Numerical simulations of tidal beach seawater-groundwater circulations using dimensionless method

Abstract

Tidally driven seawater-groundwater circulation in subterranean estuary is influenced by various factors, making it difficult to quantify. Our previous study developed a dimensionless model for numerical simulations, wherein the model parameters were non-dimensionalized. Although the model can be reasonably transformed to apply to various dimensionalized beach domains with slopes ranging from 3.16 % to 31.6 %, the model was limited by a narrow applicable range of the permeability parameter (K) values, excluding very permeable or less permeable beaches (i.e., the hydraulic conductivity K > 10^-3 m/s or < 10^-4 m/s). In this study, we expanded both the scale and the range of parameter values of the dimensionless model to encompass a broader spectrum of K values, from 10^-5 to 10^-2 m/s. Beyond our prior findings, we revealed that at a high hydraulic conductivity of approximately 10^-2 m/s, the salinity distribution within the beach aquifer varies significantly with tides. The area of the upper saline plume (USP) diminishes and eventually disappears as the hydraulic conductivity and slope of the beach aquifer increase. After transforming the dimensionless exchange flows into their dimensionalized counterparts, the dimensional results aligned closely with those transformed from numerical simulations using dimensionless models. Additionally, we introduced nomographs for submarine groundwater discharge (SGD) estimations based on beach slope, hydraulic conductivity, tidal amplitude and period. The modeling results presented can be generalized to beach aquifers with a wide range of hydraulic and tidal properties.