Groundwater response to tidal fluctuations in a leaky confined coastal aquifer with a finite length

Abstract

The study on the hydraulic properties of coastal aquifers has significant implications both in hydrological sciences and environmental engineering. Although many analytical solutions are available, most of them are based on the same basic assumption that assumes aquifers extend landward semi‐infinitely, which does not necessarily reflect the reality. In this study, the general solutions for a leaky confined coastal aquifer have been developed that consider both finitely landward constant‐head and no‐flow boundaries. The newly developed solutions were then used to examine theoretically the joint effects of leakage and aquifer length on hydraulic head fluctuations within the leaky confined aquifer, and the validity of using the simplified solution, which assumes the aquifer is semi‐infinite. The results illustrated that the use of the simplified solution may cause significant errors, depending on joint effects of leakage and aquifer length. A dimensionless characteristic parameter was then proposed as an index for judging the applicability of the simplified solution. In addition, practical application of the general solution for the constant‐head inland boundary was used to characterize the hydraulic properties of a leaky confined aquifer using the data collected from a field site at the Seine River estuary, France, and the versatility of the general solution was further justified.

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

“…One-layer, semi-infinite aquifer length (Jacob, 1950) h determine the hydraulic properties of a leaky confined aquifer using the data collected from a field site at the Seine River estuary, France. The comparison between the simulated and observed hydraulic head fluctuations in Well #3808, as shown in Figure 6, illustrated the applicability of the tidal method (Zhao et al, 2019). All of the above three-layer models assume that each layer is homogenous.…”

“…The figures are reproduced using the data for producing figs. 2 and 3 in Zhao et al (2019), respectively. The transmissivity, T, storativity, S, amplitude of tidal fluctuation, tidal angular velocity, ω, and the initial phase, φ, were assumed to be 2,000 m 2 d −1 , 0.0001, 1 m, 2π d −1 , and 0, respectively F I G U R E 6 Comparison between simulated and observed hydraulic head fluctuations in Well #3808 built at a field site at the Seine River estuary, France.…”

“…This illustrates the applicability of Huang et al's solution. Zhao et al (2019) recently derived general solutions for the hydraulic head fluctuations within a leaky confined coastal aquifer with a finite length for both constant-head and no-flow inland boundary conditions. Their model is similar to that conceptualized by Jiao and Tang (1999) but the aquifer width in the inland direction is finite (see Figure 4a).…”

Hydrogeological Characterization of Coastal Aquifer on the Basis of Observed Sea Level and Groundwater Level Fluctuations: Neretva Valley Aquifer, Croatia

“…After the main tidal constituents were determined from h OBSERVED (t), h TIDAL (t) was calculated as a linear superposition of sine functions whose total number corresponded to the number of tidal spectral constituents n with appropriate parameters being [18,28,37], amplitude a, period T, and phase θ, defined for each constituent denoted by j:…”

“…The simplest solutions have been derived with the following assumptions: (i) the aquifer is homogeneous and isotropic; (ii) the beach is assumed as a vertical line, perpendicular to aquifer geological layers; (iii) the effect of the outlet capping and subsea aquitard or semi-permeable layer roof extension are neglected; (iv) loading efficiency is set up to unity; and (v) flow is assumed as 1D, perpendicular to the vertical coastline [13,17]. Improvements in the method have been implied as follows: (i) leakance effect through the semi-permeable overlying layer [10][11][12]20,21,28], (ii) confining layer extending under the sea [10,11,15,19,21,28], and (iii) outlet capping influence [16,20,23,26,29].…”