Estimation of coastal aquifer properties: A review of the tidal method based on theoretical solutions

Abstract

AbstractDetermination of the hydraulic properties of coastal aquifer systems has important implications that are related to the issues such as seawater intrusion, submarine groundwater discharge, migration of contaminants, assessment of water resources, and geotechnical engineering. Over recent decades, many analytical solutions that consider different types of coastal aquifer systems or models have been developed. These solutions can be used as a theoretical basis for the tidal method that characterizes the hydraulic properties of a coastal aquifer system using hydraulic response measurements in an observation well or wells induced by tidal waves in the ocean. The hydraulic properties of an aquifer can be estimated through fitting a series of time‐dependent changes of hydraulic head detected in an observation well to those calculated based on theoretical solutions. For simplicity, most theoretical solutions only consider one tidal component and idealized boundary conditions, although in reality multiple tidal components exist simultaneously and boundary conditions can be more complicated. For practical applications of the tidal method and to increase its reliability, multiple tidal components should be considered and models considering more complicated boundary conditions should be developed. In addition, methods that can determine both the hydraulic conductivity and storage coefficient, rather than only the hydraulic diffusivity, that is, the ratio of hydraulic conductivity to storage coefficient of coastal aquifer, should be developed. Cautions should be taken into account when using the tidal method because earth tides and changes in local atmospheric pressure may induce similar tidal fluctuations in the hydraulic head within inland observation wells.This article is categorized under: Science of Water > Hydrological Processes Science of Water > Methods