Hydraulic characteristics of the upper Floridan aquifer in the Savannah and St Marys areas of coastal Georgia

Georgia Geologic Survey Information Circular 105, 23 pages

Cover photograph: Production well at St Marys test site, St Marys, Georgia, July 1999. Photograph by Alan M. Cressler, U.S. Geological Survey

ABSTRACT

Hydraulic characteristics (transmissivity and storage coefficient) of the Upper Floridan aquifer in the Savannah and St Marys areas of coastal Georgia were evaluated by analyzing results of water-level recovery tests. Tidal corrections were applied to data from one well for the Savannah area test, and to data from the four wells for the St Marys area test. Data from one well used in the St Marys area test also were corrected for effects of nearby pumpage. Transmissivity tensor analyses were conducted to evaluate the anisotropy of the aquifer at the Savannah and St Marys test sites.

For the Savannah area, calculated transmissivity of the Upper Floridan aquifer ranges from 32,000 to 43,000 feet squared per day, and the storage coefficient ranges from 6.3 x 10^-4 to 1.3 x 10^-3. Transmissivity of the aquifer has an anisotropy ratio of approximately 1.2:1 and an angle of anisotropy of approximately 108 degrees (measured counterclockwise from due east). Thus, the larger principal value of transmissivity is aligned approximately in the direction of north-northwest.

For the St Marys area, calculated transmissivity of the Upper Floridan aquifer ranges from 98,000 to 170,000 feet squared per day, and the storage coefficient ranges from 9.9 x 10^-4 to 2.4 x 10^-3. Transmissivity of the aquifer has an anisotropy ratio of approximately 2.5:1 and an angle of anisotropy of approximately 64 degrees (measured counterclockwise from due east). The larger principal value of transmissivity is aligned approximately in the north-northeast direction.

TABLE OF CONTENTS

Abstract

Introduction

Purpose and scope

Methods

Ackowledgments

General hydrogeology of the Georgia coastal area

Hydraulic characteristics of the Upper Floridan aquifer

Savannah area aquifer test

St Marys area aquifer test

Comparison of aquifer-test results

Summary

References Cited

Appendix--Technique for removing effects of tides and pumpage from ground-water levels measured during an aquifer-recovery test at St Marys, Georgia

Introduction

Tidal data

Regression technique for removing tidal and pumping effects

Results and discussion

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