FLORIDA GEOLOGICAL SURVEY


streamflow into the two component, base flow and direct runoff. The
methods of separating streamflow into its components of base flow
and direct runoff are hypothetical and the results are generally
subject to some limitations. During months of high runoff, July to
October 1960, streamflow was mostly from direct runoff and base
flows could not be estimated with any degree of reliability.
 Monthly values of rainfall and runoff for Horse Creek and Pony
Creek are summarized in table 7. Direct runoff was computed as
the difference between total runoff and base flow. For the months
of July, August, and September 1960, the average rainfall on the
Horse Creek basin was 38.8 inches and the runoff was 13.0 inches.
For the same period, the rainfall on the Pony Creek basin was 32.1
inches and the runoff was 19.4 inches. The greater runoff from
Pony Creek resulted from less rainfall than that which occurred
in the Horse Creek basin. This was probably caused by high
ground-water levels in the Pony Creek basin and lack of storage
capacity in the nonartesian aquifer as indicated by comparison of
the hydrographs of wells in the basins (see fig. 23, well 810-136-2;
and fig. 27, well 813-149-2).
 Comparison of the data for the year 1961 for the two stations
 in table 7 shows that Horse Creek received 37.2 inches of rainfall
 and Pony Creek received 38.4 inches. However, the runoff from
 the Horse Creek basin was 6.41 inches as compared to 0.79 inch
 from Pony Creek. The base flow or ground-water runoff for Horse
 Creek was 4.90 inches which was 76 percent of the total runoff.
 The base flow of Pony Creek was 0.40 inch which was 51 percent
 of the total runoff. Most of the additional runoff for Horse Creek
 in 1961 was probably gained by ground-water inflow. Base flow of
 the stream was sustained even during prolonged periods of little
 rainfall. On the other hand, Pony Creek basin is on top of the
 piezometric high and the stream received no ground-water flow
 during prolonged periods of low rainfall in 1961 and 1962.
 Flow-duration curves based on the 2 years of record for Horse
 Creek and Pony Creek are shown in figure 22. A comparison of the
 runoff characteristics for the two basins may be made from these
 curves. The curves have not been adjusted to a long-term base
 period, and therefore should not be used to estimate future
 long-term patterns.

 AQUIFERS
 Aquifers are classified as either nonartesian or artesian.
 Nonartesian aquifers are unconfined, and their water surface (the