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April 24-Month Study 

Date: April 12, 2024 

From: River Operations Group, Salt Lake City

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

Current Reservoir Status 

March Inflow

(unregulated)

(acre-feet)

Percent of

Average 

(percent)

April 12 Midnight

Elevation (feet)

April 12, Midnight

Reservoir Storage 

(acre-feet)

Fontenelle 50,400 89 6470.10 112,919

Flaming Gorge 94,400 89 6026.83 3,147,827

Blue Mesa 33,100 88 7484.80 537,720

Navajo 30,700 37 6041.02 1,071,390

Powell 455,200 76 3558.35 7,670,351

Expected Operations 

The operation of Lake Powell and Lake Mead in the April 2024 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 draft 2024 

Annual Operating Plan (AOP). Pursuant to the Interim Guidelines, the August 2023 24-Month Study 

projections of the January 1, 2024, system storage and reservoir water surface elevations set the 

operational tier for the coordinated operation of Lake Powell and Lake Mead during 2024.

The August 2023 24-Month Study projected the January 1, 2024, Lake Powell elevation to be less than 

3,575 feet and at or above 3,525 feet and the Lake Mead elevation to be at or above 1,025 feet. Consistent 

with Section 6.C.1 of the Interim Guidelines the operational tier for Lake Powell in water year (WY) 2024 

will be the Mid-Elevation Release Tier and the water year release volume from Lake Powell will be 7.48 

million acre-feet (maf).

The 2022 Drought Response Operations Agreement (DROA) Plan1 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.

In May of 2023, the DROA Parties agreed to the 2023 DROA Plan which is in effect through April 2024. 

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.

As of February 28, 2024, Reclamation has recovered all DROA releases at Flaming Gorge and Blue Mesa 

Reservoirs. Monthly DROA accounting, including DROA releases and recovery, can be found online at: 

https://www.usbr.gov/ColoradoRiverBasin/documents/dcp/DROA/DROSummarySheet.pdf. 

1 For more information: https://www.usbr.gov/uc/DocLibrary/Plans/20220429-2022DroughtResponseOperationsPlanApprovalMemo-508-DOI.pdf. 
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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 2023 24-Month Study projected the January 1, 2024 Lake Mead elevation to be below 1,075 

feet and above 1,050 feet. Consistent with Section 2.D.1 of the Interim Guidelines, a Shortage Condition 

consistent with Section 2.D.1.a will govern the operation of Lake Mead for calendar year (CY) 2024. In 

addition, Section III.B of Exhibit 1 to the Lower Basin Drought Contingency Plan (DCP) Agreement will also 

govern the operation of Lake Mead for CY 2024. Lower Basin projections for Lake Mead take into 

consideration additional conservation efforts under the LC Conservation Program.

The 2024 operational tier determinations for Lake Powell and Lake Mead will be documented in the 2024 

AOP, which is currently in development.

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 March was 

0.455 maf or 76% of the 30-year average from 1991 to 2020. The April 2024 unregulated inflow forecast

for Lake Powell is 0.700 maf or 78% of the 30-year average. The 2024 April through July unregulated

inflow forecast for Lake Powell is 5.70 maf or 89% of average. The WY 2024 unregulated inflow forecast 

for Lake Powell is 8.39 maf or 87% of average.

The draft 2024 AOP is available online at:

https://www.usbr.gov/lc/region/g4000/AOP2024/AOP24_draft.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/ColoradoRiverBasin/dcp/finaldocs.html. 

The Upper Basin DROA is online at:

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

The Upper Basin Hydrology Summary is available online at:

https://www.usbr.gov/uc/water/crsp/studies/24Month_04_ucb.pdf. 

Information on the LC Conservation Program is available online at:

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

As of April 07, 2024, the Fontenelle Reservoir pool elevation is 6469.56 feet, which amounts to 33 percent 

of live storage capacity. Inflows for the month of March totaled approximately 50,476 af or 89 percent of 

average. 

Fontenelle releases started the month at 600 cfs due to powerplant annual maintenance. Due to changes 

to hydrologic conditions, releases were increased to 800 cfs on April 8, 2024. Releases will be maintained 

at 800 cfs until maintenance is completed. Maintenance is scheduled to be completed on or before April 

26th, 2024. Releases will increase to approx. 1,500 cfs following annual maintenance period and pending 

hydrologic conditions. Releases from the dam will increase throughout spring to meet elevation targets, 

as subject to hydrology.

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

average conditions. April, May, and June Most Probable inflow volumes amount to 80,000 af (95 percent 

of average), 160,000 af (91 percent of average), and 320,000 af (104 percent of average), respectively. 

The next Fontenelle Working Group meeting is April 18, 2024 at 10 AM MDT at the Joint Powers Water 

Board in Green River or via Teams. Please contact Alex Pivarnik (APivarnik@usbr.gov) for a virtual meeting 

invite.

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 Reservoir

As of April 07, 2024 (end of day), Flaming Gorge Reservoir pool elevation is 6026.97 feet, which amounts 

to 86 percent of live storage capacity. Unregulated inflow volume for the month of March is 

approximately 94,500 af, which is 89 percent of the average March unregulated inflow volume. 

Current average daily release is approximately 2,000 cfs. This data is considered the most likely scenario 

given the current forecast, is general, and is subject to changing conditions.

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

May, and June forecasted unregulated inflow volumes 140,000 af (112 percent of average), 250,000 af 

(100 percent of average), and 400,000 af (103 percent of average), respectively.

The April water supply forecast of the April through July unregulated inflow volume into Flaming Gorge 

Reservoir is 960,000 acre-feet (99 percent of average). Current snowpack is 102 percent of median for the 

Upper Green Basin.

Reclamation is planning to hold Flaming Gorge Working Group meetings on March 21, 2024 and April 17, 

2024, at 10:00 am (and Teams virtual meeting). The March meeting will be held on March 21, 2024 at 10 

a.m. at the Utah Division of Wildlife Resources Northeastern Region 318 N. Vernal Ave., Vernal, Utah and 

will be held virtually. The April meeting will be held on April 17, 2024 at 10:00 a.m. at the Uintah 

Conference Center Vernal, Utah (313 E 200 S, Vernal, Utah) and will be held virtually. The Flaming Gorge 
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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 April 8, 2024, releases from Crystal Dam are approximately 1350 cfs. Flows of the Gunnison River in 

the Black Canyon are being maintained at about 520 cfs while the Gunnison Tunnel is diverting about 700 

cfs. Flows in the Whitewater Reach of the Gunnison River are about 1,700 cfs.

The unregulated inflow volume in March to Blue Mesa was 33,100 af (88 percent of average). Unregulated 

Inflow volumes forecasted for Blue Mesa for the next three months (April, May, and June) are projected to 

be: 60,000 af (77 percent of average), 200,000 af (99 percent of average), and 255,000 af (102 percent of 

average), respectively. 

The forecasted 2024 water year unregulated inflow volume to Blue Mesa is projected to be 842,000 af (93 

percent of average). The water supply period (April-July) for 2024 is forecasted currently for an 

unregulated inflow volume of to be 600,000 af of unregulated inflow (94 percent of average).

Under this forecast, operation of Aspinall under the Aspinall Record of Decision (2012) would require a 

spring peak release to provide 10 days of sustained flows in the Gunnison River in the Whitewater reach at 

or above 8,070 cfs. This forecast would also require Aspinall releases to provide a single day peak flow in 

the Black Canyon of 4,492 cfs per the Black Canyon Reserved Water Right Decree. Given this current 

projection of the most probable operating scenario, Blue Mesa is projected to fill to approximately 7,510 

feet by late June – early July with approximately 743,000 af of storage. This is approximately 9 feet from 

full pool elevation (7519.4 feet) with approximately 85,000 af of unfilled storage space in Blue Mesa 

Reservoir. 

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 on April 18, 2024 at 1:00 p.m., in Grand Junction, 

Colorado. 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 April 8th, the daily average release rate from Navajo Dam was 500 cfs while reservoir inflow was 

averaging 561 cfs. The water surface elevation was 6041.23 feet above sea level. At this elevation the live 

storage is 1.07 maf (65 percent of live storage capacity) and the active storage is 0.448 maf (44 percent of 

active storage capacity). Diversions to Cutter Reservoir for the Navajo Indian Irrigation Project (NIIP) and 

the Navajo Gallup Water Supply Project (NGWSP) were 284 cfs. The San Juan-Chama project was diverting 

54 cfs from the basin above Navajo Reservoir.
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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).

Navajo was at 6041.4 ft of pool elevation and 1.07 maf of live storage (0.449 maf of active storage) by the 

end of March, which was 83 percent of average for the end of the month. The release averaged 370 cfs 

and totaled 22.9 kaf, which was 50 percent of average for the month. Preliminary modified unregulated 

inflow (MUI) into Navajo was 30.8 af, which was 38 percent of average for the month. Calculated 

evaporation for the month was 1.4 kaf. NIIP diverted a total of 5.3 kaf. Navajo had a net storage change 

of -3.7 kaf in March.

The most probable MUI forecast for March, April, and May is 42 kaf (51 percent of average), 73 kaf (50 

percent of average), and 190 kaf (78 percent of average), respectively. 

 

The official April-July forecasts are as follows:

The most probable MUI forecast for April, May, and June is 75 kaf (51 percent of average), 195 kaf (80 

percent of average), and 135 kaf (71 percent of average), respectively. 

 

The official April-July forecasts are as follows:

MIN: 320 kaf (51 percent of average, an increase of 75 kaf from the March official forecast)

MOST: 420 kaf (67 percent of average, an increase of 30 kaf from the March official forecast)

MAX: 615 kaf (98 percent of average, a decrease of 35 kaf from the March official forecast)

There are no plans for a spring peak release at Navajo Reservoir based on this forecast. Releases through 

spring are likely to range between 350 cfs and 600 cfs. Storage is expected to peak this spring between 

71 percent and 81 percent of live capacity.

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, April 23rd 2024 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 unregulated inflow volume to Lake Powell during March was 455 kaf (76 percent of average). The 

release volume from Glen Canyon Dam in March was 675 kaf. The end of March elevation and storage of 

Lake Powell were 3,559.02 feet (140 feet from full pool) and 7.72 maf (33 percent of live capacity), 

respectively.
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Current Operations

The August 2023 24-Month study projects the January 1, 2024, Lake Powell elevation to be less than 3,575 

feet and at or above 3,525 feet and the Lake Mead elevation to be at or above 1,025 feet. Consistent with 

Section 6.C.1 of the Interim Guidelines the operational tier for Lake Powell in water year 2024 is the MidElevation Release Tier and the water year release volume from Lake Powell is 7.48 maf. 

April release volume will be 601,000 acre-feet and hourly releases will fluctuate from a low of 

approximately 8,698 cubic feet per second (cfs) during the early morning hours to a high of 13,521 cfs 

during the afternoon and evening hours on the weekdays, with a low of 8,000 cfs during the early 

morning hours to a high of 12,201 cfs during the afternoon and evening hours during the weekends. The 

anticipated monthly release volume for May is anticipated to be 599,000 acre-feet and hourly releases are 

anticipated to fluctuate from a low of approximately 6,841 cubic feet per second (cfs) during the early 

morning hours to a high of 12,232 cfs during the afternoon and evening hours on the weekdays, with a 

low of 5,649 cfs during the early morning hours to a high of 11,040 cfs during the afternoon and evening 

hours during the weekends. The pattern and volume for May will be confirmed at the end of April and is 

anticipated to vary from the current estimated pattern. 

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 2024 unregulated inflow to Lake Powell, issued on April 3, 2024, by the 

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

volume in water year 2024 will be 8.39 maf (87 percent of average). 

In addition to the April 2024 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 April to determine a possible range of reservoir elevations. The April 2024 24-

Month Study probable most, minimum and maximum probable scenarios 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 
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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 current Plan is described above and available for review here: 

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

The April forecast for WY 2024 ranges from a minimum probable of 7.11 maf (74% of average) to a 

forecasted maximum probable of 11.33 maf (118 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 2024 of 8.39 maf unregulated inflow volume, the April 24-

Month Study projects Lake Powell elevation will end calendar year 2024 near 3577.63 feet with 

approximately 9.11 maf in storage (39 percent of capacity). Note that projections of elevation and storage 

for calendar year 2024 have significant uncertainty at this point in the season. Projections of end of 

calendar year 2024 elevation using the April minimum and maximum inflow forecast results are 3,563.79 

feet and 3,602.44 feet, respectively. The annual release volume from Lake Powell during water year 2024 

is 7.48 maf under the Mid-Elevation Release Tier as determined under Section 6.C.1 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 2024 unregulated inflow to Lake Powell is projected to be 8.39 maf (87 percent of 

average).

At the beginning of water year 2024, total system storage in the Colorado River Basin was 25.27 maf (43 

percent of 58.48 maf total system capacity). This is an increase of 5.72 maf over the total storage at the 

beginning of water year 2023 when total system storage was 19.55 maf (33 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 beginning of water year 2023 with 19.55 maf (33 percent of capacity). Based on 

current inflow forecasts, the current projected end of water year 2024 total Colorado Basin reservoir 
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storage is approximately 25.38 maf (43.4 percent of total system capacity). The actual end of water year 

2024 system storage may vary from this projection, primarily due to uncertainty regarding this season’s 

runoff and reservoir inflow.