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@ARTICLE{Tang:279239,
      author       = {Tang, Q. and Kurtz, W. and Brunner, P. and Vereecken, H.
                      and Hendricks-Franssen, Harrie-Jan},
      title        = {{C}haracterisation of river–aquifer exchange fluxes:
                      {T}he role of spatial patterns of riverbed hydraulic
                      conductivities},
      journal      = {Journal of hydrology},
      volume       = {531},
      number       = {1},
      issn         = {0022-1694},
      publisher    = {Elsevier},
      reportid     = {FZJ-2015-07254},
      pages        = {111 - 123},
      year         = {2015},
      abstract     = {Interactions between surface water and groundwater play an
                      essential role in hydrology, hydrogeology, ecology, and
                      water resources management. A proper characterisation of
                      riverbed structures might be important for estimating
                      river–aquifer exchange fluxes. The ensemble Kalman filter
                      (EnKF) is commonly used in subsurface flow and transport
                      modelling for estimating states and parameters. However,
                      EnKF only performs optimally for MultiGaussian distributed
                      parameter fields, but the spatial distribution of streambed
                      hydraulic conductivities often shows non-MultiGaussian
                      patterns, which are related to flow velocity dependent
                      sedimentation and erosion processes. In this synthetic
                      study, we assumed a riverbed with non-MultiGaussian
                      channel-distributed hydraulic parameters as a virtual
                      reference. The synthetic study was carried out for a 3-D
                      river–aquifer model with a river in hydraulic connection
                      to a homogeneous aquifer. Next, in a series of data
                      assimilation experiments three different groups of scenarios
                      were studied. In the first and second group of scenarios,
                      stochastic realisations of non-MultiGaussian distributed
                      riverbeds were inversely conditioned to state information,
                      using EnKF and the normal score ensemble Kalman filter
                      (NS-EnKF). The riverbed hydraulic conductivity was oriented
                      in the form of channels (first group of scenarios) or, with
                      the same bimodal histogram, without channelling (second
                      group of scenarios). In the third group of scenarios, the
                      stochastic realisations of riverbeds have MultiGaussian
                      distributed hydraulic parameters and are conditioned to
                      state information with EnKF. It was found that the best
                      results were achieved for channel-distributed
                      non-MultiGaussian stochastic realisations and with parameter
                      updating. However, differences between the simulations were
                      small and non-MultiGaussian riverbed properties seem to be
                      of less importance for subsurface flow than
                      non-MultiGaussian aquifer properties. In addition, it was
                      concluded that both EnKF and NS-EnKF improve the
                      characterisation of non-MultiGaussian riverbed properties,
                      hydraulic heads and exchange fluxes by piezometric head
                      assimilation, and only NS-EnKF could preserve the initial
                      distribution of riverbed hydraulic conductivities.},
      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:000366769200011},
      doi          = {10.1016/j.jhydrol.2015.08.019},
      url          = {https://juser.fz-juelich.de/record/279239},
}