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Impacts of Vegetation-generated Turbulence on Hyporheic Exchange
  • Qingjun Judy Yang,
  • Shih-Hsun Huang
Qingjun Judy Yang
University of Minnesota

Corresponding Author:[email protected]

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Shih-Hsun Huang
National Taiwan University
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Abstract

Hyporheic exchange, or the exchange of water and solutes between surface and subsurface water at the sediment-water interface, regulates water quality and biogeochemical cycles in aquatic ecosystems. Vegetation, which is ubiquitous in aquatic ecosystems, is known to impact hyporheic exchange, yet how vegetation impacts hyporheic exchange remains to be characterized. Here, we show that at the same spatially and temporally averaged flow velocity U, vegetation-generated turbulence increases the rate of hyporheic exchange by a factor of four. By tracking the movement of fluorescent dye in a flume with index-matched sediment and translucent vegetation dowels, we demonstrate that turbulence-induced hyporheic exchange at the sediment-water interface can be characterized by a one-dimensional diffusion coefficient, DSWI. We further demonstrate that DSWI correlates with the total near-bed turbulent kinetic energy kt rather than mean flow velocity U. A kt-based model was developed to characterize the impacts of vegetation-generated turbulence on hyporheic exchange.