News Releases

Spring precipitation improves Missouri River Basin runoff forecast

Missouri River Water Management Division
Published May 4, 2023
The graphic is a split screen with a snowscape showing plains snow and mountain snow with snow in the clouds. and statements that say. Plains Snow - snowmelt is typically complete by mid-April. Snow Melt - the rate of snowmelt and how much becomes runoff can be impacted by rainfall, air temperatures, and soil moisture. Mountain Snow - begins to accumulate in October. Snowmelt is typically complete by July. Base Flows - river stages will be higher when the soil is saturated and lower when the soil is dry. There are two screen capture graphics on the right side of the image showing the modeled snow water equivalent (Shallow-snow Legend) comparing April 5 and May 1, 2023. The high resolution contrast shows areas with 1-2 and 2-3 and 3-4 inches of snow water equivalent in shades of red and bright pink.

The Elements of Runoff - Plains snow water equivalent for Upper Missouri River Basin Runoff - plains snow melt is typically complete by mid April. Mountain snow begins to accumulate in October, peaks in April and snowmelt is usually complete by mid-July. The May 1 runoff forecast is 26.9 million acre feet. The runoff forecast has improved thanks to late season plains and mountain snow in the upper basin and a continued precipitation trend may provide much needed moisture for the region.

Images of two tables. The first represents Reservoir data the second represents releases and energy generation data for April

MISSOURI RIVER MAINSTEM RESERVOIR DATA
 	Pool Elevation
(feet above mean sea level) 	Water in Storage
(1,000 acre-feet)
 	On April 30	Change in April	On April 30	% of 1967-2022 Average	Change in April
Fort Peck	2221.9	+2.4	12,417	86	+443
Garrison	1829.2	+4.5	15,332	86	+1,239
Oahe	1599.8	+5.0	16,403	93	+1,368
Big Bend	1420.9	+0.3	1,683	99	+24
Fort Randall	1355.1	-0.7	3,430	103	-17
Gavins Point	1206.1	-0.3	330	85	-7
 	 	Total	49,595	90	+3,050


WATER RELEASES AND ENERGY GENERATION FOR APRIL
 	Average Release in 1,000 cfs	Releases in 1,000 acre-feet	Generation in Million kWh
Fort Peck	5.0	299	45
Garrison	16.6	990	147
Oahe	9.2	544	149
Big Bend	10.3	611	61
Fort Randall	13.1	780	81
Gavins Point	16.5	983	45
 		Total	528

MISSOURI RIVER MAINSTEM RESERVOIR DATA Pool Elevation (feet above mean sea level) Water in Storage (1,000 acre-feet) On April 30 Change in April On April 30 % of 1967-2022 Average Change in April Fort Peck 2221.9 +2.4 12,417 86 +443 Garrison 1829.2 +4.5 15,332 86 +1,239 Oahe 1599.8 +5.0 16,403 93 +1,368 Big Bend 1420.9 +0.3 1,683 99 +24 Fort Randall 1355.1 -0.7 3,430 103 -17 Gavins Point 1206.1 -0.3 330 85 -7 Total 49,595 90 +3,050 WATER RELEASES AND ENERGY GENERATION FOR APRIL Average Release in 1,000 cfs Releases in 1,000 acre-feet Generation in Million kWh Fort Peck 5.0 299 45 Garrison 16.6 990 147 Oahe 9.2 544 149 Big Bend 10.3 611 61 Fort Randall 13.1 780 81 Gavins Point 16.5 983 45 Total 528

Late season plains snowpack accumulation and subsequent melting led to increased runoff throughout the upper Missouri River Basin during April. For the month, runoff was 4.7 million acre-feet, 159% of average, for the basin above Sioux City, IA.

“The runoff forecast continues to improve thanks to late season plains and mountain snowfall in the upper basin,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “We hope to see the precipitation trend continue to provide the much needed moisture for the region.”

The annual runoff forecast for the upper Missouri River Basin above Sioux City, IA is 26.9 MAF, 105% of average, and 0.5 MAF higher than last month’s forecast. However, soil moisture remains slightly below normal in eastern Montana and the western Dakotas, and well below normal in Nebraska. Even with the plains snowmelt, soils dried out in late April over a large portion of the upper basin.

“Despite the additional moisture, much of the upper basin remains in drought and is forecast to remain in drought through the month of May. The System is still recovering from drought as we continue to serve all Congressionally authorized purposes,” said Remus.

System storage is currently 49.6 MAF, 6.5 MAF below the top of the carryover multiple use zone. During April, System storage increased 3.0 MAF. Basin and river conditions continue to be monitored and System regulation will be adjusted based on the most up-to-date information.

Mountain Snowpack:
The mountain snowpack appeared to have peaked in early April, but cooler weather and additional storms resulted in additional snowpack accumulation. The Fort Peck reach peaked at 117% of normal on April 24 and has 88% of the peak remaining. The Garrison reach peaked at 109% of normal on April 6 and has 85% of the peak remaining. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.

Navigation:
Gavins Point Dam releases will continue to provide minimum-service navigation flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City) for the first half of the navigation season. The flow support season began April 1 at the mouth of the river near St. Louis, Missouri. The service level was based on the total volume of water stored within the System on March 15, which was 46.3 MAF, in accordance with the guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as navigation season length, will be based on the storage in the System on July 1.

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 for 2023 will be held Thursday, May 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 – 16,500 cfs
    • Current release rate – 17,500 cfs
    • Forecast release rate – 20,500 cfs
    • End-of-April reservoir level – 1206.1 feet
    • Forecast end-of-May reservoir level – 1206.0 feet
    • Notes: The Gavins Point release will be adjusted to provide minimum-service navigation flow support on the lower Missouri River.
       
  • Fort Randall Dam
    • Average releases past month – 13,100 cfs
    • End-of-April reservoir level – 1355.1 feet
    • Forecast end-of-May reservoir level – 1355.1 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 – 10,300 cfs
    • Forecast average release rate – 14,300 cfs
    • Forecast reservoir level – 1420.9 feet
       
  • Oahe Dam
    • Average releases past month – 9,100 cfs
    • Forecast average release rate – 14,200 cfs
    • End-of-April reservoir level – 1599.8 feet
    • Forecast end-of-May reservoir level – 1602.1 feet
       
  • Garrison Dam
    • Average releases past month – 16,600 cfs
    • Current release rate – 17,000 cfs
    • Forecast release rate – 19,500 cfs
    • End-of-April reservoir level –1829.2 feet
    • Forecast end-of-May reservoir level – 1830.5 feet
    • Notes – Releases will be increased to 22,000 cfs in mid-May.
       
  • Fort Peck Dam
    • Average releases past month – 5,000 cfs
    • Current release rate – 6,000 cfs
    • Forecast average release rate – 6,900 cfs
    • End-of-April reservoir level – 2221.9 feet
    • Forecast end-of-May reservoir level – 2224.0 feet
    • Notes: Releases will be gradually increased to 9,000 cfs by mid-May.

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 425 million kWh of electricity in April. Typical energy generation for April is 699 million kWh. The power plants are expected to generate 7.6 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 April 30

Change in April

On April 30

% of 1967-2022 Average

Change in April

Fort Peck

2221.9

+2.4

12,417

86

+443

Garrison

1829.2

+4.5

15,332

86

+1,239

Oahe

1599.8

+5.0

16,403

93

+1,368

Big Bend

1420.9

+0.3

1,683

99

+24

Fort Randall

1355.1

-0.7

3,430

103

-17

Gavins Point

1206.1

-0.3

330

85

-7

 

 

Total

49,595

90

+3,050

 

WATER RELEASES AND ENERGY GENERATION FOR APRIL

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

5.0

299

45

Garrison

16.6

990

147

Oahe

9.2

544

149

Big Bend

10.3

611

61

Fort Randall

13.1

780

81

Gavins Point

16.5

983

45

 

 

Total

528


Contact
Eileen Williamson
402-996-3802
eileen.l.williamson@usace.army.mil

Release no. 23-009