In this section
Welaka Spring main view
Welaka Spring pool
photo by H. Means, FGS
Welaka Spring boil
Welaka Spring is a third-magnitude spring with a pool about 90 feet long from east to west and 60 feet wide from north to south. The spring vent is about 20 feet in diameter in the clayey-sand bottom of the central part of the pool, with a prominent boil over the vent. The water from the spring is clear, but the spring water mixes with dark water from the St. Johns River a short distance downstream. The spring pool opens on its southwest side to a run about 200 feet wide that curves to the southwest, then to the northwest for about 1,200 feet to the St. Johns River. Backwater from the St. Johns River, at least in part associated with tidal effects, frequently makes it impracticable to measure the spring discharge.
Discharge from Welaka Spring, measured in 2001 by the St. Johns River Water Management District, was 7.91 cubic feet per second.
Welaka Spring was sampled by the district in 2000 and 2001. Summary statistics of the water quality data for selected variables are shown in the table below.
Summary statistics of water quality and discharge at Welaka Spring
|Alkalinity, total, mg/L as CaCO3||79.0||79.5||79.5||80.1||2||2000−2001|
|Calcium, total, mg/L as Ca||39.3||43.1||43.1||46.9||2||2000−2001|
|Chloride, total, mg/L as Cl||259.6||310.9||310.9||362.2||2||2000−2001|
|Fluoride, total, mg/L as F||0.13||0.14||0.14||0.14||2||2000−2001|
|Magnesium, total, mg/L as Mg||18.0||21.1||21.1||24.1||2||2000−2001|
|Nitrate + nitrite, total, mg/L as N||0.01||0.02||0.02||0.03||2||2000−2001|
|Orthophosphate, total, mg/L as P||0.05||0.05||0.05||0.06||2||2000−2001|
|Phosphorus, total, mg/L as P||0.06||0.06||0.06||0.06||1||2001|
|Potassium, total, mg/L as K||4.5||5.3||5.3||6.1||2||2000−2001|
|Sodium, total, mg/L as Na||141.1||172.0||172.0||202.9||2||2000−2001|
|Specific conductance, field, µmhos/cm at 25°C||1090||1192||1192||1294||2||2000−2001|
|Specific conductance, lab, µmhos/cm at 25°C||1047||1047||1047||1047||1||2001|
|Sulfate, total, mg/L as SO4||41.2||49.5||49.5||57.7||2||2000−2001|
|Total dissolved solids, mg/L||559||676||676||793||2||2000−2001|
|Water temperature, °C||23.2||24.0||23.7||25.0||3||1972−2001|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Welaka 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. Welaka Spring had a tritium concentration of 2.91 tritium units, which suggests that the water is less than 48 years old. Welaka Spring had a delta carbon-13 value of −8.95 parts per thousand and a carbon-14 concentration of 38% modern carbon, which results from the mixing of Upper and Lower Floridan aquifer water. The adjusted carbon-14 age is recent.