Groundwater geochemistry in the Seminole Well Field, Cedar Rapids, Iowa

Journal of the American Water Resources Association
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Abstract

The City of Cedar Rapids obtains its municipal water supply from four well fields in an alluvial aquifer along the Cedar River in east-central Iowa. Since 1992, the City and the U.S. Geological Survey have cooperatively studied the groundwater-flow system and water chemistry near the well fields. The geochemistry in the alluvial aquifer near the Seminole Well Field was assessed to identify potentially reactive minerals and possible chemical reactions that produce observed changes in water chemistry. Calcite, dolomite, ferrihydrite, quartz, rhodochrosite, and siderite were identified as potentially reactive minerals by calculating saturation indexes. Aluminosiicate minerals including albite, Ca-montmorillonite, gibbsite, illite, K-feldspar, and kaolinite were identified as potentially reactive minerals using hypothetical saturation indexes calculated with an assumed dissolved aluminum concentration of 1 microgram per liter. Balanced chemical equations derived from inverse-modeling techniques were used to assess chemical reactions as precipitation percolates to the water table. Calcite dissolution was predominate, but aluminosilicate weathering, cation exchange, and redox reactions also likely occurred. Microbial-catalyzed redox reactions altered the chemical composition of water infiltrating from the Cedar River into the alluvial aquifer by consuming dissolved oxygen, reducing nitrate, and increasing dissolved iron and manganese concentrations. Nitrate reduction only occurred in relatively shallow (3 to 7 meters below land surface) groundwater near the Cedar River and did not occur in water infiltrating to deeper zones of the alluvial aquifer.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Groundwater geochemistry in the Seminole Well Field, Cedar Rapids, Iowa
Series title Journal of the American Water Resources Association
DOI 10.1111/j.1752-1688.1999.tb04212.x
Volume 35
Issue 5
Year Published 1999
Language English
Publisher American Water Resources Association
Contributing office(s) Iowa Water Science Center
Description 12 p.
First page 1257
Last page 1268
Country United States
State Iowa
City Cedar Rapids
Online Only (Y/N) N
Additional Online Files (Y/N) N