Report Says Below Normal Runoff Continues In Upper Missouri Basin

July runoff in the Missouri River Basin above Sioux City, Iowa was 2.0 million acrefeet, 62 percent of average. Runoff was below-average runoff in the Fort Peck and Garrison reaches with average to above-average runoff in the lower four reaches. The annual runoff forecast above Sioux City, Iowa is 19.2 MAF, 75 percent of average.

“Above-normal precipitation occurred in much of the basin, though areas of western Montana and Wyoming continue to be very dry,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.

“The dry soil moisture, below-normal rainfall in the mountain regions, and below- normal mountain snowpack runoff have led to well below-average reservoir inflows into Fort Peck and Garrison this summer.”

The U.S. Drought Monitor, updated on July 29, indicated 53 percent of the basin was not experiencing drought conditions, an improvement of 15 percent since July 1. Only a small area of Extreme Drought was present in western Montana. The U.S. Drought Outlook indicates drought conditions are expected to persist or expand throughout the basin through the end of October.

System storage on Aug. 1 was 51.7 MAF, down 0.4 MAF since July 1 and 4.4 MAF below the base of the Annual Flood Control and Multiple Use zone. The monthly reservoir studies indicate System storage will continue to decline in the Carryover Multiple Use Zone during 2025. “The winter release from Gavins Point, which is based on the Sept. 1 System storage check, will likely be at the minimum rate of 12,000 cfs,” added Remus.

Basin and river conditions continue to be monitored, and System regulation will be adjusted based on the most up-to-date information.

Navigation:

Per the July 1 System storage check, navigation flow support was decreased to 4,500 cubic feet per second below the full-service level. The flow support season length will be a full 8-month season, ending Dec. 1 at the mouth of the Missouri River. Gavins Point Dam releases are currently 23,000 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).

Reservoir Forecasts: Gavins Point Dam Average releases past month – 24,200 cfs Current release rate – 23,000 cfs Forecast release rate – 25,100 cfs End-of-July reservoir level – 1206.3 feet Forecast end-of-August reservoir level – 1206.5 feet Notes: The Gavins Point release will be adjusted to provide navigation flow support on the lower Missouri River.

Fort Randall Dam

Average releases past month – 21,400 cfs End-of-July reservoir level – 1355.8 feet Forecast end-of-August reservoir level – 1355.0 feet Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up Gavins Point releases.

Big Bend Dam

Average releases past month – 21,700 cfs Forecast average release rate – 22,300 cfs Forecast end-of-August reservoir level – 1421.0 feet Oahe Dam Average releases past month – 21,800 cfs Forecast average release rate – 23,200 cfs End-of-July reservoir level – 1599.3 feet (up 0.3 feet from June 30) Forecast end-of-August reservoir level – 1598.9 feet Garrison Dam

Average releases past month – 21,900 cfs Current release rate – 21,500 cfs Forecast release rate – 21,500 cfs End-of-July reservoir level – 1834.3 feet (down 0.9 feet from June 30) Forecast end-of-August reservoir level – 1833.0 feet Notes – Releases will be maintained at 21,500 cfs through mid-September.

Fort Peck Dam

Average releases past month – 9,100 cfs Current release rate – 9,000 cfs Forecast average release rate – 9,000 cfs End-of-July reservoir level – 2226.0 feet (down 1.1 feet from June 30) Forecast end-of-August reservoir level – 2224.4 feet Notes: Releases will be maintained at 9,000 cfs through mid-September.

Hydropower:

The six mainstem power plants generated 766 million kWh of electricity in July. Typical energy generation for July is 949 million kWh. The power plants are expected to generate 8.0 billion kWh this year, compared to the longterm average of 9.4 billion kWh.

To view the detailed threeweek release forecast for the mainstem dams, go to https://go.usa.gov/xARQB.