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Scientific Investigations Report 2011-5020

National Water-Quality Assessment Program

Effects of Natural and Human Factors on Groundwater Quality of Basin-Fill Aquifers in the Southwestern United States—Conceptual Models for Selected Contaminants

By Laura M. Bexfield, Susan A. Thiros, David W. Anning, Jena M. Huntington, and Tim S. McKinney

Thumbnail of and link to report PDF (11 MB) Introduction

As part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program, the Southwest Principal Aquifers (SWPA) study is building a better understanding of the factors that affect water quality in basin-fill aquifers in the Southwestern United States. The SWPA study area includes four principal aquifers of the United States: the Basin and Range basin-fill aquifers in California, Nevada, Utah, and Arizona; the Rio Grande aquifer system in New Mexico and Colorado; and the California Coastal Basin and Central Valley aquifer systems in California. Similarities in the hydrogeology, land- and water-use practices, and water-quality issues for alluvial basins within the study area allow for regional analysis through synthesis of the baseline knowledge of groundwater-quality conditions in basins previously studied by the NAWQA Program. Resulting improvements in the understanding of the sources, movement, and fate of contaminants are assisting in the development of tools used to assess aquifer susceptibility and vulnerability.

This report synthesizes previously published information about the groundwater systems and water quality of 15 information-rich basin-fill aquifers (SWPA case-study basins) into conceptual models of the primary natural and human factors commonly affecting groundwater quality with respect to selected contaminants, thereby helping to build a regional understanding of the susceptibility and vulnerability of basin-fill aquifers to those contaminants. Four relatively common contaminants (dissolved solids, nitrate, arsenic, and uranium) and two contaminant classes (volatile organic compounds (VOCs) and pesticide compounds) were investigated for sources and controls affecting their occurrence and distribution above specified levels of concern in groundwater of the case-study basins. Conceptual models of factors that are important to aquifer vulnerability with respect to those contaminants and contaminant classes were subsequently formed. The conceptual models are intended in part to provide a foundation for subsequent development of regional-scale statistical models that relate specific constituent concentrations or occurrence in groundwater to natural and human factors.

First posted March 30, 2011

For additional information contact:
Director, Utah Water Science Center
U.S. Geological Survey
2329 Orton Circle
Salt Lake City, Utah 84119
http://ut.water.usgs.gov/

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Suggested citation:

Bexfield, L.M., Thiros, S.A., Anning, D.W., Huntington, J.M., and McKinney, T.S., 2011, Effects of natural and human factors on groundwater quality of basin-fill aquifers in the southwestern United States—conceptual models for selected contaminants: U.S. Geological Survey Scientific Investigations Report 2011-5020, 90 p.



Contents

Abstract

Introduction

Factors with the Potential to Influence Aquifer Vulnerability and Their Variability Among Case-Study Basins

Synthesis of Contaminant Occurrence and Major Factors Affecting Aquifer Vulnerability in Case-Study Basins

Conceptual Models of Important Factors Affecting Vulnerability of Southwestern Basin-Fill Aquifers with Respect to Selected Contaminants

Summary and Conclusions

References Cited


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