study projects a balancing release of 9.04 maf from Lake Powell in WY 2023; however, the 

actual release in WY 2023 will range between 7.00 and 9.50 maf and will depend on actual hydrology and 

reservoir conditions at Lake Powell and Lake Mead during the remainder of the water year. The projected 

release from Lake Powell in WY 2023 will be updated each month throughout the remainder of the water 

year. The modeling approach for 2024 and beyond will be consistent with the Interim Guidelines, based 

on projected physical elevations at Lake Powell and Lake Mead, and assume the 0.480 maf retained in 

Lake Powell under the May 2022 action was released as part of the WY 2023 balancing release only if the 

release volume is 7.48 maf or greater.

Reclamation will continue to carefully monitor hydrologic and operational conditions and assess the need 

for additional responsive actions and/or changes to operations. Reclamation will continue to consult with 

the Basin States, Basin Tribes, Mexico, and other partners on Colorado River operations to consider and 

determine whether additional measures should be taken to further enhance the preservation of these 

benefits, as well as recovery protocols, including those of future protective measures for both Lakes 

Powell and Mead.

The unregulated inflow volume to Lake Powell during June was 3,646 thousand acre-feet (kaf) (149 

percent of average). The release volume from Glen Canyon Dam in June was 1,064 kaf. The end of June 

elevation and storage of Lake Powell were 3,583.47 feet (117 feet from full pool) and 9.57 million acre-feet 

(maf) (41 percent of live capacity), respectively.

Current Operations

Hourly releases during July 2023 will fluctuate from a low of approximately 16,177 cfs during the early 

morning hours to a high of 19,570 cfs during the afternoon and evening hours. The July release volume of 

1,150,000 acre-feet. The anticipated monthly release volume for August is anticipated to be 1,020,510

acre-feet and will be confirmed toward the end of July.

In addition to daily scheduled fluctuations for power generation, the instantaneous releases from Glen 

Canyon Dam may also fluctuate to provide 40 megawatts (MW) of system regulation. These 

instantaneous release adjustments stabilize the electrical generation and transmission system and 

translate to a range of about 1,300 cfs above or below the hourly scheduled release rate. Under normal 

system conditions, fluctuations for regulation are typically short lived and generally balance out over the 

hour with minimal or no noticeable impacts on downstream river flow conditions.

Releases from Glen Canyon Dam can also fluctuate beyond scheduled releases when called upon to 

respond to unscheduled power outages or power system emergencies. Depending on the severity of the 

system emergency, the response from Glen Canyon Dam can be significant, within the full range of the 
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operating capacity of the power plant for as long as is necessary to maintain balance in the transmission 

system. Glen Canyon Dam currently maintains 30 MW (approximately 1,300 cfs) of generation capacity in 

reserve in order to respond to a system emergency even when generation rates are already high. System 

emergencies occur infrequently and typically require small responses from Glen Canyon Dam. However, 

these responses can have a noticeable impact on the river downstream of Glen Canyon Dam.

Inflow Forecasts and Model Projections

The forecast for water year 2023 unregulated inflow to Lake Powell, issued on July 3, 2023, by the 

Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow 

volume in water year 2023 will be 14.00 maf (146 percent of average). 

In addition to the July 2023 24-Month Study based on the Most Probable inflow scenario, and in 

accordance with the Upper Basin Drought Response Operations Agreement (DROA), Reclamation has 

conducted model runs in July to determine a possible range of reservoir elevations. The July 2023 24-

Month Study probable most and minimum probable inflow scenarios and the April maximum probable 

inflow scenario were used to determine the range of probable outcomes. The probable minimum and 

probable maximum model runs are conducted simultaneously in January, April, August, and October, or 

when necessary to incorporate changing conditions. The probable minimum inflow scenario reflects a dry 

hydrologic condition which statistically would be exceeded 90 percent of the time. The most probable 

inflow scenario reflects a median hydrologic condition which statistically would be exceeded 50 percent of 

the time. The probable maximum inflow scenario reflects a wet hydrologic condition which statistically 

would be exceeded 10 percent of the time. There is approximately an 80 percent probability that a future 

elevation will fall inside the range of the minimum and maximum inflow scenarios. Additionally, there are 

possible inflow scenarios that would result in reservoir elevations falling outside the ranges indicated in 

these reports. 

The DROA coordination will continue until either (i) the minimum probable projected elevation remains 

above 3,525 feet for 24 months or (ii) the process moves to the next step when the most probable 

projected elevation indicates Powell elevations below 3,525 feet and a Drought Response Operations Plan 

is developed. This 2022 Plan is described above and available for review here: 

https://www.usbr.gov/dcp/droa.html.

The July forecast for water year 2023 ranges from a minimum probable of 14.00 maf (146 percent of 

average) to a forecasted maximum probable of 16.31 maf (170 percent of average) with the most 

probable forecast for water year 2023 of 14.00 maf (146 percent of average). There is a 10 percent chance 

that inflows could be higher than the current maximum probable forecast and a 10 percent chance that 

inflows could be lower than the minimum probable forecast.

Based on the current forecast for water year 2023 of 14.00 maf unregulated, the July 24-Month Study 

projects Lake Powell elevation will end water year 2023 near 3575.32 feet with approximately 8.93 maf in 

storage (38 percent of capacity). Note that projections of elevation and storage for water year 2023 have 

significant uncertainty at this point in the season. Projections of end of water year 2023 elevation using 

the July minimum and April maximum inflow forecast results are 3,574.51 feet and 3,606.71 feet,

respectively. The annual release volume from Lake Powell during water year 2023 will be 9.04 maf under 

the Lower Elevation Balancing Tier and will balance the contents between Powell and Mead with annual 

release volumes from Glen Canyon Dam between 7.00 maf and 9.50 maf as determined under Section 

6.D.1 and 7.D of the Interim Guidelines as determined by the Department of the Interior as described 

above.
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Upper Colorado River Basin Hydrology 

Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. The 30-

year average was updated in October 2022 from 1981 through 2010 to 1991 through 2020. Shifting the 

period of record decreased the average unregulated inflow 1.20 maf. The period 2000-2022 is the lowest 

23-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.29

maf, or 93 percent of the 30-year average (1991-2020). (For comparison, the 1991-2020 total water year 

average is 9.60 maf.) The unregulated inflow during the 2000-2022 period has ranged from a low of 2.64 

maf (28 percent of average) in water year 2002 to a high of 15.97 maf (166 percent of average) in water 

year 2011. In water year 2021 unregulated inflow volume to Lake Powell was 3.50 maf (36 percent of 

average), the second driest year on record above 2002. Under the current most probable forecast, the 

total water year 2023 unregulated inflow to Lake Powell is projected to be 14.00 maf (146 percent of 

average).

At the beginning of water year 2023, total system storage in the Colorado River Basin was 19.54 maf (33 

percent of 58.48 maf total system capacity). This is a decrease of 3.33 maf over the total storage at the 

beginning of water year 2022 when total system storage was 22.87 maf (39 percent of capacity). Since the 

beginning of water year 2000, total Colorado Basin storage has experienced year to year increases and 

decreases in response to wet and dry hydrology, ranging from a high of 94 percent of capacity at the 

beginning of 2000 to the now current level of 33 percent of capacity at the beginning of water year 2023. 

Based on current inflow forecasts, the current projected end of water year 2023 total Colorado Basin 

reservoir storage is approximately 25.47 maf (44 percent of total system capacity). The actual end of water 

year 2023 system storage may vary from this projection, primarily due to uncertainty regarding this 

season’s runoff and reservoir inflow.