Numerical Solution of Ttidal Induced Fluctuation in an Inhomogeneous Island Aquifer System, and its Comparison with Analytical Solution

Tide induced head fluctuation has been considered by many researchers in coastal areas. In this paper, a numerical solution has been developed for an inhomogeneous multi-layered aquifer. This aquifer system comprises an unconfined aquifer on the top, a semi-confined aquifer at the bottom, and an aquitard between them. This coastal aquifer is bounded by coast in longitudinal direction; the coastal boundaries are parallel to each other. The results showed that the amplitude of unconfined aquifer head increases with increase of leakage, however, the amplitude of head fluctuation decreases in the semi-confined aquifer. In addition, the results of analytical solution, the head fluctuation in unconfined aquifer decreases with increase of dimensionless storage coefficient, however, it is almost constant in confined aquifer. Also, increase of dimensionless transmissivity increases the groundwater head fluctuation in both aquifers. Temporal head fluctuation illustrated that time lag has not significant changes, and is greater for semi-confined aquifer with respected to confined aquifer. Comparison between numerical and analytical solutions showed that there is little difference between.