In this section
Blue Spring main view
Blue Spring is a third-magnitude spring situated on the southeast shore of Lake Harris, in a residential area with live oak, palm, and cypress trees. The spring pool has a sand bottom with spring flow from at least nine sandy boils. The pool is enclosed by a concrete retaining wall that forms a reverse L-shaped swimming pool. The pool discharges through a weir in the retaining wall on the northeast side of the pool and then into a run about 30 feet wide, flowing southeast in a parallel direction to the lakeshore. The spring run flows about 100 feet to the south side of Lake Harris, with additional boils observed in the spring run. The site is privately owned and not open to the public. It is used as a swimming and recreational facility for local residents.
Blue Spring run
The spring discharge has been measured sporadically since 1991, with more frequent measurements since 2002. St. Johns River Water Management District currently measures discharge 12 times per year. The difference between the minimum and maximum discharges is 3.26 cubic feet per second (cfs). The maximum measured discharge of 4.05 cfs occurred in August 2010; the minimum discharge of 0.79 cfs occurred in May 2000. The mean and median discharges for the period from 1991 to 2010 are 2.56 cfs and 2.72 cfs, respectively (see the table below).
Blue Spring was sampled by the U.S. Geological Survey in 1967 and 1972. The district analyzed the spring’s water quality from 1991 to 2002. The data also include two samples by Lake County in 2004. 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 — Lake County||Min||Mean||Median||Max||Count||Period|
|Alkalinity, total, mg/L as CaCO3||94.6||104.1||104.0||126.0||18||1967−2004|
|Calcium, total, mg/L as Ca||35.8||40.4||40.0||44.0||11||1996−2004|
|Chloride, total, mg/L as Cl||6.5||10.8||11.1||14.0||18||1967−2004|
|Fluoride, total, mg/L as F||0.09||0.10||0.10||0.11||10||1996−2002|
|Magnesium, total, mg/L as Mg||6.0||6.7||6.7||7.3||12||1996−2004|
|Nitrate + nitrite, total, mg/L as N||3.09||4.19||3.97||7.18||12||1996−2004|
|Orthophosphate, total, mg/L as P||0.02||0.03||0.03||0.06||10||1996−2002|
|Phosphorus, total, mg/L as P||0.02||0.04||0.04||0.09||4||1991−2001|
|Potassium, total, mg/L as K||0.6||0.7||0.7||0.8||3||2002−2004|
|Sodium, total, mg/L as Na||5.4||5.9||6.0||6.1||12||1996−2004|
|Specific conductance, field, µmhos/cm at 25°C||270||288||288||306||16||1991−2004|
|Specific conductance, lab, µmhos/cm at 25°C||225||260||263||293||3||1967−2001|
|Sulfate, total, mg/L as SO4||2.8||8.9||9.2||12.0||16||1972−2004|
|Total dissolved solids, mg/L||129||168||170||200||17||1967−2004|
|Water temperature, °C||23.7||24.0||23.9||25.3||17||1967−2004|
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 carbon-14 and carbon-13 in the spring discharge, which was measured in May 2001. Blue Spring had a carbon-14 concentration of 35% modern carbon and a delta carbon-13 value of −8.97 parts per thousand. Fontes and Garnier (1979) interpreted carbon-14 age of Blue Spring discharge at 99 years.