Mixing interfaces,fluxes, residence times and redox conditions of the hyporheic zones induced by dune-like bedforms and ambient groundwater flow |
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| Institution: | 1. Center for Ecohydraulics Research, University of Idaho, Boise, Idaho, USA;2. Department of Civil, Environmental and Mechanical Engineering, University of Trento, Trento, Italy;3. Department of Mathematics, University of Trento, Trento, Italy;1. Lawrence Berkeley National Laboratory, Climate and Ecosystem Sciences Division, 1 Cyclotron Road, Berkeley, CA 94720, United States;2. Lawrence Berkeley National Laboratory, Energy Geosciences Division, 1 Cyclotron Road, Berkeley, CA 94720, United States;1. Civil Engineering and Engineering Mechanics, Columbia University, New York, NY 10027, United States\n;2. Department of Environmental Science, Barnard College, New York, NY 10027, United States\n;3. Department of Chemistry, Barnard College, New York, NY 10027, United States\n;1. Department of Earth and Environmental Science, Potsdam University, Germany;2. Department of Geography, University of California, Santa Barbara, USA;3. Earth Surface Geochemistry, Helmholtz Centre Potsdam, GFZ German Research Center for Geosciences, Telegrafenberg, 14473 Potsdam, Germany;4. Institute of Geological Sciences, Freie Universität Berlin, 12249 Berlin, Germany;1. College of Engineering, Peking University, Beijing 100871, PR China;2. Institute of Water Sciences, Peking University, Beijing 100871, PR China;1. Sonny Astani Department of Civil and Environmental Engineering, University of Southern California, Los Angeles, California 90089 2531, USA;2. Department of Physics, Faculty of Sciences, University of Birjand, Birjand 97178 51367, Iran;3. Mork Family Department of Chemical Engineering and Materials Science, University of Southern California, Los Angeles, California 90089 1211, USA |
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| Abstract: | Recent studies highlighted the importance of the interface between streams and their surrounding sediment, known as the hyporheic zone, where stream waters flow through the alluvium. These pore water fluxes stem from the interaction among streambed morphology, stream hydraulics and surrounding groundwater flow. We analytically model the hyporheic hydraulics induced by a spatially uniform ambient groundwater flow made of a horizontal, underflow, and a vertical, basal, component, which mimics gaining and losing stream conditions. The proposed analytical solution allows to investigate the control of simple hydromorphological quantities on the extent, residence time and redox conditions of the hyporheic zone, and the thickness of the mixing interface between hyporheic and groundwater cells. Our analysis shows that the location of the mixing zone shallows or deepens in the sediment as a function of bedform geometry, surface hydraulic and groundwater flow. The point of stagnation, where hyporheic flow velocities vanish and where the separation surface passes through, is shallower than or coincides with the deepest point of the hyporheic zone only due to underflow. An increase of the ambient flow causes a reduction of the hyporheic zone volume similarly in both losing and gaining conditions. The hyporheic residence time is lognormally distributed under neutral, losing and gaining conditions, with the residence time moments depending on the same set of parameters describing dune morphology and stream flow. |
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