Tennessee Valley Authority
A look back at the 2007 drought
normal—adj. conforming to a standard; regular, usual, typical.
2007 was anything but.
An unprecedented lack of rainfall resulted in the driest year on record in the eastern part of the Tennessee Valley. As for the challenges faced by those responsible for operating the river system, let’s just say that the folks at TVA hope it’s a record that stands for a very long time.
TVA operates the dams and reservoirs along the Tennessee River system for a wide variety of public benefits, and—except for flood damage reduction—every single one was affected to one degree or another by the drought. In some cases, the situation required extra vigilance in the form of monitoring and/or close communication with stakeholders and other agencies. In others, river flows had to be adjusted—sometimes on an hourly basis.
To learn more about just what was required to manage the river system during the drought and how Valley residents benefited from TVA’s efforts to optimize the use of what little water was available, we talked with a number of TVA staff members who were charged with oversight of the various benefit areas.
Water Supply
How it impacts you: Good quality drinking water is there when you turn on the tap. It’s also available for washing your car or watering your lawn. It’s there for your local fire department. Many industries which contribute to the Valley’s economy have located along the river because of a reliable water supply; they use the water in their operations, and they count on there being enough flow so that the wastewater they discharge into the river can be sufficiently assimilated.
TVA staffer: Mike Eiffe, Program Manager, Water Supply
Challenges in 2007: “State agencies and TVA have been working together for several years to improve regional cooperation in regard to water supply issues, and this year was a perfect scenario for testing the mechanisms for communication and coordination that we’ve developed. We held bi-weekly conference calls with representatives from all the Valley states, updating them on the status of the TVA system and exchanging critical information. While there were several areas of much concern—including Normandy, South Holston, and Watauga, in particular—we stayed in close touch with local utilities and were able to manage river flows to keep reservoir levels above both municipal and industrial water intake structures. Even here in the historically water-rich Tennessee Valley, 2007 really brought home the fact that this is a replenishable, but not an infinite, resource.”
Water Quality
How it impacts you: You have clean water to drink and clean water in which to swim. There’s enough water moving through the system and enough oxygen in the water to support a healthy population of fish and other aquatic life. Your utility bill is lower because treatment costs are reduced when water quality is higher.
TVA staffer: Tyler Baker, Environmental Scientist
Challenges in 2007: “2007 certainly called for vigilance in terms of water quality. In addition to our ongoing monitoring program, we did some additional sampling to spot check conditions, and we tapped into data collected by state agencies, universities, and municipalities. As a result, we had access to a greater quantity of really useful information—both from the reservoirs themselves and in the tailwater reaches below dams. With the benefit of this information, we were better able to protect water quality by carefully using the water in storage. It’s likely, for example, that native mussel populations in the main-stem reservoirs would have suffered had we not kept enough water moving through the system to prevent the water column from stagnating. Mussels live on the bottom, where dissolved oxygen levels may be depleted if there isn’t enough flow to mix the oxygen-rich upper layer of water and the bottom layer. We also knew when we needed to adjust the operation of the aeration equipment we’ve installed at many TVA dams to protect downstream aquatic life. As a result, impacts to water quality were minimized. We didn’t observe large areas of stagnant water, and we didn’t see water quality-related fish kills. Considering the conditions that could have developed because of the drought, it was a good year.”
Power Supply
How it impacts you: Your electric bills are lower when water flowing through generators at TVA dams is used to produce electricity, especially during periods of peak demand. This is because hydropower is a clean, low-cost method of generating electricity. Flows to provide cooling water for TVA nuclear and fossil plants also help hold rates steady, since that means that those cost-effective plants can stay online—thus reducing the need for more expensive generating methods.
TVA staffer: Mike Holt, Manager, Hydro Dispatch Control Center
Challenges in 2007: “This past year was tough for everyone, including TVA. Conventional hydro generation was only 68 percent of normal in the 2007 fiscal year. This was because—instead of maintaining the flow needed to spin the turbines at our hydroelectric plants—we were trying to conserve as much of the available water as possible in the tributary reservoir system. Diminished flows also resulted in impacts to TVA’s nuclear and fossil plants. Output had to be reduced at some of these plants in late summer in order to avoid having river temperatures exceed environmental limits. However, there were still a number of accomplishments to point to with pride. TVA continued to provide uninterrupted power on some of the hottest days on record because we were able to provide enough flow to cool our nuclear and fossil plants. And, by making good use of the minimum flows that are required to maintain other river system benefits, we were able to generate more than 9,000 gigawatt-hours (GWh) of electricity—enough to keep the lights on in about 950,000 homes for a year. During times like these, our goal of making every drop of water count takes on extraordinary importance.”
Navigation
How it impacts you: Having the Tennessee River available as a reliable transportation option boosts the Valley’s economy by about a billion dollars per year. Because shippers can turn to the river as a cost-effective way to transport their goods, you pay lower prices for many of the things you buy—from soft drinks at the grocery store to concrete mix at the home improvement store. You also see fewer trucks on the highways, which reduces traffic congestion, emissions, accidents, and highway damage.
TVA staffer: Kelie Hammond, Program Manager, Navigation
Challenges in 2007: “When all the signs began to point toward an extremely dry year, we began a process of continuous communication and coordination. Starting back in May, we established regular discussions in the form of weekly conference calls with the U.S. Army Corps of Engineers, identifying potential navigation issues on the Tennessee, Cumberland, and Lower Ohio rivers. The good rapport we’ve worked hard to maintain over the years with shippers and towing companies also served us well. For example, towing companies knew that barges might not be able to be loaded quite as heavily as in years past; there wouldn’t be much ‘wiggle room’ in the nine-foot draft requirement. Thanks to scheduled minimum flows, we were able to ensure adequate channel depths for navigation. Barge traffic was uninterrupted, resulting in the transport of more than 50 million tons of goods up and down the river in 2007. Despite some pretty significant challenges, TVA was able to maintain a safe and reliable waterway during even the driest part of the year.”
Recreation
How it impacts you: You may be one of the many Valley residents who enjoy boating, fishing, swimming, rafting, water skiing, or other types of water-based leisure activities. But even if you’re not, you still benefit from the impact of recreation on TVA reservoirs and below TVA dams. Millions of dollars are pumped into the region’s economy each year from tourism, boat manufacturing, marinas, whitewater rafting outfitters, fishing tournaments, etc.
TVA staffer: David Bowling, Manager, River Forecasting Center
Challenges in 2007: “No question about it: recreation on the tributary reservoirs was impacted by the drought. Ramp access and boating hazards became an issue, and marina owners were especially hard-hit. But the situation could have been much worse if it hadn’t been for two facts. On average, tributary reservoirs were about 13 feet higher at the beginning of 2007 due to the reservoir operating policy implemented a few years earlier. Plus, TVA began operating in a conservative mode as soon as we had the first indications that this might be a dry year. We started restricting releases in mid-February—well before our policy specifies release restrictions.
Our integrated approach to river system management made a huge difference as the drought deepened. Meeting minimum flows required to maintain navigation depths, for example, helped keep our nuclear and coal-fired plants operating. Releases needed to protect aquatic habitat resulted in benefits for tailwater recreation. In dry years, our reservoir operating policy is to only release the minimum amount we have to, in order to meet these other constraints. In 2007, we did precisely that. And we did it as fairly as possible, taking into account the total volume of each reservoir. If it seemed that one tributary reservoir was higher than another, that difference was simply the result of the size and shape of the waterbody and the amount of local rainfall.
We also worked to achieve a balance between the types of recreation that are important to Valley citizens. While reservoir recreation impacts are a function of pool levels, tailwater recreation impacts are a function of releases. Some tailwater recreation occurs during periods of low flows, such as wade fishing. Other types, such as rafting, occur during high flows. TVA tries hard to accommodate both. Although most tributary reservoirs never reached targeted summer pool elevations due to the drought, one important fact remains: recreation opportunities were available across the Valley throughout an extremely dry summer.”
Aquatic Habitat
How it impacts you: The health of aquatic plants and animals can serve as an early warning system for humans since the pollution that affects them first may eventually impact us. A diverse biological community—with species represented that are sensitive to pollution—is an indicator of good water quality. The region’s economy is also stronger because of healthy recreational and commercial fisheries.
TVA staffer: Peggy Shute, Manager, Heritage Resources
Challenges in 2007: “Given the drought conditions, we thought we might see some problems with aquatic habitat—and were pleasantly surprised when we didn’t. This may have been due to the fact that the current operating policy likely results in less stress to aquatic species than did the former policy, which exposed biological resources to a greater degree of flow variability throughout the year. There were probably some minimal impacts to the spawning of some fish or other aquatic animals, but no reported increase in the incidence of fish disease or other abnormalities.
As the driest year on record wore on, no one was sure how things would turn out—including TVA managers. In the end, they were gratified to learn that the reservoir operating policy did what it was designed to do. Even in a year that tested the limits like no other, TVA was able to maintain the benefits that Valley residents have come to depend upon.
Many wetlands remained viable, and better water clarity from reduced runoff resulted in more aquatic plant growth—which may benefit some warm-water fisheries. Even though biological communities came through the drought relatively unscathed, 2007 proved to be a helpful exercise in planning for a worst-case scenario. We projected biological impacts from a prolonged drought and formed strategies for dealing with different contingencies. Regardless of what happens in the future, this is really good information to have on hand.”