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@ARTICLE{Tang:837953,
      author       = {Tang, Q. and Kurtz, W. and Schilling, O. S. and Brunner, P.
                      and Vereecken, H. and Hendricks-Franssen, Harrie-Jan},
      title        = {{T}he influence of riverbed heterogeneity patterns on
                      river-aquifer exchange fluxes under different connection
                      regimes},
      journal      = {Journal of hydrology},
      volume       = {554},
      issn         = {0022-1694},
      address      = {Amsterdam [u.a.]},
      publisher    = {Elsevier},
      reportid     = {FZJ-2017-06714},
      pages        = {383-396},
      year         = {2017},
      abstract     = {Riverbed hydraulic conductivity (K) is a critical parameter
                      for the prediction of exchange fluxes between a river and an
                      aquifer. In this study, the role of heterogeneity patterns
                      was explored using the fully integrated hydrological model
                      HydroGeoSphere simulating complex, variably saturated
                      subsurface flow. A synthetic 3-D river-aquifer reference
                      model was constructed with a heterogeneous riverbed using
                      non-multi-Gaussian patterns in the form of meandering
                      channels. Data assimilation was used to test the ability of
                      different riverbed K patterns to reproduce hydraulic heads,
                      riverbed K and river-aquifer exchange fluxes. Both fully
                      saturated as well as variably saturated conditions
                      underneath the riverbed were tested. The data assimilation
                      experiments with the ensemble Kalman filter (EnKF) were
                      carried out for four types of geostatistical models of
                      riverbed K fields: (i) spatially homogeneous, (ii)
                      heterogeneous with multi-Gaussian distribution, (iii)
                      heterogeneous with non-multi-Gaussian distribution
                      (channelized structures) and (iv) heterogeneous with
                      non-multi-Gaussian distribution (elliptic structures). For
                      all data assimilation experiments, state variables and
                      riverbed K were updated by assimilating hydraulic heads. For
                      saturated conditions, heterogeneous geostatistical models
                      allowed a better characterization of net exchange fluxes
                      than a homogeneous approximation. Among the three
                      heterogeneous models, the performance of non-multi-Gaussian
                      models was superior to the performance of the multi-Gaussian
                      model, but the two tested non-multi-Gaussian models showed
                      only small differences in performance from one another. For
                      the variably saturated conditions both the multi-Gaussian
                      model and the homogeneous model performed clearly worse than
                      the two non-multi-Gaussian models. The two
                      non-multi-Gaussian models did not show much difference in
                      performance. This clearly shows that characterizing
                      heterogeneity of riverbed K is important. Moreover,
                      particularly under variably saturated flow conditions the
                      mean and the variance of riverbed K do not provide enough
                      information for exchange flux characterization and
                      additional histogram information of riverbed K provides
                      crucial information for the reproduction of exchange
                      fluxes.},
      cin          = {IBG-3},
      ddc          = {690},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {255 - Terrestrial Systems: From Observation to Prediction
                      (POF3-255)},
      pid          = {G:(DE-HGF)POF3-255},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000415769600028},
      doi          = {10.1016/j.jhydrol.2017.09.031},
      url          = {https://juser.fz-juelich.de/record/837953},
}