An analytical solution and case study of groundwater head response to dual tide in an island leaky confined aquifer

This paper presents an analytical solution of groundwater head response to dual-tide fluctuation in the transect of an island leaky aquifer system comprising a confined aquifer and its overlying semipermeable confining layer. Both layers terminate at the coastlines on two sides of the island. Solution analysis indicates that the tidal waves from the two sides of the island transect interfere at the middle of the island and the interference decreases to zero as the horizontal length of the aquifer increases to infinity. The leakage of the overlying confining layer enhances the landward attenuation of the tidal head fluctuation and shortens the time lag between the head and tide fluctuations. The solution agreed well with the observations in eight piezometers in Garden Island on the continental shelf of Western Australia reported by Trefry and Bekele (2004).