Hyporheic exchange in recirculating flumes under heterogeneous bacterial and morphological conditions

AbstractHyporheic exchange (HE) contributes to the biogeochemical turnover of macro- and micro-pollutants in rivers. However, the spatiotemporal complexity and variability of HE hinder understanding of its role in the overall functioning of riverine ecosystems. The present study focuses on investigating the role of bacterial diversity and sediment morphology on HE using a multi-flume experiment. A fully coupled surface–subsurface numerical model was used to highlight complex exchange patterns between surface water and the underlying flow field in the sediments. Under the experimental conditions, the surface water flow induced by bedforms has a prominent effect on both local trajectories and residence time distributions of hyporheic flow paths, whereas mean hyporheic retention times are mainly modulated by average surface flowrates. In case of complex bedform morphologies, the numerical model successfully reproduces the HE estimated by means of salt dilution tests. However, the 2D numerical representation of the system falls short in predicting HE in absence of bedforms, highlighting the intrinsic complexity of water circulation patterns in real scenarios. Finally, results show that higher bacterial diversities in the stream sediments can significantly reduce hyporheic fluxes. This work provides a framework to interpret micropollutants turnover in light of the underlying physical transport processes in the hyporheic zone. The study emphasizes the importance of better understanding the tradeoff between physically driven transport processes and bacterial dynamics in the hyporheic zone to quantify the fate of pollutants in streams and rivers.

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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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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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Influence of Streambed Heterogeneity on Hyporheic Flow and Sorptive Solute Transport

Water ◽

10.3390/w12061547 ◽

2020 ◽

Vol 12 (6) ◽

pp. 1547 ◽

Cited By ~ 1

Author(s):

Yuanhong Liu ◽

Corey D. Wallace ◽

Yaoquan Zhou ◽

Reza Ershadnia ◽

Faranak Behzadi ◽

...

Keyword(s):

Solute Transport ◽

Hyporheic Zone ◽

Preferential Flow ◽

Hyporheic Exchange ◽

Sorptive Capacity ◽

Hyporheic Flow ◽

Sedimentary Architecture ◽

Mixing Dynamics ◽

Facies Types ◽

Sediment Heterogeneity

The subsurface region where river water and groundwater actively mix (the hyporheic zone) plays an important role in conservative and reactive solute transport along rivers. Deposits of high-conductivity (K) sediments along rivers can strongly control hyporheic processes by channeling flow along preferential flow paths wherever they intersect the channel boundary. Our goal is to understand how sediment heterogeneity influences conservative and sorptive solute transport within hyporheic zones containing high- and low-K sediment facies types. The sedimentary architecture of high-K facies is modeled using commonly observed characteristics (e.g., volume proportion and mean length), and their spatial connectivity is quantified to evaluate its effect on hyporheic mixing dynamics. Numerical simulations incorporate physical and chemical heterogeneity by representing spatial variability in both K and in the sediment sorption distribution coefficient ( K d ). Sediment heterogeneity significantly enhances hyporheic exchange and skews solute breakthrough behavior, while in homogeneous sediments, interfacial flux and solute transport are instead controlled by geomorphology and local-scale riverbed topographies. The hyporheic zone is compressed in sediments with high sorptive capacity, which limits solute interactions to only a small portion of the sedimentary architecture and thus increases retention. Our results have practical implications for groundwater quality, including remediation strategies for contaminants of emerging concern.

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The Effect of Stream Discharge on Hyporheic Exchange

Water ◽

10.3390/w11071436 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1436 ◽

Cited By ~ 4

Author(s):

Brian Babak Mojarrad ◽

Andrea Betterle ◽

Tanu Singh ◽

Carolina Olid ◽

Anders Wörman

Keyword(s):

Hyporheic Zone ◽

Hyporheic Exchange ◽

Subsurface Water ◽

Stream Discharge ◽

Hyporheic Flow ◽

Sediment Permeability ◽

Natural Tracer ◽

Streambed Sediments ◽

The Impact ◽

Numerical Approaches

Streambed morphology, streamflow dynamics, and the heterogeneity of streambed sediments critically controls the interaction between surface water and groundwater. The present study investigated the impact of different flow regimes on hyporheic exchange in a boreal stream in northern Sweden using experimental and numerical approaches. Low-, base-, and high-flow discharges were simulated by regulating the streamflow upstream in the study area, and temperature was used as the natural tracer to monitor the impact of the different flow discharges on hyporheic exchange fluxes in stretches of stream featuring gaining and losing conditions. A numerical model was developed using geomorphological and hydrological properties of the stream and was then used to perform a detailed analysis of the subsurface water flow. Additionally, the impact of heterogeneity in sediment permeability on hyporheic exchange fluxes was investigated. Both the experimental and modelling results show that temporally increasing flow resulted in a larger (deeper) extent of the hyporheic zone as well as longer hyporheic flow residence times. However, the result of the numerical analysis is strongly controlled by heterogeneity in sediment permeability. In particular, for homogeneous sediments, the fragmentation of upwelling length substantially varies with streamflow dynamics due to the contribution of deeper fluxes.

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Seasonal variations in surface water groundwater interaction alter the relation of solute transport and biogeochemical processes in the hyporheic zone

10.5194/egusphere-egu21-2949 ◽

2021 ◽

Author(s):

Lara-Maria Schmitgen ◽

Tobias Schuetz

Keyword(s):

Surface Water ◽

Boundary Conditions ◽

Hyporheic Zone ◽

Treatment Plant ◽

Hyporheic Exchange ◽

Waste Water Treatment Plant ◽

Small Scale ◽

Vertical Profiles ◽

Surface Water And Groundwater ◽

Exchange Flux

The hyporheic interstitial as interface between surface water and groundwater offers a unique environment for contaminant attenuation and nutrient cycling, with steep chemical gradients and high retention times. Disentangling the effect of seasonal dynamics in exchange flux intensities and directions, we carried out 19 measurement campaigns where we sampled the continuum surface water - hyporheic zone - groundwater and the climatic and hydraulic boundary conditions of a whole year. Groundwater, surface water and hyporheic zone pore water from four depths were sampled at two vertical profiles in a second order stream about 150 m downstream a municipal waste water treatment plant effluent. Samples were analyzed for physical water parameters, major anions, ammonium, iron, manganese, NPOC and five selected pharmaceuticals (diclofenac, carbamazepine, caffeine, ethinylestradiol and clofibric acid). Surface water and groundwater levels as well as river discharge were measured to quantify the hydraulic boundary conditions. In addition, three vertical profiles, each equipped with five newly developed probes (Truebner AG) allowed a parallel monitoring of continuous bulk water temperatures and bulk electrical conductivity dynamics over two years. Furthermore, continuous hyporheic exchange flux intensities and exchange depths were calculated using analytical and numerical model schemes to allow distinguishing between small scale transport and attenuation processes.The typical behavior of the redox sensitive metals and nutrients with depth is visible in each single profile snapshot. The picture is not as clear for the examined pharmaceuticals, because dilution has a major effect on the observable low concentrations. However, a clear seasonal variation driven by hydraulic and climatic processes can be observed for all substances. We were able to trace the organic pollutants down to the groundwater. Furthermore, the influence of hyporheic exchange flux intensities and directions on nutrient and contaminant depth profiles is shown.

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Are in-stream transport and hyporheic exchange parameters identifiable from tracer test data?

10.5194/egusphere-egu2020-17523 ◽

2020 ◽

Author(s):

Andrea Bottacin-Busolin

Keyword(s):

Surface Water ◽

Water Column ◽

Transport Model ◽

Transport Processes ◽

Hyporheic Exchange ◽

Model Parameters ◽

Cross Sectional ◽

One Dimensional ◽

Stream Transport ◽

Exchange Parameters

Inverse modeling approaches based on tracer data are often used to characterize transport processes in streams and rivers. This generally involves the calibration of a one-dimensional transport model using concentrations measured in the surface water at one or multiple locations along a stream reach. A major concern is whether the calibrated model parameters are representative of the physical transport processes occurring in the water column and the underlying sediment bed. This study looks at the identifiability of the parameters of a physically based one-dimensional stream transport model that represents hyporheic exchange as a vertically attenuated mixing process in accordance with recent experimental evidence. It is shown that, if the average flow velocity and hydraulic radius are not predetermined, there are infinite sets of parameter values that generate the same space-time concentration distributions in the water column. The result implies that in-stream transport and hyporheic exchange parameters cannot be determined from sole measurements of solute breakthrough curves in the surface water unless stream discharge and average cross-sectional geometry can be independently estimated.

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A Comparison of Field Techniques for the Analysis of Groundwater-Surface-Water Interactions: Porewater Sampling and Hyporheic Temperature and EC Time Series

10.5194/egusphere-egu2020-13426 ◽

2020 ◽

Author(s):

Nicolai Brekenfeld ◽

Uwe Schneidewind ◽

Sophie Comer-Warner ◽

Hanna Schulz ◽

Nick Kettridge ◽

...

Keyword(s):

Time Series ◽

Surface Water ◽

Water Source ◽

Biogeochemical Cycles ◽

Temperature Time Series ◽

Repeated Measurements ◽

Hyporheic Exchange ◽

Ecological Processes ◽

Hyporheic Flow ◽

Temperature Time

The interactions between streamwater and hyporheic or riparian porewater are tightly linked to the biogeochemical and ecological processes within fluvial ecosystems. The analyses of hyporheic biogeochemical cycles or hyporheic exchange fluxes often involves manual sampling of porewater or measurement of temperature time series in the streambed. Here, we compare these two techniques with electrical conductivity time series from a cluster of small, hyporheic EC sensors and discuss their implications on the interpretation of groundwater &#8211; surface-water interactions in a first-order boreal stream.Based on repeated measurements and the co-located small, hyporheic EC sensors, we found that even small sampling-rates of sediment porewater alter the hyporheic flow at some locations significantly. However, since porewater samples are necessary for the analysis of hyporheic biogeochemical cycles and water source partitioning, we recommend for future experiments to either co-locate small, continuous sensors with the sampling ports or to conduct experiments quantifying the induced flux.Calculated 1D fluxes based on profiles of temperature time series are often integrated over many centimetres to a few decimetres, if the sensors spacing is not very small. This might be the reason, why fluxes based on our temperature and EC measurements do not always have the same direction, especially if the fast hyporheic exchange fluxes are very shallow.We conclude, that using several, co-located techniques together can compensate for the limitations of each technique and reduce the risk of misleading conclusions.

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Integral Flow Modelling Approach for Surface Water-Groundwater Interactions along a Rippled Streambed

Water ◽

10.3390/w11071517 ◽

2019 ◽

Vol 11 (7) ◽

pp. 1517 ◽

Cited By ~ 5

Author(s):

Tabea Broecker ◽

Katharina Teuber ◽

Vahid Sobhi Gollo ◽

Gunnar Nützmann ◽

Jörg Lewandowski ◽

...

Keyword(s):

Surface Water ◽

Hyporheic Zone ◽

Stokes Equations ◽

Three Dimensional ◽

Darcy Flow ◽

Hyporheic Exchange ◽

Navier Stokes ◽

Coupled Models ◽

Navier Stokes Equations ◽

Surface Water Flow

Exchange processes of surface and groundwater are important for the management of water quantity and quality as well as for the ecological functioning. In contrast to most numerical simulations using coupled models to investigate these processes, we present a novel integral formulation for the sediment-water-interface. The computational fluid dynamics (CFD) model OpenFOAM was used to solve an extended version of the three-dimensional Navier–Stokes equations which is also applicable in non-Darcy-flow layers. Simulations were conducted to determine the influence of ripple morphologies and surface hydraulics on the flow processes within the hyporheic zone for a sandy and for a gravel sediment. In- and outflowing exchange fluxes along a ripple were determined for each case. The results indicate that larger grain size diameters, as well as ripple distances, increased hyporheic exchange fluxes significantly. For higher ripple dimensions, no clear relationship to hyporheic exchange was found. Larger ripple lengths decreased the hyporheic exchange fluxes due to less turbulence between the ripples. For all cases with sand, non-Darcy-flow was observed at an upper layer of the ripple, whereas for gravel non-Darcy-flow was recognized nearly down to the bottom boundary. Moreover, the sediment grain sizes influenced also the surface water flow significantly.

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Methane emissions from a sediment-deposited island in a Lancang-Mekong reservoir

10.5194/bg-2018-380 ◽

2018 ◽

Author(s):

Wenqing Shi ◽

Qiuwen Chen ◽

Jianyun Zhang ◽

Cheng Chen ◽

Yuchen Chen ◽

...

Keyword(s):

Methane Emission ◽

Hyporheic Zone ◽

Sediment Accumulation ◽

Methane Flux ◽

Methane Emissions ◽

Mekong River ◽

Hyporheic Exchange ◽

Water Level Fluctuations ◽

Hyporheic Flow ◽

Methane Sink

Abstract. In dammed rivers, sediment accumulation creates potential methane emission hotspots, which have been extensively studied in forebays. However, methane emissions from sidebays remain poorly understood. We investigated methane emissions from a sediment-deposited island situated in the sidebay of the Manwan Reservoir, Lancang-Mekong River. High methane emissions (maximum 10.4 mg h−1 m−2) were observed at the island center, while a ring-like zone of low-to-negative methane emission was discovered around the island edge, whose flux varied between −0.2–1.6 mg h−1 m−2. The ring-like zone accounted for 89.1 % of the island area, of which 9.1 % was a methane sink zone. Microbial processes in the hyporheic zone, regulated by hydrological variations, were responsible for the low methane flux in this area. Under reservoir operation, frequent water level fluctuations enhanced hyporheic exchange and created redox gradients along the hyporheic flow path. Dissolved oxygen in hyporheic water decreased from 4.80 mg L−1 at the island bank edge to 0.43 mg L−1 at the center, which in turn decreased methanogen abundance for methane production and increased methanotroph abundance for methane oxidation at the ring-like zone. This study adds to our understanding of methane emissions from dammed rivers and helps to screen efficient strategies for future mitigation of the global warming effects of hydropower systems.

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Nitrogen attenuation, dilution and recycling in the intertidal hyporheic zone of a subtropical estuary

Hydrology and Earth System Sciences ◽

10.5194/hess-22-4083-2018 ◽

2018 ◽

Vol 22 (7) ◽

pp. 4083-4096 ◽

Cited By ~ 1

Author(s):

Sébastien Lamontagne ◽

Frédéric Cosme ◽

Andrew Minard ◽

Andrew Holloway

Keyword(s):

Surface Water ◽

Hyporheic Zone ◽

Isotopic Fractionation ◽

Hyporheic Exchange ◽

Biogeochemical Processes ◽

Intertidal Sediments ◽

Intertidal Zones ◽

N Removal ◽

Subtropical Estuary ◽

Biogeochemical Transformations

Abstract. Tidal estuarine channels have complex and dynamic interfaces controlled by upland groundwater discharge, waves, tides and channel velocities that also control biogeochemical processes within adjacent sediments. In an Australian subtropical estuary, discharging groundwater with elevated (> 300 mg N L−1) NH4+ and NO3- concentrations had 80 % of the N attenuated at this interface, one of the highest N removal rates (> 100 mmol m−2 day−1) measured for intertidal sediments. The remaining N was also diluted by a factor of 2 or more by mixing with surface water before being discharged to the estuary. Most of the mixing occurred in a hyporheic zone in the upper 50 cm of the channel bed. However, groundwater entering this zone was already partially mixed (12 %–60 %) with surface water via tide-induced circulation. Below the hyporheic zone (50–125 cm below the channel bed), NO3- concentrations declined slightly faster than NH4+ concentrations and δ15NNO3 and δ18ONO3 gradually increased, suggesting a co-occurrence of anammox and denitrification. In the hyporheic zone, δ15NNO3 continued to become enriched (consistent with either denitrification or anammox) but δ18ONO3 became more depleted (indicating some nitrification). A high δ15NNO3 (23 ‰–35 ‰) and a low δ18ONO3 (1.2 ‰–8.2 ‰) in all porewater samples indicated that the original synthetic nitrate pool (industrial NH4NO3; δ15N ∼ 0 ‰; δ18O ∼ 18 ‰–20 ‰) had turned over completely during transport in the aquifer before reaching the channel bed. Whilst porewater NO3- was more δ18O depleted than its synthetic source, porewater δ18OH2O (−3.2 ‰ to −1.8 ‰) was enriched by 1 ‰–4 ‰ relative to rainfall-derived groundwater mixed with seawater. Isotopic fractionation from H2O uptake during the N cycle and H2O production during synthetic NO3- reduction are the probable causes for this δ18OH2O enrichment. Whilst occurring at a smaller spatial scale than tide-induced circulation, hyporheic exchange can provide a similar magnitude of mixing and biogeochemical transformations for groundwater solutes discharging through intertidal zones.

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