1. THE ORIGIN AND AGE OF SPRING WATERS IN THE ST JOHNS RIVER WATER MANAGEMENT DISTRICT, CENTRAL FLORIDA by David J. Toth, Ph.D., P.G. St Johns River Water Management District Brian G Katz, Ph.D., P.G. U. S. Geological Survey

2. PURPOSE Determine the origin and age of water discharging from 11 springs in the St. Johns River Water Management District

3. Study Area (In SJRWMD)

4. Fig. 1 Study Area DU D U

7. Fig. 2 Thickness of the Confining Unit

8. Fig 3. Elevation of the Floridan Aquifer

9. Fig 4. Thickness of the MSCU

10. Fig 5. Elevation of the Top of the Lower Floridan Aq.

11. SODIUM CHLORIDE CALCIUM BICARBONATE SODIUM CHLORIDE, CALCIUM BICARBONATE

12. Fig 6. Water Quality

13. Fig 7. May 2001 Pot Surface

14. REACTIONS CALCIUM BICARBONATE SPRINGS Rain Water + a CH 2 O + b CaCO 3 + c CaMg(CO 3 ) 2 + d O 2 = Spring Water

15. REACTIONS SODIUM CHLORIDE SPRINGS Rain Water + Lower Floridan Water + a CH 2 O + b CaCO 3 + c CaMg(CO 3 ) 2 + d O 2 = Spring Water Upper Floridan Water + Lower Floridan Water + b CaCO 3 = Blue Spring Upper Floridan Water + Lower Floridan Water = Salt Springs

16. REACTIONS SODIUM CHLORIDE, CALCIUM BICARBONATE SPRING Rain Water + Lower Floridan Water + a CH 2 O + b CaCO 3 + c CaMg(CO 3 ) 2 + d O 2 = Spring Water

21. CONCLUSION Water discharging from these springs are locally derived and contain variable amounts of recently recharged water.