by Dana Wilbourn
posted July 23, 2007
) Photo by Dana Wilbourn Gene Gibson, manager of water supply and special projects for TVA, speaks to the Chattanooga Engineers Club. Click to enlarge. |
Mr. Gibson said that the six-month period from January to June has been one of the driest in the history of TVA. TVA has been conserving reservoir water since February, he said. The only releases of water have been for navigation and water supply purposes.
By just maintaining minimum flows, TVA releases 12 billion gallons of water daily through Kentucky Dam into the Ohio River.
The reservoirs on the Tennessee River from Knoxville to the confluence of the Ohio River are near normal simply because these are navigable reservoirs and TVA is required to maintain flows for navigation, water supply and water quality, he said.
Mr. Gibson said that TVA is maintaining a nine-foot navigation depth in the main river, which is the required minimum. Normally, he said, TVA tries to keep an 11-foot navigation depth or greater. Barge companies have been warned that any barge drafting more than nine feet may drag the bottom.
TVA’s power generation has also been impacted by the drought, Mr. Gibson said. TVA has reduced hydro generation to conserve water and the coal-fired and nuclear plants have had to increase usage of the cooling towers to avoid thermal derates at these plants, he said.
Over four million people depend on the TVA water system for their water needs, said Mr. Gibson. Unfortunately, in a drought water usage increases because people start watering their yards and washing their cars, he said.
Besides conserving water, Mr. Gibson listed several other actions TVA is taking because of the drought:
TVA is monitoring the drought, its impacts and water quality
TVA is coordinating its system operations
TVA is participating in a Tennessee Valley Water Partnership
TVA is making bi-weekly conference calls with all seven valley states
TVA has developed a long-term drought management plan
TVA is maintaining contacts with all water utilities in the valley
TVA is providing public information on drought conditions and its impacts
Mr. Gibson said he has two big concerns about the future of water supply in the Tennessee Valley.
First, he said, is the Tennessee-Tombigbee Waterway. Over 200 million gallons per day flow from the Tennessee River into the waterway, he said, for navigation purposes on the waterway. The waterway is not now authorized for water supply. Any legislation that authorizes the waterway as a water supply source could dramatically change the amount of water being drained away from the Tennessee Valley, he said.
Secondly, Mr. Gibson cited a study by Auburn University. He said that the study recommends a massive irrigation project for northern Alabama to grow fruit and vegetables. The study says that large crops in California, where water supply is scarce, could be displaced to northern Alabama if adequate irrigation could be supplied.
Both of these scenarios are what he calls inter-basin transfers (IBT). There are currently 22 small IBTs in the TVA service area, he said. Collectively, they result in just 11 million gallons per day leaving the TVA region and flowing to another. That number is small, he said, and can be put into context when compared to just one lock-through at a TVA dam. One lock-through, he said, uses between 10 and 20 million gallons, depending on which lock is being used.
Small IBTs are not a problem, Mr. Gibson said, big IBTs are. There are no official applications for large IBTs, he said, but informal discussions are ongoing.
Mr. Gibson said that TVA’s water system is not used primarily for generation of electricity. The system, he said, was designed for navigation and flood control. Power generation is a by-product. Other uses of the TVA water system include water supply, water quality and recreation.
Recent rains have helped, Mr. Gibson said, but they have not brought an end to the drought. The 10 tributary reservoirs are still between five feet and 28 feet below median levels.
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