In this section
Orange Spring main view
photo by R. Means, FGS
Orange Spring pool
Orange Spring is a third-magnitude spring with a kidney-shaped pool that measures 110 feet long by 90 feet wide, bordered by a low concrete wall. The spring issues from a deep, circular depression about 25 feet in diameter in the south-central part of the pool. Previously, divers have entered the vent to access the cavern below. The cavern is entirely within the Hawthorn Group, floored by sand, silts, and clays. Water enters the cavern from a vent to the side of the cavern. The water in the spring pool is a murky green with a hydrogen sulfide odor, with algae and aquatic vegetation on the pool bottom. Discharge is toward the northeast over a man-made, limestone waterfall. The spring run flows about 500 feet to Orange Creek.
Orange Spring outlet
Discharge at Orange Spring was measured by the U.S. Geological Survey (USGS) in 1952, 1972, and 1999. St. Johns River Water Management District measured discharge 44 times from 2000 to 2010 and currently measures discharge six times per year. The discharge measurements are taken downstream of the withdrawal for the bottling plant. The difference between the minimum and maximum discharges is 6.42 cubic feet per second (cfs) over the period. The maximum discharge of 7.60 cfs was measured in September 1972; the minimum discharge of 1.18 cfs was measured in November 2004. The mean and median discharges for the period are 2.99 cfs and 2.98 cfs, respectively (see the table below).
Orange Spring was sampled by USGS in 1972 and 1999. The district sampled the spring 41 times from 2000 to 2010 and currently samples the spring four times per year. Summary statistics of the water quality data for selected variables are shown in the table below.
Summary statistics of water quality and discharge at Orange Spring
|Alkalinity, total, mg/L as CaCO3||113.0||126.4||126.7||138.0||38||1972−2010|
|Calcium, total, mg/L as Ca||33.0||37.3||37.7||40.7||39||2000−2010|
|Chloride, total, mg/L as Cl||4.0||5.9||5.9||10.0||41||1972−2010|
|Fluoride, total, mg/L as F||0.10||0.16||0.16||0.20||10||2000−2003|
|Magnesium, total, mg/L as Mg||8.3||9.3||9.4||10.0||39||2000−2010|
|Nitrate + nitrite, total, mg/L as N||0.01||0.03||0.02||0.14||11||2001−2009|
|Orthophosphate, total, mg/L as P||0.05||0.08||0.08||0.17||40||2000−2010|
|Phosphorus, total, mg/L as P||0.07||0.09||0.09||0.11||30||2001−2010|
|Potassium, total, mg/L as K||0.8||1.1||0.8||2.1||7||2002−2007|
|Sodium, total, mg/L as Na||3.7||4.0||4.0||6.0||40||2000−2010|
|Specific conductance, field, µmhos/cm at 25°C||140||255||268||295||39||2000−2010|
|Specific conductance, lab, µmhos/cm at 25°C||240||269||271||293||32||1972−2010|
|Sulfate, total, mg/L as SO4||4.7||9.4||9.6||11.8||41||1972−2010|
|Total dissolved solids, mg/L||112||158||161||213||39||1972−2010|
|Water temperature, °C||22.1||23.9||24.0||26.1||43||1952−2010|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Orange 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. Orange Spring had a tritium concentration of 0.09 tritium units, which suggests that the water is about 75 years old. Orange Spring had a delta carbon-13 value of −9.93 parts per thousand and a carbon-14 concentration of 22% modern carbon, which results from the reaction of rainfall with calcite, dolomite, and sediment organic matter. The Fontes and Garnier (1979) carbon-14 age is approximately 4,700 years old.