Journal article
Sinuosity-Driven Hyporheic Exchange: Hydrodynamics and Biogeochemical Potentials
Water resources research, Vol.60(4), p.n/a
04/2024
DOI: 10.1029/2023WR036023
Abstract
Hydrologic exchange processes are critical for ecosystem services along river corridors. Meandering contributes to this exchange by driving channel water, solutes, and energy through the surrounding alluvium, a process called sinuosity-driven hyporheic exchange. This exchange is embedded within and modulated by the regional groundwater flow (RGF), which compresses the hyporheic zone and potentially diminishes its overall impact. Quantifying the role of sinuosity-driven hyporheic exchange at the reach-to-watershed scale requires a mechanistic understanding of the interplay between drivers (meander planform) and modulators (RGF) and its implications for biogeochemical transformations. Here, we use a 2D, vertically integrated numerical model for flow, transport, and reaction to analyze sinuosity-driven hyporheic exchange systematically. Using this model, we propose a dimensionless framework to explore the role of meander planform and RGF in hydrodynamics and how they constrain nitrogen cycling. Our results highlight the importance of meander topology for water flow and age. We demonstrate how the meander neck induces a shielding effect that protects the hyporheic zone against RGF, imposing a physical constraint on biogeochemical transformations. Furthermore, we explore the conditions when a meander acts as a net nitrogen source or sink. This transition in the net biogeochemical potential is described by a handful of dimensionless physical and biogeochemical parameters that can be measured or constrained from literature and remote sensing. This work provides a new physically based model that quantifies sinuosity-driven hyporheic exchange and biogeochemical reactions, a critical step toward their representation in water quality models and the design and assessment of river restoration strategies.
Meandering causes pressure gradients that induce water flow from the channel to the alluvial aquifer and back to the channel. This circulation process is known as sinuosity-driven hyporheic exchange, and it has traditionally been associated with ubiquitous and favorable impacts on ecosystem services. However, its presence and biogeochemical implications can vary across river networks and even result in detrimental conditions. Here, we conducted a systematic modeling study to understand the hydrodynamics of sinuosity-driven hyporheic exchange and its implications for nitrogen transformations. Our results show that the compressing effect of RGF can significantly reduce or vanish the hyporheic zone. Yet, narrow meander necks, characteristic of high-sinuosity channels, shield the hyporheic zone even under extreme regional gradients. This shielding effect has been previously ignored and highlights the persistent nature of the exchange and its resilience against external modulators. We also use our model to propose and evaluate a framework based on measurable physical and biogeochemical parameters to identify the conditions leading to a meander acting as a net source or sink of nitrogen. These mechanistic insights can guide the design and evaluation of river restoration strategies and provide a critical foundation for its representation in water quality models.
We assess the role of hydrodynamic drivers and modulators in the hyporheic exchange and the biogeochemical potential of meandering rivers The meander neck in high-sinuosity channels shields the effect of regional groundwater fluxes, resulting in persistent hyporheic zones Hyporheic denitrification potential decreases with increasing sinuosity, and dissolved and particulate organic carbon availability limits it
Details
- Title: Subtitle
- Sinuosity-Driven Hyporheic Exchange: Hydrodynamics and Biogeochemical Potentials
- Creators
- Daniel Gonzalez-Duque - Vanderbilt UniversityJesus D. Gomez-Velez - Oak Ridge National LaboratoryJay P. Zarnetske - Michigan State UniversityXingyuan Chen - Pacific Northwest National LaboratoryTimothy D. Scheibe - Pacific Northwest National Laboratory
- Resource Type
- Journal article
- Publication Details
- Water resources research, Vol.60(4), p.n/a
- DOI
- 10.1029/2023WR036023
- ISSN
- 0043-1397
- eISSN
- 1944-7973
- Publisher
- Amer Geophysical Union
- Number of pages
- 28
- Grant note
- US Department of Energy (DOE); United States Department of Energy (DOE) EAR-1830172; OIA-2020814; OIA-2312326; DE-AC05-00OR22725 / Environmental System Science Program, as part of the River Corridor Scientific Focus Area project at Pacific Northwest National Laboratory, the Watershed Dynamics and Evolution Science Focus Area at Oak Ridge National Laboratory DOE Public Access Plan National Science Foundation; National Science Foundation (NSF) U.S. Department of Energy (DOE), Office of Science, Biological and Environmental Research; United States Department of Energy (DOE) U.S. Department of Energy; United States Department of Energy (DOE)
- Language
- English
- Date published
- 04/2024
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984962628302771
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