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
Boulder Spring main view

Boulder Spring main view

Boulder Spring

Lake County

Description

Boulder Spring is a fifth-magnitude spring. The spring head is a small pool in an area of limerock outcrop, with large limestone boulders in the spring pool and run. Water flows from vents at the base of the hillside and in sand boils in the spring run as it flows about 0.3 mile toward the northwest to Sulphur Run.

Discharge

Boulder Spring run

Boulder Spring run

Discharge at Boulder Spring was measured by St. Johns River Water Management District in 2003, 2005, and 2008. The mean and median discharge was 0.23 and 0.32 cubic feet per second.

Water quality

Boulder Spring was sampled once in 2004 by Lake County and once in 2005 by the district. Summary statistics of the water quality data for selected variables are shown in the table below.

Summary statistics of water quality and discharge at Boulder Spring

Boulder Spring Min Mean Median Max Count Period
Discharge, cfs 0.06 0.23 0.32 0.32 3 2003−2008
Alkalinity, total, mg/L as CaCO3 120.0 120.5 120.5 121.0 2 2004−2005
Calcium, total, mg/L as Ca 98.8 98.8 98.8 98.8 1 2005
Chloride, total, mg/L as Cl 110.0 114.5 114.5 119.0 2 2004−2005
Dissolved Oxygen 5.80 5.80 5.80 5.80 1 2004
Magnesium, total, mg/L as Mg 25.4 25.7 25.7 26.0 2 2004−2005
Nitrate + nitrite, total, mg/L as N 0.07 0.08 0.08 0.10 2 2004−2005
Orthophosphate, total, mg/L as P 0.06 0.06 0.06 0.06 1 2005
pH, field 7.20 7.39 7.39 7.57 2 2004−2005
Phosphorus, total, mg/L as P 0.18 0.18 0.18 0.18 1 2005
Potassium, total, mg/L as K 2.4 2.7 2.7 2.9 2 2004−2005
Sodium, total, mg/L as Na 63.3 64.5 64.5 65.7 2 2004−2005
Specific conductance, field, µmhos/cm at 25°C 989 1015 1015 1041 2 2004−2005
Specific conductance, lab, µmhos/cm at 25°C 1041 1041 1041 1041 1 2005
Sulfate, total, mg/L as SO4 216.0 216.2 216.2 216.4 2 2004−2005
Total dissolved solids, mg/L 619 675 675 730 2 2004−2005
Water temperature, °C 22.7 22.9 22.9 23.0 2 2004−2005
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 Boulder Springs was determined by measuring the concentration of tritium, carbon-14, and carbon-13 in the spring discharge, which was measured in March 2005. Boulder Springs had a tritium concentration of 0.51 tritium units, a carbon-14 concentration of 29 percent modern carbon, and a delta carbon-13 value of −9.78 parts per thousand. The tritium concentration suggests that the water is between 40 and 70 years old. The carbon-14 concentration of 29% modern carbon can result from the reaction of rainfall with calcite, dolomite, and soil organic matter and from the mixing with Lower Floridan water.

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