Update: Contained within the 2007 license renewal with FERC is language regarding a "Memorandum of Agreement" (MOA) that exists between Ameren UE and the Corps of Engineers in regards to coordinating operations with Truman Dam (which is managed by the Corps) to reduce erosion and flooding along the lower Osage River and establish "ramp-down" rates after high flow conditions. There is also a MOA with the Missouri Department of Conservation allowing for the reduction of minimum outflow below the established minimum to increase the level of dissolved oxygen in the river. According to the license these non-normal conditions account for 6% of Bagnell Dams yearly operational status.
From the U.S. Army Corps of Engineers Kansas City District website FAQ section:
"Lake Visitor: Why does Truman Lake hold water when the Lake of the Ozarks is low?
Ranger: This may sound like a complicated answer. The U.S. Army Corps of Engineers manages Truman Lake and flood control is its primary mission. Often people think that the two lakes are operated by the same agency. They are not. AMEREN UE, a private enterprise that generates electricity for profit, manages the Lake of the Ozarks (LOZ). AMEREN UE may generate power and reduce the lake levels while the Corps of Engineers is either maintaining a multipurpose pool level at Truman Lake or attempting to control flooding downstream.
When it comes to flood control, Truman Lake is just one piece in a very large puzzle that includes 5 other flood control projects in the Osage River drainage basin. The other projects are Pomme de Terre Lake (Pomme de Terre River), Stockton Lake (Sac River), Hillsdale Lake in Kansas, Pomona Lake in Kansas, and Melvern Lake in Kansas. The Corps of Engineers, Kansas City District, manages all these lake projects. There are 18 flood control lakes in the Kansas City District helping to control potential floods on small rivers, the Missouri River, and the Mississippi River.
You can easily see Truman Lake is a very important piece to a very large flood control puzzle. With a quick look downstream from Truman Dam people can see a very dramatic difference between a flood control project and its neighbor operated by a private power generating corporation."
The complete FAQ can be found at:
http://www.nwk.usace.army.mil/harryst/faq.htm - link no longer works.