| Abstract/Description or Keywords |
Transient density-dependent flow and solute transport simulations were carried out for Saturna Island, using USGS SUTRA to model the behaviour of the freshwater-saltwater interface over the last 12,000 years. While Na-enriched water is present in groundwater throughout most of the island, near the coast there are higher concentrations of Cl, consistent with the presence of a saltwater wedge. The origin of Na is speculated to originate from remnant seawater, which was introduced (along with Cl) into the rock sequence during the Pleistocene when the islands were submerged. Isostatic rebound, following submergence, has removed Cl by flushing the aquifer with fresh (HCO rich) infiltrating groundwater. This study aimed firstly to test the hypothesis that a 1,000 year period (between ice retreat and post-glacial rebound roughly 12,000 years ago) was sufficient to result in at least partial saturation of the island with seawater. Secondly, the study aimed to test if Cl has had sufficient time to be removed from shallow and intermediate aquifer depths, and be at higher concentrations at depth near the coast. |
