The effect of tidal fluctuation on ground water quality in coastal aquifer of Saijo plain, Ehime prefecture, Japan Original Research Article

This study is an effort to trace the implication of tidal fluctuation on coastal groundwater quality for different aquifers in case of Saijo plain, western Japan, through major ion, heavy metal and isotopic chemistry as well as to estimate aquifer parameters by tidal response method. Time series analysis for chemical characteristics depicts that tidal fluctuation at diurnal basis significantly affects ionic signature of groundwater along with piezometric level for unconfined aquifer whereas effect is less prominent for confined aquifer. Different plots (e.g. 87Sr/86Sr vs 1/Sr and BEX vs Cl) were drawn in order to deduce mechanisms responsible for water quality change with tidal phase and it was found that cations exchange and local sea water–fresh water (SW–FW) mixing along with oxidation–reduction are likely to be main processes responsible for water quality changes. Using tide aquifer interaction technique, calculated hydraulic conductivities for different monitoring sites were 0.01 and 2.8 × 10− 6 m/s which appropriately address geological properties of aquifers, and thus it can be concluded that tide aquifer technique is a reliable technique to estimate aquifer properties.