News Releases

System operations returning to normal post flooding

Missouri River Water Management Division
Published July 4, 2024
A map of the upper Missouri River Basin showing the locations of the six dams on the main stem of the Missouri River at Fort Peck, Montana; Garrison Dam in Riverdale, North Dakota; Oahe Dam in Pierre, South Dakota; Big Bend Dam in Chamberlain, South Dakota; Fort Randall Dam in Pickstown, South Dakota and Gavins Point Dam, near Yankton, South Dakota. An area noted in pink shows where rainfall was 600% of normal on June 21. Also noted are Sioux City, Iowa; Omaha, Nebraska; Nebraska City, Nebraska; and Kansas City, Missouri where navigation flow targets are measured.

A June 21 strong weather system produced excessive rainfall in eastern South Dakota, north central and northeastern Nebraska, and northwestern Iowa. Rainfall totals exceeded 600% of normal over the 24-hour period. Releases were reduced at Fort Randall Dam to an average of 2,000 cfs and Gavins Point to 24,000 cfs.

Two tables the first showing Missouri River Mainstem Reservoir Data with the Pool Elevation at the end of the month and how much the elevation has changed during the month and how much water is in storage at the end of the month compared to the average and how much the amount of water in storage has changed in for the month. 

The second table shows water releases and energy generation in May at each reservoir. There are three columns of data Average releases in 1000 cubic feet per second, volume of releases in acre feet, and how much power was generated from releases at each project. The data is provided in the photo caption.

MISSOURI RIVER MAINSTEM RESERVOIR DATA Pool Elevation (feet above mean sea level) Water in Storage (1,000 acre-feet) On June 30 Change in June On June 30 % of 1967-2023 Average Change in June Fort Peck 2230.2 -1.4 14,014 97 -274 Garrison 1842.2 +4.4 19,245 108 +1,347 Oahe 1603.0 0.0 17,401 98 +50 Big Bend 1420.8 +0.4 1,680 99 +35 Fort Randall 1360.1 +4.7 3,868 116 +427 Gavins Point 1207.0 +1.0 349 90 +22 Total 56,557 102 +1,607 WATER RELEASES AND ENERGY GENERATION FOR JUNE Average Release in 1,000 cfs Releases in 1,000 acre-feet Generation in Million kWh Fort Peck 13.7 813 109 Garrison 21.6 1,287 200 Oahe 22.8 1,355 205 Big Bend 22.7 1,354 72 Fort Randall 19.0 1,128 122 Gavins Point 26.0 1,546 67 Total 775

Significant rainfall led to an above average runoff in the upper Missouri River Basin. June runoff was 6.6 million acre-feet, which is 119% of average and 2.6 MAF higher than forecast.

A strong weather system moved into the basin on June 21 producing excessive rainfall in eastern South Dakota, north central and northeastern Nebraska, and northwestern Iowa. The rainfall totals exceeded 600% of normal over the 24-hour period.

"In response to the rainfall, the releases from Fort Randall and Gavins Point dams were reduced,” said John Remus, chief of the Missouri River Basin Water Management Division. “The lower releases were able to reduce downstream river stages, but they could not completely offset all of the flooding in the Sioux City area.”

Rainfall persisted into the following week causing sustained high inflows both into Gavins Point as well as the river downstream. Releases were reduced at Fort Randall Dam to an average of 2,000 cubic feet per second and Gavins Point to 24,000 cfs. The lowered releases in conjunction with the high inflows caused both reservoir pools to rise, reaching elevation 1360.8 feet at Fort Randall and 1209.6 feet at Gavins Point.

“During that time, some of the outflow from Gavins Point Dam was transferred from the powerhouse to the spillway, allowing us to store more water in Gavins Point Reservoir and maintain the release rate at 24,000 cfs,” added Remus. 

As the inflows into Gavins Point continued to fall and the reservoir level began to decline, the spillway was closed and the release rate from the dam was stepped down to mitigate flood impacts downstream. Releases from Gavins Point Dam reached 13,000 cfs on June 28, and remain at that rate.

"As the river continues to recover from the flood event, we will continue to monitor inflows and pool elevations at Gavins Point, and throughout the Missouri River Mainstem System, and make adjustments as needed," said Remus.

The 2024 calendar year runoff forecast for the upper Missouri River Basin above Sioux City, Iowa is 24.6 MAF, 96% of average and 3.6 MAF higher than last month’s forecast. June runoff in the Gavins Point to Sioux City reach was nearly seven times normal. While the eastern portion of the basin received excessive rainfall, other portions were drier than normal with below average runoff in the Fort Peck, Garrison, and Oahe reaches. Soil moisture at the end of June is near normal in central Montana, below normal in western South Dakota, and above normal in the eastern Dakotas. Currently, 50% of the Basin is experiencing abnormally dry or drought conditions.

System storage on July 1 was 56.6 MAF, 0.5 MAF above the top of the carryover multiple use zone. “Based on the July 1 System storage, flow support for navigation will be maintained at 500 cfs below full-service level,” said Remus. “Per the guidelines in the Master Manual, this will also result in a full navigation flow support season ending December 1 at the mouth of the Missouri River. Gavins Point releases will be adjusted through the month of July to account for the navigation flow support.” Basin and river conditions continue to be monitored and System regulation will be adjusted based on the most up-to-date information. 

Navigation:

Gavins Point Dam releases will be set to provide flow support at an intermediate-service level, 500 cfs lower than full-service flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City). Navigation flow targets may be missed in reaches with no commercial barge traffic. The flow support season length will be a full 8-month season, ending December 1 at the mouth of the Missouri River.

Mountain Snowpack:

Mountain snowpack in the upper Missouri River Basin melted quickly due to warmer-than-normal temperatures during the spring and early summer. By June 25, all the snow had melted in both the reach above Fort Peck Dam and the Fort Peck Dam to Garrison Dam reach. The mountain snowpack peaked in the reach above Fort Peck on April 9 at 73% of average, while the mountain snowpack in the Fort Peck to Garrison reach peaked on April 10 at 82% of average. Mountain snowpack normally peaks near April 17. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.

Fort Peck Flow Test:

Test releases from Fort Peck to assess the potential benefits of alternative management scenarios for the pallid sturgeon began on April 26 and will be completed by Sept. 1. The test includes two higher flow periods, in late April and June, with target flows at Wolf Point, Montana. The first peak in releases was completed in early May with peak flows of 18,000 cfs at Wolf Point, Montana.  Releases were reduced to 10,000 cfs by May 10. The second peak began on June 19 and reached a peak flow of approximately 20,000 cfs on June 26.  Flows are currently declining at a rate of 1,000 cfs per day and should reach an average daily flow of 8,000 cfs around July 7.  The plan is to hold this flow through September 1.  After September 1 operations at Fort Peck will return to normal.

The U.S. Army Corps of Engineers will host weekly virtual meetings during the flow test to update the public on test progress and planned operations. Information on accessing the public meetings can be found at https://www.nwd.usace.army.mil/MRWM/Public-Meetings/Meetings. Call will be held on Wednesdays at 1 p.m. Central (12 p.m. Mountain).

During the flow test a number of monitoring activities will be conducted to include fish monitoring, lidar and aerial photography, physical surveys, cultural resource surveys, and water quality sampling. Interested parties can also provide information through a web-based application that can be found at https://hydroviz.ca/fort-peck-feedback.

Monthly Water Management Conference Calls

Water management calls include an update from the National Weather Service’s Missouri Basin River Forecast Center, and an update on the Missouri River mainstem reservoir system operations. The next call will be held Thursday, July 11. All calls are recorded in their entirety and are available to the public on our website at https://go.usa.gov/xARQv.

Reservoir Forecasts:

  • Gavins Point Dam
    • Average releases past month – 26,000 cfs
    • Current release rate – 13,000 cfs
    • Forecast release rate – 16,800 cfs
    • End-of-June reservoir level – 1207.0 feet
    • Forecast end-of-July reservoir level – 1206.0 feet
    • Notes: The Gavins Point release will be adjusted to mitigate flooding and provide navigation flow support on the lower Missouri River.
       
  • Fort Randall Dam
    • Average releases past month – 19,000 cfs
    • End-of-June reservoir level – 1360.1 feet (up 4.7 feet from May 31)
    • Forecast end-of-July reservoir level – 1358.1 feet
    • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up Gavins Point releases.
       
  • Big Bend Dam
    • Average releases past month – 22,700 cfs
    • Forecast average release rate – 11,700 cfs
    • Forecast reservoir level – 1420.6 feet
       
  • Oahe Dam
    • Average releases past month – 22,800 cfs
    • Forecast average release rate – 11,900 cfs
    • End-of-June reservoir level – 1603.0 feet (no change since May 31)
    • Forecast end-of-July reservoir level – 1605.6 feet
       
  • Garrison Dam
    • Average releases past month – 21,600 cfs
    • Current release rate – 22,000 cfs
    • Forecast release rate – 22,000 cfs
    • End-of-June reservoir level – 1842.2 feet (up 4.4 feet from May 31)
    • Forecast end-of-July reservoir level – 1842.3 feet
    • Notes – Releases will be maintained at 22,000 cfs through mid-September.
       
  • Fort Peck Dam
    • Average releases past month – 13,700 cfs
    • Current release rate – 12,000 cfs
    • Forecast average release rate – 8,000 cfs
    • End-of-June reservoir level – 2230.2 feet (down 1.4 feet from May 31)
    • Forecast end-of-July reservoir level – 2229.2 feet
    • Notes: Releases will be adjusted in accordance with the Fort Peck flow test.

The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.

Hydropower:

The six mainstem power plants generated 775 million kWh of electricity in June. Typical energy generation for June is 843 million kWh. The power plants are expected to generate 7.8 billion kWh this year, compared to the long-term average of 9.4 billion kWh.

To view the detailed three-week release forecast for the mainstem dams, go to https://go.usa.gov/xARQB.

The Missouri Basin Web App provides links to these reports and others that are updated more frequently. http://go.usa.gov/xE6fC

MISSOURI RIVER MAINSTEM RESERVOIR DATA

 

Pool Elevation
(feet above mean sea level)

Water in Storage
(1,000 acre-feet)

 

On June 30

Change in June

On June 30

% of 1967-2023 Average

Change in June

Fort Peck

2230.2

-1.4

14,014

97

-274

Garrison

1842.2

+4.4

19,245

108

+1,347

Oahe

1603.0

0.0

17,401

98

+50

Big Bend

1420.8

+0.4

1,680

99

+35

Fort Randall

1360.1

+4.7

3,868

116

+427

Gavins Point

1207.0

+1.0

349

90

+22

 

 

Total

56,557

102

+1,607

 

WATER RELEASES AND ENERGY GENERATION FOR JUNE

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

13.7

813

109

Garrison

21.6

1,287

200

Oahe

22.8

1,355

205

Big Bend

22.7

1,354

72

Fort Randall

19.0

1,128

122

Gavins Point

26.0

1,546

67

 

 

Total

775


Contact
Eileen Williamson
402-996-3802

Release no. 24-022