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Posted 7/7/2017

Release no. 17-063


Contact
Eileen Williamson
402-996-3802
cenwd-pa@usace.army.mil

OMAHA, NE -  Drought conditions in the upper Missouri River basin have expanded and intensified during the past month, reducing inflows to the Missouri River Mainstem Reservoir System. As a result, the U.S. Army Corps of Engineers, Missouri River Basin Water Management Division made a slight reduction in Gavins Point releases this week, from 33,000 cubic feet per second (cfs) to 32,000 cfs. Gavins Point releases were held steady at 33,000 cfs during June.

The total volume of water stored in the reservoir system is currently 61.8 MAF and is nearing its annual peak. “System storage currently occupies 5.7 MAF of the 16.3 MAF flood control zone,” said Jody Farhat, chief of the Corps’ Missouri River Basin Water Management Division. “The reservoir system began this runoff year with the full flood control capacity available. Spring and early summer runoff from the melt of the plains and mountain snowpack was captured in the reservoirs reducing flood risk along the river. Water stored in the annual flood control pool will be used for the remainder of the year to provide service to the other authorized purposes including navigation, hydropower, irrigation, water supply, water quality control, recreation, and fish and wildlife.” With approximately 65 percent of the flood control storage remaining, the reservoirs remain well positioned to capture runoff from summer rainfall events in the upper basin. The vacant flood control storage will also allow for future reductions in Gavins Point releases in response to summer rainfall events in the lower basin if necessary.

The 2017 runoff forecast in the Missouri River Basin above Sioux City, Iowa, is 28.5 MAF, 113 percent of normal. Runoff above Sioux City, Iowa in June was 5.8 MAF, 106 percent of normal. “The annual runoff forecast was reduced 1.4 MAF from the June 1 forecast, resulting in a reduction in releases from the reservoir system,” said Farhat. The melt of the mountain snowpack is complete and inflows to the reservoirs are declining. 

“Based on the July 1 System storage check, flow support for Missouri River navigation will be at least full service for the second half of the navigation season which runs from July through November,” said Farhat. Full service flow support is designed to provide a 9-feet deep navigation channel from Sioux City, Iowa to the mouth of the river near St. Louis, Missouri. Flow support is normally provided for an 8-month season from April through November. 

Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/weeklyupdate.pdf

USACE will continue to monitor basin conditions and will adjust the regulation of the reservoir system based on the most up-to-date information. 

Reservoir Forecasts 

Gavins Point Dam releases averaged 33,000 cfs during June. Releases were reduced to 32,000 cfs on July 7. The Gavins Point reservoir ended June at elevation 1206.3 feet and will remain near 1206.0 feet during July. 

Fort Randall Dam releases averaged 32,700 cfs in June. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The reservoir ended June at elevation 1355.4 feet and is expected to rise about a foot in July. 

Big Bend Dam releases averaged 28,800 cfs in June. Releases are expected to average 32,100 cfs this month. The reservoir will remain near its normal elevation of 1420.0 feet during July. 

Oahe Dam releases averaged 31,500 cfs during June. Releases are expected to average 32,200 cfs in July. The reservoir ended June at elevation 1610.3 feet, rising 0.5 feet during the month. The reservoir level is expected to remain nearly steady during July, ending the month near elevation 1610.1 feet. 

Garrison Dam releases averaged 34,400 cfs during the month of June. Releases will be reduced to 33,000 cfs in mid-July. Garrison reservoir ended June at elevation 1846.4 feet, rising 3.3 feet during the month. The reservoir level is expected to peak in mid-July and then slowly fall, ending the month near elevation 1846.3 feet. 

Fort Peck Dam releases averaged 9,800 cfs during June and are expected to average 10,000 cfs during July. The reservoir ended June at elevation 2240.2 feet, rising 1.2 feet during the month. The reservoir is expected to fall during July ending the month near elevation 2239.0 feet. 

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 1,053 million kWh of electricity in June. Typical energy generation for June is 831 million kWh. The power plants are projected to generate 9.8 billion kWh of electricity this year, compared to the long-term average of 9.3 billion kWh. 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

MISSOURI RIVER MAINSTEM RESERVOIR DATA


 

Pool Elevation

(feet above mean sea level)

Water in Storage

(1,000 acre-feet)

 

On June 30

Change in May

On June 30

% of 1967-2016 Average

Change in June

Fort Peck

2240.2

+1.2

16,134

107

+252

Garrison

1846.4

+3.3

20,675

109

+1,130

Oahe

1610.3

+0.5

19,562

104

+156

Big Bend

1420.0

-0.2

1,630

96

-14

Fort Randall

1355.4

-0.7

3,442

89

-63

Gavins Point

1206.3

+0.8

335

88

+19

 

 

Total

61,778

105

+1,480

WATER RELEASES AND ENERGY GENERATION FOR JUNE


 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

9.8

583

94

Garrison

34.4

2,047

321

Oahe

31.5

1,874

283

Big Bend

28.8

1,714

104

Fort Randall

32.7

1,946

168

Gavins Point

33.0

1,964

83

 

 

Total

1,053