THE USE OF AQUEOUS GEOCHEMISTRY AS AN INDICATOR OF FLOW SYSTEM INTERACTION WITHIN A BEACH-RIDGE COMPLEX OF LAKE HURON

The interaction between groundwater and surface-water systems is a fundamental component of the hydrology, development, and persistence of wetlands found within beach-ridge filled embayments around the Great Lakes. The nature and type of interactions between these flow systems can be viewed as occurring within a hydrologic continuum between local (shallow) flow systems and regional (deep) flow systems.

We collected 70 samples from “wetland” surface water and shallow groundwater wells driven into the upper aquifer in Albert E. Sleeper State Park near Caseville, Michigan. The samples were distributed along a transect of 55 beach ridges originating at Lake Huron and extending approximately 1500 meters inland to ridges of Nipissing age. All 70 samples collected have been analyzed in the field for parameters of specific conductance, temperature, pH, Eh, and alkalinity. The samples are also being analyzed for major ions of K⁺, Na⁺, Ca²⁺, Mg²⁺, Fe²⁺, Fe³⁺, F^-, NO₃^-, SO₄^2-, Cl^-, PO₄^3-, and isotopes of oxygen and deuterium.

Initial results indicate that end members of the hydrologic continuum can be identified using water chemistry indicators. These data, along with sedimentological and stratigraphic data collected with vibracores, are providing detailed insight into the relative and absolute contributions that both surface-water and groundwater make to wetland communities in the study area. It is hoped that these results will be useful in efforts to classify and manage the ecosystems found in these beach-ridge filled embayments in light of potential climate change.