Insight into the influence of local streambed heterogeneity on hyporheic-zone flow characteristics
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PAPER
Insight into the influence of local streambed heterogeneity on hyporheic-zone flow characteristics Robert Earon 1
&
Joakim Riml 1 & Liwen Wu 2 & Bo Olofsson 1
Received: 5 March 2020 / Accepted: 13 September 2020 # The Author(s) 2020
Abstract Interaction 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. Keywords Heterogeneity . Electrical resistivity tomography . Tracer tests . Groundwater/surface-water relations . Geophysical methods
Introduction Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10040-020-02244-5) contains supplementary material, which is available to authorized users. * Robert Earon [email protected] Joakim Riml [email protected] Liwen Wu [email protected] Bo Olofsson [email protected] 1
Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Teknikringen 10B, 100 44 Stockholm, Sweden
2
Department of Ecohydrology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Müggelseedamm 310, 12587 Berlin, Germany
The interaction between surface water and groundwater is an important process in water resources management, influencing aquatic ecosystems (Findlay 1995; Brunke and Gonser 1997; Briggs et al. 2015) as well as water quality (Boulton et al. 1998; Boano et al. 2013; Lewandowski et al. 2019). Pressure-driven exchange of water and solutes across the water–streambed interface prolongs the solute residence time in the subsurfa
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