In this section
Sanlando Springs main view
Sanlando Springs run looking upstream toward the pool
Sanlando Springs vent
Sanlando Springs is a second-magnitude spring that flows mostly from an oblong cavity beneath a limestone ledge about 7 feet below the water surface. The cavity is about 2 to 3 feet high and 10 feet wide. The spring forms a circular pool about 30 feet in diameter, enclosed by a stone and concrete retaining wall, except for a wide opening that lets water flow to a large oval-shaped pond. The large pond is about 200 feet long and 180 feet wide and is dammed for swimming. The pond is bordered by a low concrete retaining wall, with a narrow white sand beach on its west side and the opening on its east side to the spring pool. Flow from the pond is westward to the Little Wekiva River through two weirs, one each in the retaining wall at the north and south ends of the pond.
Sanlando Springs outlet
Discharge at Sanlando Springs was measured sporadically by the U.S. Geological Survey (USGS) from 1941 to 1960, then frequently from 1972 to 2002. St. Johns River Water Management District measured discharge from 1993 to 2010 and currently performs bimonthly discharge measurements. The difference between the minimum and maximum discharges is 27.0 cubic feet per second (cfs) over the period. The maximum measured discharge of 36.0 cfs occurred in November 1996; the minimum discharge of 8.99 cfs occurred in November 2000. The mean and median discharges for the period from 1941 to 2010 are 19.65 cfs and 19.28 cfs, respectively (see the table below).
Sanlando Springs was sampled by USGS six times from 1956 to 1995, with periodic field measurements only at other times. The district sampled Sanlando Springs 56 times from 1993 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 Sanlando Springs
|Alkalinity, total, mg/L as CaCO3||85.0||139.2||141.5||167.0||60||1956−2010|
|Calcium, total, mg/L as Ca||37.0||43.1||43.6||46.1||55||1993−2010|
|Chloride, total, mg/L as Cl||8.5||19.1||19.2||25.3||62||1956−2010|
|Fluoride, total, mg/L as F||0.15||0.17||0.17||0.20||29||1993−2003|
|Magnesium, total, mg/L as Mg||10.9||12.1||12.0||13.0||55||1993−2010|
|Nitrate + nitrite, total, mg/L as N||0.04||0.62||0.56||1.40||53||1977−2010|
|Orthophosphate, total, mg/L as P||0.11||0.17||0.16||0.43||55||1972−2010|
|Phosphorus, total, mg/L as P||0.14||0.18||0.17||0.24||33||1972−2010|
|Potassium, total, mg/L as K||1.2||1.7||1.7||2.2||55||1993−2010|
|Sodium, total, mg/L as Na||9.0||12.0||11.9||15.0||55||1993−2010|
|Specific conductance, field, µmhos/cm at 25°C||210||348||357||402||56||1993−2010|
|Specific conductance, lab, µmhos/cm at 25°C||211||338||351||398||48||1956−2010|
|Sulfate, total, mg/L as SO4||4.7||12.6||12.8||19.0||62||1960−2010|
|Total dissolved solids, mg/L||146||199||200||230||57||1972−2010|
|Water temperature, °C||21.5||24.3||24.0||28.5||118||1956−2010|
mg/L = milligrams per liter
cfs = cubic feet per second
Age of discharge water
The age of water discharging from Sanlando Springs was determined by measuring the concentration of tritium, delta carbon-13, and carbon-14 in the spring discharge, which was measured in September 1995, and tritium and helium-3, as measured in February 2001. Sanlando Springs had a tritium concentration of 2.90 tritium units, which suggests that the water is less than 42 years old. The tritium/helium-3 age was 23 years. Sanlando Springs had a delta carbon-13 value of −10.49 parts per thousand and a carbon-14 concentration of 57% modern carbon, which results from the reaction of rainfall with calcite, dolomite, and sediment organic matter. The adjusted carbon-14 age of Sanlando Springs is recent.