Selected geochemical characteristics of ground water from the Saginaw aquifer in the central Lower Peninsula of Michigan

Chemical and stable-isotope data of water from wells completed in the Saginaw aquifer in the central Lower Peninsula of Michigan were used to prepare maps that show areal variation of δ¹⁸O; distribution of dissolved solids, dissolved chloride, dissolved iron, dissolved sulfate; and distribution of hydrochemical facies. Delta oxygen-18 values indicate the presence of modern meteoric water (δ¹⁸O approximately -10 parts per thousand) and glacial-age meteoric water, which is isotopically light (δ¹⁸O less than -15 parts per thousand). Isotopically light ground water is present in the Saginaw Bay Area in the eastern part of the study area. Dissolved-solids concentration ranges from 41 to 92,300 milligrams per liter, and dissolved-chloride concentrations range from less than 1 to 55,000 milligrams per liter. Dissolved-solids and dissolved-chloride concentrations increase toward Saginaw Bay. Dissolved-iron and dissolved-sulfate concentration ranges from 0.01 to 7.80 and 0.2 to 3,500 milligrams per liter, respectively. Most ground water from the Saginaw aquifer is classified as calcium bicarbonate, calcium sulfate, or sodium chloride.