Collaborative Research: Interaction of Saline-Formation Water, Near-Surface Ground Water, and Large Lakes

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9317244 Long Saline ground-water seeps have been recently found entering Lake Ontario. Although stable isotope and geochemical analyses indicate that the saline ground water is from regional saline formation water, the source for the formation water is not well constrained. Geochemical and isotopic evidence indicates that high Cl values in the water of Saginaw Bay, Lake Huron may be in part caused by the direct discharge to the bay of saline ground water from saline formation water from the Michigan basin. Since the source and hydrogeology of the Saginaw Bay area is better constrained than in Lake Ontario, Saginaw Bay is an excellent site to study the interaction of saline-formation water, near-surface ground water, and large lakes. The objectives of this research are to 1) document the occurrence and source of saline water in the sediments of Saginaw Bay by geochemical and isotopic determinations; (2) relate the occurrence of the saline water in the bay sediments to the surrounding ground-water chemistry by comparing spatial iso- chemical trends in the pore waters of the bay with that of the ground water; and (3) determine the effect of the saline water on pore-water chemistry by chemical modeling. This will be accomplished by examining geochemical and isotopic characteristics of pore water in sediments of Saginaw Bay and in water of the streams in the major watershed entering the bay. The data will be studied in the context of the hydrogeochemistry of the regional as well as local ground-water systems. Results from this study will be important in understanding the importance of direct ground-water discharge to large lakes and the interaction of large lakes and regional ground-water flow particularly that part of the flow that involves deep saline formation water. ***