Preprints
https://doi.org/10.5194/hess-2021-148
https://doi.org/10.5194/hess-2021-148

  08 Apr 2021

08 Apr 2021

Review status: this preprint is currently under review for the journal HESS.

The influence of hyporheic fluxes on regional groundwater discharge zones

Brian Babak Mojarrad1, Anders Wörman1, Joakim Riml1, and Shulan Xu2 Brian Babak Mojarrad et al.
  • 1Department of Sustainable Development, Environmental Science and Engineering, KTH Royal Institute of Technology, Stockholm, 100 44, Sweden
  • 2Xu Environmental Consulting AB, Stockholm, 168 61, Sweden

Abstract. The importance of hyporheic water fluxes induced by hydromorphologic processes at the streambed scale and their consequential effects on stream ecohydrology have recently received much attention. However, the role of hyporheic water fluxes in regional groundwater discharge is still not entirely understood. Streambed-induced flows not only affect mass and heat transport in streams but are also important for the retention of solute contamination originating from deep in the subsurface, such as naturally occurring solutes as well as leakage from the future geological disposal of nuclear waste. Here, we applied a multiscale modeling approach to investigate the effect of hyporheic fluxes on regional groundwater discharge in the Krycklan catchment, located in a boreal landscape in Sweden. Regional groundwater modeling was conducted using COMSOL Multiphysics constrained by observed or modeled representations of the catchment infiltration and geological properties, reflecting heterogeneities within the subsurface domain. Furthermore, streambed-scale modeling was performed using an exact spectral solution of the hydraulic head applicable to streaming water over a fluctuating streambed topography. By comparing the flow fields of watershed-scale groundwater discharge with and without consideration of streambed-induced hyporheic flows, we found that the flow trajectories and the distribution of the travel times of groundwater were substantially influenced by the presence of hyporheic fluxes near the streambed surface. One implication of hyporheic flows is that the groundwater flow paths contract near the streambed interface, thus fragmenting the coherent areas of groundwater upwelling and resulting in narrow “pinholes” of groundwater discharge points.

Brian Babak Mojarrad et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'Comment on hess-2021-148', Ulrik Kautsky, 17 May 2021
    • RC2: 'Review of article', Anonymous Referee #2, 29 May 2021
    • AC1: 'Response to the Community Comments #1', Brian Babak Mojarrad, 10 Jul 2021
  • RC1: 'Comment on hess-2021-148', Anonymous Referee #1, 20 May 2021
  • CC2: 'Comment on hess-2021-148', Ulrik Kautsky, 31 May 2021
  • RC3: 'Comment on hess-2021-148', Anonymous Referee #3, 31 May 2021

Brian Babak Mojarrad et al.

Brian Babak Mojarrad et al.

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Short summary
A multi-scale modelling framework was applied to investigate the impact of hyporheic fluxes on deep groundwater discharge in aquatic sediments. Regional groundwater flow and hyporheic fluxes were evaluated using numerical modelling and exact solutions, respectively. Groundwater flow trajectories were found substantially contracted near the bed surface due to the impact of hyporheic flow. This led to increased groundwater discharge intensity focused to small areas of the streambed sediment.