The U.S. Geological Survey (USGS), in cooperation with Miami-Dade County, mapped the approximate inland extent of saltwater intrusion in eastern Miami-Dade County in 2018. This approximation required acquisition and compilation of relevant data collected by the organizations: Florida Department of Environmental Protection (FDEP), Florida Keys Aqueduct Authority (FKAA), Florida Power & Light Company (FPL), MacVicar Consulting Inc., Miami-Dade County Regulatory and Economic Resources (MD-RER), the South Florida Water Management District (SFWMD), and the USGS. Data from the selected monitoring wells were entered into a geographic information system (GIS) for analysis and mapping. The approximate saltwater interface is represented by the 1,000-mg/L isochlor at the base of the Biscayne aquifer. The word “approximate” is used because the spatial distribution of monitoring wells is generally insufficient to create a precise representation.

The U.S. Geological Survey (USGS), in cooperation with Miami-Dade County, mapped the approximate inland extent of saltwater intrusion in eastern Miami-Dade County in 2018. This approximation required acquisition and compilation of relevant data collected by the organizations: Florida Department of Environmental Protection (FDEP), Florida Keys Aqueduct Authority (FKAA), Florida Power & Light Company (FPL), MacVicar Consulting Inc., Miami-Dade County Regulatory and Economic Resources (MD-RER), the South Florida Water Management District (SFWMD), and the USGS. Data from the selected monitoring wells were entered into a geographic information system (GIS) for analysis and mapping. The approximate saltwater interface is represented by the 1,000-mg/L isochlor at the base of the Biscayne aquifer. The word “approximate” is used because the spatial distribution of monitoring wells is generally insufficient to create a precise representation.

The U.S. Geological Survey (USGS) cooperated with Miami-Dade County to map the approximate inland extent of saltwater intrusion in the Biscayne aquifer in eastern Miami-Dade County, Florida in 2022. This map is a continuation of a series of maps, the most recent of which was published in 2018, which have helped to track the position of the saltwater interface over time and have improved understanding of the rate of movement of the saltwater interface. To estimate the position of the saltwater interface, relevant data including chloride concentrations, specific conductance, and bulk conductivity from time-series electromagnetic induction logs collected by various organizations including the Florida Keys Aqueduct Authority (FKAA), Florida Power and Light Company (FPL), MacVicar Consulting Inc., and the USGS were acquired and compiled. These data were entered into a geographic information system for mapping. The approximate location of the saltwater interface is represented by the 1,000-mg/L isochlor at the base of the Biscayne aquifer. The term “approximate” is used here because certain areas of the map lack sufficient spatial distribution of monitoring wells to create a precise representation. This data release includes a shapefile of the 1,000-mg/L isochlor and tables of construction information for wells used to create the map and the maximum chloride concentration in those wells in 2022.

A shapefile was created that shows the approximate inland extent of saltwater intrusion at the base of the Biscayne aquifer in 2022 in Miami-Dade County, Florida. The approximate location of the saltwater interface is represented by the 1,000-mg/L isochlor at the base of the Biscayne aquifer. The term “approximate” is used here because certain areas of the map lack sufficient spatial distribution of monitoring wells to create a precise representation. The approximate location of the 1000-mg/L isochlor was identified using chloride concentrations and specific conductance data from groundwater wells. These data are provided in the child item, "Summary tables for the approximate inland extent of saltwater intrusion at the base of the Biscayne aquifer in 2022, Miami-Dade County, Florida".

Data pertaining to mapping the approximate inland extent of saltwater at the base of the Biscayne Aquifer in the Model Land Area of Miami-Dade County, Florida in 2016. The inland extent of saltwater at the base of the Biscayne aquifer in the Model Land area of Miami-Dade County, Florida, was last mapped in 2011. Since that time, the saltwater interface has continued to move inland. The interface is near several active well fields; therefore, an updated approximation of the inland extent of saltwater and an improved understanding of the rate of movement of the saltwater interface are necessary. A geographic information system was used to create a map using the data collected by the organizations that monitor water salinity in this area. A rate of saltwater interface movement of 140 meters per year was estimated by dividing the distance between two monitoring wells (TPGW-7L and Sec34-MW-02-FS) by the travel time. The travel time was determined by estimating the dates of arrival of the saltwater interface at the wells and computing the difference. This estimate assumes that the interface is traveling east to west between the two monitoring wells. Although monitoring is spatially limited in this area and some of the wells are not ideally designed for salinity monitoring, the monitoring network in this area is improving in quality and spatial distribution. The approximation of the inland extent of the saltwater interface and the estimated rate of movement of the interface are dependent on existing data. Improved estimations could be obtained by installing uniformly-designed monitoring wells in systematic transects extending landward of the advancing saltwater interface. This release of data includes the chloride concentration and specific conductance of water samples, and the water conductance profiles provided by other organizations that were used for this mapping effort and to determine the rate of movement of the saltwater interface. Also included are GIS files of the 1,000 mg/L islochlor and well information

Tables were created to summarize well information, maximum chloride concentrations and specific conductance data sourced from Florida Keys Aqueduct Authority (FKAA), Florida Power and Light Company (FPL), MacVicar Consulting Inc., and the U.S. Geological Survey (USGS) during 2022. The summary tables here provide the information used to create the 1,000-mg/L isochlor in ArcGIS Pro. A table listing the USGS sites used to develop a regression between chloride concentration and specific conductance is also included in this release.

This release of data includes the chloride concentration of water samples provided by the USGS or other organizations that were used for this mapping effort. The inland extent of saltwater at the base of the Biscayne aquifer in the Model Land area of Miami-Dade County, Florida, was mapped in 2011. Since that time, the saltwater interface has continued to move inland. The interface is near several active well fields; therefore, an updated approximation of the inland extent of saltwater and an improved understanding of the rate of movement of the saltwater interface are necessary. A geographic information system was used to create a map using the data collected by the organizations that monitor water salinity in this area. A rate of saltwater interface movement of 140 meters per year was estimated by dividing the distance between two monitoring wells (TPGW-7L and Sec34-MW-02-FS) by the travel time. The travel time was determined by estimating the dates of arrival of the saltwater interface at the wells and computing the difference. This estimate assumes that the interface is traveling east to west between the two monitoring wells. Although monitoring is spatially limited in this area and some of the wells are not ideally designed for salinity monitoring, the monitoring network in this area is improving in quality and spatial distribution. The approximation of the inland extent of the saltwater interface and the estimated rate of movement of the interface are dependent on existing data. Improved estimations could be obtained by installing uniformly-designed monitoring wells in systematic transects extending landward of the advancing saltwater interface.

A three-dimensional, variable-density solute-transport model (SEAWAT) was developed to examine causes of saltwater intrusion and predict the effects of future alterations to the hydrologic system on salinity distribution in eastern Broward County, Florida. The model was calibrated to conditions from 1970 to 2012, the period for which data are most complete and reliable, and was used to simulate historical conditions from 1950 to 2012. The model was used to (1) evaluate the sensitivity of the salinity distribution in groundwater to sea-level rise and groundwater pumping , and (2) simulate the potential effects of increases in pumping, variable rates of sea-level rise, movement of a salinity control structure, and use of drainage recharge wells on the future distribution of salinity in the aquifer. This USGS data release contains all of the input and output files for the simulations described in the associated model documentation report (https://doi.org/10.3133/sir20165022). This data release also includes (1) preprocessing python scripts and associated input data files for creating the sensitivity and scenarios runs, (2) flopy source code, and (3) SEAWAT (v4) source code.

Statistical analyses and maps representing mean, high, and low water-level conditions in the surface water and groundwater of Miami-Dade County were made by the U.S. Geological Survey, in cooperation with the Miami-Dade County Department of Regulatory and Economic Resources, to help inform decisions necessary for urban planning and development. Sixteen maps were created that show contours of (1) the mean of daily water levels at each site during October and May for the 2000-2009 water years; (2) the 25th, 50th, and 75th percentiles of the daily water levels at each site during October and May and for all months during 2000-2009; and (3) the differences between mean October and May water levels, as well as the differences in the percentiles of water levels for all months, between 1990-1999 and 2000-2009. The 80th, 90th, and 96th percentiles of the annual maximums of daily groundwater levels during 1974-2009 (a 35-year period) were computed to provide an indication of unusually high groundwater-level conditions. These maps and statistics provide a generalized understanding of the variations of water levels in the aquifer, rather than a survey of concurrent water levels. Water-level measurements from 473 sites in Miami-Dade County and surrounding counties were analyzed to generate statistical analyses. The monitored water levels included surface-water levels in canals and wetland areas and groundwater levels in the Biscayne aquifer. Maps were created by importing site coordinates, summary water-level statistics, and completeness of record statistics into a geographic information system, and by interpolating between water levels at monitoring sites in the canals and water levels along the coastline. Raster surfaces were created from these data by using the triangular irregular network interpolation method. The raster surfaces were contoured by using geographic information system software. These contours were imprecise in some areas because the software could not fully evaluate the hydrology given available information; therefore, contours were manually modified where necessary. The ability to evaluate differences in water levels between 1990-1999 and 2000-2009 is limited in some areas because most of the monitoring sites did not have 80 percent complete records for one or both of these periods. The quality of the analyses was limited by (1) deficiencies in spatial coverage; (2) the combination of pre- and post-construction water levels in areas where canals, levees, retention basins, detention basins, or water-control structures were installed or removed; (3) an inability to address the potential effects of the vertical hydraulic head gradient on water levels in wells of different depths; and (4) an inability to correct for the differences between daily water-level statistics. Contours are dashed in areas where the locations of contours have been approximated because of the uncertainty caused by these limitations. Although the ability of the maps to depict differences in water levels between 1990-1999 and 2000-2009 was limited by missing data, results indicate that near the coast water levels were generally higher in May during 2000-2009 than during 1990-1999; and that inland water levels were generally lower during 2000-2009 than during 1990-1999. Generally, the 25th, 50th, and 75th percentiles of water levels from all months were also higher near the coast and lower inland during 2000-2009 than during 1990-1999. Mean October water levels during 2000-2009 were generally higher than during 1990-1999 in much of western Miami-Dade County, but were lower in a large part of eastern Miami-Dade County.

Statistical analyses and maps representing mean, high, and low water-level conditions in the surface water and groundwater of Miami-Dade County were made by the U.S. Geological Survey, in cooperation with the Miami-Dade County Department of Regulatory and Economic Resources, to help inform decisions necessary for urban planning and development. Sixteen maps were created that show contours of (1) the mean of daily water levels at each site during October and May for the 2000-2009 water years; (2) the 25th, 50th, and 75th percentiles of the daily water levels at each site during October and May and for all months during 2000-2009; and (3) the differences between mean October and May water levels, as well as the differences in the percentiles of water levels for all months, between 1990-1999 and 2000-2009. The 80th, 90th, and 96th percentiles of the annual maximums of daily groundwater levels during 1974-2009 (a 35-year period) were computed to provide an indication of unusually high groundwater-level conditions. These maps and statistics provide a generalized understanding of the variations of water levels in the aquifer, rather than a survey of concurrent water levels. Water-level measurements from 473 sites in Miami-Dade County and surrounding counties were analyzed to generate statistical analyses. The monitored water levels included surface-water levels in canals and wetland areas and groundwater levels in the Biscayne aquifer. Maps were created by importing site coordinates, summary water-level statistics, and completeness of record statistics into a geographic information system, and by interpolating between water levels at monitoring sites in the canals and water levels along the coastline. Raster surfaces were created from these data by using the triangular irregular network interpolation method. The raster surfaces were contoured by using geographic information system software. These contours were imprecise in some areas because the software could not fully evaluate the hydrology given available information; therefore, contours were manually modified where necessary. The ability to evaluate differences in water levels between 1990-1999 and 2000-2009 is limited in some areas because most of the monitoring sites did not have 80 percent complete records for one or both of these periods. The quality of the analyses was limited by (1) deficiencies in spatial coverage; (2) the combination of pre- and post-construction water levels in areas where canals, levees, retention basins, detention basins, or water-control structures were installed or removed; (3) an inability to address the potential effects of the vertical hydraulic head gradient on water levels in wells of different depths; and (4) an inability to correct for the differences between daily water-level statistics. Contours are dashed in areas where the locations of contours have been approximated because of the uncertainty caused by these limitations. Although the ability of the maps to depict differences in water levels between 1990-1999 and 2000-2009 was limited by missing data, results indicate that near the coast water levels were generally higher in May during 2000-2009 than during 1990-1999; and that inland water levels were generally lower during 2000-2009 than during 1990-1999. Generally, the 25th, 50th, and 75th percentiles of water levels from all months were also higher near the coast and lower inland during 2000–2009 than during 1990-1999. Mean October water levels during 2000-2009 were generally higher than during 1990-1999 in much of western Miami-Dade County, but were lower in a large part of eastern Miami-Dade County.