Missouri River Basin Has Average Month In July

July was about as close to normal as you can get, when it comes to runoff into the Missouri River Basin, the Corps of Engineers reports. The month’s runoff was 3.3 million acre-feet (maf.), which is 99 percent of average. Runoff was near or above average in all reaches of the upper-basin reservoir except the Fort Peck reach, which was just 68 percent of average.

“Soil moisture conditions deteriorated in Montana, North Dakota and northern South Dakota over the last month and improved across southern South Dakota and into the lower basin,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division.

Precipitation was below normal over most of the upper basin last month except for small areas in Wyoming and southern South Dakota.  The lower basin saw a mix of above- and below-normal precipitation.

The Corps’ forecast for full-year runoff above Sioux City, Iowa, is 28.5 maf., 111 percent of average.

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System storage peaked on July 22 at 56.6 maf. System storage on August 1 was 56.3 maf., 0.2 maf. above the base of the Annual Flood Control and Multiple Use zone.

“Reservoir inflows in July declined due to warmer and drier conditions in the upper Missouri River basin,” Remus said. “After peaking in late July, system storage is expected to continue declining into the Carryover Multiple Use Zone during the remainder of 2023 as we make releases during the summer and fall periods to meet the authorized purposes.”

Per the July 1 system storage check, navigation flow support was increased to 1,500 cfs. below the full-service level. As announced last month, the flow-support season length will be a full eight-month season, ending December 1 at the mouth of the Missouri River.

Gavins Point Dam releases are currently 31,500 cfs.  Releases will be set to provide flow support at the intermediate-service level at all four target locations (Sioux City, Omaha, Nebraska City and Kansas City).

The six mainstem power plants generated 877 million kWh of electricity in July. Typical energy generation for July is 956 million kWh. The power plants are expected to generate 7.8 billion kWh this year, compared to the long-term average of 9.4 billion kWh.