surface map may not be evaluated until the new potentiometric surface map is constructed. This
could pose a significant limitation when topics such as the effects of future pumping increases
need to be addressed.
2.2.2 Level II Delineations Analytical Modeling
The second method applied to delineate WHPAs in Hernando County is analytical ground-water
flow modeling. Analytical models are exact mathematical solutions to the partial differential
equation of ground-water flow., However, in order to obtain an exact mathematical solution, a
number of simplifying assumptions must be made concerning the physical system. These
assumptions generally include, but may not be limited to, two-dimensional areal ground-water
flow; fully penetrating pumping/recharge wells; homogeneous aquifer properties (e.g.
transmissivity and porosity); and fully penetrating boundary conditions such as streams or
barriers. Different analytical solutions may be superposed to simulate flow fields of varying
complexity. For example, the analytical solution for a pumping well in a homogeneous, leaky-
confined aquifer may be added to the analytical solution for uniform ambient ground-water flow
within the aquifer. When the limiting assumptions are not violated too badly, analytical models
are an efficient, powerful tool for the delineation of WHPAs. The widely used EPA WHPA
code (Blandford and Huyakorn, 1991) was selected for use to perform the analytical delineations.
The analytical modeling delineation approach requires that a variety of site-specific data be
acquired for each well or well field. The typical input parameters to the WHPA code are the
well pumping rate, the aquifer transmissivity and thickness, the angle of regional (ambient)
ground-water flow and the ambient hydraulic gradient. Once these key data were collected, the
WHPA code was used to delineate the two, five and ten-year capture zones for May and
September, 1988 (the reasons for selecting 1988 are presented later in the report).
For sites where the use of analytical modeling is appropriate, this method has significant
advantages over the flow-net delineation method. Using the WHPA code, capture zones may
be delineated extremely efficiently, and it is a simple effort to perform sensitivity analysis on