Impacts of Streambed Heterogeneity and Anisotropy on Residence Time of Hyporheic Zone

摘要: The hyporheic zone (HZ), which is the region beneath or alongside a streambed, plays an important role in stream's ecology. duration that water molecule solute remains within HZ, residence time (RT), one of most common metrics used to evaluate function HZ. RT greatly influenced by streambed's hydraulic conductivity (K), intrinsically difficult characterize due its heterogeneity and anisotropy. Many laboratory numerical studies HZ have simplified streambed K constant, thus producing values may differ from those gathered field. Some considered but very few accounted for anisotropy natural distributions typically found real streambeds. This study developed models MODFLOW examine influence anisotropy, distribution on Heterogeneity were both shorten mean median RTs while increasing range RTs. Moreover, heterogeneous fields arranged more orderly pattern had longer than with random distributions. These results could facilitate design achieve desired during river restoration. They also assist translation commonly homogeneous and/or isotropic conditions into anisotropic field situations.