OMAHA, Nebraska -- Recent rains are bringing more changes to releases from the Missouri River Mainstem System of dams.
According to the National Weather Service, rainfall during first two weeks of September have brought between 200 and 600% of normal rainfall over the entire Missouri River Basin. The NWS has issued river several river flood alerts and warnings.
In response to these changing conditions the U.S. Army Corps of Engineers is planning the following changes to the releases at Gavins Point Dam. Intra-system releases will be adjusted to account for the changes at Gavins Point Dam.
“The Missouri River Basin Water Management Division continues to monitor the conditions on the ground and we will make adjustments as necessary,” John Remus, chief of the Corps’ Missouri River Basin Water Management Division.
Lowered releases
Saturday morning, Sept. 14, releases from Gavins Point Dam will be reduced by 5,000 cubic feet per second (cfs). Releases will be reduced an additional 5,000 cfs Sunday morning, Sept. 15.
Current models suggest lowering releases from Gavins Point Dam may lower the peak flood stage forecast on the Missouri River between Sioux City, Iowa and Omaha, Nebraska.
“We are reducing releases from Gavins Point Dam to try to reduce the chances of flood water reaching Interstate 29 north of Omaha,” said Remus.
Releases at 60,000 cfs from Gavins Point Dam will last no longer than three days.
Increased releases
After the brief reduction to 60,000 cfs, releases from Gavins Point will then be incrementally increased by 5,000 cfs a day going up to 80,000 cfs.
The increased releases are aimed at ensuring the 16.3 MAF of designated flood control storage will be available before the 2020 runoff season.
“We have already seen four times the normal precipitation for September over the entire upper Missouri River basin,” said Remus.
Second highest runoff on record
As of Sept. 13 runoff in the upper Missouri River Basin, above Sioux City, Iowa, is 49.9 MAF, surpassing the 1997 runoff of 49.0 million acre feet, making 2019 the second highest runoff in the 121 year record. Only the 2011 runoff of 61.0 million acre feet is higher.
The Sept. 1 runoff forecast for 2019 was 54.6 Million Acre Feet (MAF). As of Sept. 13, the projected 2019 runoff is now 58.8 MAF.
Since September 1, runoff into the Big Bend, Fort Randall and Gavins Point reservoirs, as well as the unregulated James and Vermillion Rivers in South Dakota and the Big Sioux River in South Dakota and Iowa have seen between 3-8 inches of rainfall.
Over the same two-week period, all of North Dakota received between 2-8 inches of rain.
Communicating with stakeholders
On Monday, Sept. 16, the U.S. Army Corps of Engineers will host an ad-hoc call to update to basin stakeholders including Congressional representatives; Tribes; state, county and local government officials; levee and drainage districts; and the media on the system status and planned releases.
The National Weather Service provides official river stage and weather forecasts. Its website -- www.weather.gov/mbrfc -- provides river observations and forecasts; weather observations and forecasts, and additional information including the spring flood outlook under items of seasonal interest. The Corps’ Missouri River Basin Water Management Division shares all release forecasts with the National Weather Service for incorporation into their forecast products.