John Remus, chief of the managers of the Upper Missouri River Basin in the U.S. Army Corps of Engineers office in Omaha, is feeling better, which is good.
“I’m more comfortable now,” he said Thursday, Nov. 7, to the Capital Journal during a teleconference with about 60 from several states.
“We have not had any major event” the past few weeks that would make the Army Corps revise its plan drastically as winter approaches, he said.
But that comfort comes because the Army Corps is not laying back, relaxing, sort of the way the price of liberty is eternal vigilance, according to Remus’ remarks on Thursday.
“We will be as aggressive as we can,” said Remus, about how long and hard the Army Corps would keep releases from the six mainstem dams on the Missouri — including Oahe Dam, seven miles upstream of Pierre and Fort Pierre — going into the winter and coming out of it next spring.
The goal every year is to lower the six reservoirs by mid-December to below the “annual flood control and multiple use” zone, with is under the thinner “exclusive flood zone” on top which is more of an emergency usage, and the “carryover-multiple use zone” that makes up the bulk of the reservoirs.
Total “system storage” in the six reservoirs — Gavins Point, Fort Randall, Big Bend, Oahe, Garrison and Fort Peck, upriver south to north — is 72.4 million acre-feet (MAF). That’s about how much was actually stored in that record flood year of 2011 in the summer. The goal each year is to get enough water — 16.3 MAF, to be exact — evacuated from the system by late December by regulating releases from the dam, so the system’s storage is down to 56.1 MAF.
As of Nov. 5, there were still 4.2 MAF of the 16.3 MAF of flood control storage occupying space in the six reservoirs, meaning that’s how much more water has to get released and moved downstream before the big freeze hits.
Very little water can be released during the cold winter months because ice formations can cause damaging and rapid flooding if the dam releases are too heavy.
Normally, the main problem for much of an average year in the Upper Missouri River Basin --from Sioux City on north and west — is not enough water.
The Army Corps has eight purposes for the water it must balance, from water use to recreation to irrigation to flood control, trying to keep enough for everybody, but not too much so that the reservoirs can’t handle a huge storm or a wet season.
Since March 2018,though, the main concern of the Army Corps on the Upper Missouri has been flood control, Remus reiterated Thursday, the same message he brought to a big meeting in Fort Pierre last month.
Runoff — from mountain snow pack, plains snow pack and precipitation — into the Missouri has been coming in at a record or near-record pace all this season.
Until this week, the Army Corp had been saying for a couple months that it appeared that 2018’s total runoff would match the record 61 MAF seen in 2011, as the second-highest in the 121 years of records was surpassed months ago, at 49 MAF hit in 1997.
But days ago, the Army Corps said that by the end of December it now looks as if the runoff for the year will hit “only” 60.2 MAF.
Sometimes it’s good when expectations aren’t met.
Meanwhile, the Army Corps’ stepped-up release schedule that has wet a few lawns in Fort Pierre has been working, mitigating the super-high runoff experienced in September and October, which normally are pretty dry that way.
In October, runoff into the stretch, or “reach” from Garrison Dam to Oahe Dam was more than six times the long-term average runoff, while the runoff in the Gavins Point to Sioux City “reach,” was 10 times normal, according to the Army Corps’ report on Thursday.
That means the Army Corps is going to keep the releases at high levels until sleigh bells can be heard: at 80,000 cubic-feet-per-second (cfs) at Gavins Point, the “bottom” release valve for the Upper Missouri dam system, until mid December or later, Remus said. That’s more than twice the normal release rate for this time of year at Gavins Point, he said.
Releases from Oahe Dam will remain at the current level of 65,000 cfs as a daily average as it fluctuates hourly due in part of electric power needs for the turbines, until mid-December or so, and then be stepped down to about 25,000 cfs for the winter.
The Army Corps will work to keep releases as high as possible as long as possible, so if the winter starts out meek and mild, it might allow for more water to be released.
But the pace so far is encouraging,
Remus said the system is releasing about 120,000 to 130,000 MAF per day. At that rate, about 3.8 MAF would be released in 30 days, or by about Dec. 7. That makes the goal of 4.2 MAF evacuated from the six-dam system by mid-December seem plausible.
Lake Oahe was at 1613.1 feet above sea level on Oct. 31, down 2 feet since Sept. 30. It was down to 1612.6 by Monday, Nov. 5 and is slated to be down to 1609.3 by the end of November, only 1.8 feet above the target of 1607.5 feet above sea level by winter.
Getting all six reservoirs down below that flood control level gives the system the room needed to handle next year’s runoff, Remus said.
The wild card is that the soils across the Basin, nearly universally in all eight states and more affected by the Missouri River, are so wet that there’s little to no storage in them to allow rains, snow melt and other runoff to be stopped in place, according to Remus.
Which could mean, if the current soaked soils situation gets frozen in place, an April shower of 5 inches could carry a lot more punch in 2020 than it would in a dry time with thirsty ground.
The high water has meant lots of electricity made by the turbines at the dams. Total electrical generation at the dams this year is projected to total 13.1 billion kWh, 139 percent of the long-term average of 9.4 billion kWh per year. October generation was 1.37 billion kWh, 169 percent of the average October generation of 0.81 billion.