U.S. Army Corps of Engineers, Missouri River Joint Information Center
August 4, 2011
Record runoff in the Missouri River Basin continued in July. July runoff above Sioux City, Iowa was 10 million acre feet (MAF), making it the wettest July on record and fifth highest single runoff month the basin has experienced since detailed record keeping began in 1898.
"This is by far the wettest season and the wettest year the basin has experienced," said Jody Farhat, Chief of the Water Management Division here. "The good news is we are finally to the point where reservoir outflows are exceeding inflows and we have a strategy in place to evacuate the flood water and prepare the reservoir system for next year."
The basin has experienced three consecutive months of record runoff above Sioux City since May. June was the highest single month on record with 1 3.8 MAF of runoff. The previous record monthly runoff was 13.2 MAF in April o f 1952. May runoff was 10.5 MAF, the third highest single month since 1898 and July was the fifth highest. "The combined runoff for May through July totaled 34.3 MAF, nearly 40 percent greater than the normal total annual runoff of 24.8 MAF," said Farhat. "In addition, the three-month runoff volume was greater than the total annual runoff in 102 of the 113 years in the historic record."
Runoff for the calendar year is projected to reach 61.8 MAF, 249 percent of normal. The previous record of 49 MAF was reached in 1997. Total system storage peaked at 72.8 MAF on July 1. It ended July at 69.6 MAF, down 3.2 MAF. The previous storage record was 72.1 MAF in 1975.
On July 29, the Corps announced its strategy for evacuating the 2011 flood water and preparing the basin for 2012. "We reviewed each of eight drawdown options with techni cal experts and leadership within the Northwestern Division, Omaha and Kansas City Districts," said Farhat. "This release strategy pu ts us in the best position to drawdown the water as quickly and as responsibly as possible, while allowing us time to inspect, assess and repair damages."
For the corresponding detailed three-week release forecast for the main stem dams, go to: http://www.nwd-mr.usace.army.mil/rcc/reports/twout.html
Gavins Point releases are currently 150,000 cfs and are forecast to be reduced beginning in mid-August. Releases will be decreased by 5,000 cfs daily reaching 90,000 cfs near the end of the month. Releases will stay at 90,000 cfs for approximately 2 weeks and then will drop 5,000 cfs every two days, until reaching 40,000 cfs, which is slightly above the typical fall release rate, on or about Sept. 30. Average releases for the month of July were 159,700 cfs.
Fort Randall relea ses are currently at 148,000 cfs. They will remain near that rate until mid-August and will then be reduced corresponding to the reductions in Gavins Point releases. Releases for the month of July averaged 156,000 cfs, compared to a long-term average of 29,300 cfs. The reservoir ended the month at elevation 1369.3 feet, a record high for the month. The reservoir will continue to drop during August and is forecast to end the month near 1362 feet.
Big Bend releases are currently 130,000 cfs. Releases are expected to be gradually reduced to 80,000 cfs during the month of August. Average releases for the month of July were 141,600 cfs. The reservoir will remain near its normal elevation of 1 420 during the month.
Oahe releases are currently 130,000 cfs, and are expected to be gradually reduced to 80,000 cfs by the end of August. Average releases for the month of July were 144,200 cfs. The reservoir ended the month near eleva tion 1617.5 feet, 2.5 feet below the top of the spillway gates. The reservoir is expected to end the month near elevation 1614.
Garrison releases are currently 105,000 cfs. Releases will be gradually reduced during the month reaching 65,000 cfs by the end of August. Average releases for the month of July were 127,700 cfs. The reservoir ended July at elevation 1851.6 feet. The reservoir is forecast to continue dropping and will end the month at approximately elevation 1845.
Fort Peck releases are currently 30,000 cfs. Releases will be reduced to 25,000 cfs later in August. Average releases for the month of July were 41,500 cfs, com pared to a long-term average of 9,900 cfs. The reservoir ended the month at elevation 2246.6 feet. It is expected to gradually drop ending August near elevation 2242 feet mean sea level. The reservoir releases and elevations discussed above should not be assumed to be definitive. Additional heavy rain in th e basin could cause adjustments to the drawdown schedule.
The six main stem power plants generated 1,134 million kilowatt hours (kWh) of electricity in July, 120 percent of normal. This year’s forecast for power production is projected to reach 12.2 billion kilowatt hours. The long-term average is approximately 10 billion kilowatt hours.
For general questions regarding our flood response information efforts, please call (402) 996-3877, (877) 214-9110 or e-mail us at MRJIC@usace.army.mil. Please follow us on Facebook (http://www.facebook.com/OmahaUSACE), (http://www.facebook.com/OperationMightyMo), Twitter (http://www.twitter.com/OmahaUSACE), YouTube (http://www.youtube.com), and FLICKR (http://www.flickr.com) for the latest updates regarding our flood response operations.
View daily and forecasted reservoir and river information on the Water Management section of the Northwestern Division homepage at: http://www.nwd-mr.usace.army.mil/rcc.