HR: 13:55h
AN: H42I-02    [PDF]
TI: Hyporheic Exchange with Heterogeneous Streambeds: Laboratory Experiments and Modeling
AU: * Salehin, M
EM: m-salehin@northwestern.edu
AF: Northwestern University, Department of Civil and Environmental Engineering 2145 Sheridan Road, Evanston, IL 60208 United States
AU: Packman, A I
EM: a-packman@northwestern.edu
AF: Northwestern University, Department of Civil and Environmental Engineering 2145 Sheridan Road, Evanston, IL 60208 United States
AU: Paradis, M
EM: m-paradis@northwestern.edu
AF: Northwestern University, Department of Civil and Environmental Engineering 2145 Sheridan Road, Evanston, IL 60208 United States
AB: The hyporheic exchange process is often analyzed considering a homogeneous hyporheic zone. In reality, the streambed sediments are typically heterogeneous, which may result in complex hyporheic exchange patterns and spatially variable interfacial fluxes. We performed salt and dye injection experiments to study hyporheic exchange under different flow and sedimentary conditions in a recirculating laboratory flume packed with a heterogeneous sediment bed, designed as a correlated random hydraulic conductivity field. We analyzed the experimental results using a numerical hyporheic exchange model developed on the basis of pressure-driven advective pore water flow (pumping) and explicit representation of the detailed sediment structure. We also compared these results with an analytical solution for pore water flow. Both analytical and numerical exchange models reasonably predicted the bulk hyporheic exchange. However, the numerical model gave a better prediction of the faster exchange during early times, and predicted the heterogeneity-induced complex hyporheic pathways with good accuracy. The numerical model also explained the effect of heterogeneity on interfacial water flux, solute penetration depth and hyporheic residence time. In general, heterogeneity caused greater average water flux through the bed surface, but decreased both the solute penetration depth and residence time compared to an equivalent homogeneous bed.
DE: 1800 HYDROLOGY
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2003 Fall Meeting