Variations in recharge between the surficial and underlying Floridan aquifer systems were estimated by analyzing continuous daily water-level differentials at 29 monitoring-well cluster sites. By Darcy’s law, changes in these differentials are proportional to changes in the vertical flux of water between the systems. From 2000-2004, the mean daily differential ranged from less than 1 foot to more than 100 feet at the project sites. Sites with greater mean differentials exhibited lower percentage-based ranges in fluctuations than did sites with lower mean differentials. When averaged for all sites, the monthly differentials exhibited a decreasing trend that reflected about a 15-percent reduction in Floridan aquifer system recharge rates between 2000-2004. On an annual basis, the differentials varied between 3 and 120 percent relative to 5-year daily means, and between 8 and 200 percent relative to daily means on a monthly-averaged basis. Inferred recharge rates were greatest in the dry spring months (about 8 percent above the 5-year average) and least in the wet summer months (about 5 percent below the 5-year average), a result that is somewhat counterintuitive. Inspection of the individual aquifer water levels indicates, however, that as pumpage decreased in the summer months, the subsequent recovery in Floridan aquifer system levels exceeded the precipitation-induced increase in surficial aquifer system levels, reducing the differential between the systems. In the dry spring months, when pumpage is maximized during the dry growing season, drawdown in the Upper Floridan aquifer exceeds the decrease in surficial aquifer levels induced by sparse rainfall to increase the differential. Finally, the average water-level differentials were positively correlated (p-values of less than 0.05) with land-surface altitude and with model-calibrated leakance of the intervening confining unit.