112 REPORT OF INVESTIGATIONS NO. 50
caused only a relatively small decline in water levels. Most of the fluctuations shown by the hydrograph on figure 53 are caused by variations in recharge; however, as pumpage increases in the future, continuing decline of average water levels near the centers of heavy pumping can be expected.
Before man began to withdraw and inject water, the artesian aquifer was in hydrologic equilibrium; that is, over climatic cycles the amount of discharge from the aquifer equalled the recharge. The average slope of the piezometric surface adjusted to the average discharge and the average recharge. Withdrawal of water by wells is a new discharge from the system which must be balanced by a reduction in natural discharge, an increased recharge or a combination of the two if a new equilibrium is to be reached. To reduce natural discharge, the slope of the piezometric surface between the area of pumping and the area of natural discharge must be reduced so that less water flows to the discharge points. When piezometric levels are lowered in recharge areas, the head difference between the water table and the artesian aquifer is increased which tends to cause an increased rate of recharge, thereby salvaging water that would normally flow off in streams or be lost to evapotranspiration. Thus, it is obvious that some lowering of the average piezometric levels is necessary if water is used. *
If pumping rates are stabilized, the piezometric surface eventually will stabilize at a new equilibrium slope-providing the average pumpage does not exceed the reduction in natural discharge and the increase in recharge. A continued increase in pumping will will result in a continued lowering of average piezometris level.
RECHARGE AREAS
Most of the recharge to the Floridan aquifer in Orange County is from infiltration of rain through the relatively thin, semipermeable confining beds in the highlands section and through the more than 300 drainage wells in the county. A lesser quantity enters the county by underground flow from southern Lake County and a small amount enters frorh Osceola County. A knowledge of the areas where rainfall can recharge the Floridan aquifer is necessary if development of Orange County is to be planned to protect the future water supplies of the area. Several methods can be used to delineate these areas. One method is by analysis of hydrologic and geologic data. Figure 54 shows the limits of the