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
St. Johns River Water Management District - floridaswater.com
Water bodies, watersheds and storm water
Croaker Hole Spring main view

Croaker Hole Spring main view

Croaker Hole Spring

Putnam County

Description

Croaker Hole Spring is a second-magnitude spring. Croaker Hole is a relatively deep, small-diameter hole in the bottom of the St. Johns River. The river is generally about 5 feet to 9 feet deep in this area, except in the immediate vicinity of Croaker Hole, where it plunges to a depth of about 48 feet.

Discharge

Discharge at Croaker Hole Spring was measured by the U.S. Geological Survey (USGS) six times from 1981 to 2000. St. Johns River Water Management District measured discharge 38 times from 2000 to 2010. The difference between the minimum and maximum discharges is 28.48 cubic feet per second (cfs) over the period. The maximum measured discharge of 90.5 cfs occurred in November 1998; the minimum discharge of 62.02 cfs occurred in September 2001. The mean and median discharges for the period are 74.52 cfs and 73.73 cfs, respectively (see the table below).

Croaker Hole Spring Discharge Graph
Discharge Graph

Water quality

Croaker Hole Spring was sampled by USGS in 1981, 1991, and 1998. The District sampled Croaker Hole Spring 28 times from 1998 to 2010. Summary statistics of the water quality data for selected variables are shown in the table below.

Croaker Hole Spring Water Quality Graph
Water Quality Graph

Summary statistics of water quality and discharge at Croaker Hole Spring

Croaker Hole Spring Min Mean Median Max Count Period
Discharge, cfs 62.02 74.52 73.73 90.50 44 1981−2010
Alkalinity, total, mg/L as CaCO3 61.6 65.7 64.0 74.8 27 1995−2010
Calcium, total, mg/L as Ca 69.0 73.6 72.9 86.0 27 2001−2010
Chloride, total, mg/L as Cl 322.9 631.3 640.3 736.0 31 1981−2010
Dissolved Oxygen 1.77 1.77 1.77 1.77 1 2002
Fluoride, total, mg/L as F 0.10 0.12 0.12 0.14 11 1995−2003
Magnesium, total, mg/L as Mg 34.0 39.4 39.0 47.0 27 2001−2010
Nitrate + nitrite, total, mg/L as N 0.06 0.09 0.08 0.22 23 1995−2010
Orthophosphate, total, mg/L as P 0.01 0.02 0.02 0.03 24 1995−2010
pH, field 6.73 7.33 7.42 8.03 10 1995−2003
Phosphorus, total, mg/L as P 0.01 0.02 0.02 0.04 16 2006−2010
Potassium, total, mg/L as K 7.7 8.7 8.7 10.5 27 2001−2010
Sodium, total, mg/L as Na 308.0 342.6 342.4 394.2 27 2001−2010
Specific conductance, field, µmhos/cm at 25°C 2089 2486 2520 2887 9 1995−2003
Specific conductance, lab, µmhos/cm at 25°C 2270 2427 2400 2600 15 2002−2010
Sulfate, total, mg/L as SO4 118.0 147.9 147.0 170.0 30 1981−2010
Total dissolved solids, mg/L 1190 1383 1367 1600 30 1981−2010
Water temperature, °C 21.6 22.9 22.5 25.7 9 1995−2002
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 Croaker Hole Spring was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in July 1995. Croaker Hole Spring had a tritium concentration of 4.5 tritium units, which suggests that the water is less than 43 years old. Croaker Hole Spring had a delta carbon-13 value of −8.47 parts per thousand and a carbon-14 concentration of 31% modern carbon, which results from the mixing of Upper and Lower Floridan aquifer water. The adjusted carbon-14 age is recent.

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