Groundwater conditions in southern Florida
|Florida Water Science Center||Real-time conditions (detrended data)||Real-time conditions (standard data)||End-of-month conditions (detrended data)||End-of-month conditions (standard data)||Periodic measurements (standard data)||Salinity and chloride measurements|
Current Water-level Conditions in South Florida
Site status is calculated based on long-term water-level trends, where identified
A 7-day running average of daily recorded water levels is compared to the statistical distribution of daily water levels for the site period of record for selected sites in southern Florida. More detailed information for each site is available through the map links and the pages listed below. Detailed information on how the map was created, and the information used to derive the mapped data are also available on this site. A KML file for the stations shown on the map is also available. (Right-click link to download file.)
Postscript and Adobe PDF versions of the map are available for printing. The Adobe Reader program is available, at no cost, from Adobe. When viewed as a PDF file, the map image may be re-sized for viewing or printing.
Groundwater resources in South Florida are under increasing stress caused a rapid growth in population. As a result of increased demands on aquifers, water managers need more timely and accurate assessments of groundwater conditions to avoid or reduce adverse effects such as saltwater intrusion, loss of pumpage in residential water-supply wells, land-surface subsidence, and aquifer compaction.
Hydrologic data were analyzed from three aquifer systems in southern Florida: the surficial aquifer system, which includes the Biscayne aquifer; the intermediate aquifer system, which includes the sandstone and mid-Hawthorn aquifers; and the Florida aquifer system represented by the lower Hawthorn producing zone. Long-term water-level trends were analyzed using the Seasonal Kendall trend test in 83 monitoring wells with a daily-value record spanning 26 years (1974-99). The majority of the wells with data for this period were in the Biscayne aquifer in southeastern Florida. Only 14 wells in southwestern Florida aquifers and 9 wells in the surficial aquifer system of Martin and Palm Beach Counties had data for the full period. Because many monitoring wells did not have data for this full period, several shorter periods also were evaluated. The trend tests revealed small but statistically significant upward trends in most aquifers, but large and localized downward trends in the sandstone and mid-Hawthorn aquifers.
Monthly means of maximum daily water levels from 246 wells were compared to monthly rainfall totals from rainfall stations in southwestern and southeastern Florida to determine which monitoring wells most clearly indicated decreases in water levels that corresponded to prolonged rainfall shortages. Of this total, 104 wells had periods of record greater than 20 years and could be compared against several drought periods. After factors such as lag, seasonal cyclicity, and cumulative functions were considered, the timing of minimum values of water level from 15 groundwater monitoring wells and average minimum rainfall values agreed 57 to 62 percent of the time over a 20- to 26-year period. On average, the timing of water-level minimums and rainfall minimums agreed about 52 percent of the time, and in some cases only agreed 29 percent of the time.
A regression analysis was used to evaluate daily water levels from 203 monitoring wells that are currently, or recently had been, part of the network to determine which wells were most representative of each aquifer. The regression also was used to determine which wells provided data that could be used to provide estimations of water levels at other wells in the aquifer with a coefficient of determination (R2 value) from the regression of 0.64 or greater. In all, the regression analysis alone indicated that 35 wells generally had 10 years or more of data and could be used to directly monitor water levels or to estimate water levels at 180 of 203 wells (89 percent of the network). Ultimately, factors such as existing instrumentation, well construction, long-term water-level trends, and variations of water level and chloride concentration were considered together with the R2 results in designing the final network.
The Seasonal Kendall trend test was used to examine trends in groundwater chloride concentrations in 113 wells. Of these wells, 61 wells showed statistically significant trends. Fifty-six percent (34 of 61 wells) of the observed trends in chloride concentration were upward and 44 percent (27 of 61 wells) were downward. The relation between water level and chloride concentration in 114 groundwater wells was examined using Spearman's r and Pearson's r correlation coefficients. Statistically significant results showed both positive and negative relations. Based on the results of statistical analyses, period of record, well construction, and existing satellite telemetry, 33 monitoring wells were selected that could be used to assess groundwater conditions in 167 monitoring wells in southern Florida on an interim basis.
This website was designed to provide this information and to provide water managers with daily updates on groundwater conditions in southern Florida. Many of the same analytical tools used to select monitoring wells representative of aquifer conditions are also employed to analyze data for this website. These tools include regression analysis, the Seasonal Kendall trend test, and frequency analysis. This website also includes image maps showing the current conditions for stations in selected geographical areas and aquifers and statistical comparison plots for each station.
For more information on the methods used and the data analyzed, the project report is available on this website. A PDF version of the report, Design of a Real-Time Ground-water Level Monitoring Network and Portrayal of Hydrologic Data in Southern Florida(WRI 01-4275, download 6.3 MB), is also available.
Links to additional sites of interest
Funding for the USGS to design and maintain this site has been provided through a cooperative agreement with the South Florida Water Management District (SFWMD). Water-level conditions are monitored by the USGS with support from Federal, State, and local cooperators.