Due to the awareness of degrading groundwater quality in Florida’s freshwater 7 springs and beginning in the early 1990s, the state’s water management districts, the Florida 8 Department of Environmental Protection, and the U.S. Geological Survey began efforts to 9 coordinate monitoring of Florida’s first-and second-magnitude springs. This study investigates 10 changes in spring discharge and the concentrations of two saline indicators sodium (Na +) and 11 chloride (Cl-) from 1991 through 2020 (30 years) in the Floridan aquifer system (FAS). Data were 12 obtained from 32 major springs and three additional discharge gaging stations. Spring discharge 13 was observed to decrease, while concentrations of sodium and chloride increased. As a group, the 14 FAS springs experienced passive saline encroachment. Not only did encroachment occur along 15 Florida’s coasts, but also in the interior. Median concentrations of sodium and chloride increased 16 by an estimated range of 7 to 11% per decade. Evidence suggests the major driver is decreasing 17 rainfall and subsequent declines in recharge to the FAS, followed by sea-level rise. The sources 18 of the saline water are from salt water near Florida’s coasts and relict sea water from the deeper 19 portions of the FAS. The observed changes agree with those predicted by the Ghyben-Herzberg 20 principle for coastal, carbonate aquifers. 21