SIOUX CITY, Iowa (KCAU) — As the year inches closer to winter, some changes are coming, and that doesn’t just mean the temperatures.
According to the Army Corp of Engineers, releases from Gavins Point Dam will be reduced in late November as the navigational support season comes to an end the year on December 1.
Current releases from the dam are around 32,000 cubic feet per second (cfs) as flow support has been reduced to an intermediate level, or 1,500 cfs less than full service and will ultimately be reduced to the winter rate of 13,000 cfs.
Flow reductions will begin around November 22nd, with gradual daily reductions of 3,000 cfs until a rate of 15,000 cfs is achieved. Releases will then be paused and then reductions will be 1,000 cfs every five days until that winter rate of 13,000 cfs is reached.
The chief of the USACE Missouri River Water Management Division, John Remus said the winter releases from Gavins Point Dam will be slightly higher this year than last winter, when they were at a minimum rate.
Also of note, October runoff in the Missouri River basin above Sioux City was well above normal, at 1.5 million acre-feet, or 24% above average. However, runoff within Sioux City was below average for the month.
As of a November 1 update, the 2023 runoff forecast for the Upper Missouri River Basin is at 29.8 MAF (116% of average).
However, system storage is forecast to be below normal for the start of the 2024 runoff season, around 52.9 MAF. Fort Peck, Garrison, and Oahe reservoirs are anticipated to be somewhere between 4 to 5 feet below the base of their flood control zones on March 1st.
Average releases last month at Gavins Point Dam were 34,100 cfs. The current release rate as of November 1 was down to 32,000 cfs and the forecast average rate for the rest of the month is 29,000 cfs. At the end of October, the reservoir level was at 1207.6 feet and is expected to remain at that level through the end of this month.
At Fort Randall Dam, average releases through the past month were 30,800 cfs and at the end of October, the reservoir level was 1337.5 feet. Releases from Fort Randall Dam will begin near the end of the month of November, around a day before releases are scheduled to begin at Gavins Point Dam.
Finally, the six mainstem powerplants produced 752 million kWh of energy in October, below the normally generated 814 million kWh. By the end of the year, these plants are expected to generate 7.9 billion kWh of electricity, well below the long-term average energy production of 9.4 billion kWh.