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FLORIDA

GEORGIA

84°00′

30°30′

30°00′

29°30′

29°00′

83°30′ 83°00′ 82°30′ 82°00′

0

0

10 20 MILES

10 20 KILOMETERS

5 15

5 15

Atlantic Ocean

Location of

Suwannee River Water

Management District

Gulf of Mexi

c

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HAMILTON

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MADISON

COUNTY JEFFERSON

COUNTY

TAYLOR

COUNTY

LAFAYETTE

COUNTY

DIXIE

COUNTY

GILCHRIST

COUNTY

LEVY

COUNTY

MARION

COUNTY

BRADFORD

COUNTY

UNION

COUNTY

BAKER

COUNTY

SUWANNEE

COUNTY

COLUMBIA

COUNTY

MADISON

LIVE OAK

LAKE CITY

STEINHATCHEE

Prepared in cooperation with OPEN-FILE REPORT 2006-1310

Verdi, Richard J., and Sepúlveda, A.A., 2006, Potentiometric Surface of the Upper Floridan Aquifer

in the Suwannee River Water Management District, Florida, May 2005

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY SUWANNEE RIVER WATER MANAGEMENT DISTRICT

by

Richard Jay Verdi and A. Alejandro Sepúlveda

POTENTIOMETRIC SURFACE OF THE UPPER FLORIDAN AQUIFER IN THE

SUWANNEE RIVER WATER MANAGEMENT DISTRICT, FLORIDA, MAY 2005

Base from U.S. Geological Survey digital data, 1:2,000,000, 1995

Albers Equal-Area Conic projection

Standard parallels and , central meridian 29°30′ 45°30′ 83°.

Copies of this map can be purchased from:

U.S. Geological Survey

Branch of Information Services

Box 25286

Denver Federal Center

Denver, Colorado 80225-0286

Table 1. Precipitation data from May 2004 to

April 2005 at Lake City showing monthly rainfall

totals and departures from normal.

[Amounts are in inches]

May 2004 1.79 -1.92

June 2004 8.09 1.18

July 2004 9.04 2.30

August 2004 8.39 1.20

September 2004 28.01 23.34

October 2004 2.03 -0.79

November 2004 3.49 1.07

December 2004 4.21 1.25

January 2005 1.95 -2.57

February 2005 4.12 0.51

March 2005 7.20 2.30

April 2005 5.30 2.15

Total 83.62 30.02

Month and year Departure

from

normal

Total

50

EXPLANATION

POTENTIOMETRIC CONTOUR Shows altitude at which

water level would have stood in tightly cased wells.

Hachures indicate depressions. Contour interval 10 feet

Datum is NGVD 29. Dashed were inferred.

–

SUWANNEE RIVER WATER

MANAGEMENT DISTRICT BOUNDARY

NOTE: The potentiometric contours are generalized to portray

synoptically the head in a dynamic hydrologic system taking

into account the variations in hydrogeologic conditions such

as differing depths of wells, nonsimultaneous measurements

of water levels, variable effects of pumping, and changing

climatic influence. The potentiometric contours thus may not

conform exactly with individual measurements of water level.

OBSERVATION WELL

Precipitation

Introduction

Upper Floridan Aquifer

Summary of Hydrologic Conditions

Acknowledgments

This map depicts the potentiometric

surface of the Upper Floridan aquifer in the

Suwannee River Water Management District

(SRWMD) during May 2005. Potentiometric

contours are based on water-level measurements

taken at more than 400 observation wells during the

period of May 1-31, 2005. A potentiometric surface is

defined as an areal representation of the levels to which

water would rise in tightly cased wells open to an aquifer

(Fetter, 1988). Since these water-level measurements from

the Upper Floridan aquifer were taken over a 31-day period,

they do not represent a “snapshot” of the conditions at a

specific date and time.

The Upper Floridan aquifer is a thick unit of carbonate rock and extends

beneath most of Florida and southern parts of Alabama, Georgia, and South

Carolina. The aquifer is highly permeable because of widening fractures

that develop over geologic time and the formation of conduits within the

aquifer through dissolution of the limestone. Numerous karstic features,

such as springs, disappearing streams, and sinkholes, have also formed in

northern Florida as a result of this process. These features influence the

ground-water flow direction throughout the aquifer (Sepúlveda and others,

2006). The Upper Floridan aquifer is the primary source of freshwater

throughout the SRWMD.

Water levels in observation wells that penetrate the Upper Floridan

aquifer are typically at their lowest levels during late spring following the dry

season. Monthly water-level fluctuations of up to 4 ft (feet) are common in

some observation wells within the SRWMD and are in response to rainfall

and pumpage (Mahon and others, 1997). Measured water levels ranged

from 1.08 ft above the National Geodetic Vertical Datum of 1929 (NGVD 1929)

at Steinhatchee to 93.48 ft above NGVD 1929 southwest of Madison during

May 2005. The average water level measured in wells was 41.29 ft above

NGVD 1929 within the SRWMD during May 2005. Water levels measured in

May 2005 averaged above normal and fell in the 72nd percentile (Tom Mirti,

Suwannee River Water Management District, written commun., 2006); that is,

an average of 72 percent of historic water levels fall below those levels

measured in May 2005.

Precipitation was above average within the SRWMD during the

preceding 12 months (May 2004 – April 2005). Precipitation in Lake City

(Columbia County), for example, totaled 83.62 in. (inches), which was 30.02

in. above normal (table 1). The greatest departure from normal rainfall in

Lake City occurred in September 2004 (23.34 in. above normal), and was the

result of Hurricanes Frances and Jeanne and a stationary frontal system

situated over southern Georgia (Verdi, 2005).

The authors wish to acknowledge the contributions of the Suwannee

River Water Management District. Their collection and compilation of the

water-level data used in the construction of this potentiometric surface map

were invaluable.

References

Fetter, C.W., 1988, Soil moisture and ground

water, in Applied Hydrogeology: Macmillan

Publishing Company, chap. 4, p. 63-114.

Mahon, G.L., Sepúlveda, A.A., and Choquette, A.F., 1997,

Potentiometric surface of the Upper Floridan aquifer in

Florida, May and June 1995: Florida Geological Survey

Map Series Number 140, 1 sheet.

Sepúlveda, A.A., Katz, B.G., and Mahon, G.L., 2006,

Potentiometric surface of the Upper Floridan aquifer in the

Ichetucknee Springshed, northern Florida, September 2003:

U.S. Geological Survey Open-File Report 2006–1031.

Verdi, R.J., 2005, Hydrologic effects of the 2004 hurricane

season in northwest Florida: U.S. Geological Survey

Open-File Report 2005–1277, 18 p.