Corrected interface flow model for seawater intrusion in confined aquifers: relations to the dimensionless parameters of variable-density flow

Koussis, Antonis D.; Mazi, Katerina

Corrected interface flow model for seawater intrusion in confined aquifers: relations to the dimensionless parameters of variable-density flow | Modèle d'écoulement d'interface corrigé pour l'intrusion d'eau de mer dans des aquifères captifs: relations avec les paramètres sans dimension d'écoulement à densité variable Modelo corregido del flujo en la interfaz de la intrusión de agua de mar en acuíferos confinados: relaciones con los parámetros adimensionales del flujo de densidad variable 承压含水层海水入侵校正的界面-水流模型 : 与可变密度水流无量纲参数的关系 Modelo corretor de interface-fluxo para intrusão de água marinha em aquíferos confinados: relações com os parâmetros adimensionais do fluxo de densidade variável

2018

Koussis, Antonis D. | Mazi, Katerina

Sharp-interface (or interface) flow models with Dupuit-Forchheimer approximation are widely used to assess, to first order, an aquifer’s vulnerability to seawater intrusion (SWI) and to evaluate sustainable management options for coastal groundwater resources at the screening level. Recognising that interface flow models overestimate SWI, corrections have been proposed to account for the neglected mixing and also for the outflow through a finite gap. These corrections, however, were introduced in the context of specific studies and may not be generally applicable as proposed. The interface model is revisited, placing its corrections in the context of variable-density flow (VDF) theory, by expressing them in terms of the dimensionless parameters governing VDF in schematised (aspect ratio = thickness/length) homogeneous confined coastal aquifers: the coupling parameter (α), a Péclet number (Pe), and the dispersivities ratio (rα). Interfaces are compared to the 50%-salinity lines of VDF numerical solutions and regression equations are developed for estimating the outflow gap and for correcting the length of the interface (terminating with a blunted edge); the dispersion correction, which modifies the interface curvature, is restated with a variable exponent. The corrections for dispersion and for the interface length appear to be the most effective; an outflow gap is important only at small α values (strong advection relative to vertical flow due to density differences). These concepts are applied successfully to calculate the interface position in the lowermost confined sub-unit of the Coastal Plain aquifer of Israel, as an estimate of SWI.

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