Drought Update: Rainfall Levels Improve, Runoff Lags

More precipitation in the new year improves drought conditions and hydro generation, even though runoff levels are still playing catch-up.

JANUARY 9, 2017—Mother Nature brought the coldest weather of the season to the Tennessee Valley last week. But she also brought another marked change: more precipitation and improvement of the region’s dry-weather status from “severe” or “extreme” drought to “moderate drought” or even to simply “abnormally dry.”

You can view improvements for yourself on the US Drought Monitor map.

Overall, the past 30 days have been near normal, yielding 4.48 inches of observed precipitation, against the 4.62 inches normally seen in the Valley. Over the past week, we’ve had 0.81 inches, against 1.10 for normal.

James Everett

Though the rain/snow levels improved, that didn’t necessarily translate into runoff improvements. “Over the last 30 days, we’ve been just about normal on precipitation, but we’ve only been about at 60 percent of normal of normal of runoff,” explains James Everett (pictured above), manager of Operations Support for the River Operations Center. “With snow especially, it tends to evaporate or slowly sink into the ground, evaporating or recharging groundwater, but not reaching the river system.”

Still, it’s an improvement over last month’s 50 percent level. And most of the system is at normal winter fill levels, with the exception of one tributary reservoir: Watauga. “So long as we continue to get normal precipitation throughout the winter, runoff levels will slowly but surely catch up,” Everett explains.

“We’ve had adequate storage and for the most part haven’t had to spill any water for flood control,” he says. “Rather, the rains have allowed us to improve our hydro generation levels at the time we need it most.”

Everett notes that River Management constantly monitors and adjusts to weather conditions to ensure optimal long-term benefit to Valley residents in terms of navigation, water supply, hydro generation, recreation, water quality, power operations and—especially important during the winter months—flood control. “As rainfall and runoff conditions improve, we’ll be closely following the weather to make sure the reservoirs are in a ‘ready state’ for any heavy rainfall,” he says.

The River Forecasting Center

TVA's River Forecasting Center, located in Knoxville, Tenn., helps monitor the Tennessee River system to prevent flooding—but also to manage the system in times of drought as well. Their duties include:

• Issuing forecasts of reservoir levels and releases at TVA dams
• Setting hourly generation release schedules for power-producing dams
• Providing notifications during flood events
• Evaluating cooling water needs for coal and nuclear plants
• Monitoring aquatic health

Read more about the River Forecasting Center.