Precipitation during September was more than 200% of normal in eastern Montana, much of North Dakota, portions of South Dakota and northern Nebraska. As a result, the US Army Corps of Engineers says September runoff into the upper Missouri River basin was nearly twice the record set in 1986.
Chief of the U.S. Army Corps of Engineers Missouri River Basin Water Management Division John Remus says the 2019 upper basin runoff forecast is 61-million acre-feet. If realized, he says the runoff total would equal the amount seen in 2011– the highest amount in 121 years of record-keeping. The January-September observed runoff of 53.6 MAF has already exceeded the second highest runoff of 49.0 MAF observed in 1997.
Data from the Corps shows runoff between the Garrison Dam in central North Dakota and the Oahe Dam at Pierre/Fort Pierre was over 4 times average. Runoff between Oahe and the Fort Randall Dam at Pickstown was over 12 times average, setting a new record.
In other parts of the upper Missouri River basin, runoff between Fort Peck in Montana and Garrison was over 2 times average. Runoff from Fort Randall to Gavins Point Dam at Yankton was over 4 times average and almost twice the previous record. Runoff in the Gavins Point to Sioux City reach was more than 16 times the long-term average and more than twice the previous record.
Releases from Gavins Point Dam– the last place the Corps can regulate the amount of water flowing from the upper basin into the lower basin– have been increased to 80,000 cubic feet per second. In comparison, expected average releases from the other upper Missouri River basin reservoirs this month are:
- Fort Randall– 74,000 cfs
- Big Bend– 59,000 cfs
- Oahe– 61,000 cfs
- Garrison– 46,000 cfs
- Peck– 15,000 cfs
All three of the upper three reservoirs– Fort Peck, Garrison and Oahe– have fallen out of their exclusive flood control zones but remain high. Remus says as a result of the high reservoir levels and the forecast above-average runoff for the remainder of the fall, releases from all System projects will be much above average through November to get rid of stored flood water before the start of the 2020 runoff season. He says failure to evacuate the stored flood water will lead to increased risk of flooding next year. The Corps is monitoring the situation and will make any necessary adjustments.
Seven public meetings will be conducted throughout the basin later this month (Oct. 22-25). The annual fall public meeting in Fort Pierre will be held Oct. 23 at 10am CT at the Casey Tibbs Conference Center.
The Corps’ fall meetings will provide an update on the current year’s runoff and reservoir operations as well as planned operations for the next year’s runoff season. The Annual Operating Plan for the next year’s runoff season was released for public comment last month (Sept.). It’ll be presented at the public meetings and finalized by the end of this year.
Reservoir Forecasts:
◾Big Bend Dam ◦Average releases past month – 53,900 cfs
◦Forecast average release rate – 60,900 cfs
◦Forecast reservoir level – 1420.5 feet
◾Oahe Dam ◦Average releases past month – 55,600 cfs
◦Forecast average release rate – 61,000 cfs
◦End-of-September reservoir level – 1615.1 feet (falling 0.6 foot during September)
◦Forecast end-of-October reservoir level – 1612.9 feet
Updates on basin conditions, reservoir levels and other topics of interest can be viewed here: https://www.nwd.usace.army.mil/MRWM/MRWMApp/.
To view the detailed three-week release forecast for the mainstem dams, go to http://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf.
Meeting times and locations are available at the following link: https://www.nwd.usace.army.mil/MRWM/Public-Meetings/
