In this section
Messant Spring main view
Messant Spring is a second-magnitude spring that has also been referred to as Messinger Spring. Spring discharge issues from a conical vent about 15 feet in diameter at its top, tapering to about 4 feet at its bottom. A rock ledge extends out at a depth of 20 to 25 feet on the north side of the hole. A horizontal cavern opens under the ledge. The spring forms a circular pool about 45 feet in diameter, with a gentle boil at the pool surface over the vent. The sides of the pool are steep, sloping rapidly to the cavern opening in the central part of the pool. Flow from the pool is east, down a run about 20 feet wide and 5 to 6 feet deep. The run meanders eastward for about 300 feet and then turns southeast to discharge to Black Water Creek (Rosenau et al. 1977). The spring is situated in open hardwood, palm, and pine woods at the edge of low sand hills to the west. Vegetation is thinned and forest debris is cleaned from around the pool and spring run to improve access, yet a natural, undeveloped appearance is retained. The spring is located on private land and not open to the public.
Sampling at Messant Spring
Discharge at Messant Spring was measured by the U.S. Geological Survey (USGS) 17 times from 1946 to 1995. St. Johns River Water Management District measured the spring’s discharge 12 times from 1993 to 1995. Beginning in 1995, the landowner refused to grant permission to enter the property. The difference between the minimum and maximum discharges is 14.2 cubic feet per second (cfs) over the period. The maximum discharge of 25.0 cfs was measured in November 1960; the minimum discharge of 10.8 cfs was measured in November 1960. The mean and median discharges for the period from 1946 to 1995 are 14.7 cfs and 14.0 cfs, respectively (see the table below).
Messant Spring was sampled by USGS four times from 1960 to 1993, with field data measurements taken six times from 1986 to 1992. The district sampled the spring eight times from 1993 to 1995. Summary statistics of the water quality data for selected variables are shown in the table below.
Summary statistics of water quality and discharge at Messant Spring
|Alkalinity, total, mg/L as CaCO3||95.0||106.3||105.0||130.0||9||1960−1995|
|Calcium, total, mg/L as Ca||86.8||96.8||100.0||103.0||5||1993−1995|
|Chloride, total, mg/L as Cl||9.7||11.6||10.0||24.0||12||1960−1995|
|Fluoride, total, mg/L as F||0.24||0.25||0.25||0.28||5||1994−1995|
|Magnesium, total, mg/L as Mg||18.3||20.7||20.4||23.1||5||1993−1995|
|Nitrate + nitrite, total, mg/L as N||0.01||0.51||0.51||1.01||2||1972−1985|
|Orthophosphate, total, mg/L as P||0.03||0.03||0.03||0.03||5||1985−1995|
|Phosphorus, total, mg/L as P||0.04||0.04||0.04||0.04||1||1985|
|Potassium, total, mg/L as K||1.0||1.3||1.4||1.5||5||1993−1995|
|Sodium, total, mg/L as Na||6.0||6.7||7.0||7.0||5||1993−1995|
|Specific conductance, field, µmhos/cm at 25°C||672||689||692||703||5||1993−1995|
|Specific conductance, lab, µmhos/cm at 25°C||610||673||675||730||18||1960−1995|
|Sulfate, total, mg/L as SO4||196.0||227.5||231.0||241.0||12||1960−1995|
|Total dissolved solids, mg/L||424||479||480||503||10||1972−1995|
|Water temperature, °C||23.0||24.9||25.0||25.7||21||1960−1995|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Messant Spring was determined by measuring the concentration of tritium and carbon-14 in the spring discharge, which was measured in July 1995. A tritium concentration of 0.2 tritium units was measured, which suggests that the water is between 40 and 70 years old. The carbon-14 concentration of 23% modern carbon can result from the reaction of rainfall with calcite, dolomite, and soil organic matter.