USGS OFR 2007-1215 --- Kinnaman & Dixon

Open-File Report 2007-1215

2007

Prepared in cooperation with
St. Johns River Water Management District
South Florida Water Management District
Southwest Florida Water Management District

Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2006

Sandra L. Kinnaman and Joann F. Dixon

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Introduction

This map depicts the potentiometric surface of the Upper Floridan aquifer in the St. Johns River Water Management District and vicinity for September 2006. Potentiometric contours are based on water-level measurements collected at 571 wells during the period September 11-29, near the end of the wet season. Some contours are inferred from previouspotentiometric-surface maps with larger well networks. The potentiometric surface of the carbonate Upper Floridan aquifer responds mainly to rainfall, and more locally, to ground-water withdrawals and spring flow. Potentiometric-surface highs generally correspond to topographic highs where the aquifer is recharged. Springs and areas of diffuse upward leakage naturally discharge water from the aquifer and are most prevalent along the St. Johns River. Areas of discharge are reflected by depressions in the potentiometric surface. Ground-water withdrawals locally have lowered the potentiometric surface. Ground water in the Upper Floridan aquifer generally flows from potentiometric highs to potentiometric lows in a direction perpendicular to the contours.

Summary of Hydrologic Conditions

Measured values of the potentiometric surface ranged from 8 feet below NGVD 29 near Fernandina Beach, Florida, to 127 feet above NGVD29 in Polk County, Florida. The average water level of the network in September 2006 was about a foot higher than the average in May 2006 following below-average rainfall during the previous 9 months. Seasonal differences in network average water levels generally range from 4 to 6 feet. For 553 wells with previous measurements, September 2006 levels ranged from about 19 feet below to about 37 feet above May 2006 water levels. Water level increases of 20 feet or more occurred in 5 of the 12 wells measured in Polk County and all 3 wells measured in Hardee County.

For 554 wells with previous measurements, September 2006 levels ranged from about 21 feet below to about 6 feet above September 2005 water levels. Water levels decreased more than 20 feet in only 1 of the 13 wells measured in southeastern Georgia. The average water level of the network in September 2006 was about 3 feet lower than the average in September 2005.

Additional Reference

Long-term hydrographs of ground-water levels for continuous and periodic wells are available at internet site: http://waterdata.usgs.gov/fl/nwis/gw

Suggested Citation:

Kinnaman, S.L., and Dixon, J.F., 2007, Potentiometric Surface of the Upper Floridan Aquifer in the St. Johns River Water Management District and Vicinity, Florida, September 2006: U.S. Geological Survey Open-File Report 2007-1215, 1 sheet.

For additional information, contact:

U.S. Geological Survey
Florida Integrated Science Center
12703 Research Parkway
Orlando, FL 32826

(407) 803-5541

kinnaman@usgs.gov

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