Lake Of The Ozarks Rises A Foot In 24 Hours, As Heavy Rainfall Hits The Area

LAKE OF THE OZARKS, Mo. — The Lake of the Ozarks is nearly at full pool, after rising a foot in only 24 hours, between Saturday and Sunday. That's due to at least three inches of rain that fell in multiple heavy thunderstorms at the Lake throughout last weekend.

Full pool is when the water level reaches 660 feet of elevation. As of Sunday, May 20, at 8 p.m., the Lake was at 659.84 feet, and rising. Only a day before, the Lake level was at 658.86 feet, at 8 p.m. on Saturday. By Sunday night, Ameren had generators running at maximum flow, with about 40,054 cubic feet per second (cfs) passing through the dam. The generators are only able to handle around 40,000 cfs; beyond that, if the water level needs to be lowered, Ameren must open the dam’s floodgates.

However, despite the water flow surpassing 41,000 cfs after midnight, Ameren says the floodgates were not opened, but the dam was simply operating at maximum generation capacity. Dam Operator Warren Witt explained to LakeExpo.com that when the Osage River level is low, the generators can pass well over 40,000 cfs in the short-term, sometimes even up to 45,000 cfs. But as the river rises, that flow rate is reduced back to about 40,000 cfs at max generation. Witt said whenever Ameren opens the floodgates, it typically brings the water flow quickly up to a minimum of 50,000 cfs. Witt said the floodgates weren't opened over the weekend, but they got close, as the Lake was just inches from its full-pool level of 660. He added Ameren is permitted by the Federal Energy Regulatory Commission (FERC)—which regulates the dam activities—to allow the water level to rise up to 661 without opening the floodgates, in very unique circumstances such as what the Lake experienced last weekend, as long as there's clear evidence that the water level can be brought back down to the guide curve quickly. The guide curve is the target dam operators aim to keep Lake levels at, throughout the year.

Ameren typically drops the Lake level by about six feet in the winter, in anticipation of spring rains. Those spring rains came in abundance through the weekend, with multiple rounds of heavy thunderstorms on Saturday and Sunday bringing powerful winds and torrential rainfall. Ameren kept water passage through the dam at a relative trickle—between 1,100 and 1,400 cfs over the past few days—until Sunday afternoon, when the flow was increased quickly.

That increased flow through Bagnell Dam also rapidly brought up the Osage River level. It had been hovering at around 552 feet, until around noon on Sunday: then the river rose by 15 feet in a matter of 10 hours (as measured at the dam’s tailwaters). Ameren says they expect the dam to be at heavy generation levels through Wednesday, as water from Truman Lake is passed through Lake of the Ozarks, which is still dealing with inflows from the weekend rains.

In the spring of 2017, the dam's floodgates were open for 26 days straight, as spring rains kept the Lake of the Ozarks area soggy, week after week.

Click here to view Ameren’s hourly Lake level reports: http://apps.ameren.com/HydroElectric/Reports/Osage/HeadWaterTailWater.aspx

Read stories of recent floodgate openings, below: