Missouri River Basin runoff forecast improves but remains below average; Fort Peck Flow Test underway

Photo By Eileen Williamson | The graphic on the left is the snow water equivalent map showing the remaining...... read more read more

Photo By Eileen Williamson | The graphic on the left is the snow water equivalent map showing the remaining mountain snowpack which is peaked at 73% of normal on April 9 and has 88% of the peak remaining as of May 1 in the Fort Peck reach and the Garrison reach peaked at 82% of normal on April 10 with 89% of the peak remaining as of May 1. The graphic on the right shows the rainfall observed in the Missouri River Basin for the previous 30 days. Eastern Montana saw the least amount of rain while areas downstream of the Mainstem system saw an average of 4-5 inches of precipitation in northeast Nebraska and much of Missouri saw between 6-10 inchs of rain. The May forecast for upper basin runoff is 19.2 million acre feet.  see less | View Image Page

OMAHA, NE, UNITED STATES

05.03.2024

Story by Eileen Williamson 

U.S. Army Corps of Engineers, Northwestern Division

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As warmer weather moves into the Missouri River Basin, spring precipitation brought some much-needed moisture throughout the basin. For the month of April, runoff was 2.1 million acre-feet, 71% of average, for the basin above Sioux City, Iowa.

“While the calendar year forecast remains below average, the runoff forecast continues to improve thanks to higher-than-expected rainfall in April,” 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 is 19.2 MAF, 75% of average, and 1.7 MAF higher than last month’s forecast. Soil moisture is above normal in South Dakota, below normal in eastern Montana and western North Dakota, and near normal for the rest of the upper Basin. Drought or abnormally dry conditions are currently present in 52% of the Basin. Drought conditions in most of the upper Basin are likely to persist during May.

“Despite the additional moisture, much of the upper basin remains in drought and is expected to remain in drought through the month of May. However, drought conditions in the lower Basin are expected to improve or be removed during May. The System is still recovering from drought as we continue to serve all Congressionally authorized purposes,” said Remus.

System storage is currently 49.9 MAF, 6.2 MAF below the top of the carryover multiple use zone. 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 was below normal all season long and peaked approximately one week earlier than normal. The Fort Peck reach peaked at 73% of normal on April 9 and has 88% of the peak remaining as of May 1. The Garrison reach peaked at 82% of normal on April 10 and has 89% of the peak remaining as of May 1. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.

Navigation:
Gavins Point Dam releases will continue to provide navigation flow support at 500 cfs below full service 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 54.1 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.

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 September 1. The test includes two higher Fort Peck release periods, in late April and June, with target flows at Wolf Point, Montana. Releases were made from the Fort Peck spillway in late April and early May as part of the first higher release period. The Fort Peck releases will be adjusted depending on the runoff and reach conditions downstream of Fort Peck during the test period. The flow test may need to be modified with lower flows and a lower second peak due to the low runoff forecast. The test releases will not affect river stages below Gavins Point Dam. The flow test has been extensively coordinated with local stakeholders and was discussed in depth at a public meeting held in Poplar, Montana on March 28, 2024. 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/.

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 for 2023 will be held Thursday, May 9. 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
o Average releases past month – 29,400 cfs
o Current release rate – 24,000 cfs
o Forecast release rate – 31,000 cfs
o End-of-April reservoir level – 1207.8 feet
o Forecast end-of-May reservoir level – 1206.0 feet
o Notes: The Gavins Point release will be adjusted to provide minimum-service navigation flow support on the lower Missouri River.

Fort Randall Dam
o Average releases past month – 25,000 cfs
o End-of-April reservoir level – 1356.5 feet
o Forecast end-of-May reservoir level – 1355.3 feet
o 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
o Average releases past month – 27,100 cfs
o Forecast average release rate – 20,700 cfs
o Forecast reservoir level – 1420.5 feet

Oahe Dam
o Average releases past month – 25,400 cfs
o Forecast average release rate – 20,200 cfs
o End-of-April reservoir level – 1602.2 feet
o Forecast end-of-May reservoir level – 1602.4 feet

Garrison Dam
o Average releases past month – 15,900 cfs
o Current release rate – 16,000 cfs
o Forecast release rate – 19,300 cfs
o End-of-April reservoir level – 1835.5 feet
o Forecast end-of-May reservoir level – 1836.7 feet
o Notes – Releases will be increased to 21,000 cfs in mid-May.

Fort Peck Dam
o Average releases past month – 6,200 cfs
o Current release rate – 17,500 cfs
o Forecast average release rate – 12,800 cfs
o End-of-April reservoir level – 2231.3 feet
o Forecast end-of-May reservoir level – 2229.3 feet
o 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 723 million kWh of electricity in April. Typical energy generation for April is 694 million kWh. The power plants are expected to generate 8.4 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.