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Salt Springs main view
Salt Springs pool
Largest of the four Salt Springs vents
Salt Springs is a second-magnitude spring that derives its name from its saline waters. The spring pool measures about 190 feet by 130 feet, with spring flow emerging from four vents in the limestone rock floor of the pool. Prominent, gentle boils are usually observed at the water’s surface over the vents. Limestone and sand are on the pool bottom near the vents, with the rest of the bottom covered with aquatic grasses. The north, west, and south sides of the pool are surrounded by a concrete wall that rises about 5 feet above the surface of the pool. The wall is topped by a concrete railing and edged by a 4-foot-wide concrete walkway. From the pool, water flows southeast about 4 miles down a broad run to discharge into the northwest corner of Lake George.
The spring is part of the USDA Forest Service’s Salt Springs Recreation Area. The recreation area is used for swimming, snorkeling, fishing, and boating.
Salt Springs pool and run
Discharge at Salt Springs was measured by the U.S. Geological Survey (USGS) 56 times from 1929 to 2002. St. Johns River Water Management District measured discharge 192 times from 1983 to 2010 and currently measures discharge six times per year. The difference between the minimum and maximum discharges is 79.83 cubic feet per second (cfs) over the period. The maximum measured discharge of 133.83 cfs occurred in January 1985; the minimum discharge of 54.0 cfs occurred in October 1935. The mean and median discharges for the period from 1929 to 2010 are 80.50 cfs and 79.75 cfs, respectively (see the table below).
Salt Springs was sampled by USGS eight times from 1956 to 1983, and in 1998 and 2000, with additional field measurement at other times through 1999. The District sampled Salt Springs 99 times from 1984 to 2005 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 Salt Springs
|Alkalinity, total, mg/L as CaCO3||7.4||65.8||66.0||105.0||108||1956−2010|
|Calcium, total, mg/L as Ca||116.7||158.6||158.0||219.0||90||1992−2010|
|Chloride, total, mg/L as Cl||1076.0||1772.6||1800.0||2500.0||109||1956−2010|
|Fluoride, total, mg/L as F||0.08||0.10||0.10||0.12||52||1989−2009|
|Magnesium, total, mg/L as Mg||66.5||100.7||100.0||149.0||89||1992−2010|
|Nitrate + nitrite, total, mg/L as N||0.02||0.10||0.10||0.20||97||1984−2010|
|Orthophosphate, total, mg/L as P||0.01||0.02||0.01||0.08||40||1994−2010|
|Phosphorus, total, mg/L as P||0.01||0.02||0.02||0.20||47||1990−2010|
|Potassium, total, mg/L as K||18.2||29.1||29.0||40.4||87||1992−2010|
|Sodium, total, mg/L as Na||590.5||948.3||944.9||1360.0||90||1992−2010|
|Specific conductance, field, µmhos/cm at 25°C||3309||5796||5820||8540||91||1984−2010|
|Specific conductance, lab, µmhos/cm at 25°C||4430||6006||6000||8120||90||1956−2010|
|Sulfate, total, mg/L as SO4||277.0||405.6||407.9||540.0||109||1956−2010|
|Total dissolved solids, mg/L||2200||3454||3440||4600||100||1956−2010|
|Water temperature, °C||21.7||23.8||23.7||29.6||127||1956−2010|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Salt Springs 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. Salt Springs had a tritium concentration of 3.3 tritium units, which suggests that the water is less than 43 years old. The tritium/helium-3 age was 32 years. Salt Springs had a delta carbon-13 value of −8.30 parts per thousand and a carbon-14 concentration of 22% modern carbon, which results from the mixing of Upper and Lower Floridan aquifer water. The adjusted carbon-14 age is recent.