23
66
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FIGURE 14.-Effect of rain on ground-water levels.
In the area of free recharge ground-water levels rise quickly owing to local rain. As shown, in a well east of Orlando the water level rose more than 6 feet in less than 24 hours after 2 inches of rain fell. A rise so rapid indicates that water infilters readily to the aquifer. In most wells the water level responds to rainfall more slowly.
field, 1936, p. 148). Ordinarily, they are not open holes but are floored with sand, and the sand allows water to filter through slowly (fig. 16). Thus, the rate of recharge is limited by the number of sinkholes and by the permeability of the sand and other material they contain. It may be observed that in this case the recharge is limited neither by the amount of rainfall nor by the capacity of the aquifer to receive water, but by the rate at which water may seep through the overlying material. The aquifer would receive more water if it were offered. Accordlingly, the water running off