Preprints
https://doi.org/10.5194/hess-2024-196
https://doi.org/10.5194/hess-2024-196
22 Aug 2024
 | 22 Aug 2024
Status: a revised version of this preprint is currently under review for the journal HESS.

Effects of boundary conditions and aquifer parameters on salinity distribution and mixing controlled reactions in high-energy beach aquifers

Rena Meyer, Janek Greskowiak, Stephan L. Seibert, Vincent E. Post, and Gudrun Massmann

Abstract. In high-energy beach aquifers fresh groundwater mixes with recirculating saltwater and biogeochemical reactions modify the composition of groundwater discharging to the sea. Changing beach morphology, hydrodynamic forces as well as hydrogeological properties control density-driven groundwater flow and transport processes that affect the distribution of chemical reactants. In the present study, density-driven flow and transport modelling of a generic 2-D cross-shore transect was conducted. Boundary conditions and aquifer parameters were varied in a systematic manner in a suite of twenty-four cases. The objective was to investigate their individual effects on flow regime, salt distribution, and potential for mixing controlled chemical reactions in a system with a temporally-variable beach morphology. Our results show that a changing beach morphology causes the migration of infiltration and exfiltration locations along the beach transect that lead to transient flow and salt transport patterns in the subsurface, thereby enhancing mixing controlled reactions. The shape and extent of the zone where mixing controlled reactions potentially take place as well as the spatio-temporal variability of the freshwater-saltwater interfaces are most sensitive to variable beach morphology, storm floods, hydraulic conductivity and dispersivity.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Rena Meyer, Janek Greskowiak, Stephan L. Seibert, Vincent E. Post, and Gudrun Massmann

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on hess-2024-196', Anonymous Referee #1, 20 Oct 2024
    • AC1: 'Reply on RC1', Rena Meyer, 06 Nov 2024
  • RC2: 'Comment on hess-2024-196', Anonymous Referee #2, 25 Oct 2024
    • AC2: 'Reply on RC2', Rena Meyer, 06 Nov 2024
Rena Meyer, Janek Greskowiak, Stephan L. Seibert, Vincent E. Post, and Gudrun Massmann
Rena Meyer, Janek Greskowiak, Stephan L. Seibert, Vincent E. Post, and Gudrun Massmann

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Short summary
The subsurface of sandy beaches under high energy conditions where tides, waves and storms constantly reshape the beach surface are globally common and relevant for the alteration of solute fluxes across the land-sea continuum. Our generic modelling study shows that a dynamic beach morphology paired with aquifer properties results in spatio-temporal variable flow and solute transport regimes in the subsurface and enhances mixing reactions.