|  | Geostatistical Analysis of Effective Vertical Hydraulic       Conductivity and Presence of Confining Layers in the     Shallow Glacial Drift Aquifer, Oakland County, MichiganBy E.G. Bissell and S.S. AicheleScientific Investigations Report 2004-5167 |
|--|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

ABSTRACT

            About 400,000 residents of Oakland County, Mich., rely on ground water for their primary drinking-water supply. More than 90 percent of these residents draw ground water from the shallow glacial drift aquifer. Understanding the vertical hydraulic conductivity of the shallow glacial drift aquifer is important both in identifying areas of ground-water recharge and in evaluating susceptibility to contamination. The geologic environment throughout much of the county, however, is poorly understood and heterogeneous, making conventional aquifer mapping techniques difficult. Geostatistical procedures are therefore used to describe the effective vertical hydraulic conductivity of the top 50 ft of the glacial deposits and to predict the probability of finding a potentially protective confining layer at a given location.

	        The results presented synthesize the available well-log data; however, only about 40 percent of the explainable variation in the dataset is accounted for, making the results more qualitative than quantitative. Most of the variation in the effective vertical hydraulic conductivity cannot be explained with the well-log data currently available (as of 2004). Although the geologic environment is heterogeneous, the quality-assurance process indicated that more than half of the wells in the county’s Wellkey database (statewide database for monitoring drinking-water wells) had inconsistent identifications of lithology.

CONTENTS

Abstract

Introduction

Approach and Methods

Calculation of Effective Vertical Hydraulic Conductivity

Identification of Distinct Geologic Settings

Quality Assurance of Well Logs

Prediction of Effective Vertical Hydraulic Conductivity

Prediction of Confining Layer Presence

Error Analysis

Results

Conclusions and Limitations

Acknowledgments

References Cited

Glossary

## FIGURES 

1. Map showing surficial geology of Oakland County, Michigan

2–4. Graphs showing:

2. Sample variogram showing the nugget, sill, and range, and the random	        and structured parts of the variation

3. Driller-specific sample variogram showing spatial structure in well-log data

4. Driller-specific sample variogram showing lack of spatial structure in	      well-log data

5. Map showing till and outwash settings in Oakland County

 6–9. Graphs showing:

6. Sample variogram and model variogram for outwash setting

7. Sample variogram and model variogram for till setting

8. Sample variogram and model variogram for indicator kriging of confining	      layers in outwash setting

9. Sample variogram and model variogram for indicator kriging of confining	      layers in till setting

10–13. Maps showing:

10. Predicted effective vertical hydraulic conductivity in the shallow glacial	        drift aquifer, Oakland County

11. Predicted probability of confining-layer (10 ft thick or greater) presence in          the shallow glacial drift aquifer, Oakland County

12. Uncertainity associated with prediction of effective vertical hydraulic          conductivity in the shallow glacial drift aquifer, Oakland County

13. Uncertainty associated with prediction of confining-layer presence in the          shallow glacial drift aquifer, Oakland County

## TABLES 

 1. Results of Student-Newman-Keuls Multiple Comparison Test

2. Cross-validation results for ordinary kriging and indicator kriging

----

## AVAILABILITY

This report is presented in Portable Document Format (PDF).

Toview and print report you will need to use PDF Viewer or Adobe Acrobat Reader (available as freeware)

Users with visual disabilities can visit this site for conversion tools and information to help make PDF files more accessible
Printable tabloid cover   (973 KB)--1 page

Whole report (7.7 MB)--24 pages

 
The citation for this report, in USGS format, is as follows:
*Bissell, E.G., and Aichele, S.S., 2004, Geostatistical analysis of effective vertical hydraulic conductivity		 and presence of confining layers in the shallow glacial drift aquifer, Oakland County, Michigan: U.S. Geological Survey Scientific		  Investigations Report 2004-5167, 19 p.*
 For more information about USGS activities in Michigan District, visit the USGSMichigan Home PageAccessibilityFOIAPrivacyPolicies and Notices
U.S. Department of the Interior, U.S. Geological SurveyPersistent URL: http://pubsdata.usgs.gov/pubs/sir/2004/5167/		Page Contact Information: USGS Publishing NetworkLast modified: Thursday, December 01 2016, 08:09:03 PM