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 37

Based on the potentiometric surface mapping conducted for this investigation, general flow 

directions on the karst plain are identified (Figure 25). Werner (2000) gives information on the 

position of a stagnation point within the Wakulla Springs conduit system. He notes that a 

separation between north-flowing and south-flowing waters is observable in the main conduit 

system and that it occurs at distances ranging between 2,100 ft and 7,500 ft south of the spring, 

depending on flow conditions. 

Data collected on and near the City of Tallahassee southeast sprayfield (SESF) indicate a 

southwesterly flow direction into the zone of high conductivity. Such an interpretation is 

counterintuitive, given the proximity of the sprayfield to the St. Marks River. St. Marks Rise 

(located near the Leon/Wakulla county line and about half the distance between the SESF and 

Wakulla Springs) is a significant source of ground water outflow from the Floridan Aquifer. 

Presumably, the drain effect of the St. Marks Rise should perturb Floridan Aquifer flow 

directions in southeast Leon County to the southeast. This does not seem to be the case, 

although the reason for this is not clear. A southwesterly flow direction near the sprayfield, 

while based in this instance on a limited number of wells is substantiated by previous 

potentiometric surface mapping at the sprayfield itself (Pruitt et al., 1988 and Berndt, 1990). 

Additional water level data along the lower St. Marks River would be of value in refining 

localized flow directions. 
Incorporated Areas

Unconfined

Semi-Confined U.S. Highways

Conduit System

Rivers

State/County Roads

County Boundary

Regional Ground Water

Flow Direction

N

GROUND WATER FLOW DIRECTIONS

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Y #

#Newport

Wakulla

St.

Marks

Woodville

Crawfordville

LEON CO.

WAKULLA CO.

River

St. Mark

Wakulla

River

Wakulla 

 Springs

St. Marks

Rise

A P A L A C H E E

B A Y

Y

LEON CO.

WAKULLA CO.

Y

Spring

 Creek

Miles

0 5

01-06-011

FIGURE 25
 39

Surface Waters

Wakulla Springs and River 

Wakulla Springs is a major Floridan Aquifer ground water discharge point within the St. Marks 

and Wakulla rivers basin. The output from the spring is sufficient to form the Wakulla River, 

which flows southeast about nine miles and discharges into the Gulf of Mexico. Based on 

USGS data, the period of record median flow from Wakulla Springs is 340 cfs (n=297, 

mean=397, stdev=266, Figure 26). The lowest observed flow was 25.2 cfs, on June 18, 1931. 

The largest observed flow, 1,910 cfs, occurred on April 11, 1973. Beneath the spring pool of 

Wakulla Springs lies an extensive network of large-diameter conduits. The main trunk of the 

conduit system lies more or less horizontally at depths ranging between 230 ft and 280 ft below 

sea level. This conduit system runs northeast and south away from the spring, consists of 

multiple branches, and has been extensively traversed and mapped by divers. 

Another large conduit system has been mapped by divers starting in the Leon Sinks Geologic 

Area. This system connects Big Dismal Sink on the north end, with Cheryl Sink, River Sink 

Group and Turner Sink on the south end (Werner, 2000). It also receives surface water inflow 

from Fisher Creek. River Sink Group is a collection of three tunnel collapse features that have a 

significant perennial flow. In each case, water emerges from the ground on the upstream end of 

the sink, flows along the length of the sink and disappears into the ground on the downstream 

end. Middle River Sink, which has been measured seven times, has a median discharge of 160 

cfs, or about 47 percent of the median discharge of Wakulla Springs. Cave divers have 

explored several smaller conduit systems on the karst plain including Chip’s Hole, Indian 

Springs, Sally Ward Spring, McBride’s Slough (Werner, 2000). Though the Big Dismal-Turner 

Sink and Wakulla Springs systems have not been shown to connect through direct exploration, 

it is reasonable to presume some degree of interconnection. 

In the last 25 years, Wakulla Springs has experienced a significant increase in NO3

concentrations (Figure 27). These data were gleaned from USGS and EPA STORET 

databases and represent a compilation of analyses for (1) NO3, total (as N); (2) NO3, dissolved 

(as N); (3) NO2+NO3, total (as N); (4) and NO2+NO3, dissolved (as N). These analyses were 

considered to yield relatively equivalent results for the purpose of illustrating the increase in NO3

experienced at Wakulla Springs. Historically, there has been no measurable NO2 in the ground 

waters of the study area and, presumably, all detectable NO3 in ground water is dissolved. 

Based on data from 1971 through 1977, the median NO3 concentration was 0.26 mg-N/L 

(n=22). Based on data from 1989 through 2000, the median concentration had increased to 

0.89 mg-N/L (n=26). Concentrations appear to have peaked in the early 1990s and have 

declined slightly since. Over similar periods, the NO3 concentration in Middle River Sink 

increased from a median of 0.06 mg-N/L (n=14) to 0.19 mg-N/L (n=3). The postulated 

increases are considered accurate, as the data from the 1970s are reported as NO3-N, total and 

the data from the 1980s and 1990s are reported as NO3-N, dissolved. Based on a median flow 

of 340 cfs (3.04x1011 L/yr), and a median NO3 concentration of 0.89 mg-N/L, the NO3 load 

discharged from Wakulla Springs is 270,000 kg-N/yr. 

 

The difference in the NO3 concentration histories of Wakulla Springs and Middle River Sink is of 

note. Both show increases with time. River Sink had what are generally considered 

background concentrations during the 1970s. Currently, River Sink nitrate concentrations are 

similar to what Wakulla Springs experienced 25 years previously. River Sink lies northwest of 

Wakulla Springs and, presumably, passes water to the spring from the western edge of the area 

contributing water to the spring. This water has a much lower nitrate concentration than 
 40

ure 26. Wakulla Springs and Middle River Sink Spring Historic Discharge (data from USGS).

1920 1934 1947 1961 1975 1988

Date

a Springs

 River Sink
 41

pilation of NO3-N and NO2+NO3-N Concentration Data for Wakulla Springs and Middle River Sink Spring. 

1976 1982 1987 1993 1998

Date

a Springs

 River Sink
 42

Wakulla Springs itself. If it is true that River Sink discharges to Wakulla Springs, and if the three 

recent River Sink nitrate concentration measurements are representative of current conditions, 

the source of elevated nitrates in Wakulla Springs must lie north and east of the Big Dismal—

Turner Sink conduit system. If the flow through River Sink bypasses Wakulla Springs, the same 

conclusion is true. 

NO3 concentrations in waters currently discharging from the spring are promoting the growth of 

undesirable vegetation. Hydrilla and filamentous algae are particularly problematic. According 

to the FDEP EcoSummary (FDEP, 2000) for Wakulla Springs, “nitrate-nitrite concentrations 

(ranging from 0.77-0.84 mg/L) at the sampling site were consistently higher than the values 

found in 90% of Florida streams.” Based on four determinations made during 2000, “the stream 

condition index (SCI) ranked the site ‘very poor’ once, ‘poor’ twice, and at the lowest end of 

‘good’ category once” during 2000. The report further observes that the periphyton community 

is dominated by taxa that are tolerant of nutrient enriched conditions. Further, they conclude 

that “the poor macroinvertebrate health was related to the habitat and dissolved oxygen 

problems caused by Hydrilla, which in turn was due to high nitrate levels” (FDEP, 2000). 

 

Katz (2001) performed sampling and isotopic analysis of ground and surface waters from the 

Woodville Karst Plain, including Wakulla Springs, Fisher Creek, Lost Creek and Munson 

Slough. Water from most sampled wells and from Wakulla Springs had δ15 N-NO3 values 

ranging between 6.8 and 8.9 per mil, indicating that their NO3 originates from a blend of organic 

and inorganic sources. Using 3

H/3He age-dating techniques, Katz (2001) determined that the 

average residence time of ground water discharging from Wakulla Springs was 38.7 +/-1.07 

years. He also concluded that surface water inflows from sinking streams contributed little NO3-

N to ground waters on the karst plain. 

St. Marks River 

The St. Marks River is a second major source of Floridan Aquifer discharge on the Woodville 

Karst Plain. The St. Marks River originates in the Tallahassee Hills physiographic subdivision. 

The river headwaters were originally what are now the Lakes Miccosukee and Lafayette 

drainage basins. Erosion modified the headwater basins to the point where drainage became 

predominantly internal and the basins closed. Between these basins and the St. Marks River 

Rise, overland surface flows are intermittent, depending on the amounts of rainfall and overland 

runoff. 

In periods of low flow, the St. Marks Rise is the head of the perennial St. Marks River (Rosenau 

et al., 1977). Based on 42 years of record, the USGS St. Marks River gage (0.65 miles south of 

the rise) has the following statistics; Q10—1090 cfs; Q50—635 cfs; Q90—408 cfs. Median stage 

at this station is 8.9 ft, NGVD (Marvin Franklin, personal communication, 2001). 

Interaction between Wakulla Springs and Up-gradient Surface Water Features 

Ames Sink

Ames Sink lies about 5.5 miles due north of Wakulla Springs and is within the capture zone of 

the spring. Accordingly, waters that enter Ames Sink eventually discharge from the spring. 

Ames Sink is on the downstream end of Munson Slough, which conveys surface waters from 

the lake to the sink. In turn, Lake Munson receives water from the urban drainage system that 

drains much of the southern part of the City of Tallahassee. 
 43

Conductivity data collected at Ames Sink and flow data collected on Munson Slough above 

Lake Munson are given in Figure 16. Collection of flow data at Ames Sink was beyond the 

scope of this investigation. Conductivity and flow data are given for the period 03/99 to 11/00, 

which includes the very dry summer of 2000. For much of this period, inflows at the sink were 

minimal to nonexistent. However, the water quality meter used to collect these data was 

continually submerged. Measured conductivity values ranged from 60 and 250 μmhos/cm. 

Typically, conductivities dipped after rainfall events and rose during dry periods. It is possible 

that the elevated conductivities observed during dry periods reflect re-circulation of Floridan 

Aquifer waters into the sink in the absence of surface water inflows. Otherwise, conductivity 

decreases during rainy periods seem to reflect the inflow of stormwater derived from low 

conductivity rainfall. 

1999 Surface Water Conductivity Data

During 1999, specific conductivities of water from Wakulla Springs ranged between 275 and 340 

μmhos/cm (Figure 28). These data are typical of Floridan Aquifer conductivities found upgradient of Wakulla Springs. 238 conductance samples collected in Leon County between 1986 

and 1999 had a median conductance of 247 μmhos/cm (mean=241, stdev=62). Elevated 

conductivity is primarily due to dissolved carbonate from the limestone aquifer. As a function of 

time, the 1999 Wakulla Springs conductivity data exhibit relatively little variability. 

1999 conductivities in the three other surface water features were lower (Figure 28). Fisher 

Creek is a black-water sinking stream whose watershed lies within the Apalachicola National 

Forest. During 1999, it had the lowest range of conductivity values, between 30 and 75 

μmhos/cm and exhibited little variability during the year. Fisher Creek conductivities were 

lowest during dry periods and (curiously) rose following rain events. Lowest observed values for 

Lost Creek (another black-water sinking stream draining the national forest) were similar to 

Fisher Creek, in the vicinity of 30 μmhos/cm. However, during dry periods, conductivities in Lost 

Creek rose well above those of Fisher Creek, to about 170 μmhos/cm. This increase is likely 

attributable to the discharge of Floridan Aquifer water into Lost Creek during low-flow periods. 

Conductivities in Ames Sink were typically higher than in either Fisher or Lost creeks. 

2000 Surface Water Conductivity Data

During much of 2000, conductivities in Wakulla Springs were similar (>300 μmhos/cm) to the 

previous year (Figure 29). However, September rains were sufficient to perturb the prevailing 

pattern. During September a total of 19.29 inches of rain fell at the River Sink Station. Of this, 

8.31 inches fell during the first week, 1.09 inches fell on September 17 and an additional 9.53 

inches were associated with the passage of Tropical Storm Helene on September 22. During 

September, conductivities in Wakulla Springs declined rather sharply from 310 μmhos/cm to 

250 μmhos/cm, or by about 20 percent. Within about three weeks of Tropical Storm Helene’s 

passage through the area, conductivities in the spring rebounded to 320 μmhos/cm. 

Middle River Sink had a 2000 conductivity history similar to that of Wakulla Springs. During 

much of the year values varied through a small range (between 220 to 240 μmhos/cm). These 

high values reflect the high proportion of Middle River Sink water originating in the Floridan 

Aquifer. Rains occurring around the first of September were sufficient to reduce the conductivity 

by about 20 percent. A precipitous decline followed Tropical Storm Helene (Figure 30). During 

a six-day period, conductivities fell from 220 μmhos/cm to 60 μmhos/cm. For a short period of 

time, flow through Middle River Sink consisted entirely of surface water, much of it undoubtedly 

originating from Fisher Creek. The high surface water inflow following rains associated with 
 44

pecific Conductivity and Rainfall versus Time for Fisher Creek, Ames Sink, Lost Creek and Wakulla Springs. 

05/23/99 06/22/99 07/22/99 08/21/99 09/20/99 10/20/99 11/19/99 12/19/99

Date

012345

River Sink Station Rainfall (inches/day)

all Wakulla Springs Lost Creek Ames Sink Fisher Creek

ta No Data

No Data 

Calibration Drift Correction
 45

ecific Conductivity and Rainfall versus Time for Fisher Creek, Ames Sink, Lost Creek, Middle River Sink and 

Wakulla Springs. 

3/20/00 4/19/0005/19/00 6/18/00 7/18/00 8/17/00 9/16/0010/16/00

Dates

012345678910

River Sink Station Rainfall (inches/day)

Wakulla Springs River Sink Spring Lost Creek Ames Sink Fisher Creek

No Data

Calibration Drift Correction

rift 
 46

onductivity and Rainfall versus Time Prior to and Following Tropical Storm Helene, July-November, 2000.

7/31/00 8/30/00 9/29/00 10/29/00

Date

012345678910

River Sink Station Rainfall (inches/day)

Wakulla Springs Middle River Sink Lost Creek Ames Sink Fisher Creek

Calibration Drift Correction Calibration Drift Correction
 47

Tropical Storm Helene completely overwhelmed the ground water component of Middle River Sink 

Spring. During this period, waters in Ames Sink, Fisher Creek, Middle River Sink and Lost Creek all 

had similar conductivities, on the order of 60 μmhos/cm. By late October, Middle River Sink returned 

to its typical, Floridan Aquifer dominated flow regime. Wakulla Springs recovered to its typical 

conductivities over the same period. 

In Ames sink, Fisher Creek and Lost Creek, conditions during 2000 were similar to 1999. During the 

prolonged dry period that began around the first of April and ended around mid-July, conductivities in 

Lost Creek and Ames sink rose well above typical wet period values. For the year Fisher Creek had 

a fairly narrow range of values, between 30 and 90 μmhos/cm. 

Surface Water Temperature Data

Figures 31 and 32 give temperature versus time data for Fisher Creek, Ames Sink, Lost Creek, 

Middle River Sink, Spring Creek and Wakulla Springs for 1999 and 2000. The Wakulla Springs 

temperature data given in these figures were collected with the S4 meter inside A-tunnel. Meandaily air temperature data from the Tallahassee Airport are also given. For both years, the 

temperature profile of Wakulla Springs is virtually invariant. During the entire period the only 

perturbation followed Tropical Storm Helene and that disturbance was slight. Middle River Sink (for 

which only 2000 data was collected) is only slightly less invariant. The two most significant 

disturbances occurred in mid-January 2000, during a period of very cold air temperatures, and in 

September 2000, during periods of high rainfall. In contrast, temperature data for the surface water 

features closely follow the average daily air temperature, being cooler than Wakulla Springs in winter 

and warmer in summer. 

The invariant nature of the temperature data from Wakulla Springs partially substantiates the 

observation that the spring is deeply imbedded in the regional flow system. Likely, much of the 

seasonal temperature signal is removed from recharge water by the time it reaches the Floridan 

Aquifer. There are observations of seasonal temperature fluctuations in individual Floridan Aquifer 

wells on the order of 2 °C. Wakulla Springs undoubtedly integrates waters over a wide range of 

temporal scales. In the process, any remaining seasonal (or other) temperature signals are almost 

completely removed. 

Wakulla Springs Velocity and Conductivity Data

Specific conductivity and velocity data from Wakulla Springs are given in Figures 33 and 34 for 1999 

and 2000. Specific conductivity data were collected from the data logger installed beneath the boat 

dock (Station #4, above). These data show a generally inverse relationship between conductivity 

and velocity. Inflows of relatively low conductivity rainfall via sinking streams will undoubtedly mix 

with and dilute Floridan Aquifer waters discharging from the spring, reducing conductivity in the 

process. 

Hurricane Floyd and Tropical Storm Helene passed through the area in September 1999, 

contributing to a monthly total rainfall of 13.31 inches at the Tallahassee Airport and 19.29 inches at 

the River Sink Station. In August, A-tunnel velocities were on the order of 8 cm/s and specific 

conductivities were on the order of 325 μmhos/cm. In mid-September, tunnel velocities increased to 

∼17 cm/s. Concurrently, the conductivity declined to ∼300 μmhos/cm. The observed increase in 

velocity from 8 cm/s to 17 cm/s should represent roughly a doubling of the spring discharge. 

Assuming that 325 μmhos/cm represents 100 percent Floridan Aquifer water and assuming a 

surface water conductivity of about 40 μmhos/cm, a blending ratio of 93 percent Floridan Aquifer 

water to 7 percent surface water is required to reduce the conductivity from 325 to 300 μmhos/cm. 

This mixing ratio is independent of spring flow. 
 48

9 Temperature and Rainfall versus Time for Fisher Creek, Ames Sink, Lost Creek and Wakulla Springs.

995/5/99 5/19/996/2/99 6/16/99 6/30/99 7/14/99 7/28/99 8/11/99 8/25/999/8/99 9/22/99 10/6/99 10/20/99 11/3/99 11/17/99 12/1/99 12/15/99 12/29/99

Date

012345

River Sink Station Rainfall (inches/ day)

nfall Wakulla Springs Spring Creek Lost Creek Ames Sink Fisher Creek Air Temperature

o Data No Data
 49

mperature and Rainfall versus Time for Fisher Creek, Ames Sink, Lost Creek, Middle River Sink and Wakulla 

Springs.

0 3/1/00 3/31/00 4/30/00 5/30/00 6/29/00 7/29/00 8/28/00 9/27/0010/27/00

Date

012345678910

River Sink Station Rainfall (inches/ day)

Wakulla Springs Middle River Sink Lost Creek Ames Sink Fisher Creek Air Temperature
 50

Figure 33. 1999 Wakulla Springs Velocity versus Specific Conductivity.

7/18/99 08/02/9908/17/9909/01/9909/16/9910/01/9910/16/9910/31/9911/15/99 11/30/9912/15/9912/30/99

Date

260270280290300310320330

Conductivity (umhos/cm)

y (cm/s)

ctivity (umhos/cm)

Calibration Drift Correction
 51

Figure 34. 2000 Wakulla Springs Velocity versus Specific Conductivity. 

03/01/0003/16/0003/31/0004/15/0004/30/0005/15/0005/30/0006/14/0006/29/0007/14/0007/29/0008/13/0008/28/0009/12/0009/27/0010/12/0010/27/0011/11/00

Date

240250260270280290300310320330340

Conductivity (umhos/cm)

y (cm/s)

ctivity (umhos/cm)

Calibration Drift Correction
 52

The addition of surface water inflow from sinking streams is not sufficient to double discharge 

from the spring. Rather, the increase in flow is mostly accounted for by additional discharge 

from the Floridan Aquifer. The increase in Floridan Aquifer discharge through the spring results 

from a slight increase in Floridan Aquifer water levels attributable to short-term, relatively 

intense rainfall events. Given the extremely high hydraulic conductivity of the Floridan Aquifer, it 

is not surprising that small increases in hydraulic head result in a significant increase in 

discharge. 
 53

WATER QUALITY IN THE FLORIDAN AQUIFER 

Historic Nitrate Concentrations

Two previous studies (1986 and 1997) by the Department of Health (DOH) provide insight into 

historic NO3 concentrations in the Floridan Aquifer. Wells used in these studies are described in 

Table 5. One study performed in 1986 concentrated on Leon County. When these data were 

examined, it appeared that they had significant quality assurance problems. For this reason 

NO3 data obtained by the DOH in 1986 were not mapped. The data are included in time series 

representations for several wells. 

The second DOH study, performed in 1997, focused on Wakulla County (Figures 35 and 36). 

Data from the FDEP GWIS data set, USGS databases and the City of Tallahassee were 

combined with the DOH data to produce data sets as complete as possible for 1997. The data 

represent a compilation of analyses for (1) NO3, total (as N); (2) NO3, dissolved (as N); (3) 

NO2+NO3, total (as N); (4) and NO2+NO3, dissolved (as N). These analyses were considered to 

yield relatively equivalent results for the purpose of illustrating NO3 concentrations in the 

Floridan Aquifer. Historically, there has been no measurable NO2 in the ground waters of the 

study area and, presumptively, all detectable NO3 in ground water is dissolved. 

Results of the 1997 study show that NO3 concentrations are quite variable over the study area. 

Most results from the semi-confined and unconfined areas are above detection limits, reflecting 

a widespread distribution of NO3 from anthropogenic sources. There is a scattering of values 

below detection limits (BDLs) in the unconfined portions of Leon and Wakulla counties. BDLs 

are even more prevalent in Wakulla County where the Floridan Aquifer is under confined 

conditions (western half of county). This reflects the relatively low population density in this 

area and the greater degree of aquifer confinement. 

Project-specific Ground and Surface Water Sampling

Six surface water sites and 41 Floridan Aquifer wells were sampling as part of the project 

(Figure 9, Appendix A, Table A3). A complete list of sampling results is presented in Table 7. 

Six of the sampled wells were constructed for the project. They, along with Middle River Sink 

and Wakulla Springs were sampled twice more—during low-flow and high-flow conditions—for 

various isotopes. Analytical results from these data collection efforts are described in greater 

detail in Katz et al. (in preparation). 

NO2+NO3

The overall distribution of NO2+NO3-N (Figure 37) is consistent with the historical data—few 

BDL concentrations and a variable distribution on the karst plain, with concentrations below 

detection limits in the undeveloped eastern portion of Wakulla County and along the coast. 

Concentrations in ground water ranged from below the detection limit of 0.020 mg-N/L to 7.3 

mg-N/L. The primary drinking water standard for nitrate is 10 mg/L. In surface water inflows 

(Lost Creek, Fisher Creek and Munson Slough) NO2+NO3-N concentrations are below detection 

limits. In surface water outflows (Wakulla Springs, Sally Ward Spring, Middle River Sink Spring, 

and McBride Slough) NO2+NO3-N concentrations ranged from 0.19 mg-N/L to 1.0 mg-N/L. 

The six wells constructed for the project, Middle River Sink and Wakulla Springs were sampled 

for nitrogen isotopes to obtain a δ15N-NO3 value. δ15N-NO3 values are helpful in distinguishing 
Y

(X

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Marks

Wildlife

Refuge St. Marks

National

Apalachicola

National

Forest

GADSDEN CO.

SRWMD

NWFWMD

JEFFERSON CO.

Lake

Iamonia

 Lake 

 Miccosukee

Lake

Lake

Lafayette

A P A L A C H E E 

B A Y

River

River

St. Marks

Ochlockonee

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Crawfordville

Tallahassee

Woodville

Wakulla

Panacea

Lake Talquin

#

FRANKLIN CO.

LIBERTY CO.

LEON CO.

WAKULLA CO.

Lake

Munson

River

Wakulla 

 Springs

231

251

276

280

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399

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Gretna

2706

LOCATION OF WELLS USED IN 1997 SAMPLING EVENT

N

(X Control Well Location

U.S. Highways

State/County Roads Major Lakes

Rivers

Incorporated Areas

Public Lands

0 510

Miles

01-06-013

FIGURE 35
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1.60 1.20 1.30

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12.00

BDL (0.05)

BDL (0.05)

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BDL (0.05)

BDL (0.05)

BDL (0.05) BDL (0.05) BDL (0.05)

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BDL (0.05)

BDL (0.02)

BDL (0.05)

BDL (0.05)

BDL (0.05)

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BDL (0.01)

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BDL (0.02)

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0.74

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BDL (0.05)

Quincy

Newport

Wakulla

Sopchoppy

Midway

St.

Marks

Wildlife

Refuge St. Marks

National

Apalachicola

National

Forest

GADSDEN CO.

Lake

Lake

Lafayette

A P A L A C H E E 

B A Y

River

River

St. Marks

Ochlockonee

Jackson

Crawfordville

Tallahassee

Woodville

Wakulla

Panacea

Lake Talquin

WAKULLA CO.

#

FRANKLIN CO.

LIBERTY CO.

LEON CO.

WAKULLA CO.

Lake

Munson

WAKULLA CO.

LEON CO.

River

Wakulla 

 Springs

N

Sampling Locations

(Concentration mg-N/L) #S

U.S. Highways

State/County Roads

Rivers

County Boundary

Incorporated Areas

Public Lands

Major Lakes

0 510

Miles

BDL-Below Detection Limit

 (Individual Detection Limit)

COMPILATION OF NO -N AND NO +NO -N CONCENTRATIONS IN THE FLORIDAN AQUIFER, 1997 3 2 3

01-06-014

FIGURE 36
NO + NO - N CONCENTRATIONS, 1999 - 2000 2 3

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River

LEON CO.

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L.

Miccosukee

St. Marks

Rise

Lake

Munson

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N BDL - Below Detection Limit (Individual Detection Limit)

0 510

Miles

(Concentration mg-N/L)

$T SW Sampling Location

#S GW Sampling Location

Y Springs

District Boundary

Lakes

Incorporated Areas

Public Lands

County Boundary

U.S. Highways

Rivers

Conduit System

State/County Roads

01-06-016

FIGURE 37
 57

between organic and inorganic sources of nitrate. Low values (0 to 3 per mil) indicate an 

inorganic nitrate source such as artificial fertilizer. Higher values (10 to 20 per mil) indicate an 

organic nitrate source such as septic tanks, waste disposal or manure spreading (Katz et al., 

1999). With four of six wells constructed for the project having BDL NO3-N concentrations, four 

additional wells from the sampling network with elevated NO3-N concentrations were selected to 

replace them. Values for δ15N-NO3 are shown below: 

Table 4. δ15N-NO3 Values. 

Site name (NWF ID) δ15N-NO3 (per mil) 

Wakulla Springs (749) 6.3 

Middle River Sink (7757) 4.5 

Nitrate #1 (7492) 4.6 

Nitrate #5 (7498) 7.4 

Claycomb (6493) 2.6 

Johnson (674) 0.6 

Garcia (663) 3.1 

Blackstead (641) 7.6 

Wakulla Springs data are consistent with previous sampling results (Katz, 2001) and indicate a 

mixture of nitrogen sources. Middle River Sink, Nitrate #1 and Garcia also indicate a mixing of 

sources, tending toward the inorganic. Claycomb and Johnson, both adjacent to agricultural 

land uses, have a strong inorganic source indication. Nitrate #5 and Blackstead indicate a 

mixture of sources. 

Previous δ15N analysis in the study area was perfomed by the USGS (Berndt, 1990) at the 

SESF. Sampling for δ15N analyses in Floridan and surficial aquifer was conducted during 

January 1988 and the reported median δ15N ratio was 7.2 per mil (n=13, mean=8.1, stdev=2.3, 

range=5.9 to 12.4). From this data, Berndt concluded that the application of inorganic fertilizer 

at the SESF was influencing N isotopic ratios in ground waters at the site. 

Dissolved Organic Carbon 

Dissolved organic carbon (DOC) values ranged from below a detection limit of 0.1 mg-C/L to 

31.0 mg-C/L (Figure 38). Highest levels occurred in surface water inflows (Fisher Creek, 

Munson Slough and Lost Creek). Concentrations in ground water were generally low. 

However, some wells had concentrations sufficiently elevated to indicate a possible influence 

from surface water. 

Dissolved Oxygen 

Dissolved oxygen (DO) was determined as a field parameter at the time laboratory samples 

were collected. DO values ranged from zero mg-O/L (in one of the wells constructed for the 

project) to 11.9 mg-O/L (Figure 39). Surface water and ground water concentrations are 

scattered throughout this range, although the lowest values (<1.0 mg/L) are all from ground 

waters. 

pH 

Values for pH were measured in the field at the time of sample collection. Values ranged from 

3.5 to 8.5 standard units (Figure 40). Surface water inflow sites (Fisher Creek, Munson Slough 

and Lost Creek) generally had low pH, ranging from 3.5 to 6.4 standard units (su). One ground 

water site (Seminole Golf Course) had a pH indicative of surface water influence (5.3 su). 
DISSOLVED ORGANIC CARBON CONCENTRATIONS, 1999 - 2000

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River

LEON CO.

WAKULLA CO.

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St. Marks

River

GADSDEN CO.

Apalachicola

National

Forest

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BDL(0.10)

L.

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Lake Talquin

St. Marks

Rise

Lake

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Lake

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Lake

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 Creek

0 510

Miles

BDL - Below Detection Limit (Individual Detection Limit) N

(Concentration mg-C/L)

$T SW Sampling Location

#S GW Sampling Location

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District Boundary

County Boundary

U.S. Highways

Rivers

Conduit System

State/County Roads

Lakes

Incorporated Areas

Public Lands

01-06-017

FIGURE 38