As water levels rose on the six upstream reservoirs, the Army Corps of Engineers increased releases to 160,000 cubic feet per second, their present level.
Water Management Division Chief Jody Farhat plans to drop the releases to 155,000 the end of this month, dropping to 150,000 in August. Farhat cautions that it will take time for the Missouri River to recede.
“I would think all through the month of August our releases are going to be higher than our previous records,” Farhat tells Nebraska Radio Network. “They may slowly be going down and allowing some of that water to start moving back into the river, but it’ll probably be September before folks see the river well back within the channels.”
Runoff into the Missouri River Basin above Sioux City, Iowa during the month of June set a record, according to the Corps which has kept such records since 1898. The Missouri River system hadn’t seen such large runoff since the great flood of 1952, when in April runoff totaled 13.2 million acre feet. Runoff this June totaled 13.8 million acre feet.
Two factors caused the pressure on the dams upstream, which resulted in the widespread flooding downstream.
Rain in May exceeded the normal rainfall by as much as 400% in Montana and around 200% in the Dakotas and Wyoming. Larger than normal snowfall in the mountains added to the huge runoff into the upstream reservoirs system, placing unprecedented pressure on the six upstream dams. Additionally, the snowpack peaked later than normal, accumulating until early May. The Corps reports that 90% of the snowpack has melted and run off into the system.