REPORT OF INVESTIGATIONS NO. 42


surfaces of November 1959 (fig. 35) and May 1962 (fig. 36). These
computations exclude the ground-water inflow from the Pasco high
to the Green Swamp area in the vicinity of Dade City.
 Outflows from each major basin were computed using ground-
water areas enclosed by the divides as shown in figure 34. The
distribution of the outflows from the Polk high to the major
drainage basins is shown in table 16.
 Most of the natural outflow is contributed to the Kissimmee and
Withlacoochee River basins. Increased pumping for mining,
irrigation, and municipal supplies in the southern part of the area
(from Lakeland to Haines City) during the dry period caused about
50 percent increase in outflow to the Peace and Alafia River basins.
Significant changes in outflow in the dry period also were
experienced in the Withlacoochee and St. Johns River basins. The
decrease in outflow to the Kissimmee River basin and the
corresponding increase to the Peace River Basin were caused by
slight shifting of the ground-water divides. The ground-water
outflow in 1959 is considered to be more representative of natural
outflow.
 Net ground-water outflow (U) from the Green Swamp area was
computed using the same method as used for the eastern and
western areas. The total outflow via the nonartesian aquifer was
determined to be an insignificant quantity (0.08 inch per year).
The total outflow via the Floridan aquifer was computed along the
boundary of the 870 square-mile area.
 The net ground-water outflow from the Floridan aquifer during
November 1959 and May 1962, adjusted to equivalent amounts of
runoff in inches per year, are presented in table 17. The estimated
mean annual ground-water outflows interpolated for 1959, 1960, and
1961, on the basis of yearly totals in table 17, are presented in
table 18.
 The net change in ground-water storage in both the nonartesian
 and Floridan aquifers for 1959 and 1960 are considered to be
 negligible. However, water levels in both aquifers declined
 significantly in 1961. The average net decline of water levels in
 the nonartesian aquifer in 1961 was equivalent to about 4.3 inches
 of water over the Green Swamp area. The average net decline of
 the piezometric surface of the Floridan aquifer in 1961 was
 equivalent to an insignificant change in storage (0.2 to 0.3 inch)
 because of artesian storage coefficients.
 Rainfall, surface-water outflow (table 15), ground-water outflow
 (table 17), and changes in ground-water storage are combined in


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