Spring has arrived across the Southern Appalachians and Mid-Atlantic. On April 10, 2022, the Operational Land Imager (OLI) on Landsat 8 captured this natural-color scene of the area around Knoxville, Tennessee.
According to data from the National Phenology Network, the first leaves and flower blooms in eastern Tennessee came in late-March and early April, about a week earlier than usual. Seasonal greening comes earlier to low-lying parts of the Tennessee Valley, as grasses, bulbs, herbaceous perennials, and shrubs awake from their winter slumber. Elevation effects keep the tops of the region’s long ridges cool and brown in early spring.
On average, every 1,000 feet (300 meters) of increased elevation amounts to a 3-degree Fahrenheit (5-degree Celsius) decrease in temperature. Across the state of Tennessee, average annual temperatures vary from over 62°F (16°C) in the extreme southwestern part of the state to 46°F (8°C) atop the highest peaks in the east. Clinch Mountain, for instance, rises 1,018 feet (310 meters) above the surrounding landscape at a lookout tower in Hawkins County.
The image also highlights some of the hydropower resources found in the Tennessee Valley, including Norris, Cherokee, and Douglas reservoirs. Begun in October 1933 and finished in March 1936, Norris Dam was the first hydroelectric project completed by the Tennessee Valley Authority (TVA). The public power company was created in 1933 in response to the Great Depression and headquartered in Knoxville.
Tennessee is the third-largest hydroelectric power producing state east of the Rocky Mountains (after New York and Alabama) according to U.S. Energy Administration Statistics. Tennessee is home to 26 hydroelectric power plants, plus a large pumped storage hydroelectric facility. Hydroelectric power provides 13 percent of the state’s total electricity generation and almost 90 percent of the state’s renewable generation.
NASA Earth Observatory image by Lauren Dauphin, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland.