The U.S. Army Corps of Engineers Missouri River Basin Water Management Division reports runoff in the Missouri River Basin above Sioux City, Iowa, for August was 1.5 million acre feet (MAF), 108 percent of normal. The 2015 runoff forecast is 25.0 MAF, 99 percent of average. Average annual runoff is 25.2 MAF.

The total volume of water stored in the Mainstem Reservoir System is currently 60.1 MAF, occupying 4.0 MAF of the 16.3 MAF combined flood control storage zones. “Water that was captured in the reservoirs during the spring and summer is being released to serve navigation and other downstream purposes,” said Jody Farhat, chief of the Missouri River Basin Water Management Division.

System storage peaked in early July at 61.9 MAF, occupying 36 percent of the available flood storage. “Our plan is to evacuate all water stored in the flood zones of the reservoirs prior to the start of next year’s runoff season, which typically begins around March 1,” said Farhat. “Full-service navigation support and normal winter releases should be sufficient to accomplish that goal; however, releases will be adjusted as needed in response to changing basin conditions throughout the fall and winter.”

Based on the Sept. 1 reservoir system storage, Gavins Point winter release will be at least 17,000 cfs. The winter release may be increased up to 20,000 cfs if flood water remains in storage after the navigation season. Winter releases are normally near 17,000 cfs.

The Corps previously announced it is providing an eight-month navigation season with full-service flow support based on the July 1 storage check. Full-service flow support is generally sufficient to provide a navigation channel that is 9 feet deep and 300 feet wide. Flow support for navigation service at the mouth of the Missouri River will end on Dec. 1.

The Corps will continue to monitor basin conditions and fine tune the regulation of the reservoir system based on the most up-to-date information.

Draft Annual Operating Plan and Fall Public Meetings

In late September, the Corps will post the 2015–2016 Draft Annual Operating Plan (AOP) for the Missouri River Mainstem Reservoir System on its website at http://www.nwd.usace.army.mil/MRWM/Public-Meetings/  Fall public meetings will be held in five cities throughout the basin during the last week of October to discuss the draft report and take comments on the proposed operating plan. The public meetings will include a presentation from the Corps regarding 2015 operations and plans for regulating the reservoir system in 2016, followed by a question and answer session.

The public meetings will be conducted at the times and locations listed below.

Tuesday, Oct. 27 – Smithville, Mo.

• Start time:  11 a.m.
• Jerry Litton Visitor Center
• 16311 DD Hwy

Wednesday, Oct. 28 – Pierre, S.D.

• Start time:  11 a.m.
• Capitol Lake Visitor Center
• 500 E Capitol Ave.

Wednesday, Oct. 28 - Bismarck, N.D.

• Start time:  6 p.m.
• Bismarck Civic Center
• 315 South 5th Street

Thursday, Oct. 29 – Fort Peck, Mont.

• Start time:  9 a.m.
• Fort Peck Interpretative Center
• Lower Yellowstone Road

Thursday, Oct. 29 - Council Bluffs, Iowa

• Start time:  6 p.m.
• Western Historic Trails Center
• 3434 Richard Downing Ave

Reservoir Forecasts

Gavins Point Dam releases ranged from 22,900 to 28,000 cfs in August, averaging 26,400 cfs. September releases are expected to average 29,500 cfs but will be adjusted to meet downstream navigation targets. The reservoir behind Gavins Point Dam ended August at elevation 1206.2 feet and will gradually rise to its normal seasonal pool elevation of 1207.5 feet in September.

Fort Randall Dam releases averaged 25,500 cfs in August. Fort Randall releases will be adjusted as necessary to maintain the desired elevation at Gavins Point. The reservoir ended August at elevation 1356.9 feet, down 1.5 feet during the month. The reservoir is expected to end September near elevation 1353.5 feet. The reservoir is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend. The annual drawdown will continue in October and November.

Big Bend Dam releases averaged 21,200 cfs during August. They are expected to average 23,800 cfs this month. The reservoir will remain near its normal elevation of 1420 feet during September.

Oahe Dam releases averaged 24,100 cfs during August. Releases are expected to average 23,600 cfs this month. The reservoir ended August at elevation 1612.6 feet, down 0.7 feet during the month. The reservoir is expected to drop 1.5 feet in September.

Garrison Dam releases averaged 20,200 cfs in August. Releases will be reduced to 13,000 cfs later in September. Garrison ended August at elevation 1842.6 feet, down 1.7 feet from the end of July. It is expected to drop less than 1 foot during September.

Fort Peck Dam releases averaged 7,900 cfs for the month of August. Releases will be reduced from 8,000 cfs to 4,500 cfs in mid-September. The reservoir ended August at elevation 2235.3 feet, down 0.9 feet from the previous month. The reservoir is forecast to fall less than 1 foot during September.

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.

The six mainstem power plants generated 821 million kilowatt hours (kWh) of electricity in August. Typical energy generation for the month of August is 1,001 million kWh. The power plants are projected to generate 8.7 billion kWh of electricity this year, compared to the normal of 10 billion kWh.

To view the detailed three-week release forecast for the mainstem dams, go to: https://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf

Missouri River Mainstem Reservoir Data

 Water Releases and Energy Generation for August