Records from an observation well in the Floridan aquifer near the headwaters of Crystal River show that the water level in the aquifer fluctuates with the tide. The water level remains generally about one-half to one foot above mean sea level, figure 14. The level of fresh water is sufficient to depress the salt water at this point about 20 to 40 feet below mean sea level. The rivers and springs tend to be fresher upstream from the gulf, where water levels in the aquifer are generally higher. Rivers and springs also tend to be fresher during the summer and early fall when water levels in the aquifer are highest. When the fresh-water level declines the salt water moves inland during high tide and may mix with the fresh water flowing upward toward the spring openings.
The Crystal, Homosassa and Chassahowitzka spring systems are much more subject to variations in chemical quality of water between extremes of fresh and salty than Weekiwachee Springs. During the 1964-66 study period, the measured range of dissolved solids in Crystal River was 300 to 15,000 mg/l; in Homosassa River was 550 to 9,100 mg/l; in Chassahowitzka River was 300 to 2,000 mg/i; and Weekiwachee Springs was 125 to 150 mg/1. The wider range in variation in chemical quality occurs because the water level at the former springs is about one foot above msl whereas the level at the main springs at Weekiwachee is about 10 to 12 feet above mean sea level.
Any set of conditions, either natural or influenced by man, that markedly decreases the level of the fresh water, decreases the fresh water discharge and permits sea water to move further inland. This can, in turn, cause increased salinity in water discharging from the low-lying springs. For example, excessive pumping from the fresh-water aquifer in the area adjacent to the springs or extensive drainage by canals, or deepening of natural river channels in and adjacent to springs may permit reduction in the level of the fresh water and allow more frequent discharge of salt water or saltier water from the springs, figure 15.
Various state, county, water-management districts, and citizen groups are aware of the fresh-salt water balance in the area of the springs. Suggestions and proposals are under study and data are being collected for realistic water-management programs to safeguard the unique spring system for use by future generations.
EXTENT OF KNOWLEDGE ON THE SPRINGS
Completed elements of hydrologic investigations in the area include: (1) extensive field reconnaissance to locate all springs and points of potential spring flow under changing hydrologic