In this section
Alexander Springs aerial view
photo by H. Means, FGS
Alexander Springs beach
Alexander Springs swim area
Alexander Springs is a first-magnitude spring that flows from the large, cavernous opening in the bottom of the central part of the pool. The large pool measures over 300 feet from north to south and 250 feet from east to west. The pool bottom near the beach is mostly sandy. Aquatic vegetation surrounds the area of the main spring vent, where the pool bottom falls away to reveal a large open area of exposed limestone rock and boulders to a depth of about 25 to 28 feet. Flow from the discharging water creates a large and powerful surface boil over the spring opening that is readily visible from the shore. A broad sand beach forms the southwest edge of the pool, with mixed hardwood and palm forests around the spring. The pool discharges to Alexander Springs Creek that flows approximately 10 river miles until reaching the St. Johns River. Forests and wetlands surround the spring area.
The spring area has been developed by the U.S. Forest Service into a multiple-use recreational facility open to the public. Activities include camping, swimming, snorkeling, scuba diving, hiking, fishing, bicycling, and canoeing.
Ocala National Forest Visitor Center
10863 E. Highway 40
Silver Springs, FL 34488
Discharge at Alexander Springs has been measured since 1956, with frequent measurements since 1982. Currently, the St. Johns River Water Management District measures the spring discharge 12 times per year.
Discharge at the spring has varied greatly over the years. The difference between the minimum and maximum discharges is 146 cubic feet per second (cfs), as shown in Table 1. The maximum measured discharge of 202 cfs occurred in January 1984; the minimum discharge of 56 cfs occurred in May 1986. The lowest periods of discharge correspond to periods of below-normal rainfall in Florida. The mean and median discharges for the period from 1956 to 2010 are 103 cfs and 102 cfs, respectively.
Diver Sampling Water
The U.S. Geological Survey analyzed the spring’s water quality sporadically from 1956 to 1999. The district has analyzed the spring’s water quality since 1983 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 Alexander Springs
|Alkalinity, total, mg/L as CaCO3||73.0||81.8||81.0||115.0||113||1956−2010|
|Calcium, total, mg/L as Ca||40.0||45.7||46.0||53.5||98||1993−2010|
|Chloride, total, mg/L as Cl||169.0||250.0||249.0||333.0||120||1956−2010|
|Fluoride, total, mg/L as F||0.09||0.13||0.12||0.25||50||1994−2009|
|Magnesium, total, mg/L as Mg||17.6||20.5||20.4||24.0||99||1992−2010|
|Nitrate + nitrite, total, mg/L as N||0.01||0.05||0.05||0.10||103||1977−2010|
|Orthophosphate, total, mg/L as P||0.02||0.04||0.05||0.08||77||1972−2010|
|Phosphorus, total, mg/L as P||0.03||0.05||0.05||0.08||63||1972−2010|
|Potassium, total, mg/L as K||3.0||4.0||4.0||5.0||99||1992−2010|
|Sodium, total, mg/L as Na||114.7||136.6||136.1||176.0||99||1992−2010|
|Specific conductance, field, µmhos/cm at 25°C||695||1070||1084||1430||103||1984−2010|
|Specific conductance, lab, µmhos/cm at 25°C||813||1105||1100||1650||107||1956−2010|
|Sulfate, total, mg/L as SO4||51.0||65.0||64.5||85.3||118||1956−2010|
|Total dissolved solids, mg/L||490||592||590||756||112||1967−2010|
|Water temperature, °C||19.1||23.5||23.5||26.2||151||1960−2010|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
Alexander Springs Run
The age of water discharging from Alexander Springs was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in July 1995, and the concentration of tritium and helium-3 in the discharge, as measured in March 2001. Alexander Springs had a tritium concentration of 2.7 tritium units, which suggests that the water is less than 42 years old. The tritium/helium-3 age was 25 years. Alexander Springs had a delta carbon-13 value of −9.50 parts per thousand and a carbon-14 concentration of 28% modern carbon, which results from the mixing of Upper and Lower Floridan aquifer water. The adjusted carbon-14 age is recent.