Flow and transport in coastal aquifer-aquitard systems

The numerical and laboratory results are in close agreement, revealing that upward leakage from the semi-confined aquifer into the saltwater wedge of the overlying unconfined aquifer caused buoyant instabilities to form. The development of freshwater fingers created complex saltwater-freshwater mixing, leading to mixed saltwater influx-efflux patterns across the sloping aquifer-ocean interface. Compared with non-tidal conditions, tidal forces reduced the net upward leakage from the semi-confined aquifer to the overlying unconfined aquifer.