How the System Works

Dams and locks

TVA’s reservoir operations help to maintain year-round passage for commercial vessels with a nine-foot “draft”—that is, the amount of water it takes for them to float.

Nine main and four auxiliary locks on the Tennessee River make it possible for both recreational and commercial vessels to pass easily from one reservoir to another. Much like an elevator, these locks raise or lower barges and other boats from one water level to the next.

When a boat enters the lock, the gates close and the water level inside the lock is raised to the upstream level or lowered to the downstream level, depending on which way the boat is moving. The locks are filled and emptied by gravity—no pumps are used.

If the boat is going downstream, the water level in the lock is lowered by opening the downstream valves so the water can drain out. If the boat is moving upstream, the downstream valves are closed and the upstream valves are opened. This allows water from the upstream side to flow into the lock, filling the chamber to the upstream water level. In about 45 minutes, when the water level inside the lock is equal to the level of the next reservoir, gates at the other end of the lock are opened and the boat can continue on its way.

The largest lock, at Pickwick Dam, is 110 feet wide and 1,000 feet long. The lock at Kentucky Dam is the busiest on the entire system, handling about 35 million tons of river freight per year. Almost all of these locks are in operation 24 hours a day, 365 days a year—and all are available for use without charge.

Tennessee River System

Nine main-river dams form a “staircase” of quiet, pooled water and controlled current—a continuous series of reservoirs that stretches along the entire length of the Tennessee River. From its beginning just above Knoxville, the Tennessee drops a total of 513 feet in elevation before it empties into the Ohio River.

River responsibilities

TVA, the U.S. Army Corps of Engineers (Corps), and the U.S. Coast Guard (USCG) work together to provide a safe and reliable passage for commercial and recreational vessels on the Tennessee River.

The Tennessee River system is managed through a series of dams and navigation locks owned by the United States and operated by TVA and the United States Army Corps of Engineers. In accordance with the TVA Act, TVA is entrusted with the possession, operation and control of the dams, and all appurtenant buildings, machinery, and lands, with the exception of the navigation locks which are entrusted to the Corps. The Coast Guard installs and maintains the navigation aids — buoys, lights, and shoreline markers — along roughly 800 miles of commercial channel. TVA installs and maintains the navigation aids on about 375 miles of secondary, or recreational, channels across the Tennessee Valley.

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