Stored Flood Water Being Used to Generate Hydropower at Mark Twain Lake

St. Louis, July 14, 2008 - The U.S. Army Corps of Engineers St. Louis District announced Thursday that it was beginning 24-hour power generation at its Clarence Cannon Power Plant at Mark Twain Lake, Mo. The multi-purpose reservoir located in northeast Missouri has been storing excessive amounts of storm water since June 11, aiding in reducing river stages on the Mississippi River south of Louisiana, Mo. Mark Twain Lake is located on the Salt River, which enters the Mississippi River just north of Louisiana.

The lake had been cleared to begin power generation only after river stages on the Mississippi River were within a safe, acceptable level. Close coordination has been made with downstream communities, the St. Louis District’s Water Control Office, and the Southwestern Power Administration. The power plant has a 58 megawatt unit, capable of generating enough power to sustain a town of 20,000 people.

Mark Twain Lake’s crest for this recent flood event was 628, utilizing about 60 percent of its flood storage capacity. Approximately 8,000 cubic feet per second (cfs) of water is being released from the dam as part of the power generation. One cfs is approximately 7.5 gallons per second.

This release has necessitated the restriction of boating on the re-regulation dam pool, approximately 9.5 miles of the Salt River just downstream of Clarence Cannon Dam. Releases will drop the lake elevation approximately five to six inches a day. Discharges are expected until the lake reaches an elevation of 615. As of Monday morning at 8 a.m. the lake was at 626.20.

The high water elevation at the lake is impacting recreation infrastructure and local roads. The lake’s two beaches are currently closed, major boat ramps are flooded and portions of several county roads are closed. Boaters are currently utilizing high water boat ramps which were installed after the 1993 flood. The lake staff said that all major road access areas are open and hazards are marked to keep the public safe.

During the height of June’s flooding, Mark Twain Lake (Monroe City, Mo.) in conjunction with the Harry S. Truman Dam and Reservoir (Warsaw, Mo.), another Corps of Engineers operated reservoir, contributed to reducing the Mississippi River’s stage at St. Louis and points south to Cape Girardeau, Mo., by approximately 3.5 feet.

Mark Twain Lake held back inflows of over 21,000 cubic feet per second (cfs) several times in June, while releasing only 50 cfs during the time the Mississippi River was cresting.

With the prolonged crest occurring on the Mississippi River from Louisiana, Mo., to Grafton, Ill., this reduced the crests on the Mississippi, in this reach, by 1+ feet.

Truman Lake, the largest flood control lake in Missouri, is operated by the Corps’ Kansas City District, and at the height of the flood utilized 50 percent of its flood control storage. The lake is located on the Osage River and its flows eventually end up in the Missouri River.

Truman has held back inflows in the 80,000 cfs range throughout June, and only released lesser flows when downstream conditions allow. Truman is also a hydropower producing facility with 6 turbine-generators and operates the Clarence Cannon Power Plant remotely from its Warsaw control room.

The combined flood control activities of Mark Twain Lake and Truman Lake (100,000 cfs held back) have reduced the stages at St. Louis and points south by approximately 3.5 feet. A 30,000 cfs increase at St. Louis is approximately a 1 foot rise as it relates to current high water river stages.

A detailed analysis will be conducted to examine the flood control benefits of all reservoirs. There are many other reservoirs in Missouri, Illinois, Kansas and Iowa that have had significant impacts in reducing the river stages. These two lakes demonstrate the system of reservoirs working together to help reduce stages downstream.