Abstract
Downstream flow in rivers is repeatedly delayed by hydrologic exchange with off-channel storage zones where biogeochemical processing occurs. We present a dimensionless metric that quantifies river connectivity as the balance between downstream flow and the exchange of water with the bed, banks, and floodplains. The degree of connectivity directly influences downstream water quality — too little connectivity limits the amount of river water exchanged and leads to biogeochemically inactive water storage, while too much connectivity limits the contact time with sediments for reactions to proceed. Using a metric of reaction significance based on river connectivity, we provide evidence that intermediate levels of connectivity, rather than the highest or lowest levels, are the most efficient in removing nitrogen from Northeastern United States’ rivers. Intermediate connectivity balances the frequency, residence time, and contact volume with reactive sediments, which can maximize the reactive processing of dissolved contaminants and the protection of downstream water quality. Our simulations suggest denitrification dominantly occurs in riverbed hyporheic zones of streams and small rivers, whereas vertical turbulent mixing in contact with sediments dominates in mid-size to large rivers. The metrics of connectivity and reaction significance presented here can facilitate scientifically based prioritizations of river management strategies to protect the values and functions of river corridors.
Original language | English |
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Pages (from-to) | 369-381 |
Number of pages | 13 |
Journal | Journal of the American Water Resources Association |
Volume | 55 |
Issue number | 2 |
DOIs | |
State | Published - Apr 2019 |
Externally published | Yes |
Funding
The work is a product of the John Wesley Powell Center River Corridor Synthesis Group, supported by U.S. Geological Survey and National Science Foundation Hydrologic Sciences Program. USGS authors received additional support from the USGS National Water Quality Program. Gomez-Velez received additional support from the DOE Office of Biological and Environmental Research (BER) in the Subsurface Biogeochemistry Program (SBR) as part of SBR’s Scientific Focus Area at the Pacific Northwest National Laboratory (PNNL). The synthesis is based entirely on analysis of published information and publicly available data sources. Any use of trade, firm, or product is for descriptive purposes only and does not imply endorsement by the U.S. Government. The work is a product of the John Wesley Powell Center River Corridor Synthesis Group, supported by U.S. Geological Survey and National Science Foundation Hydrologic Sciences Program. USGS authors received additional support from the USGS National Water Quality Program. Gomez-Velez received additional support from the DOE Office of Biological and Environmental Research (BER) in the Subsurface Biogeochemistry Program (SBR) as part of SBR's Scientific Focus Area at the Pacific Northwest National Laboratory (PNNL). The synthesis is based entirely on analysis of published information and publicly available data sources. Any use of trade, firm, or product is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Funders | Funder number |
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DOE Office of Biological and Environmental Research | |
John Wesley Powell Center River Corridor Synthesis Group | |
U.S. Government | |
National Science Foundation | 1831623 |
U.S. Geological Survey | |
Biological and Environmental Research | |
Pacific Northwest National Laboratory |
Keywords
- Clean Water Rule
- hydrologic connectivity
- hyporheic flow
- river corridor