The Lake of the Ozarks is at the mercy of Mother Nature.
As the winter drawdown begins, Ameren Missouri and Bagnell Dam Plant officials ― and lakefront homeowners ― are keeping a watchful eye on lake levels as the area continues to see little rain.
As noted by Bagnell Plant consulting engineer Alan Sullivan, “there is no external supply of water available to the lake if it does not rain.”
Despite a decent rainfall last week, the lake area remains drier than usual. No comparative data is available for the lake, but from July through November only ten inches of rain has been recorded at the Bagnell Dam Plant. In fact, November was the driest since last spring with only .83 of an inch recorded.
Yet, the lake was only 3.2 feet below full pool of 660 feet above sea level as of Dec. 1. That is 1.2 feet below the FERC guide curve of 658 for December, but compares favorably with three out of the last five years.
Ameren officials met with the Corps of Engineers, which regulates Truman Dam, before Thanksgiving to discuss coordinated operation of Truman Dam and Bagnell Dam during times of flooding and of drought. Sullivan said the Corps has agreed to release a small amount of water monthly from Truman Lake into the Lake of the Ozarks as long as the drought continues.
Like Lake of the Ozarks, Truman Lake has a minimum elevation. As of Tuesday, Truman Lake was three-tenths of a foot above its minimum of 704.
“So, there isn’t much water available in storage at Truman,” Sullivan said.
Ameren is required in its FERC License to supply at least a 900 cfs minimum flow each day down the Osage River, as well as additional water during select times for fish sampling, another FERC requirement, according to Sullivan.
“These flows are defined in our FERC license and supported by state and federal environmental agencies,” Sullivan said. “With current dry conditions, this minimum flow will draw down the lake level about three hundredths of a food per day. This doesn't seem like much until we multiply that times 30 days each month, resulting in nearly a one foot draft from the lake each month in order to provide minimum flow. Each little rain we receive helps somewhat; however, only rain that falls directly on the lake provides inflow, and upland rains soak into the dry ground.”
The Bagnell Plant has only been able to provide no more than the minimum flow (with few exceptions) since June. Occasionally, the plant is called on to supply short-term (one hour or less) emergency energy to the Ameren power system. These instances are rare, Sullivan said, but are valuable to the electrical grid. The short generation runs have little effect on the lake levels, he said.
The guide curve in the FERC license shows a winter drawdown (January to April) to 654 The absolute low lake level limit generally runs three feet below the guide curve, except in emergency situations. An annual fluctuation of six feet is normal for the Lake of the Ozarks, Sullivan noted, which is far less than other lakes in Missouri, especially those that are government owned.
Will the lake fall below the 654 mark this winter because of continued drought conditions?
“At this point, we can’t say. It depends on if we receive some significant amounts of much-needed rain fall,” Sullivan said. “Depending on other needs and factors, it may very well get to that point simply by the required flows we must run.”
Ameren recommends that waterfront property owners take normal winter precautions to protect their docks by adjusting cables to allow for lower lake levels. It is also important to have a dock de-icer available if the winter is colder than expected.
Also, Ameren has a lake level line that is available 24/7 by calling 573-365-9205. Lake level forecasts are updated on that recording.