Analysis of groundwater response to tidal effect in a finite leaky confined coastal aquifer considering hydraulic head at source bed

Groundwater response to tidal effect in a finite leaky confined coastal aquifer is analyzed considering the impact of hydraulic head at the source bed (upper unconfined aquifer). For the groundwater response analysis, the impact of head at the source bed and the effect of boundary condition on the inland side are discussed. The shape of hydraulic head at the source bed is considered in two cases; (1) constant head, using mean groundwater level of concerning domain that may or may not be equal to mean sea level, and (2) linearly increasing head with distance from the coastline. The dimensional and nondimensional boundary value problems are solved for hydraulic head in the aquifer using Laplace transform technique, and the results are obtained by the numerical inversion of the transformed solution. Evaluation of the solution indicates that, near the coastline, the hydraulic head in a leaky confined aquifer is mostly influenced by the tidal effect, while the distance from the coastline increases, the effect of head in the source bed rises. A sensitivity analysis is conducted to show the importance of the hydraulic head and its shape at the source bed as well as leakance, which affects the head in a confined leaky coastal aquifer. The solution derived in this study is useful for there may be a natural or an artificial barrier on the inland side that acts as a no flux boundary. The study considering this boundary condition implies that care must be taken when aquifer parameters are estimated using previous analytical solutions, since boundary conditions on the inland side affect the head of leaky confined aquifer, and thus may mislead to erroneous aquifer parameter estimation.