Releases of water from upstream dams on the Missouri River are being dropped again, as the U.S. Army Corps of Engineers enters the final stage of ending the summer-long flooding.
Kim Thomas, chief of the Corps’ Readiness Branch in Omaha, says holding water releases steady the past several weeks allowed pressure on levees to stabilize, reducing underseepage and sand boils.
“At the start of the operational pause, we still had a tremendous amount of boils going on and every day that we’ve held at this pause, we’ve seen less and less of those boils,” Thomas says. “That’s another sign this pause was a good thing for the levees, to let them equalize.”
Releases at Gavins Point Dam at Yankton, South Dakota, totaled 160,000 cubic feet per second earlier this year — more than a million gallons per second. The Corps slowly dropped releases to 90,000 CFS, then held at that level for three weeks.
Last night (Sunday), the releases were cut back again. Jody Farhat, chief of the Corps of Engineers’ Missouri River Basin Management Office, says the tactic kept releases stable for a reason. Farhat says, “The pause was primarily to allow the water pressure in the levees and the embankment just downstream of Gavins Point Dam, that whole Lake Yankton area, to allow the water pressure in those levees to stabilize.”
It was feared some levees might collapse without the force of the water against them, but she says thankfully, that didn’t happen. “The levees have not failed us as the water pressure went off them and Lake Yankton is still there,” Farhat says, “so I think we achieved the overall objective.”
The Corps plans to drop releases by 5,000 cubic feet per second every other day until they reach 40,000 CFS on October 6th, about one-quarter of what it was during the worst of the flooding.