The Suwannee River Basin (SRB) in Florida contains an abundance of springs discharging groundwater from the Floridan aquifer system (FAS). Historic large-scale groundwater withdrawals in northeastern Florida and southeastern Georgia may have contributed to the lowering of the potentiometric surface of the Upper Floridan Aquifer (UFA) more than 10 feet over a very large area (Bush and Johnston, 1988).
This project involved collection of historic hydrologic data (groundwater levels, rainfall, streamflow, spring discharge) and compilation groundwater withdrawal estimates in counties in the SRB in Florida and Georgia from 1980 to 2007. Statistical trend, correlation and cluster analyses of these data were conducted on time series that had more than 10 years of consistent data within the January 1980 to December 2007 study period.
Results from statistical trend analyses showed that 12 out of 132 groundwater wells had statistically significant downward trends at the 95% confidence level for the 1980-2007 time period. For the rainfall data, 1 out of 44 stations had a statistically significant downward trend at the 95% confidence level for the 1980-2007 time period. No statistically significant trends were detected for the 22 streamflow stations over the study period. There was insufficient spring flow data (i.e., less than 10 years of observations with sporadic measurements) to conduct the statistical analyses.
Uncertainty regarding the accuracy of the groundwater withdrawal records compiled, and conflicting results from the various statistical trend analyses of these records, suggest that these groundwater withdrawal data were not of sufficient quality to draw reliable conclusions about trends in these data or correlations with groundwater level trends.In the supplement report, the entire period of record for historic groundwater levels (upper Floridan) data in the Suwannee River basin and northeast Florida were analyzed for long-term trends and cluster analysis. In the final report under the original contract, groundwater level data available prior to 1980 was neglected since other time series of interest (principally groundwater withdrawal estimates) were not consistently available before then. |