| Climate resilience
might benefit hydropower and ecosystems but would also negatively impact many rural and indigenous families’ livelihoods and food security. Ding et al say their results provide evidence that future approaches must incorporate possible impacts from both climate and upstream land use change to be able to judge future hydropower outcomes in a robust manner. Although they say their results indicate that win-win situations across all sectors are elusive in the Andean Amazon, the authors go on to state that: “robust planning with a trans-sectoral approach to watershed processes, climate, and engineered systems will be critical for effective and equitable climate mitigation and efforts to restore terrestrial ecosystems in the Andes-Amazon and beyond”.
TVA flood mitigation Flood mitigation strategies prevented approximately
US$406 million of potential damages when two months of normal rainfall fell in three days on the Tennessee River Watershed, during September 2024. Tennessee Valley Authority data collected during
and after Tropical Storm Helene landed in the US, provided insight into the magnitude of the storm that swept across the Appalachian region from 27 September. The seven-day rainfall average in the eastern
Tennessee River Valley on September 29 was 719.5cm, approximately ten times the normal amount of rainfall that occurs in a normal week in late September. And between 29 September to 5 October, TVA’s hydro units generated an average of 2869MW a day, which is 1600MW greater than the average during the same timeframe in 2023. Significant and catastrophic flood damage
to communities occurred throughout northeast Tennessee and western North Carolina. These were areas where its flood control operations could not mitigate impact, TVA said. When that floodwater began flowing into the Tennessee River watershed, its network of dams, and employees, were already at work to protect people downstream.
“Greene County was aided immeasurably by engineer representatives from TVA from the very early stages of the storm and flooding affecting Greene County,” said Greene County Mayor Kevin Morrison. “TVA’s timely, accurate, and wise forecasting and professional advice to our leadership team on the conditions of the Nolichucky River and the Nolichucky Dam saved lives.” Providing flood control of the Tennessee River is a
core mission of TVA and has been since its inception more than 91 years ago. Evaluating rainfall and stream flow data from across the valley provides engineers in TVA’s state-of-the-art river forecast centre the information to make operational decisions to minimise flood impacts along the river system. Using computer modelling, TVA tracks what might have happened without dams and flood mitigation as a way of helping determine how well its system is operating. That data collectively informs “flood damage averted” calculations. Data from this event shows that flood mitigation
strategies enacted by TVA prevented approximately US$406 million of potential damages in Lenoir City, Chattanooga, Kingsport, Elizabethton, Clinton, and South Pittsburg. Since TVA’s inception in 1933, more than US$10 billion in potential flood damage has been averted. “This was some of the highest flood levels we’ve seen in the Tennessee Valley in its entire history,” says James Everett, TVA’s General Manager of River Management. “We saw a record amount of flooding and we saw tremendous amounts of rainfall that caused that flooding. TVA’s dams and the people who manage these dams stepped up to the challenge and managed this record setting event.” The reservoir system and its ability to store water during floods led to significant overall reduction in flood crests in communities along the river system. Without TVA’s system of dams, the river stages at Lenoir City and Chattanooga would have been about 6.4-7m higher than the observed levels during Helene.
Above: TVA’s Watauga Dam on the Watauga River in Carter County, Tennessee, reached a record elevation during the flooding event. It broke the previous record by about 0.9m
References
Sustainable land and irrigation management to limit loss of hydropower in the Andes-Amazon headwaters by Zhaowei Ding, HectorAngarita, Christian Albert Montesinos Cáceres,Waldo Lavado-Casimiro, Jesse A Goldstein, Natasha Batista, Tong Wu, Dave Fishe, Andrea Baudoin Farah, Hua Zheng & Rafael J. P. Schmitt. Communications Earth & Environment (2024) 5:648
https://doi.org/10.1038/ s43247-024-01738-4
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