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@ARTICLE{Hrachowitz:897476,
      author       = {Hrachowitz, Markus and Stockinger, Michael and
                      Coenders-Gerrits, Miriam and van der Ent, Ruud and Bogena,
                      Heye and Lücke, Andreas and Stumpp, Christine},
      title        = {{R}eduction of vegetation-accessible water storage capacity
                      after deforestation affects catchment travel time
                      distributions and increases young water fractions in a
                      headwater catchment},
      journal      = {Hydrology and earth system sciences},
      volume       = {25},
      number       = {9},
      issn         = {1607-7938},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {FZJ-2021-03809},
      pages        = {4887 - 4915},
      year         = {2021},
      abstract     = {Deforestation can considerably affect transpiration
                      dynamics and magnitudes at the catchment scale and thereby
                      alter the partitioning between drainage and evaporative
                      water fluxes released from terrestrial hydrological systems.
                      However, it has so far remained problematic to directly link
                      reductions in transpiration to changes in the physical
                      properties of the system and to quantify these changes in
                      system properties at the catchment scale. As a consequence,
                      it is difficult to quantify the effect of deforestation on
                      parameters of catchment-scale hydrological models. This in
                      turn leads to substantial uncertainties in predictions of
                      the hydrological response after deforestation but also to a
                      poor understanding of how deforestation affects principal
                      descriptors of catchment-scale transport, such as travel
                      time distributions and young water fractions. The objectives
                      of this study in the Wüstebach experimental catchment are
                      therefore to provide a mechanistic explanation of why
                      changes in the partitioning of water fluxes can be observed
                      after deforestation and how this further affects the storage
                      and release dynamics of water. More specifically, we test
                      the hypotheses that (1) post-deforestation changes in water
                      storage dynamics and partitioning of water fluxes are
                      largely a direct consequence of a reduction of the
                      catchment-scale effective vegetation-accessible water
                      storage capacity in the unsaturated root zone (SU, max)
                      after deforestation and that (2) the deforestation-induced
                      reduction of SU, max affects the shape of travel time
                      distributions and results in shifts towards higher fractions
                      of young water in the stream. Simultaneously modelling
                      streamflow and stable water isotope dynamics using
                      meaningfully adjusted model parameters both for the pre- and
                      post-deforestation periods, respectively, a hydrological
                      model with an integrated tracer routine based on the concept
                      of storage-age selection functions is used to track fluxes
                      through the system and to estimate the effects of
                      deforestation on catchment travel time distributions and
                      young water fractions Fyw.It was found that deforestation
                      led to a significant increase in streamflow accompanied by
                      corresponding reductions of evaporative fluxes. This is
                      reflected by an increase in the runoff ratio from CR=0.55 to
                      0.68 in the post-deforestation period despite similar
                      climatic conditions. This reduction of evaporative fluxes
                      could be linked to a reduction of the catchment-scale water
                      storage volume in the unsaturated soil (SU, max) that is
                      within the reach of active roots and thus accessible for
                      vegetation transpiration from ∼258 mm in the
                      pre-deforestation period to ∼101 mm in the
                      post-deforestation period. The hydrological model,
                      reflecting the changes in the parameter SU, max, indicated
                      that in the post-deforestation period stream water was
                      characterized by slightly yet statistically not
                      significantly higher mean fractions of young water
                      (Fyw∼0.13) than in the pre-deforestation period
                      (Fyw∼0.12). In spite of these limited effects on the
                      overall Fyw, changes were found for wet periods, during
                      which post-deforestation fractions of young water increased
                      to values Fyw∼0.37 for individual storms. Deforestation
                      also caused a significantly increased sensitivity of young
                      water fractions to discharge under wet conditions from
                      dFyw/dQ=0.25to 0.36.},
      cin          = {IBG-3},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IBG-3-20101118},
      pnm          = {2173 - Agro-biogeosystems: controls, feedbacks and impact
                      (POF4-217)},
      pid          = {G:(DE-HGF)POF4-2173},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000695408400002},
      doi          = {10.5194/hess-25-4887-2021},
      url          = {https://juser.fz-juelich.de/record/897476},
}