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TVA River Neighbors

Frequently asked questions about the spring fill

image of skierWhen will the water level in my reservoir start going up?

TVA begins aggressively storing water to fill tributary reservoirs in mid-March. This is because rainfall and stream flow records over the past 100 years show that the chance of major flood-producing storms begins to decrease after mid-March. Less flood storage space is needed as plants begin to grow and their roots intercept and reduce runoff from rainfall. In addition, weather patterns begin to change with less chance for larger, more organized storm systems.

Main-river reservoirs are kept at lower levels until mid-April or May because they have less flood storage space. However, since there is not as much difference between winter and summer levels on main-river reservoirs as on tributary reservoirs, it doesn’t take long to bring main-river reservoirs to summer elevations.

When will my reservoir reach “full pool”?

TVA tries to fill tributary reservoirs to summer levels by Memorial Day weekend. Most main-river reservoirs are targeted to fill by mid-April. Watts Bar, Chickamauga, and Fort Loudoun Reservoirs are targeted to fill by mid-May to help reduce the risk of flooding at Chattanooga, Tennessee.

When reservoirs actually reach targeted levels depends on rainfall and stream flows. Beginning in mid-March, tributary reservoirs are allowed to fill as quickly as possible, as long as reservoir levels do not significantly exceed flood guide elevations (which allow for higher reservoir levels in the spring). If low rainfall prevents reservoirs from filling at the desired rate, TVA stores as much water as possible, allowing only minimum releases to protect downstream aquatic habitat.

Do you expect tributary reservoirs to fill on schedule this year?

It’s too early to tell. It’s been really dry the past few months. In fact, rainfall totals for the eastern part of the Tennessee Valley for the two-month period of December and January were only about 56 percent of normal—making it the 6th driest December-through-January period in 117 years of record-keeping. Unfortunately, February isn’t looking any better. As a result, the ground below the top-most layer of soil is getting dry, which means that more water will sink into the ground when it does rain instead of running off into the reservoirs.

March, April, and May are key months for reservoir filling. If rainfall returns to normal during the next three months, we should be able to fill tributary reservoirs to flood guide levels by June 1. However, if conditions remain dry, fill rates will be impacted. In this case, TVA will schedule the reservoir system to conserve water. We will release just enough water to protect downstream water quality and store the rest to ensure that summer elevations are as close to target as possible.

Why isn’t my reservoir filling as fast as other reservoirs?

If your reservoir doesn’t seem to be filling as fast as a neighboring reservoir, it could be because your area isn’t getting as much rain. Rainfall amounts often vary widely even over adjacent watersheds, with direct impacts on the rate that reservoirs in each watershed fill.

Fill rates also can vary significantly from one reservoir to another due to differences in the size of the land area draining into each reservoir, the amount of ground cover, soil characteristics, and reservoir shape and surface area.

What is the “full pool” level on my reservoir?

To see the targeted summer pool level for TVA-managed reservoirs, go to TVA’s Reservoir Information web page. Choose your reservoir from the pull-down menu and then select Operating Guide. You’ll see a graph with a blue line labeled Flood Guide. This is the targeted Memorial Day pool elevation. It is set to support recreation while still preserving a small amount of flood storage capacity as a protection against a potential flood-producing summer storm.

How do I get information about other reservoirs in the region?

Center Hill, Cheatham, Cordell Hull, Dale Hollow, J. Percy Priest, and Old Hickory reservoirs, located in middle Tennessee, and Barkley and Wolf Creek reservoirs, located in Kentucky, are managed by the U.S. Army Corps of Engineers.

Santeetlah, Cheoah, Calderwood, and Chilhowee reservoirs, located on the Little Tennessee and Cheoah rivers in eastern Tennessee and western North Carolina, are managed by Alcoa Power Generating, Inc.




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