Gauging Summer Flow

Knowing whether river forecasters are running the Tennessee River properly all comes down to gauging the flow of water that passes through Chickamauga Reservoir.

Much like gauging the amount of gas you have in your car so that you'll be able to do errands all day without running out of fuel, TVA's river forecasters must gauge the flow of the river to make sure it's providing all of its public benefits, everywhere in the system. How long can river forecasters maintain a continuous flow of water from all reservoirs to meet downstream flow requirements without draining the tributary reservoirs.

Meeting minimum flow release year-round is essential, but most challenging in the summer. Without releases from the cool tributary reservoirs, riverbeds downstream of dams would dry out, tailwater fisheries would wane, water quality would suffer and commercial barge traffic would be grounded.

In July and August, when air and river temperature is the warmest, the need for river flow increases. Municipalities and industries need a plentiful supply of flowing water to operate and protect their assimilative capacity. Likewise, the call for hydro, nuclear and fossil power is at its peak and cannot be generated without a cool, steady river flow during the long, hot summer.

The Fuel for the Flow

The 10 tributary reservoirs in the eastern Tennessee Valley (Watauga, South Holston, Cherokee, Douglas, Fontana, Norris, Chatuge, Nottley, Hiwassee and Blue Ridge) are like fuel tanks, filled with water amassed by Mother Nature via winter and spring rain and runoff. That water is fuel for summer's flow. Chickamauga Reservoir is the point where all calculations and river models tell river forecasters if they're on track in delivering enough flow for the entire system.

Whether rain is plentiful or scarce, river forecasters strive to get it right!

Accumulative, proportionally rationed and meticulously measured water releases from tributary reservoirs must equal minimum flow requirements at Chickamauga. Downstream, Kentucky Reservoir, too, has minimum flow requirements. Here's what they look like:

Chickamauga In a Year of Ample Rain

• July 1 to July 31—25,000 cubic feet per second
• August 1 to Labor Day—29,000 cubic feet per second

Chickamauga In a Dry Year

• July 1 to July 31—13,000 cubic feet per second
• August 1 to Labor Day—25,000 cubic feet per second

Kentucky Minimum Flow

• July 1 to July 31—18,000 cubic feet per second
• August 1 to Labor Day—25,000 cubic feet per second