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Updated: Oct 26, 2025

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Published on: September 26, 2017
How Hydrologic Connectivity Regulates Water Quality in River Corridors
Jud Harvey1, Jesus Gomez-Velez1, Noah Schmadel1
1Earth Surface Processes Division (Harvey, Schmadel, Choi), and Integrated Modeling and Prediction Division (Alexander, Eng, Schwarz), U.S. Geological Survey, Reston, Virginia, USA; Civil and Environmental Engineering (Gomez-Velez), Vanderbilt University, Nashville, Tennessee, USA; Department of Biological Systems Engineering (Scott), Virginia Tech, Blacksburg, Virginia, USA; Department of Ecosystem Science and Management (Boyer), Pennsylvania State University, State College, Pennsylvania, USA; Office of Research and Development (Golden), U.S. Environmental Protection Agency, Cincinnati, Ohio, USA; Institute of Arctic and Alpine Research (Kettner), University of Colorado, Boulder, Colorado, USA; Washington Water Science Center (Konrad), U.S. Geological Survey, Tacoma, Washington, USA; New England Water Science Center (Moore), U.S. Geological Survey, Pembroke, New Hampshire, USA; College of Earth, Ocean, and the Environment (Pizzuto), University of Delaware, Newark, Delaware, USA; and School of Geosciences (Soulsby), University of Aberdeen, Aberdeen, Scotland, GRB.
River connectivity, a balance between flow and water exchange, impacts water quality. Intermediate connectivity best removes nitrogen by optimizing contact with reactive sediments.
Area of Science:
- Environmental Science
- Hydrology
- Biogeochemistry
Background:
- River flow is influenced by water exchange with off-channel storage zones, impacting biogeochemical processes.
- River connectivity, the balance between downstream flow and water exchange with sediments, is crucial for water quality.
Purpose of the Study:
- To introduce a dimensionless metric quantifying river connectivity.
- To assess the relationship between river connectivity and water quality, specifically nitrogen removal.
- To identify optimal connectivity levels for maximizing biogeochemical processing and protecting downstream water quality.
Main Methods:
- Developed a dimensionless metric to quantify river connectivity.
- Utilized a metric of reaction significance based on river connectivity.
- Conducted simulations to understand nitrogen removal processes in rivers of varying sizes.
Main Results:
- Intermediate river connectivity levels are most effective for nitrogen removal in Northeastern US rivers.
- Optimal connectivity balances water exchange frequency, residence time, and sediment contact volume.
- Denitrification primarily occurs in hyporheic zones of smaller rivers and through turbulent mixing in larger rivers.
Conclusions:
- River connectivity is a key factor influencing water quality and contaminant processing.
- Intermediate connectivity maximizes nitrogen removal by optimizing sediment contact.
- The developed metrics can guide river management strategies for improved water quality and ecosystem function.
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