TY - JOUR
T1 - Scale issues and the effects of heterogeneity on the dune-induced hyporheic mixing
AU - Su, Xiaoru
AU - Jim Yeh, Tian Chyi
AU - Shu, Longcang
AU - Li, Kuangjia
AU - Brusseau, Mark L.
AU - Wang, Wenke
AU - Hao, Yonghong
AU - Lu, Chengpeng
N1 - Funding Information:
This research was supported by the China Scholarship Council (Grant 201706710023 ), funded by the National Natural Science Foundation of China project entitled “Study on Water Cycle Evolution of Groundwater Reservoir in the Arid Area under Artificial Regulation” (No. 41572210). T.-C. Jim Yeh acknowledges support from US Global Civilian Research Development Foundation ( CRDF ) under the award number (DAA2-15-61224-1): Hydraulic tomography in shallow alluvial sediments: Nile River Valley, Egypt. He also acknowledges support from US NSF grant EAR1931756. The program and the data used in this study can be downloaded from doi:10.5281/zenodo.3338006.
Publisher Copyright:
© 2020
PY - 2020/11
Y1 - 2020/11
N2 - Hyporheic mixing plays a vital role in physical, biogeochemical, and thermal processes in river networks. While many studies have emphasized the role of streambed heterogeneity in hyporheic mixing processes, this study articulates the scale issues inherent in concentration, mixing, heterogeneity, and modeling approaches. It subsequently conducted simulations of hyporheic mixing in synthetic, heterogeneous, 2-D cross-sectional river beds based on prescribed hydraulic conductivity defined at the local-scale. It then investigated the flux variation distribution and the mixing zone under different degrees of heterogeneity and flow scenarios. Since the characterization of the heterogeneities in detail at the local scale is practically impossible, Monte Carlo simulation based on stochastic theory was used to demonstrate the hyporheic mixing under the large-scale control volume (macromixing). Afterward, a first-order stochastic analysis was undertaken to explore the relationship between local-scale flux variance distribution and the mixing zone under different heterogeneity and flow scenarios. The results of this study show that the flux variance in the streambed is an appropriate metric for assessing the magnitude of hyporheic mixing at all scales. Further, surface water velocity and upwelling groundwater are found to be the dominant controlling factors of the flux variance and in turn, the mixing process, followed by the streambed heterogeneity. In addition, it demonstrates that the hyporheic mixing process is significantly affected by the complex surface and groundwater circulation regimes and the stagnation zone under steady-state flow conditions.
AB - Hyporheic mixing plays a vital role in physical, biogeochemical, and thermal processes in river networks. While many studies have emphasized the role of streambed heterogeneity in hyporheic mixing processes, this study articulates the scale issues inherent in concentration, mixing, heterogeneity, and modeling approaches. It subsequently conducted simulations of hyporheic mixing in synthetic, heterogeneous, 2-D cross-sectional river beds based on prescribed hydraulic conductivity defined at the local-scale. It then investigated the flux variation distribution and the mixing zone under different degrees of heterogeneity and flow scenarios. Since the characterization of the heterogeneities in detail at the local scale is practically impossible, Monte Carlo simulation based on stochastic theory was used to demonstrate the hyporheic mixing under the large-scale control volume (macromixing). Afterward, a first-order stochastic analysis was undertaken to explore the relationship between local-scale flux variance distribution and the mixing zone under different heterogeneity and flow scenarios. The results of this study show that the flux variance in the streambed is an appropriate metric for assessing the magnitude of hyporheic mixing at all scales. Further, surface water velocity and upwelling groundwater are found to be the dominant controlling factors of the flux variance and in turn, the mixing process, followed by the streambed heterogeneity. In addition, it demonstrates that the hyporheic mixing process is significantly affected by the complex surface and groundwater circulation regimes and the stagnation zone under steady-state flow conditions.
KW - First-order analysis
KW - Flux variance
KW - Heterogeneity
KW - Hyporheic mixing
KW - Scales
KW - Uncertainty
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U2 - 10.1016/j.jhydrol.2020.125429
DO - 10.1016/j.jhydrol.2020.125429
M3 - Article
AN - SCOPUS:85089898987
VL - 590
JO - Journal of Hydrology
JF - Journal of Hydrology
SN - 0022-1694
M1 - 125429
ER -