OMAHA, Neb. – July runoff in the Missouri River Basin above Sioux City, Iowa, was 2.3 million acre feet (MAF), 69 percent of average, according to the U.S. Army Corps of Engineers (Corps). This follows a June runoff that was 74 percent of average. The 2016 calendar year runoff forecast is 22.7 MAF, which is 89 percent of the historic average.

The total volume of water stored in the Mainstem Reservoir System is currently 59.4 MAF, occupying 3.3 MAF of the 16.3 MAF combined flood control storage zones. “System storage peaked on June 22 at 60.1 MAF and is gradually declining. The water currently stored in the annual flood control zone will be released during the remainder of the year to serve navigation, water supply and other downstream purposes and will be completely evacuated prior to the start of next year’s runoff season,” said Jody Farhat, chief of the Corps’ Missouri River Basin Water Management Division.

The September 1 system storage check will determine the winter releases from Gavins Point. As previously announced, the Corps will be providing flows to support full-service navigation as well as a full, eight-month navigation season. Full-service flow support is generally sufficient to provide a navigation channel that is 9 feet deep and 300 feet wide. “Gavins Point releases will be adjusted as necessary to meet full-service navigation targets in reaches with commercial navigation,” added Farhat.

The Corps 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 releases averaged 25,000 cfs during July. Releases currently remain at 25,000 cfs and may be gradually increased later in August if needed to meet navigation targets in reaches with commercial traffic as flows on tributaries in the lower basin recede. The reservoir behind Gavins Point Dam ended July at elevation 1206.2 feet and will remain near elevation 1206.0 feet during August.

Fort Randall Dam releases averaged 23,900 cfs in July. Releases will be adjusted as necessary to maintain the desired elevation at Gavins Point Dam. The reservoir ended July at elevation 1355.2 feet, falling 1.1 feet during the month. The reservoir is expected to remain near elevation 1355.2 feet during August.

Big Bend Dam releases averaged 20,900 cfs in July. Releases are expected to average 24,900 cfs this month. The reservoir will remain near its normal elevation of 1420.0 feet during August.

Oahe Dam releases averaged 23,500 cfs during July. Releases are expected to average 24,700 cfs in August. The reservoir ended July at elevation 1611.6 feet, falling 0.6 feet during the month. The reservoir level is expected to fall approximately 1 foot during August.

Garrison Dam releases were reduced from 21,000 cfs to 20,000 cfs in mid-July, averaging 20,300 cfs during the month. Releases will be remain near 20,000 cfs during August. Garrison ended July at elevation 1841.3 feet, falling 0.7 feet during the month. The reservoir level is expected to fall less than 2 feet during August.

Fort Peck Dam releases were reduced from 9,000 cfs to 8,000 cfs in July, averaging 8,300 cfs for the month. Releases will be remain near 8,000 cfs in August. The reservoir ended July at elevation 2235.1 feet, down 0.7 feet during the month. The reservoir level is forecast to fall less than 2 feet during August ending the month near elevation 2233.4 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 810 million kWh of electricity in July. Typical energy generation for July is 942 million kWh. The power plants are projected to generate 8.0 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 http://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf

MISSOURI RIVER MAIN STEM RESERVOIR DATA

 

WATER RELEASES AND ENERGY GENERATION FOR JULY

 

	Pool Elevation (feet above mean sea level)		Water in Storage (1,000 acre-feet)
	On July 31	Change in July	On July 31	% of 1967-2015 Average	Change in July
Fort Peck	2235.1	-0.7	15,022	100	-158
Garrison	1841.3	-0.7	18,951	98	-226
Oahe	1611.6	-0.6	19,996	108	-195
Big Bend	1420.6	+0.5	1,664	98	+25
Fort Randall	1355.2	-1.1	3,427	90	-90
Gavins Point	1206.2	-0.0	331	84	-1
		Total	59,391	101	-645