In this section
Blue Spring main view
photo by T. Scott, FGS
Blue Spring pool with swimmers
Blue Spring run
Blue Spring is a first-magnitude spring with a nearly circular pool about 135 feet long from north to south and 100 feet from east to west. Steep banks 10 feet to 20 feet high surround the pool except to the south, where the spring opens to the spring run. The pool bottom is mostly limestone and sand; the spring vent is an elongated opening in the limestone about 15 feet from the north edge of the pool. From the limestone ledge, the vent slopes precipitously to about 40 feet in depth. A limited underwater cave system has been mapped at Blue Spring. From the pool, the spring run flows 0.2 mile to the south, then to the southwest for another 0.2 mile to the St. Johns River. The run varies from 70 feet to 100 feet in width and is bounded by steep wooded slopes except for the lower southeast bank, where the terrain flattens considerably. Flow of the spring is retarded by backwater during high stages of the St. Johns River.
Blue Spring State Park is owned and operated by the state of Florida, providing a wide range of recreational activities, including swimming, diving, canoeing, fishing, hiking, and camping. Manatees commonly frequent the spring run during the winter months when the spring water is considerably warmer than the St. Johns River.
Blue Spring run to the St. Johns River
Discharge at Blue Spring was measured by the U.S. Geological Survey (USGS) from 1932 to 2010, and USGS currently performs continuous discharge measurements. St. Johns River Water Management District measured discharge from 1983 to 2001. The difference between the measured minimum and maximum discharges is 131 cubic feet per second (cfs). The maximum measured discharge of 218 cfs occurred in February 1983; the minimum discharge of 87.0 cfs occurred in November 2001. The mean and median discharges for the period from 1932 to 2010 are both 154 cfs (see the table below).
Blue Spring was sampled by USGS from 1960 to 2000. The district sampled Blue Spring from 1984 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 Blue Spring
|Blue Spring — Volusia County||Min||Mean||Median||Max||Count||Period|
|Alkalinity, total, mg/L as CaCO3||105.0||135.8||138.0||170.0||85||1960−2010|
|Calcium, total, mg/L as Ca||41.0||66.9||66.8||81.7||58||1992−2010|
|Chloride, total, mg/L as Cl||110.0||396.6||390.0||700.0||238||1960−2010|
|Fluoride, total, mg/L as F||0.07||0.08||0.09||0.10||19||1996−2009|
|Magnesium, total, mg/L as Mg||12.8||24.9||24.8||39.1||58||1992−2010|
|Nitrate + nitrite, total, mg/L as N||0.04||0.47||0.42||1.20||82||1976−2010|
|Orthophosphate, total, mg/L as P||0.01||0.07||0.07||0.10||58||1972−2010|
|Phosphorus, total, mg/L as P||0.01||0.07||0.07||0.14||74||1972−2010|
|Potassium, total, mg/L as K||4.1||7.3||7.4||11.3||58||1992−2010|
|Sodium, total, mg/L as Na||78.8||196.6||196.8||314.0||58||1992−2010|
|Specific conductance, field, µmhos/cm at 25°C||729||1535||1501||2320||60||1984−2010|
|Specific conductance, lab, µmhos/cm at 25°C||808||1662||1650||2610||242||1960−2010|
|Sulfate, total, mg/L as SO4||25.1||56.6||55.0||100.0||99||1960−2010|
|Total dissolved solids, mg/L||462||828||827||1230||95||1960−2010|
|Water temperature, °C||21.5||23.2||23.0||25.6||351||1932−2010|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Blue Spring was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in May 1996, and the concentration of tritium and helium-3 in the discharge, as measured in February 2001. Blue Spring had a tritium concentration of 3.8 tritium units, which suggests that the water is less than 43 years old. The tritium/helium-3 age was 22 years. Blue Spring had a carbon-14 concentration of 45% modern carbon and a delta carbon-13 value of −10.10 parts per thousand, which results from the mixing of Upper and Lower Floridan aquifer water. The adjusted carbon-14 age is recent.