Hydrogeology and Groundwater Quality of Highlands ... - USGS

0
100
20
Magnesium
40
Measured total dissolved-solids values (app. 2, table 4)
indicate that total dissolved solids in water in the Upper
Floridan aquifer in Highlands County ranged from 96 to
1,050 mg/L, with a median value of 199 mg/L. Most calculated
total dissolved-solids values determined from specific
conductance (fig. 33) also fell within this range. With the
exception of the areas in the extreme southwestern and
extreme eastern Highlands County, total dissolved-solids
concentrations were below the 500-mg/L recommended
FDEP limits.
Chloride concentrations in the Upper Floridan aquifer
in Highlands County ranged from 4.4 to 403 mg/L (fig. 45,
app. 2), with a median value of 12 mg/L (table 4). The lowest
concentrations, less than 10 mg/L, generally occurred along
the recharge area of the Lake Wales Ridge. Concentrations
ranging from 26 to 250 mg/L occurred in the southwestern
and eastern parts of the county. Chloride concentrations were
below the 250-mg/L recommended limit for drinking water
throughout most of the county, with the exception of the
extreme southwestern and extreme eastern parts of the county.
Bradner (1994) reported chloride concentrations greater than
400 mg/L in Okeechobee County just east of Brighton, and
80
60
PERCENT
80
100 0
60
40
Calcium
0
20
0
Sulfate plus Chloride
20
20
40
60
20
40
Sodium plus Potassium
40
60
60
80
100
0
80
80
100
100
100
100
80
80
PERCENT
100
0
Calcium plus Magnesium
60
60
80
40
40
60
20
20
20
40
Carbonate plus Bicarbonate
0
0
20
40
Assessment of Groundwater Quality 55
0
100
60
PERCENT
80
60
80
Sulfate
Klein and others (1964) reported chloride concentrations
exceeding 1,000 mg/L in the extreme northeastern part of
Glades County.
Chloride concentration often is used as an indicator to
delineate the extent of saltwater intrusion within an area.
Most of the mineralized water in the Upper Floridan aquifer
in southeastern Highlands County (and into Glades County)
probably is a mixture of freshwater and relict seawater that
entered the aquifer during a higher stand of sea level in the
geologic past and has not been completely flushed from the
aquifer. Natural salts of chloride (halite) are not present in the
Upper Floridan aquifer (Sprinkle, 1989).
Sulfate concentrations in the Upper Floridan aquifer in
Highlands County ranged from less than 0.18 to 255 mg/L
(fig. 46, app. 2), with a median value of 23 mg/L (table 4).
Concentrations of less than 10 mg/L generally occurred in the
northwestern and west-central parts of the county and from
30 to 250 mg/L in much of the western and eastern parts of
the county. Sulfate concentrations exceeded 250 mg/L in the
extreme southeastern part of the county near the Kissimmee
River, and possibly in the extreme western part of the county
near the DeSoto/Hardee County line.
40
20
100
Chloride, Fluoride, Nitrate plus Nitrite
Figure 43. Chemical composition of water from the Upper Floridan aquifer.
0