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 Relationship of Water Volume to Water Surface Area

 Figures 22 and 23 are depth-area, depth-volume, and

 area-volume curves for freshwater areas of the three-county

 study area. The relationships in these curves served as

 the basis for linking seasonal variation in water surface

 area to the monthly rainfall record in the water model.

 From the curve in Figure 22 it can be seen that an increase

 in depth results in a relatively small increase in surface

 water area as ponds and sloughs are filled, but small

 increments in depth cause large changes in water surface

 area when the water expands into wet prairies and pine

 flatwoods. Relationships between the volume of water

 standing on the land, the area of land surface covered by

 water, and water depth are governed by local variation in

 land elevation, or land contours. Following are the

 measurements and observations that formed the basis for the

 curves in Figures 22 and 23.



 Ponds

 Table 6 offers for comparison the number of ponds per

square mile counted for different areas on the 1:250,000

scale 1950 Hurd infrared aerial index sheets and ponds per

mile counted on ASCS 1:20,000 scale infrared aerials of

approximately the same areas. According to the index sheet

count, there were 7,573 ponds in Hendry County, 11,894

ponds in Collier County and 5,171 ponds in Lee County. The

difference between the counts on the index sheet and counts