Water bodies, watersheds and storm water
Shands Bridge Spring lies under this section
of the St. Johns River.
Shands Bridge Spring
Location
Shands Bridge Spring is a submarine spring located in the St. Johns River about 3 miles east of the town of Green Cove Springs. The spring is situated about 1,850 feet north of the Shands Bridge.
Latitude 29°59’16” N, Longitude 81°37’28” W
Description
Shands Bridge Spring is a submerged third-magnitude spring. The St. Johns River is about 17 to 20 feet deep near the spring. An almost circular depression (recorded by Fathometer) was observed in the bottom of the river at the spring (Spechler 1996). Groundwater is discharged from a vent at the deepest point in the spring, about 30 feet below the surface.
Discharge
No actual discharge measurements have been done at Shands Bridge Spring. Discharge was estimated at 1 cubic foot per second (cfs) in 1995 (Spechler 1996).
Water quality
Shands Bridge Spring was sampled by St. Johns River Water Management District in 1994 and 2007. The water quality data for selected variables are shown in the table below.
Summary statistics of water quality data at Shands Bridge Spring
| Shands Bridge Spring | Min | Mean | Median | Max | Count | Period |
|---|---|---|---|---|---|---|
| Alkalinity, total, mg/L as CaCO3 | 99.1 | 99.1 | 99.1 | 99.1 | 1 | 2007 |
| Calcium, total, mg/L as Ca | 92.0 | 92.0 | 92.0 | 92.0 | 1 | 2007 |
| Chloride, total, mg/L as Cl | 12.0 | 12.4 | 12.4 | 12.7 | 2 | 1994–2007 |
| Fluoride, total, mg/L as F | 0.52 | 0.52 | 0.52 | 0.52 | 1 | 2007 |
| Magnesium, total, mg/L as Mg | 42.0 | 42.0 | 42.0 | 42.0 | 1 | 2007 |
| pH, field | 7.58 | 7.58 | 7.58 | 7.58 | 1 | 1994 |
| Potassium, total, mg/L as K | 2.6 | 2.6 | 2.6 | 2.6 | 1 | 2007 |
| Sodium, total, mg/L as Na | 10.0 | 10.0 | 10.0 | 10.0 | 1 | 2007 |
| Specific conductance, field, µmhos/cm at 25°C | 826 | 886 | 886 | 945 | 2 | 1994–2007 |
| Specific conductance, lab, µmhos/cm at 25°C | 810 | 810 | 810 | 810 | 1 | 2007 |
| Sulfate, total, mg/L as SO4 | 337.0 | 338.5 | 338.5 | 340.0 | 2 | 1994–2007 |
| Total dissolved solids, mg/L | 595 | 595 | 595 | 595 | 1 | 2007 |
| Water temperature, °C | 25.1 | 26.1 | 26.1 | 27.0 | 2 | 1994–2007 |
mg/L = milligrams per liter
cfs = cubic feet per second
