skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


Title: The Fragility of Bedform‐Induced Hyporheic Zones: Exploring Impacts of Dynamic Groundwater Table Fluctuations
Abstract Hyporheic zones are commonly regarded as resilient and enduring interfaces between groundwater and surface water in river corridors. In particular, bedform‐induced advective pumping hyporheic exchange (bedform‐induced exchange) is often perceived as a relatively persistent mechanism in natural river systems driving water, solutes, and energy exchanges between the channel and its surrounding streambed sediments. Numerous studies have been based on this presumption. To evaluate the persistence of hyporheic zones under varying hydrologic conditions, we use a multi‐physics framework to model advective pumping bedform‐induced hyporheic exchange in response to a series of seasonal‐ and event‐scale groundwater table fluctuation scenarios, which lead to episodic river‐aquifer disconnections and reconnections. Our results suggest that hyporheic exchange is not as ubiquitous as generally assumed. Instead, the bedform‐induced hyporheic exchange is restricted to a narrow range of conditions characterized by minor river‐groundwater head differences, is intermittent, and can be easily obliterated by minor losing groundwater conditions. These findings shed light on the fragility of bedform‐induced hyporheic exchange and have important implications for biogeochemical transformations along river corridors.  more » « less
Award ID(s):
2142686
PAR ID:
10523021
Author(s) / Creator(s):
 ;  ;  ;  
Publisher / Repository:
DOI PREFIX: 10.1029
Date Published:
Journal Name:
Water Resources Research
Volume:
60
Issue:
7
ISSN:
0043-1397
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; (, Hydrology and Earth System Sciences)
    null (Ed.)
    Abstract. Groundwater table dynamics extensively modify the volume of the hyporheic zoneand the rate of hyporheic exchange processes. Understanding the effects ofdaily groundwater table fluctuations on the tightly coupled flow and heattransport within hyporheic zones is crucial for water resourcesmanagement. With this aim in mind, a physically based model is used to explorehyporheic responses to varying groundwater table fluctuationscenarios. The effects of different timing and amplitude of groundwater tabledaily drawdowns under gaining and losing conditions are explored in hyporheiczones influenced by natural flood events and diel river temperaturefluctuations. We find that both diel river temperature fluctuations and dailygroundwater table drawdowns play important roles in determining thespatiotemporal variability of hyporheic exchange rates, temperature ofexfiltrating hyporheic fluxes, mean residence times, and hyporheicdenitrification potentials. Groundwater table dynamics present substantiallydistinct impacts on hyporheic exchange under gaining or losing conditions. Thetiming of groundwater table drawdown has a direct influence on hyporheicexchange rates and hyporheic buffering capacity on thermaldisturbances. Consequently, the selection of aquifer pumping regimes hassignificant impacts on the dispersal of pollutants in the aquifer and thermalheterogeneity in the sediment. 
    more » « less
  2. ; ; ; ; ; (, Water Resources Research)
    Abstract Hyporheic exchange is a crucial control of the type and rates of streambed biogeochemical processes, including metabolism, respiration, nutrient turnover, and the transformation of pollutants. Previous work has shown that increasing discharge during an individual peak flow event strengthens biogeochemical turnover by enhancing the exchange of water and dissolved solutes. However, due to the nonsteady nature of the exchange process, successive peak flow events do not exhibit proportional variations in residence time and turnover, and in some cases, can reduce the hyporheic zones' biogeochemical potential. Here, we used a process‐based model to explore the role of successive peak flow events on the flow and transport characteristics of bedform‐induced hyporheic exchange. We conducted a systematic analysis of the impacts of the events' magnitude, duration, and time between peaks in the hyporheic zone's fluxes, penetration, and residence times. The relative contribution of each event to the transport of solutes across the sediment‐water interface was inferred from transport simulations of a conservative solute. In addition to temporal variations in the hyporheic flow field, our results demonstrate that the separation between two events determines the temporal evolution of residence time and that event time lags longer than the memory of the system result in successive events that can be treated independently. This study highlights the importance of discharge variability in the dynamics of hyporheic exchange and its potential implications for biogeochemical transformations and fate of contaminants along river corridors. 
    more » « less
  3. ; ; ; ; ; (, Water Resources Research)
    Abstract Coupled groundwater flow and heat transport within hyporheic zones extensively affect water, energy, and solute exchange with surrounding sediments. The local and cumulative implications of this tightly coupled process strongly depend on characteristics of drivers (i.e., discharge and temperature of the water column) and modulators (i.e., hydraulic and thermal properties of the sediment). With this in mind, we perform a systematic numerical analysis of hyporheic responses to understand how the temporal variability of river discharge and temperature affect flow and heat transport within hyporheic zones. We identify typical time series of river discharge and temperature from gauging stations along the headwater region of Mississippi River Basin, which are characterized by different degrees of flow alteration, to drive a physics‐based model of the hyporheic exchange process. Our modeling results indicate that coupled groundwater flow and heat transport significantly affects the dynamic response of hyporheic zones, resulting in substantial differences in exchange rates and characteristic time scales of hyporheic exchange processes. We also find that the hyporheic zone dampens river temperature fluctuations increasingly with higher frequency of temperature fluctuations. This dampening effect depends on the system transport time scale and characteristics of river discharge and temperature variability. Furthermore, our results reveal that the flow alteration reduces the potential of hyporheic zones to act as a temperature buffer and hinders denitrification within hyporheic zones. These results have significant implications for understanding the drivers of local variability in hyporheic exchange and the implications for the development of thermal refugia and ecosystem functioning in hyporheic zones. 
    more » « less
  4. ; ; ; ; (, Water Resources Research)
    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. 
    more » « less
  5. ; ; ; ; ; ; (, Water Resources Research)
    Abstract Many water quality and ecosystem functions performed by streams occur in the benthic biolayer, the biologically active upper (~5 cm) layer of the streambed. Solute transport through the benthic biolayer is facilitated by bedform pumping, a physical process in which dynamic and static pressure variations over the surface of stationary bedforms (e.g., ripples and dunes) drive flow across the sediment‐water interface. In this paper we derive two predictive modeling frameworks, one advective and the other diffusive, for solute transport through the benthic biolayer by bedform pumping. Both frameworks closely reproduce patterns and rates of bedform pumping previously measured in the laboratory, provided that the diffusion model's dispersion coefficient declines exponentially with depth. They are also functionally equivalent, such that parameter sets inferred from the 2D advective model can be applied to the 1D diffusive model, and vice versa. The functional equivalence and complementary strengths of these two models expand the range of questions that can be answered, for example, by adopting the 2D advective model to study the effects of geomorphic processes (such as bedform adjustments to land use change) on flow‐dependent processes and the 1D diffusive model to study problems where multiple transport mechanisms combine (such as bedform pumping and turbulent diffusion). By unifying 2D advective and 1D diffusive descriptions of bedform pumping, our analytical results provide a straightforward and computationally efficient approach for predicting, and better understanding, solute transport in the benthic biolayer of streams and coastal sediments. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email