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Open-File Report 2008-1282

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National Water-Quality Assessment Program

Framework for Evaluating Water Quality of the New England Crystalline Rock Aquifers

By Philip T. Harte, Gilpin R. Robinson, Jr., Joseph D. Ayotte, and Sarah M. Flanagan


This report is available online only in PDF Format (without cover)(6.87 MB)


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Abstract

Little information exists on regional ground-water-quality patterns for the New England crystalline rock aquifers (NECRA). A systematic approach to facilitate regional evaluation is needed for several reasons. First, the NECRA are vulnerable to anthropogenic and natural contaminants such as methyl tert-butyl ether (MTBE), arsenic, and radon gas. Second, the physical characteristics of the aquifers, termed “intrinsic susceptibility,” can lead to variable and degraded water quality. A framework approach for characterizing the aquifer region into areas of similar hydrogeology is described in this report and is based on hypothesized relevant physical features and chemical conditions (collectively termed “variables”) that affect regional patterns of ground-water quality.

A framework for comparison of water quality across the NECRA consists of a group of spatial variables related to aquifer properties, hydrologic conditions, and contaminant sources. These spatial variables are grouped under four general categories (features) that can be mapped across the aquifers: (1) geologic, (2) hydrophysiographic, (3) land-use land-cover, and (4) geochemical. On a regional scale, these variables represent indicators of natural and anthropogenic sources of contaminants, as well as generalized physical and chemical characteristics of the aquifer system that influence ground-water chemistry and flow. These variables can be used in varying combinations (depending on the contaminant) to categorize the aquifer into areas of similar hydrogeologic characteristics to evaluate variation in regional water quality through statistical testing.

Contents

Foreword

Acknowledgments

Abstract

Introduction

Physical Setting

Geohydrology

Identification of Regional Water-Quality Issues

Factors Affecting Water Quality

Physical Processes

Chemical Processes

Considerations for Development of Regional Framework

Review of Other Framework Approaches

Discussion of Regional Framework Factors

Framework Approach

References

Appendix 1. Summary of Regional Ground-Water Quality Issues in Ground Water of the New England Area, by State, as Reported by State Environmental Agencies

Figures

1–4. Maps showing—

1.
Location of the New England crystalline rock aquifers.
2.
Long-term mean annual precipitation (1960–1991) and physiography for the northeastern United States.
3.
Land use patterns in the New England area.
4.
Geologic provinces in the New England crystalline rock aquifers.
5.
Schematic diagrams showing hypothetical depth of well and fracture patterns in (A) shallow wells and (B) deep wells in the New England crystalline rock aquifers.
6.
Scatterplots showing relation between residence time and (A) pH, (B) dissolved oxygen, and (C) arsenic from crystalline rock ground water of the New England Coastal Basins.
7.
Flowchart showing objectives from a proposed 1990 study of the hydrogeology of bedrock of New England.

8–9. Maps showing—

8.
General lithology distribution of rock group A in the New England crystalline rock aquifers.
9.
Lithology distribution of rock group B in the New England crystalline rock aquifers.
10.
Flowchart showing preliminary framework approach for the evaluation of regional ground-water quality in the New England crystalline rock aquifers.

Tables

  1. Approximate land use distribution, by percent, in the New England crystalline rock aquifers.
  2. Summary of well characteristics in crystalline rock aquifers in New England, by State.
  3. Summary of regional ground-water quality issues in the New England crystalline rock aquifers as reported by previous NAWQA studies.
  4. Summary of factors affecting regional water quality in crystalline rocks of the New England area.
  5. Lithology groups and their respective area fractions for the New England crystalline rock aquifers.
  6. Categories of spatial features, associated explanatory variables, sources of information, and ground-water contaminants to be evaluated for the regional study of the New England crystalline rock aquifers.
  7. Ground-water contaminants in relation to explanatory variables in regional studies in the New England crystalline rock aquifers.

Suggested citation:

Harte, P.T., Robinson, G.R., Jr., Ayotte, J.D., and Flanagan, S.F., 2008, Framework for evaluating water quality of the New England crystalline rock aquifers: U.S. Geological Survey Open-File Report 2008–1282, 47 p., available only online at http://pubs.usgs.gov/ofr/2008/1282.


For more information please contact:

Director
U.S. Geological Survey
New Hampshire-Vermont Water Science Center
361 Commerce Way
Pembroke, NH 03275

dc_nh@usgs.gov

(603) 226-7807

or visit our Web site at: http://nh.water.usgs.gov


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