In this section
Wadesboro Spring main view
Wadesboro Spring is a fourth-magnitude spring with water flowing from the Hawthorn Group sediments. The spring is situated at the head of a wooded ravine that is a tributary to Doctors Lake, a branch of the St. Johns River. The spring is enclosed by a 5-foot-high, five-sided concrete and wood enclosure about 15 feet wide by 35 feet long. The spring issues from two closely spaced horizontal cavities in rock below the base of the southwest end of the enclosure. One cavity is about 1 foot wide and the other about 2 feet wide. The head pool is deepest at the spring boil, where turbulence from the discharging spring causes continuous disturbance of the sand bottom. Water depth within most of the enclosure is 1 foot to 1.5 feet, except for the area adjacent to the spring orifices that is 5 feet deep. Water exits through a 13-foot opening on the southeast side of the concrete enclosure. Water from the spring flows about 0.3 mile down a small natural run to Doctors Lake.
Wadesboro Spring run downstream
Discharge at Wadesboro Spring was measured by the U.S. Geological Survey (USGS) in 1972 and 1993. St. Johns River Water Management District measured discharge 52 times from 2000 to 2010. The difference between the minimum and maximum discharges is 0.77 cubic feet per second (cfs). The maximum measured discharge of 1.51 cfs occurred in August 2009; the minimum discharge of 0.74 cfs occurred in May 2007. The mean and median discharges for the period are 0.98 cfs and 0.95 cfs, respectively (see the table below).
Wadesboro Spring was sampled by USGS in 1960, 1972, and 1993. The district sampled Wadesboro Spring in 2000, 2001, and 2002. Summary statistics of the water quality data for selected variables are shown in the table below.
Summary statistics of water quality and discharge at Wadesboro Spring
|Alkalinity, total, mg/L as CaCO3||83.0||109.0||121.5||129.0||5||1960−2002|
|Calcium, total, mg/L as Ca||45.9||46.8||46.5||48.0||3||2000−2002|
|Chloride, total, mg/L as Cl||7.0||14.3||17.1||19.0||6||1960−2002|
|Fluoride, total, mg/L as F||0.17||0.18||0.18||0.20||3||2000−2002|
|Magnesium, total, mg/L as Mg||8.9||8.9||8.9||9.0||3||2000−2002|
|Nitrate + nitrite, total, mg/L as N||0.02||0.02||0.02||0.02||1||2002|
|Orthophosphate, total, mg/L as P||0.13||0.13||0.13||0.14||2||2001−2002|
|Phosphorus, total, mg/L as P||0.14||0.14||0.14||0.14||1||2001|
|Potassium, total, mg/L as K||1.1||1.1||1.1||1.2||3||2000−2002|
|Sodium, total, mg/L as Na||10.0||10.1||10.1||10.2||3||2000−2002|
|Specific conductance, field, µmhos/cm at 25°C||354||356||356||357||2||2001−2002|
|Specific conductance, lab, µmhos/cm at 25°C||206||275||272||351||4||1960−2001|
|Sulfate, total, mg/L as SO4||6.4||17.0||20.8||22.1||6||1960−2002|
|Total dissolved solids, mg/L||115||170||190||200||6||1960−2002|
|Water temperature, °C||21.5||22.3||22.3||22.8||5||1960−2001|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Wadesboro Spring was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in April 2001. Wadesboro Spring had a tritium concentration of 2.85 tritium units, which suggests that the water is less than 48 years old. Wadesboro Spring had a delta carbon-13 value of −11.41 parts per thousand and a carbon-14 concentration of 52% modern carbon, which results from the reaction of rainfall with calcite, dolomite, and sediment organic matter. The adjusted carbon-14 age is recent.