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dc.contributor.authorHan, Q.*
dc.contributor.authorChen, D.*
dc.contributor.authorGuo, Yakun*
dc.contributor.authorHu, W.*
dc.date.accessioned2018-04-18T13:38:14Z
dc.date.available2018-04-18T13:38:14Z
dc.date.issued2018-07-31
dc.identifier.citationHan Q, Chen D, Guo Y et al (2018) Saltwater-freshwater mixing fluctuation in shallow beach aquifers. Estuarine, Coastal and Shelf Science. 207: 93-103.en_US
dc.identifier.urihttp://hdl.handle.net/10454/15542
dc.descriptionYesen_US
dc.description.abstractField measurements and numerical simulations demonstrate the existence of an upper saline plume in tidally dominated beaches. The effect of tides on the saltwater-freshwater mixing occurring at both the upper saline plume and lower salt wedge is well understood. However, it is poorly understood whether the tidal driven force acts equally on the mixing behaviours of above two regions and what factors control the mixing fluctuation features. In this study, variable-density, saturated-unsaturated, transient groundwater flow and solute transport numerical models are proposed and performed for saltwater-freshwater mixing subject to tidal forcing on a sloping beach. A range of tidal amplitude, fresh groundwater flux, hydraulic conductivity, beach slope and dispersivity anisotropy are simulated. Based on time sequential salinity data, the gross mixing features are quantified by computing the spatial moments in three different aspects, namely, the centre point, length and width, and the volume (or area in a two-dimensional case). Simulated salinity distribution varies significantly at saltwater-freshwater interfaces. Mixing characteristics of the upper saline plume greatly differ from those in the salt wedge for both the transient and quasi-steady state. The mixing of the upper saline plume largely inherits the fluctuation characteristics of the sea tide in both the transverse and longitudinal directions when the quasi-steady state is reached. On the other hand, the mixing in the salt wedge is relatively steady and shows little fluctuation. The normalized mixing width and length, mixing volume and the fluctuation amplitude of the mass centre in the upper saline plume are, in general, one-magnitude-order larger than those in the salt wedge region. In the longitudinal direction, tidal amplitude, fresh groundwater flux, hydraulic conductivity and beach slope are significant control factors of fluctuation amplitude. In the transverse direction, tidal amplitude and beach slope are the main control parameters. Very small dispersivity anisotropy (e.g., α_L⁄α_T <5) could greatly suppress mixing fluctuation in the longitudinal direction. This work underlines the close connection between the sea tides and the upper saline plume in the aspect of mixing, thereby enhancing understanding of the interplay between tidal oscillations and mixing mechanisms in tidally dominated sloping beach systems.en_US
dc.description.sponsorshipShenzhen Key Laboratory for Coastal Ocean Dynamics and Environment (No. ZDSY20130402163735964), National High Technology Research & Development Program of China (No. 2012AA09A409).en_US
dc.language.isoenen_US
dc.rights© 2018 Elsevier. Reproduced in accordance with the publisher's self-archiving policy. This manuscript version is made available under the CC-BY-NC-ND 4.0 license.en_US
dc.subjectCoastal aquifer; Saltwater-freshwater mixing fluctuation; Tidal effects; Mixing quantification; Upper saline plume; Subterranean estuaryen_US
dc.titleSaltwater-freshwater mixing fluctuation in shallow beach aquifersen_US
dc.status.refereedYesen_US
dc.date.Accepted2018-03-30
dc.date.application2018-04-03
dc.typeArticleen_US
dc.type.versionAccepted Manuscripten_US
dc.identifier.doihttps://doi.org/10.1016/j.ecss.2018.03.027
refterms.dateFOA2019-04-04T09:08:53Z


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