The hydraulic properties of coastal aquifer systems are relevant to
various hydrogeological, hydro-ecological and engineering problems. This
study presents an analytical solution for predicting groundwater head
fluctuations induced by dual-tide in multilayered island aquifer
systems, consisting of an unconfined aquifer on the top and any number
of leaky aquifers below. The solution was derived via the methods of
matrix differential calculus and separation of variables. It is more
general than any existing analytical solutions for the tidal pressure
propagation since the new solution can consider multilayered aquifer
systems along with the effects of leakage and aquifer length. Using this
solution, we illustrated potential errors that may occur due to
neglecting one or more vital factors affecting groundwater fluctuations.
Besides, we articulated the groundwater response to the dual-tide in
complex coastal aquifers. Considering that some thin semipermeable
layers may be ignored in practical field investigation, we also
demonstrated the effects due to simplification of aquifer layers. The
results showed that with the increase in the number of overlapped leaky
layers, the tidal propagation in the bottom part of multilayered aquifer
system approaches that in a single confined aquifer with the same
transmissivity and storage.