The U.S. Army Corps of Engineers manages the surging Missouri River — including six large reservoirs in Montana, North Dakota, South Dakota and Nebraska — all swollen with water from historic rainfall and snowmelt.
The World-Herald met recently with top Corps of Engineers officials to discuss the conditions and decisions behind flooding in the Missouri River basin.
The meeting at the corps' Omaha District headquarters downtown included Brig. Gen. John McMahon, commander of the Northwestern Division, based in Portland, Ore.; Col. Robert Ruch, commander of the Omaha District; Jody Farhat, who regulates the dams as chief of the district's water management division; John Bertino Jr., the district engineering chief who oversees dam safety; John Remus, district hydrologic engineering chief; and Kimberly Thomas, district emergency and disaster chief.
Here is an abridged account, in question-and-answer form. Remarks were edited for clarity.
Q. How much space is devoted in the reservoir system for floods?
Farhat: The system has 16.3 million acre-feet of storage reserved for floods. It's always had about that number. They sized that to handle a very large flood, the historic flood of 1881.
Q. Is that enough?
Farhat: Throughout the historic record, from that time until today — and we have good hydrologic records going back to 1898 — that 16.3 million acre-feet of flood-control storage was sufficient to handle the big runoff years every year without having to make releases that are outside the channel capacity. This is the first time we've ever had to make releases that create downstream flooding.
Q. How much water is coming this way?
Farhat: This year we're estimating that we'll have 54.6 million acre-feet of runoff. More than twice the normal runoff. Our previous record was 49 million acre-feet. So more than 10 percent above our previous record, which was in 1997.
This really is a historic flood event. It's something that is unprecedented in our history of the hydrologic records of the Missouri River basin.
McMahon: That is a forecast, and it will change as the year goes on.
Farhat: Most likely it will go up, because our June runoff is tracking higher than we had forecast.
Q. What's normal?
Farhat: We've spent very little time in the last 20 years in what we would like to say is our normal 24.8 million acre-feet of runoff. We've either been very wet or very dry.
Q. What happened to mountain snowpack this year?
Farhat: Up until mid-April, it was tracking just a little bit above normal — 110 percent to 115 percent of normal.
Then it simply skyrocketed.
We expect mountain snowpack to peak in mid-April. So even as it started to diverge, it wasn't a real concern, because any day now it should start going down. But instead it just skyrocketed and it peaked in early May at 135 percent to 140 percent of normal.
But even then we were in good shape with the reservoir system. We ran our May 1 runoff forecast. We knew it was going to be an abundant water year. We were going to have above-normal releases. We would be in flood evacuation mode all year. But we still had nothing to tell us we were going to need record releases from any of the dams at that point.
So here we sat on the first of May, still in good shape. Big water year, but nowhere even near a record water year. Our forecast was about 44 million acre-feet.
Q. What changed?
Farhat: This was the real kicker. About the second weekend in May, we got two or three inches of rain in eastern Montana. We had a good rise on the Yellowstone River. Again, still manageable.
We were going to have to increase our releases from Garrison Dam and the dams downstream. But the weekend of May 20 to 22, much of the eastern half of Montana got 5 to 8 inches of rain.
Down here we can get 5 or 8 inches of rain. It happens once in a while over a small area. A county or a community gets a heavy rainstorm. But this was over the whole eastern half of Montana. A tremendous volume of water came in. Then it was followed by more rain in the following weeks into June.
As a result, we had a tremendous volume of water come into the reservoir system. We're estimating that this rainfall event was between 4 million and 5 million acre-feet of runoff — and it used up all the storage that we had remaining into the reservoirs that we were planning to use for the snow.
So now we're full.
Q. The winter snowpack runoff wouldn't exceed 4 million to 5 million acre-feet?
Farhat: The volume would have, but we would have releases at the same time. We had enough storage to manage that runoff. It usually takes two and a half months to get the snow out.
Q. Tell us more about the May 22 rains. It seemed that you were increasing the Gavins Point Dam releases daily that week.
Farhat: It took a couple of days to really get a good handle on the volumes that we were going to be looking at and also the potential timing for that snowmelt, because we were already late into the season. We were concerned it would melt off rapidly, so we ran different scenarios of our snowmelt and, of course, with additional rain in the forecast as well.
We thought we would be right at 110,000 cubic feet per second to 120,000 cfs from Gavins Point. That following weekend, they forecast three or four inches more rain over this same saturated area. We knew at that point that those releases would have to go up.
During that period we had some of the highest storage gains in the reservoirs. Over 400,000 acre-feet a day. I worked here a long time before I ever saw a storage change of 100,000 acre-feet a day.
It was just an unbelievable amount of water coming into the reservoir.
McMahon: So it might have looked like we weren't on our game, but we're monitoring it closely, making adjustments on the best available information and not wanting to incite panic, because now we were edging up into historic releases.
It looked like what it looked like, but it was the best we could do under the circumstances.
Each one of those bumps up of releases were “Oh, my God,” because we hadn't been there before. Oh, my God, 100,000. Oh, my God, 120,000. Oh, my God, 150,000.
Q. A lot of people wonder why you didn't start releasing in April when you saw the snowpack rise.
Farhat: On the 28th of January we had all of the flood-control capacity available.
The fact that 2010 was a big runoff year didn't reduce our ability to provide flood control this year because we had evacuated all of last year's water. The full flood-control capacity was available.
Q. With the Mississippi River flooding earlier in the spring, was there any thought given or any attempt to hold water back on the Missouri so that we didn't add to the problems below St. Louis?
McMahon: The short answer is yes, there was some consideration given, but ...
Farhat: But the answer is no. We are not authorized to operate solely for the Mississippi River basin. We provide them a forecast of what we think the flows are going to be on the lower end of the Missouri River, but we did not make any decisions this year for the benefit of the Mississippi River.
Q. What were the projected Gavins Point releases looking like in April and May?
Farhat: Our April 1 study showed that we were expecting peak releases from Gavins Point this year to be between 39,000 and 45,000 cfs. Very much in the normal range. We were watching the mountain snowpack. We were watching the Plains snowpack. Some of it had already come into the reservoir system, and we're still talking very normal releases.
We had no reason to evacuate. There was nothing telling us (we were) getting record rainfall in May. If that record rainfall didn't fall in May, we would be on a release somewhere around 50,000 to 60,000 cfs.
McMahon: We have to have good reasons to bump the release. We just can't do it on a whim. It's transparent. Everybody sees it. We've got to have good, hard reasons for doing these things. We didn't have it until we had it, and then we started bumping them up.
Ruch: Every one of those (authorized) uses has a constituency attached to it. So if you start going outside your parameters without a very sound reason, you will hear from people immediately. We get regulated a lot of ways here.
Farhat: The other important thing is that we watch Gavins Point releases. But the water doesn't come from Gavins Point Dam. The water comes from the upper three dams.
So you have to be able to release the water from Montana and North Dakota and South Dakota. In the winter, until the middle of March, those stretches of the river are frozen, and if we were to increase releases at that time, we would cause tremendous ice jam flooding. We're very restricted on what our releases can be in the winter.
The key thing here is we didn't have a reason to increase releases. Our studies showed that we would have releases within the normal level. We didn't have a crystal ball that said, “Watch out, the rain is coming.''
Q. If it had been a normal May in Montana, how would this year compare with last year?
Farhat: We were predicting on the first of May we were going to have about 44 million acre-feet of runoff. That would have been our second-highest year on record. So it was going to be a wet year.
Q. So it was already going to be worse than last year?
Farhat: Yeah. What made last year bad was not the releases from Gavins Point. It was the inflows (into the Missouri) from all the rain below the dam, coupled with our releases. We had a lot of rain fall below Gavins. We can't control that.
McMahon: So last year we adjusted releases from the main stem downward to allow that rain to move through the system. Even with those adjustments, it still inundated many farms and put levees in jeopardy. It overtopped and breached some levees that have since been repaired.
We were sensitive to learn from what happened last year and try to avoid it (this year), to the extent you can. But, on the other hand, when water manifests itself in the system and you need to begin to evacuate it, you need to evacuate it because that's the responsibility we have.
Farhat: In April and early May this year, we were getting flooding from rain between the reservoirs, rain in the upper basin.
My office received many, many phone calls from folks who live below Gavins Point Dam saying we should cut back our releases. They felt that the river was already high and was beginning to interfere with drainage. They would have liked to see lower releases. We get a lot of advice, I'll just say that.
Q. Did the lesson from last year, when you cut back releases because you were worried about rain and flooding below Gavins Point, influence this year's releases?
McMahon: No. It did not influence the schedule that developed as the rain developed.
Farhat: We're just sensitive to the concerns.
I think the question goes back to why didn't we release a lot more water. The reason is because we have to balance both upstream and downstream.
We know the folks downstream do not want us to release more water than we have to. Neither do the people upstream. So we're always walking that fine line between the upstream and downstream interests, and we really try to base our releases on studies that look at the volume of water coming in and tell us what we need to do to manage that water from now until the start of next year's runoff season.
Q. Sometimes people get gut feelings about these massive events, or have historical knowledge that doesn't feed into a computer. Can you say this is what the study says, but this is what we're going to do?
Ruch: It's never a gut feeling. It's got to be backed up by numbers.
Q. But can you say this is what the data says, but we're going to do something different?
Farhat: We want to make our decisions on the best real information that we have.
We have to be sensitive about how quickly conditions can change in this basin. We went to public meetings in April in Montana, North Dakota and South Dakota and people stood up and said be careful not to release too much water. We could return to a drought at any moment. This was in April, just a month before the rains started. Folks are very sensitive to us dumping what they see as their water unnecessarily.
We're managing for all those authorized purposes. We try to base it on good, solid info, not on hunches.
Q. Some people say that managing river flows for barge traffic or the pallid sturgeon and other endangered species takes your eye off your flood-control mission.
Farhat: The endangered species had no impact on this year's regulation at all. It does not have impact in any year on flood control. No decisions this year were made based on operating for terns and plovers or the pallid sturgeon.
Q. Has there been any consideration to flooding one place to avoid a more populated place?
McMahon: We don't have that flexibility. There's so much water in the system that everybody's going to be flooded. When you fly over it, it's bluff to bluff. The historic flood plain has water in it.
Q. So there is no parallel to the decisions made on the Mississippi to blow a levee?
Ruch: Could we flow the water around Omaha and Council Bluffs? Upstream from Omaha, the water is bluff to bluff. There is no channel there. The space doesn't exist even if you wanted to plan it.
Q. Are we in uncharted territory, wondering if a levee holds or whatever else happens?
Bertino: We're hitting peak river stages on a number of our gauges. The height and the duration of this flood is unprecedented. We haven't been here before.
McMahon: You have levees here that are sand core, clay blankets. The way I see it is we have lots of vulnerabilities. I think we're going to have a lot of overtopped or breached levees.
The big cities, Omaha, Kansas City, Council Bluffs, I think are OK. I'm not anticipating any issues in the big cities' levee systems.
But we're going to have overtops (and) breaches continue through August and later.
It's going to be a devastating season in terms of how the levees do.
Then we'll have to go back once the water subsides and inspect, make repairs, a whole bunch of things before next season.
Ruch: We did about $20 million worth of levee repairs after a lot less floodwater last year. We're going to have an incredible amount of work to try to get the system back in shape for next year.
McMahon: There's going to be a lot of pain and suffering continuing. I don't think we've seen nearly as much as there's going to be all the way down the system.
Q. Is it a big fear that you won't get the levees repaired for next year?
Ruch: There's a lot of work to be done in getting ready for next flood season. It will be an incredible amount of work.
Q. Do we need to be concerned about the integrity of the dams?
Bertino: We have a very, very aggressive dam safety program. All the surveillance we're doing indicates they are performing the way they were designed to. We don't see anything that concerns us.
Q. What do people who live behind levees need to know about their own personal preparedness?
McMahon: They need to be tuned in to local officials and take very seriously all the warnings, evacuation plans and precautions. A levee doesn't necessarily guarantee protection. It's a risk-reduction measure. There's still risk. We Americans unfortunately are very complacent about the risk associated with living in the flood plain and living behind levees.
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