The Influence of Streambed Heterogeneity on Hyporheic Flow in Gravelly Rivers

Rivers and streams are the dominant transport vectors for microplastic (MP) input into marine environments. During transport, complex physicochemical interactions between particles, water and river sediments influence particle mobility and retention. The specific transport mechanisms of MP in fluvial systems are not yet fully understood, and the main reason lies in the limitation in reliable data derived from experimental analysis.In our subproject of the &#8216;CRC 1357 Microplastics&#8217;, we investigate the hydrodynamic mechanisms that control the transport and retention behavior of MP in open channel flows and streambed sediments. In an experimental flume environment, we create realistic hydrodynamic and hyporheic flow conditions by using various porous media (e.g. glass beads or sand) and bedform structures (e.g. riffle-pool sequences, ripples and dunes), modelled from real stream systems.The method developed here can quantitatively analyze the transport of pore-scale particles (1-40 &#181;m) based on fluorometric techniques. Particle velocity distributions and particle transport are measured using Particle-Image-Velocimetry and Laser-Doppler-Velocimetry. With our setup, we can quantitatively investigate time-resolved MP transport and retention through the aqueous and solid phase in a flume scale experiment.

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Insight into the influence of local streambed heterogeneity on hyporheic-zone flow characteristics

Hydrogeology Journal ◽

10.1007/s10040-020-02244-5 ◽

2020 ◽

Vol 28 (8) ◽

pp. 2697-2712

Author(s):

Robert Earon ◽

Joakim Riml ◽

Liwen Wu ◽

Bo Olofsson

Keyword(s):

Surface Water ◽

Hydraulic Conductivity ◽

Penetration Depth ◽

Hyporheic Zone ◽

Flow Characteristics ◽

Time Lapse ◽

Hyporheic Exchange ◽

Tracer Injection ◽

Hyporheic Flow ◽

Exchange Processes

AbstractInteraction between surface water and groundwater plays a fundamental role in influencing aquatic chemistry, where hyporheic exchange processes, distribution of flow paths and residence times within the hyporheic zone will influence the transport of mass and energy in the surface-water/groundwater system. Geomorphological conditions greatly influence hyporheic exchange, and heterogeneities such as rocks and clay lenses will be a key factor for delineating the hyporheic zone. Electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) were used to investigate the streambed along a 6.3-m-long reach in order to characterise geological layering and distinct features which may influence parameters such as hydraulic conductivity. Time-lapse ERT measurements taken during a tracer injection demonstrated that geological features at the meter-scale played a determining role for the hyporheic flow field. The penetration depth of the tracer into the streambed sediment displayed a variable spatial pattern in areas where the presence of highly resistive anomalies was detected. In areas with more homogeneous sediments, the penetration depth was much more uniformly distributed than observed in more heterogeneous sections, demonstrating that ERT can play a vital role in identifying critical hydraulic features that may influence hyporheic exchange processes. Reciprocal ERT measurements linked variability and thus uncertainty in the modelled resistivity to the spatial locations, which also demonstrated larger variability in the tracer penetration depth, likely due to local heterogeneity in the hydraulic conductivity field.

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Analytical modeling of hyporheic flow for in-stream bedforms: Perturbation method and implementation

Environmental Modelling & Software ◽

10.1016/j.envsoft.2018.09.015 ◽

2019 ◽

Vol 111 ◽

pp. 375-385 ◽

Cited By ~ 1

Author(s):

Sven Frei ◽

Morvarid Azizian ◽

Stanley B. Grant ◽

Vitaly A. Zlotnik ◽

Daniel Toundykov

Keyword(s):

Perturbation Method ◽

Analytical Modeling ◽

Hyporheic Flow

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Correction: Laboratory and numerical study of hyporheic flow-mediated DNAPL dissolution in karst conduits

Hydrogeology Journal ◽

10.1007/s10040-018-1874-3 ◽

2018 ◽

Vol 27 (1) ◽

pp. 435-435

Author(s):

Yuexia Wu ◽

Daniel Hunkeler ◽

Nico Goldscheider

Keyword(s):

Numerical Study ◽

Hyporheic Flow ◽

Dnapl Dissolution

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Transient hyporheic exchange during rainfall events in a gaining stream: Field investigation, conceptual model, and numerical interpretation

10.5194/egusphere-egu2020-4386 ◽

2020 ◽

Author(s):

Chengpeng Lu ◽

Keyan Ji ◽

Yong Zhang ◽

Jan Fleckenstein ◽

Chunmiao Zheng ◽

...

Keyword(s):

Numerical Modeling ◽

Conceptual Model ◽

Hyporheic Zone ◽

Flow Model ◽

Surface Flow ◽

Hyporheic Exchange ◽

Biogeochemical Processes ◽

Cross Sectional ◽

Rainfall Events ◽

Hyporheic Flow

Hyporheic exchange is transient in nature, considering the temporal fluctuations in hydrological and/or biogeochemical conditions in surface water and groundwater (SW/GW).&#160; Efforts are needed to further identify the patterns and driving mechanisms of transient hyporheic exchange.&#160; This study combined a reach-scale field survey and numerical modeling analysis to reveal the pattern of transient hyporheic exchange during rainfall events in the Zhongtian River, southeast of China. Field observations revealed hydrodynamic properties and temperature variations in SW/GW, suggesting that the regional groundwater recharged the study reach.&#160; A one-dimensional heat transport solution was built and used to generate the planar and cross-sectional hyporheic flow fields. A two-step numerical modeling procedure, including a hydraulic surface flow model and a groundwater flow model, was then used to simulate the observed flow system. The hyporheic exchange exhibited strong temporal evolution, as indicated by the rainfall event-driven hyporheic exchange, the depth-dependent hysteretic response to rainfall, and the area of local downwelling flow increasing with rainfall. Dynamics of the hyporheic exchange in the study reach, therefore, significantly changed in space and time due to rainfall. The reversal of hydraulic gradient and transient hyporheic exchange were observed and validated using the numerical simulation. Anisotropic hydraulic conductivity is the key to generate transient hyporheic exchange. A revised conceptual model was used to interpret the observed temporal patterns in hyporheic exchange &#160;The pattern of transient hyporheic exchange indicates that transient hyporheic exchange only appears after an increased phase of river stage but does not last for a long time. The temporal pattern of hyporheic exchange can significantly affect the evolution of biogeochemical processes in the hyporheic zone for a gaining stream by, for example, temporally facilitating special biogeochemical processes.

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