Corps hydraulic engineer Nicole Shorney says they expect runoff much higher than usual.
“April runoff was 182% of average above Sioux City,” Shorney says. “Runoff was above average partly due to the heavy Plains snowpack in Montana melting. Mountain snowpack accumulation has peaked in both reaches.”
Corps engineer Joel Knofczynski says they still have plenty of storage space in the reservoir system to handle the runoff.
“Reservoir system storage is currently 60.9 million acre feet or 4.8 million acre feet into the 16.3 million acre feet of available flood storage,” Knofczynski says.
He notes they expect to ramp up outflows in the next couple of weeks. The average release from Gavins Point Dam during April was around 34,000 cubic feet per second.
“Due to the higher-than-average runoff being forecast in the Missouri River basin above Sioux City, the service level has been increased 15,000 cubic feet per second above full service to facilitate the evacuation of stored floodwaters. As downstream flows recede, Gavins Point releases will be increased to about 42,000 cfps by around mid-May.”
Even with the increased releases, Corps officials say river levels below Gavins Point Dam should stay well below flood stage.
By Jerry Oster, WNAX, Yankton