Tennessee Valley Authority
River Forecast Center
TVA’s River Forecast Center, located in Knoxville, Tennessee, is staffed around the clock, 365 days a year. River schedulers continually monitor weather conditions and water quality data, as well as water availability and demand — all with the goal of routing the water through the river system so that it is available where and when it is needed. Their duties include:
- Issuing forecasts of reservoir levels and water releases at TVA dams.
- Providing hourly generation schedules for TVA hydroelectric projects, as well as for eight projects operated by the U.S. Army Corps of Engineers on the Cumberland River system and for the four reservoirs that make up Alcoa Power’s Tapoco project.
- Providing special notifications to the public during flood events.
- Evaluating cooling water needs for TVA coal-fired and nuclear plants.
- Monitoring water quality conditions below TVA dams so that aeration equipment can be turned on when needed to maintain adequate dissolved-oxygen concentrations.
- Serving as the main point of contact in the event of a river system emergency.
Scheduling water releases
River Forecast Center staff issue a daily schedule for water releases from each TVA dam, including the rate and total quantity of water to be released to achieve the multiple purposes of the reservoir system. These purposes include flood damage reduction, navigation, power production, water quality, water supply, and recreation.
Daily release schedules are developed using advanced computer models, an extensive data collection system including more than 300 rainfall and stream-flow gauges, and state-of-the-art radar technology. These schedules take into account the total amount of water stored in the reservoir system, the time it takes to move water through the system, and other reservoir-specific factors such as storage capacity and seasonal operating guides.
Adjustments in water release schedules are made throughout the day in response to ever-changing weather conditions, fluctuations in power demand, and emergencies such as drownings and barge groundings. Releases from multipurpose dams along the main Tennessee River must be adjusted frequently because there is so little storage in these reservoirs. Similarly, tributary dams at summer pool levels must be adjusted frequently during rainy weather to ensure the best use of limited flood storage space. Other uses, such as providing flows for recreation downstream of TVA dams and cooling water for TVA’s coal-fired and nuclear power plants, also require adjustments in release schedules to optimize water use.
Operating flexibility
While many reservoir systems in the United States are operated within specified zones or pool levels, TVA’s river schedulers are authorized to make the best decision based on up-to-the-minute assessments of current and expected conditions and needs. Around-the-clock staffing allows TVA to respond to storms quickly and effectively.
This is important because TVA typically reserves less storage space in its reservoirs than do most other federal dam owners. Most TVA tributary reservoirs can only store an additional inch of runoff at summer pool levels, compared with four or five inches of runoff in many federal reservoirs. This enhances recreational use, but it gives TVA river schedulers less time to refine their forecasts and decide on a release rate from affected dams.
Around-the-clock staffing also helps TVA deal with the challenge presented by uncertainty about the timing or volume of rain and runoff that will be received in the future. In other locations where snowmelt is the primary source of runoff, precise measurements can be made of the depth and density of the snow pack. This gives water managers advance notice of the volume of runoff likely to occur during the spring thaw and weeks, or even months, to prepare. In contrast, most reservoir scheduling for flood damage reduction in the TVA region must be done based on short-term weather forecasts and in reaction to rainfall as it occurs.