The latest 2023 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa is showing improvement.
“Spring precipitation, including increased mountain snowpack and late season plains snow, has provided improved runoff conditions in the upper basin,” said John Remus, chief of the U.S. Army Corps of Engineers’, Missouri River Basin Water Management Division. “We prefer to see a slower plains snowmelt to improve soil conditions. The longer the snow persists, the greater risk of flooding caused by rapid snowmelt from a spring rain event.”
The 2023 calendar year runoff forecast above Sioux City is 26.4 million acre-feet (MAF), 103% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks. March runoff in the Missouri River Basin above Sioux City was 1.7 MAF, 57% of average.
System storage is currently 46.8 MAF, 9.3 MAF below the top of the carryover multiple use zone.
“Despite these improvements, the System is still recovering from drought, and it will take time to return System storage to the top of the carryover multiple use zone while continuing to serve all Congressionally authorized purposes during 2023,” said Remus.
Basin and river conditions continue to be monitored, including plains and mountain snow accumulation, and System regulation will be adjusted based on the most up-to-date information.
Navigation:
Beginning in mid-March, releases from Gavins Point Dam were adjusted to provide flow support for Missouri River navigation. Navigation flow support for the Missouri River is at minimum service for the first half of the 2023 season, which 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.
Mountain and Plains Snowpack:
Mountain snowpack in the upper Missouri River Basin improved during March. The April 1, mountain snowpack in the Fort Peck reach was 117% of average, while the mountain snowpack in the Fort Peck to Garrison reach was 108% of average. By April 1, about 95% of the total mountain snowfall has typically accumulated. Mountain snow normally peaks near April 17. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.
The plains snowpack, which typically melts from mid-February into April, is hanging on longer in 2023 and the plains snow on April 1 showed widespread areas of 4-8 inches of snow water equivalent (SWE) across North Dakota and eastern South Dakota following a blizzard that occurred in late March. The blizzard that occurred April 4-5 in the upper plains was not included in this forecast.
Monthly Water Management Conference Calls for 2023:
The next monthly conference call will be held Thursday, May 11, to inform basin stakeholders of current weather and runoff forecasts and the planned operation of the reservoir system in the coming months. Presentation materials will be available via webinar. The call is intended for Congressional delegations; Tribes; state, county and local government officials; and the media. It will be recorded in its entirety and made available to the public on our website at https://go.usa.gov/xARQv.
Spring Public Meetings:
The Northwestern Division, Missouri River Basin Water Management Division held a series of public meetings the week of April 3. The meetings in South Dakota were canceled due to weather. The meeting held in Bismarck, North Dakota was recorded and is available online at https://dvidshub.net/r/3rfarx.
Reservoir Forecasts:
- Gavins Point Dam
- Average releases past month – 16,200 cfs
- Current release rate – 18,500cfs
- Forecast release rate –19,500 cfs
- End-of-March reservoir level –1206.4 feet
- Forecast end-of-April 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 – 12,100 cfs
- Forecast average release rate – 15,300 cfs
- End-of-March reservoir level – 1355.8 feet
- Forecast end-of-April reservoir level – 1355.2 feet
- Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up the Gavins Point releases.
- Big Bend Dam
- Average releases past month – 17,600 cfs
- Forecast average release rate – 9,800 cfs
- Forecast reservoir level – 1421.0 feet
- Oahe Dam
- Average releases past month –17,200cfs
- Forecast average release rate – 10,300 cfs
- End-of-March reservoir level – 1594.8 feet
- Forecast end-of-April reservoir level – 1600.0 feet
- Garrison Dam
- Average releases past month –17,300 cfs
- Current release rate –17,000 cfs
- Forecast average release rate –17,000 cfs
- End-of-March reservoir level – 1824.7 feet
- Forecast end-of-April reservoir level – 1827.6 feet
- Notes: Releases were increased from 16,000 cfs to 17,000 cfs in early April.
- Fort Peck Dam
- Average releases past month – 5,200cfs
- Current release rate – 5,000cfs
- Forecast average release rate – 5,000 cfs
- End-of-March reservoir level – 2219.5 feet
- Forecast end-of-April reservoir level – 2220.8 feet
- Notes: Releases will remain at 5,000 cfs through April.
Hydropower:
The six mainstem power plants generated 529 million kWh of electricity in March. Typical energy generation for March is 638 million kWh. Forecast generation for 2023 is 7.7 billion kWh 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
http://go.usa.gov/xVgWr.
| MISSOURI RIVER MAINSTEM RESERVOIR DATA | |||||
| Pool Elevation(feet above mean sea level) | Water in Storage(1,000 acre-feet) | ||||
| On March 31 | Change in March | On March 31 | % of 1967-2022 Average | Change in March | |
| Fort Peck | 2219.5 | +0.9 | 11,974 | 83 | +154 |
| Garrison | 1824.7 | -1.0 | 14,093 | 79 | -263 |
| Oahe | 1594.8 | +0.7 | 15,035 | 85 | +182 |
| Big Bend | 1420.6 | -0.3 | 1,659 | 97 | -22 |
| Fort Randall | 1355.8 | +6.2 | 3,447 | 104 | +474 |
| Gavins Point | 1206.4 | 0.0 | 337 | 86 | 0 |
| Total | 46,545 | 84 | +525 | ||
| WATER RELEASES AND ENERGY GENERATION FOR MARCH | |||
| Average Release in 1,000 cfs | Releases in 1,000 acre-feet | Generation in Million kWh | |
| Fort Peck | 5.2 | 322 | 45 |
| Garrison | 17.3 | 1,061 | 147 |
| Oahe | 17.2 | 1,056 | 149 |
| Big Bend | 17.6 | 1,081 | 61 |
| Fort Randall | 12.1 | 742 | 81 |
| Gavins Point | 16.2 | 994 | 45 |
| Total | 528 | ||
Original source can be found here.