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Goal: Sustain Our Nation’s Forests and Grasslands Water and wildfire in the southern Appalachians

After a wildfire, watersheds in the southern Appalachians are at risk of floods and water quality problems. Previous studies suggest that fire in the southern Appalachians has minimal impact on water quality and quantity. However, new research shows that water supply from this region—an important source of drinking water—could be affected by wildfire, especially as the fire season lengthens and droughts make wildfire more likely.

Director’s Choice
An overlook of an Appalachian forest that burned in a wildfire.
Forests of the southern Appalachian Mountains provide many people with clean drinking water. However, after wildfires, water quality can be drastically reduced. USDA Forest Service photo by Joel Scott.

In autumn of 2016, large wildfires burned more than 150,000 acres across the southern Appalachian Mountains. Shortly after rain extinguished a fire near the Coweeta Hydrologic Laboratory, Southern Research Station scientists and Nantahala Ranger District staff met to identify watersheds where the team could study impacts on water quality and supply. Within days and over the next two years, streamflow measurements, water quality samples, and vegetation surveys were conducted. Changes in water quality were closely related to burn severity. In some of the burned watersheds, all of the trees died. Streams in these watersheds were full of dirt, or sediment. In streams, sediment is considered a pollutant and can harm aquatic animals.

The researchers compared the burned watersheds to unburned reference watersheds. The concentration of sediment was up to 168 times greater in burned watersheds. The amount of water flowing through streams also increased. Some streams in burned watersheds had almost 40% more water than similar streams in unburned watersheds.

The extensive forests of the southern Appalachians provide many people downstream with clean drinking water. Understanding how wildfire affects water quality and quantity in the southern Appalachians is critical, especially as the fire season lengthens and wildfires become more likely.

We thank Katie Bower, Patsy Clinton, Andrew Danner, Jason Love, Charles Marshall, Joel Scott, Dani Thornton, and Brandon Welch for assistance in field sampling; and Cindi Brown, Kyle Coleman, Sheila Gregory, and Carol Harper for chemical analyses. We also thank Paul Bolstad for consultation on initial study design.

Principal Investigators
Peter V. Caldwell, Research Hydrologist
Katherine Elliott - SRS (Retired)
Ning Liu, ORISE Fellow Hydrologist
Jim Vose - SRS (Retired)
Jennifer D. Knoepp, Emeritus Research Soil Scientist
4855 - Center for Integrated Forest Science
Strategic Program Areas
Water, Air, and Soil
Wildland Fire and Fuels
Watershed‐scale vegetation, water quantity, and water quality responses to wildfire in the southern Appalachian mountain region, United States
CompassLive Article
Future water supply depends on forested lands
Research Partners
David Zietlow - Northern Research Station
Toral Patel-Weynand - Washington Office, Sustainable Forest Management Research
Mike Wilkins - Nantahala National Forest, Southern Region
Greg Brooks - Nantahala National Forest, Southern Region
Brian Browning - Nantahala National Forest, Southern Region
External Partners
Julie DeMeester - The Nature Conservancy
National Science Foundation Long-Term Ecological Research (LTER) Program