Georgia Water Science Center

Water-Resources Investigations Report 02-4244

Stream-Aquifer Relations and the Potentiometric Surface of the Upper Floridan Aquifer in the Lower Apalachicola–Chattahoochee–Flint River Basin in parts of Georgia, Florida, and Alabama, 1999–2000

This report is available online in pdf format (3 MB): USGS WRIR 02-4244 (Opens the PDF file in a new window. )

Melinda S. Mosner

U.S. Geological Survey Water-Resources Investigations Report 02-4244, 45 pages (Published 2002)


Radium Springs, Albany, Georgia, 1995
Photograph by: Alan M. Cressler, U.S. Geological SurveyThe Upper Floridan aquifer is the principal source of water for domestic and agricultural use in the lower Apalachicola – Chattahoochee –Flint (ACF) River Basin. Recent drought and increased water use have made understanding surface- and ground-water relations a priority for water-resource managers in the region. From July 1999 through August 2000, less than normal precipitation reduced streamflow in the area to less than 12 percent of average mean-daily streamflow and ground-water levels reached record or near-record lows. Effects of drought on stream-aquifer interactions in the basin were evaluated using baseflow estimation, ground-water seepage calculations, and potentiometric-surface maps. Ground-water discharge to streams, or baseflow, was estimated using three methods: field measurements, hydrograph separation, and linear regression analysis. Results were evaluated seasonally—October 1999, April 2000, and August 2000—and for the period of record at four surface-water stations located on Kinchafoonee, Spring, Muckalee, and Turkey Creeks. Estimates of baseflow also were compared annually; ground-water discharge during the drought years, 1999 – 2000, was compared with ground-water discharge during a relatively wet year, 1994.

Hydrograph separation indicated decreased base-flow of streams as the water level in the Upper Floridan aquifer declined. Mean-annual baseflow for Kinchafoonee, Spring, Muckalee, and Turkey Creeks ranged from 36 to 71 percent of total streamflow during the period of record. In 1994 baseflow accounted for only 37 to 56 percent of total streamflow, in 1999 baseflow comprised from 60 to 73 percent of total streamflow, and in 2000 baseflow comprised from 56 to 76 percent of streamflow. The percentage of total streamflow attributed to ground water increased during the drought, whereas other components of streamflow decreased (overland flow, interflow, and channel precipitation). Even though relative ground-water contributions were increased, the volume of water discharged from the aquifer to streams decreased during the drought as the Upper Floridan aquifer water level declined. Unit-area mean-annual ground-water discharge ranged from 0.60 to 0.79 cubic foot per second per square mile ([ft3/s]/mi2) in 1994, from 0.24 to 0.58 (ft3/s)/mi2 in 1999, and from 0.13 to 0.33 (ft3/s)/mi2 in 2000. Ground-water contributions to streamflow are high in winter, when evaporative demands are low, and low in summer, when evaporative demands are high. Linear regression analysis of stream-aquifer relations in the lower ACF River Basin shows 85- or 90-percent flow durations as reasonable estimates of baseflow.




Purpose and scope

Description of study area


Hydrogeologic setting

Ground-water level


Previous investigations

Well- and stream-numbering systems



Estimation of ground-water seepage

Precipitation trends

Stream-aquifer relations

Conceptual model of stream-aquifer flow system

Ground-water contribution to streamflow (baseflow)

Linear regression analysis

Hydrograph separation

Analysis of baseflow estimation methods and discussion of error

Potentiometric surface


References cited

Appendix A—Wells measured in the lower Apalachicola – Chattahoochee –Flint River Basin, 1999 – 2000

Appendix B—Streamgaging stations measured in the lower Apalachicola – Chattahoochee – Flint River Basin, 1999 – 2000

Appendix C—Springs measured in the lower Apalachicola – Chattahoochee - Flint River Basin, 1999 – 2000

Plate 1. Location of wells, surface-water sites, and springs measured in the lowerApalachicola – Chattahoochee – Flint River Basin, October 1999 –August 2000



This report is available online in pdf format (3 MB): USGS WRIR 02-4244 (Opens the PDF file in a new window. )
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