High water levels threatened Cumberland River dams

Wednesday, May 5, 2010 at 1:00am
Staff reports

With more than 13.5 inches of rainfall recorded Saturday and Sunday, the U.S. Army Corps of Engineers Nashville District had to act fast to make sure the dams it operates on the Cumberland River and its tributaries remained secure.

Typically, the dams hold back floodwater and limit the amount of water that reaches Nashville and other cities along the river, but over the weekend lakes reached record levels and forced the Corps to release water.

Old Hickory Dam in Hendersonville was one of the lakes that reached a record elevation, the unit of measure used to calculate water levels.

Old Hickory Lake reached an elevation of 451.4 feet. At 452 feet, water would have begun to flow over the dam, the Corps said in a statement. Instead, floodgates were opened to release water downstream.

With the Cumberland River receding (It crested Monday at 51.9 feet, about 12 feet above flood stage.) the Corps is working to reduce water levels behind the dams to more normal levels. As flooding subsides more water will be released from the dams.

Here’s the latest on what the Corps is doing at each dam.

Wolf Creek Dam on the Cumberland River, Jamestown, Ky.
• Two hydropower units at Wolf Creek Dam were brought online at midnight Monday.
• As local runoff subsides, other hydropower units will be brought on-line to start the process of pulling the lake level back down toward the 680 target elevation. That process is likely to begin late Tuesday or early Wednesday.

Old Hickory Dam on the Cumberland River, Hendersonville
• Old Hickory Lake has been used to hold back water from Nashville and was hit with heavy rainfall on Saturday and Sunday.
• Releases from the dam began Sunday in order to bring the lake down to a safe level and to prevent overtopping of the dam.
• Releases were cut Sunday night to reduce flooding in Nashville.
• The lake level at Old Hickory is showing a slight rise, which should stop and begin to fall over the next few days, allowing water managers to reduce the discharge from Old Hickory Dam.

J. Percy Priest Dam on the Stones River, Nashville
• J. Percy Priest Lake has captured runoff water that has considerably reduced the flooding in Nashville and points downstream.
• Holding back water at J. Percy Priest has resulted in an unusually high lake level.
• The spillway gates were partially opened at 11:30 p.m. Monday, and were opened further Tuesday morning.
• The plan is to continue with the current releases unless the lake level rises higher and the gates have to be opened in small increments.

Dale Hollow Dam on the Obey River, Celina
• One hydropower unit was brought on at 3 p.m. Monday.
• As local runoff subsides the hydropower units will be brought online to start the process of pulling the lake level down. There is a good chance that spillway gates will need to be opened to pull the lake level down in a timely manner.

Cordell Hull Dam on the Cumberland River, Carthage
• The Cordell Hull lake level crested at elevation 508.33.
• The process is currently underway to make flow reductions at Cordell Hull. The Cordell Hull reductions will result in smaller inflows to Old Hickory and ultimately to lower river stages at Carthage and points downstream, including Nashville.
• Over the next several days the lake level will be brought back down to the summer pool level of 504.0.

Center Hill Dam on the Caney Fork River, Lancaster, Tenn.
• One hydropower unit was brought on at midnight Monday. The release through the orifice gate continues.
• As local runoff subsides and the Cumberland River at Carthage returns to a nonflooding level, the additional hydropower units will be brought online to start the process of pulling the lake level back down toward the 630 feet target elevation.

Cheatham Dam on the Cumberland River, Ashland City
• Cheatham Dam is in free flow with water flowing over the top of the dam’s spillway. The dam was designed to operate in this manner in high water situations.
• Cheatham Lake reached a record level of 404.15 feet, and the lock and resource manager’s facilities have flooded in the process.
• Cheatham will remain in free flow until river flows reach a point that the gates can be placed back in the water and water control capabilities are regained. This will be followed some time later by placing the hydropower units back in service.

Barkley Dam on the Cumberland River in Grand Rivers, Ky.
• The Great Lakes and Ohio River Division (LRD) Water Management Office has an ongoing flood control operation for the Ohio River. This means they are in control of operations at both Barkley Dam and Kentucky Dam. The Nashville District is working closely with LRD and Tennessee Valley Authority staff to develop operation plans.