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June 24-Month Study

Date: June 15th 2023 

From: Water Resources Group, Salt Lake City

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

Current Reservoir Status

April Inflow

(unregulated) 

(acre-feet)

Percent of

Average

(percent)

June 14 Midnight

Elevation (feet)

June 14, Midnight

Reservoir Storage

(acre-feet)

Fontenelle 322,500 184 6,502.12 304,069 

Flaming Gorge 521,300 209 6,023.39 3,026,653 

Blue Mesa 327,400 163 7,506.01 708,857 

Navajo 488,200 200 6,060.64 1,300,641 

Powell 4,520,200 218 3,574.51 8,862,532 

Expected Operations

The operation of Lake Powell and Lake Mead in the June 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 percent of average) during the 2023 

April-July runoff period, Reclamation has 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; new completed system conservation agreements under the 

Lower Colorado River Basin System Conservation and Efficiency Program (LC Conservation Program); and 

updated Lower Basin tributary inflow projections (reflecting current conditions) above Lake Mead and for 

the Gila River. 

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

24-Month Study projects a balancing release of 9.16 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 
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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. 

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 and are as follows. The observed unregulated inflow into Lake Powell for the month 

of May was 4.52 maf or 218 % of the 30-year average from 1991 to 2020. The June 2023 unregulated 

inflow forecast for Lake Powell is 3.70 maf or 151 % of the 30-year average. The 2023 April through July 

unregulated inflow forecast is 10.70 maf or 167% 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. 
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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. 

The Upper Basin Hydrology Summary is available online at:

https://www.usbr.gov/uc/water/crsp/studies/24Month_06_ucb.pdf. 

Information on the LC Conservation Program is available online at: 

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

Fontenelle Reservoir 

As of June 12, 2023, the Fontenelle Reservoir pool elevation is 6501.65 feet, which amounts to 90 percent 

of live storage capacity. Inflows for the month of May totaled approximately 322,542 acre-feet (af) or 184 

percent of average. 

May 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. Release rates are 

expected to remain high throughout the remainder of June and into early July, pending hydrology. 

The June final forecast for unregulated inflows into Fontenelle for the next three months projects below 

average conditions. June, July, and August Most Probable inflow volumes amount to 310,000 af (101 

percent of average), 122,000 af (72 percent of average), and 60,000 af (92 percent of average), 

respectively.

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

National Wildlife Refuge, WY, tentatively. 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 June 11, 2023 (end of day), Flaming Gorge Reservoir pool elevation is 6022.73 feet, which amounts 

to 82 percent of live storage capacity. Unregulated inflow volume for the month of May is approximately 

521,000 acre-feet (af), which is 209 percent of the average May unregulated inflow volume. Releases are 

currently ramping down at approximately 2,000 cfs per day starting on June 11 from approximately 8,550 

to 900 cfs on June 16.

The Spring Release -- The Larval Trigger Study Plan (LTSP) to assist in the recovery of the Razorback 

sucker (protected under the Endangered Species Act) will be completed by June 15, 2023. Larval 

razorback suckers were identified in Reach 2 of the Green River on 5/31/2023. The experiment releases 

started on June 6. Partial bypass started on June 6, 2023, with full bypass starting on June 8, 2023. Down 

ramping started on June 12, 2023 at approximately 2,000 cfs per day. In reach 2 (measured at the Jensen 

gage), as part of this spring operation, as of June 12, 5 days was greater than 14,000 cfs and one day was 

greater than 18,600 cfs. 
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The smallmouth bass (SMB) flow spike is the next operational plan to occur this summer and is contingent 

on a few factors. The timing of the SMB flow is depending on weather, temperature and is based on a 

biological trigger. A smallmouth bass (SMB) flow spike release may occur (optional due to hydrology and 

biological trigger) in late June to early July and will include the use of the selective withdrawal structure 

(SWS) to influence temperature. The SMB flow spike release will consist of a one day ramp up to full 

power plant capacity (4,600 cfs), three consecutive days at power plant capacity, and a ramp down at the 

rate of 2,000 cfs/day. 

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

July, and August forecasted unregulated inflow volumes amount to 430,000 af (110 percent of average), 

141,000 af (70 percent of average), and 70,000 af (98 percent of average), respectively. The June water 

supply forecast of the April through July unregulated inflow volume into Flaming Gorge Reservoir is 

1,280,000 acre-feet (133% of average). Due to the May official forecast Upper Green April – July forecast 

being at a 31% exceedance value, spring operations will use an average hydrologic classification 

operation. 

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 

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 June 11, 2023, releases from Crystal Dam are approximately 2,000 cfs. Flows of the Gunnison River 

in the Black Canyon are being maintained at about 1,040 cfs while the Gunnison Tunnel is diverting 1,050 

cfs. Flows in the Whitewater Reach of the Gunnison River are about 6,400 cfs.

The unregulated inflow volume in May to Blue Mesa was 327,400 af (163 percent of average). Unregulated 

Inflow volumes forecasted for Blue Mesa for the next three months (June, July and August) are projected 

to be: 326,000 af (130 percent of average), 115,000 af (106 percent of average) and 60,000 af (105 percent 

of average), respectively. The June 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 1,095,000 af 

(121 percent of average). The water supply period (April-July) for 2023 is forecasted to be 845,000 af of 

unregulated inflow (133 percent of average).

Blue Mesa elevation has increased dramatically over the past month and as of June 11, 2023, was 7,503.21 

feet above sea level corresponding to a live storage of 685,050 acre-feet which is 83 percent of capacity. 

By the end of water year 2023 (September 30, 2023) Blue Mesa elevation is projected to be approximately 

7,502 feet with about 675,000 acre-feet of storage which will be 82 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 
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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.

Navajo Reservoir

On June 12th, the daily average release rate from Navajo Dam was 4,300 cfs while reservoir inflow was 

averaging 1,520 cfs. The water surface elevation was 6061.06 feet above sea level. At this elevation the live 

storage is 1.31 maf (79 percent of live storage capacity) and the active storage is 1.03 maf (66 percent of 

active storage capacity). An average of 520 cfs is currently being diverted to Cutter Reservoir for the 

Navajo Indian Irrigation Project (NIIP). Approximately 870 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 May was 488 kaf, which was 201 percent of 

average for the month. The release averaged 2,080 cfs and totaled 128 kaf, which was 120 percent of 

average for the month. The total April-July modified unregulated inflow observed so far through June 

12th is 864 kaf

The most probable MUI forecast for June, July, and August, is 237 kaf (125 percent of average), 40 kaf (83 

percent of average), and 21 kaf (64 percent of average), respectively.

The official April-July forecasts are as follows:

MIN: 945 kaf (150 percent of average, an increase of 40 kaf since the May Forecast. There is 81 kaf 

forecast modified unregulated inflow remaining through the end of July)

MOST: 1,010 kaf (161 percent of average, no change since the May Forecast. There is 146 kaf forecast 

modified unregulated inflow remaining through the end of July)

MAX: 1,110 kaf (177 percent of average, a decrease of 50 kaf since the May Forecast. There is 236 kaf 

forecast modified unregulated inflow remaining through the end of July)

As per the Reclamation Record of Decision for Navajo Dam (2006), a spring peak release is currently 

underway. The release is scheduled to begin ramping down over the next two weeks. The schedule is 

updated at the following link: https://www.usbr.gov/uc/wcao/water/rsvrs/notice/nav_rel.html

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 
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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 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 

has 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 June 2023 

24-Month Study projects a balancing release of 9.16 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 June 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 May was 4,520 kaf (218 percent of average). The 

release volume from Glen Canyon Dam in April was 1,088 kaf. The end of May elevation and storage of 

Lake Powell were 3,561.42 feet (138 feet from full pool) and 7.89 million acre-feet (maf) (33 percent of live 

capacity), respectively. 

Current Operations

Hourly releases during June 2023 will fluctuate from a low of approximately 13,200 cfs during the early 

morning hours to a high of 19,500 cfs during the afternoon and evening hours. The June release volume 

of 1,064,000 acre-feet. The anticipated monthly release volume for July is anticipated to be 1,150,000 

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

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 June 6, 2023, by the 

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

volume in water year 2023 will be 13.85 maf (144 percent of average). 

In addition to the June 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 June to determine a possible range of reservoir elevations. The June 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 June forecast for water year 2023 ranges from a minimum probable of 12.80 maf (133 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 13.85 maf (144 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.
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Based on the current forecast for water year 2023 of 13.85 maf unregulated, the June 24-Month Study 

projects Lake Powell elevation will end water year 2023 near 3575.57 feet with approximately 8.94 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 June minimum and April maximum inflow forecast results are 3,570.48 feet and 3,606.71 feet,

respectively. The annual release volume from Lake Powell during water year 2023 will be 9.16 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.

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 13.85 maf (144 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 25.45 maf (43.5 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.