LAKE OF THE OZARKS, Mo. — In 2015, the Lake of the Ozarks has seen two of its 10 worst floods, in its 84-year-history. As water poured through the Bagnell Dam floodgates, homes on the Lake and downstream on the Osage and Missouri rivers were flooded. Some have approached the floods with a grim realism: if you live on a body of water, sometimes it floods, they say. But others have expressed frustration with Ameren Missouri — the corporation that owns the dam and manages the Lake level — saying the company was unprepared for the storm despite forecasts, and blaming much of the damage on Ameren.
Could Ameren have preemptively dropped the Lake level as the storms approached? Warren Witt, the Director of Hydro Operations at Bagnell Dam, says it’s not that simple.
‘Sharing The Pain’
With two massive floods at the Lake within a six-month period, some are wondering whether Ameren has changed its policies. Are dam operators waiting longer to open the floodgates? Witt’s answer is an emphatic “No.”
“It is definitely a fluke,” he said of the frequency of the floods. But he emphasized, the policies and guidelines that set the course for dam operators have not changed.
Like it or not, Witt said, “It’s about sharing the pain… we don’t flood the river to save the Lake. We also don’t save the river to flood the Lake.”
That principle is not an arbitrary one. Before the Federal Energy Regulatory Commission (FERC) renewed the operating license for the dam in 2007, Witt explained, significant input was garnered from stakeholders all along the Lake of the Ozarks and Osage and Missouri rivers—that means Lake property owners, resort owners, government officials, the Army Corps of Engineers, farmers downstream, and Ameren had input “from a [power] generation perspective.”
All of the requests are boiled down into the criteria for the FERC license, Witt said, and those criteria regulate how he and his team operates for the next 30-40 years.
Could more have been done before the rain came? Yes, Witt acknowledges, citing the old adage about hindsight. But he stressed, “You never make significant moves based just on a forecast.”
“As we know, predictions can often change significantly,” he pointed out, explaining that if the Lake had been dropped by several feet in anticipation of the three-day rainstorm, and the weather had not behaved like forecasters predicted, dam operators would have been in hot water—with people downstream flooded for no reason, and an abnormally low Lake level without rain to refill it.
Witt says he feels the pain too: he has a lake home and dock. But his primary residence is on the Osage River, so he is doubly affected by the flooding. Other members of his team also own lakefront property. But, he emphasized, their pain can not govern how they respond to catastrophic rainfall like the area saw last weekend. They are required to follow regulatory standards and legal precedent.
The worst flood on record at the Lake of the Ozarks was in 1943. “There were some lawsuits that came out of that,” Witt explained, “and a court actually established criteria for how to calculate flows that the river ought to be seeing under these flood conditions.”
“Those rules,” he said, “have carried through in our FERC licenses ever since the 1940s.” At the core of the court decision was the question, “what would the flooding on the river naturally be if there wasn’t a dam and a lake?” The answer to that question is largely mathematical, and it is what defines the “natural flow” rules. Those rules do not rely at all on long-term weather forecasts, but only on the present weather.
This weekend’s actions were completely in line with the precedent set by that court decision and Ameren’s actions since then, Witt contends. He also points out his team did actually open the floodgates earlier than they were required to, once rain began to fall and it was obvious there would be much more. The gates were opened when the Lake level hit 659.5 feet, which is half a foot below full pool and a foot-and-a-half below the level (661) at which they are required to open them.
It has appeared to some that Ameren was caught off-guard by the storm, but Witt points out his team always has access to high-tech weather forecasts and is constantly monitoring predictions. Those forecasts are run through a complex computer algorithm which helps dam operators understand how runoff might behave based on potential rainfall patterns.
But the reality is, while the team has some leeway to act on the front end of a storm, they are mainly constrained to responding to conditions on the ground. Other entities also have influence in the decision: Witt pointed out the Army Corps of Engineers may opt to open the Truman Dam floodgates, which would raise the Lake of the Ozarks level if Bagnell Dam did not also increase its flow. The Corps might also request Bagnell Dam close its floodgates and only pass local inflows through the dam, if the Osage or Missouri rivers have swelled too much.
Could the floodgates be closed before the Lake drops back down to 660? Witt says it’s a real possibility.
While Witt gave this interview on Monday evening at 5 p.m., the Bagnell Dam floodgates were passing more water than at any time during the current flood. The total flow of the dam was 104,617.10 cubic feet per second (cfs) — more than 750,000 gallons per second. The Lake rose for two and a half days straight, but not because the floodgates couldn’t keep up. The dam was still only running at less than half its capacity, Witt said. The maximum possible flow is 225,000 cfs. During the infamous 1943 flood, the dam was allowing 220,000 cfs.
The Lake level nearly reached 664 before it crested at 663.83 on Monday evening, but Witt says Ameren’s flooding rights go even higher than that. For much of the lake, Ameren is protected even if waters reach 665; further upstream, the flooding rights reach 674. “If we’re at 660 at the dam in a pretty good flood,” he said, “[upstream properties] may be at 665.” The way the Lake was developed provides a very slim margin of error for flooding, as evidenced by many homes that were filled with water twice in 2015. Truman Lake, by contrast, was built for flood control, and Truman Dam can help lessen flooding at Lake of the Ozarks. During July’s flood, flows through Truman were completely stopped, to mitigate the high waters at Lake of the Ozarks.
Witt says he understands property owners’ frustration, and in these situations he hopes to educate people. “It’s not as simple as they think it is… and we can’t just penalize people on the river to protect people on the Lake.”
“Some people understand that,” he said. “A lot of people don’t.”
This was not the worst flood on record, but Witt says it, along with last summer’s deluge, are definitely in the top ten for Lake of the Ozarks.