Army Corps implements drought conservation on MO River
Water conservation measures were enacted for the second half of the navigation flow support season based on the July 1 Missouri River Mainstem Reservoir System storage, per the guidelines outlined in the Master Manual.
Very dry conditions continue to impact the upper Missouri River Basin above Sioux City, Iowa (upper Basin) despite recent heavy rainfall in the lower Basin. As a result of the low precipitation and widespread drought conditions, June runoff in the upper Basin was 52 percent of average.
The updated 2021 upper Basin runoff forecast is 15.6 million acre-feet (MAF), 60 percent of average. If realized, this runoff amount would be the 10th driest year in the upper Basin since 1898. System storage on July 1 was 55.2 MAF, 0.9 MAF below the base of the Annual Flood Control and Multiple Use Zone. System storage is expected to decline further into the Carryover Multiple Use Zone during the remainder of 2021.
“We reduced the service level to support navigation by 1,500 cubic feet per second from the full-service level,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “This intermediate service level will be maintained through the end of the navigation flow support season, which will end on December 1 at the mouth of the Missouri. The intermediate service level is a necessary water conservation measure to ensure authorized purposes will be served in the short and long term,” added Remus.
The Gavins Point release was reduced from 30,500 cfs to 28,500 cfs on July 1 in accordance with the reduced service level. USACE will evaluate lower Missouri River flow conditions daily to set Gavins Point releases to ensure that flows at the four downstream navigation target locations will be at or above the reduced service level. The monthly study also indicates that the winter release from Gavins Point, which is based on the September 1 storage check, will likely be at a minimum rate of 12,000 cfs.
Full-Service Level Intermediate-Service Level
Sioux City 31,000 cfs 29,500 cfs
Omaha 31,000 cfs 29,500 cfs
Nebraska City 37,000 cfs 35,500 cfs
Kansas City 41,000 cfs 39,500 cfs
Mountain snowpack in the upper Basin melted out in mid- to late-June, several weeks earlier than normal. The mountain snowpack peaked above Fort Peck in late March at 86% of average, while the mountain snowpack in the Fort Peck to Garrison reach peaked in late April at 96% of average. Mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.
Soil conditions in the upper basin are very dry. Drought conditions throughout the entire Basin, particularly the upper basin worsened in June. According to the National Drought Mitigation Center, approximately 74% of the Missouri River basin is currently experiencing some form of abnormally dry or drought conditions, an increase of 9% since the end of May. The seasonal drought outlook, which extends through the end of September, shows drought conditions will persist or expand across the upper basin. Drought information can be viewed at: https://droughtmonitor.unl.edu/.
Gavins Point Dam releases will be set to provide flow support at an intermediate-service level, 1,500 cfs lower than full-service flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City). Flow support for the second half of the navigation season, as well as the navigation season length, are based on July 1 System storage. The flow support season length will be a full 8-month season, ending December 1 at the mouth of the Missouri River.
Winter Release Rate
The winter release rate is determined based on the September 1 System storage. Per the July 1 reservoir studies, the winter releases from Gavins Point Dam will likely be at the minimum rate of 12,000 cfs.
Gavins Point Dam
Average releases past month – 29,700 cfs
Current release rate – 28,500 cfs
Forecast release rate – 30,000 cfs
End-of-June reservoir level – 1206.4 feet
Forecast end-of-July reservoir level – 1206.0 feet
Notes: The Gavins Point release will be adjusted to provide intermediate-service navigation flow support on the lower Missouri River through December 1, the second half of the navigation season.
Fort Randall Dam
Average releases past month – 27,400 cfs
End-of-June reservoir level – 1354.7 feet (down 0.5 foot from May 31)
Forecast end-of-June reservoir level – 1355.2 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 – 27,800 cfs
Forecast average release rate – 30,800 cfs
Forecast reservoir level – 1420.7 feet
Average releases past month – 27,800 cfs
Forecast average release rate – 30,900 cfs
End-of-June reservoir level – 1604.9 feet (down 1.0 foot from May 31)
Forecast end-of-July reservoir level – 1603.1 feet
Average releases past month – 21,900 cfs
Current release rate – 22,000 cfs
Forecast release rate – 22,000 cfs
End-of-June reservoir level – 1836.5 feet (up 1.3 feet from May 31)
Forecast end-of-July reservoir level – 1835.9 feet
Notes – Releases will be maintained at 22,000 cfs through August.
Fort Peck Dam
Average releases past month – 9,300 cfs
Current release rate – 9,500 cfs
Forecast average release rate – 9,500 cfs
End-of-June reservoir level – 2232.5 feet (down 0.5 foot from May 31)
Forecast end-of-July reservoir level – 2231.3 feet
Notes: Releases will be maintained at 9,500 cfs through August.
The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.
The six mainstem power plants generated 853 million kWh of electricity in June. Typical energy generation for June is 850 million kWh. The power plants are expected to generate 8.9 billion kWh this year, compared to the long-term average of 9.5 billion kWh.
To view the detailed three-week release forecast for the mainstem dams, go to https://go.usa.gov/xARQB.