St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District St. Johns River Water Management District
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Water bodies, watersheds and storm water
Island Spring main view

Island Spring main view

Island Spring

Seminole County

Description

Island Spring is a third-magnitude spring. The spring is submerged in the eastern part of the Wekiva River channel.

Discharge

Discharge at Island Spring was measured four times by the U.S. Geological Survey (USGS) from 1982 to 1997. St. Johns River Water Management District measured discharge 33 times from 2001 to 2010. The difference between the minimum and maximum discharges is 4.8 cubic feet per second (cfs) over the period. The maximum measured discharge of 10.2 cfs occurred in March 2003; the minimum discharge of 5.39 cfs occurred in June 2001. The mean and median discharges for the period are 8.29 cfs and 8.34 cfs, respectively (see the table below).

Island Spring Discharge Graph
Discharge Graph

Water quality

Island Spring was sampled by USGS in 1982 and 1996. The district sampled the spring 27 times from 2001 to 2010. Summary statistics of the water quality data for selected variables are shown in the table below.

Island Spring Water Quality Graph
Water Quality Graph

Summary statistics of water quality and discharge at Island Spring

Island Spring Min Mean Median Max Count Period
Discharge, cfs 5.39 8.29 8.34 10.19 37 1982−2010
Alkalinity, total, mg/L as CaCO3 118.0 129.5 128.5 154.0 27 2001−2010
Calcium, total, mg/L as Ca 190.0 217.9 215.3 250.0 26 2001−2010
Chloride, total, mg/L as Cl 1200.0 1756.7 1780.0 2098.5 29 1982−2010
Dissolved Oxygen 0.63 0.63 0.63 0.63 1 2001
Fluoride, total, mg/L as F 0.20 0.22 0.23 0.25 10 2001−2003
Magnesium, total, mg/L as Mg 92.0 108.3 108.0 126.0 26 2001−2010
Nitrate + nitrite, total, mg/L as N 0.01 0.24 0.06 1.20 6 2002−2009
Orthophosphate, total, mg/L as P 0.06 0.08 0.08 0.10 22 2001−2010
pH, field 6.75 7.43 7.32 9.31 10 1982−2003
Phosphorus, total, mg/L as P 0.07 0.11 0.09 0.51 17 2001−2010
Potassium, total, mg/L as K 21.0 24.8 25.0 28.0 26 2001−2010
Sodium, total, mg/L as Na 793.0 924.1 930.3 1100.0 26 2001−2010
Specific conductance, field, µmhos/cm at 25°C 5420 5900 5900 6380 2 2001−2003
Specific conductance, lab, µmhos/cm at 25°C 4500 5947 5870 6910 21 1982−2010
Sulfate, total, mg/L as SO4 350.0 489.2 496.0 580.0 29 1982−2010
Total dissolved solids, mg/L 2680 3760 3767 4500 28 1982−2010
Water temperature, °C 22.3 23.6 23.7 24.1 11 1982−2003
Units: µmhos/cm = micromhos per centimeter
         mg/L = milligrams per liter
         cfs = cubic feet per second

Age of discharge water

The age of water discharging from Island Spring was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in March 2001. Island Spring had a tritium concentration of 0.55 tritium units, which suggests that the water is about 48 years old. Island Spring had a delta carbon-13 value of −8.45 parts per thousand and a carbon-14 concentration of 23% modern carbon, which results from the mixing of Upper and Lower Floridan aquifer water. The Fontes and Garnier (1979) carbon-14 age of Island Spring is 2,932 years old.

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St. Johns River Water Management District
4049 Reid Street, Palatka, FL 32177
(800) 725-5922