Despite two consecutive months of higher-than-normal runoff, drought conditions persist across much of the Missouri River basin and mainstem reservoir levels remain below normal.
“Even though June rainfall was two to three times normal in eastern Montana, runoff in the upper basin was only slightly above normal,” said Jody Farhat, Chief of the Missouri River Water Management Division. “The basin continues to recover from the 2012 drought and reservoir levels in Fort Peck, Garrison and Oahe remain 2 to 7 feet below the desired operating levels.”
Runoff in the Missouri River Basin above Sioux City, Iowa, for the month of June was 116 percent of normal. The July 1 forecast for annual runoff in the upper basin is 22.3 million acre feet, 88 percent of normal. “The above normal rainfall over the last couple months has improved soil moisture conditions in the northern and eastern regions of the basin,” said Farhat. “However, moderate to extreme drought persists in much of Wyoming, Colorado, Nebraska and Kansas. The mountain snowpack has melted and we expect to see the reservoir levels in the upper three projects begin to decline as we make releases during the drier summer and fall periods to meet the authorized purposes.”
“Gavins Point releases will remain near the current rate of 21,000 cubic feet per second (cfs) in early July; however, adjustments will be made if weather and basin conditions change,” said Farhat. “Thunderstorms can cause localized flooding even during droughts, so reducing flood risk remains a primary consideration during the summer.”
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. “Reductions in releases for flood risk management also allow us to conserve water in the reservoirs,” she added.
The July 1 storage check called for an increase in the service level for navigation flow support as well as a full, eight-month navigation season length. Flow support for navigation during the second half of the season will increase 3,000 cfs from the minimum service level provided in the first half of the season. Full service level is 6,000 cfs above the minimum service level.
Flow targets for the second half of the season will now range from 28,000 cfs at Sioux City, Iowa, to 38,000 cfs at Kansas City, Missouri. The increase in service level should result in a slight improvement in the navigation channel. Minimum service flow support is generally sufficient to provide a navigation channel that is 8 feet deep by 200 feet wide, and full service flow support provides a navigation channel 9 feet deep and 300 feet wide.
Gavins Point releases during the winter of 2013–2014 are forecast to be at the minimum rate of 12,000 cfs. Reduced support to navigation and low winter releases are the primary drought conservation measures utilized in the regulation of the mainstem reservoir system. These measures help ensure the reservoir system can continue to serve the authorized purposes during an extended period of drought.
Page 2 of 2 - View mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf