Author(s): L. P. S. K. Fernando; M. Stewardson; M. Arora
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Keywords: No Keywords
Abstract: Hyporheic zone (HZ), the region where surface and subsurface water exchange happens, is an important location for nitrogen cycling in rivers. Water exchange across the stream-sediment interface and biogeochemical characteristics of the HZ are critical for fate and transport of nitrogen. HZ acts as a sink of nitrogen when water and its dissolved nitrogen get longer contacting times in the sediment bed than reaction time of nitrogen processes. Many geomorphic features contribute to hyporheic flow; dunes; ripples; riffle-pools; meanders; and bars, resulting different flow behaviors in the HZ. Meanders are particularly important for biogeochemical cycling and nitrogen attenuation in streams as they allow for longer hydrological flow paths and residence times in the HZ, which provides more complete treatment than the other channel features. However few laboratory experiments have dealt with meandering morphology and thus there is lack of understanding in how this stream morphology feature can be utilized for nutrients removal within the stream to improve water quality. Our study will be the first laboratory examination of solute transport in the HZ of meandering streams. In this study we conducted a set of laboratory experiments to examine the effect of meander wavelength and discharge on the solute transport in the HZ. Hyporheic flow and solute transport were estimated directly from the concentration decay of a conservative tracer (Rhodamine WT) added into the surface flow. Comparison of the observed tracer profiles showed that the stream flow rates and meandering wavelengths have impact on the surface-subsurface exchange of solutes.
Year: 2018