BULLETIN NO. 68


APPENDIX 1. COMMENTARY ON FLORIDA HYDROSTRATIGRAPHIC
 NOMENCLATURE.

 Considerable debate exists with regard to hydrostratigraphic nomenclature in the study area. While it
is beyond the scope of the present study to formally rename principal aquifer systems in southwestern
Florida, especially given the pending recommendations of the CFHUD II (Copeland et al., in review),
some discussion is warranted. This is due in part to the lack of a formal hydrostratigraphic code (Seaber,
1988), unlike that available for lithostratigraphic nomenclature (North American Commission on
Stratigraphic Nomenclature, 2005). Hydrostratigraphic unit definitions and nomenclatural guidelines,
however, do exist. Poland et al. (1972) define an aquifer system as "A heterogeneous body of intercalated
permeable and poorly permeable material that functions regionally as a water-yielding hydraulic unit; it
comprises two or more permeable beds separated at least locally by aquitards that impede groundwater
movement but do not greatly affect the regional continuity of the system." Neuendorf et al. (2005) define
an aquifer system as "A heterogeneous body of intercalated permeable and less permeable material that
acts as a water-yielding hydraulic unit of regional extent." According to nomenclature guidelines set
forth by Laney and Davidson (1986), aquifer system names should not be derived from relative position.
In consideration of these definitions and guidelines, all or part of the SAS and IAS/ICU may be
considered inappropriately named. On the other hand, Macfarlane (2000) suggests that aquifer system
names should be retained if they are entrenched in the scientific literature or legally defined in a state's
regulatory framework.

 With regard to naming confining units, Laney and Davidson (1986) suggest that the name could be
based on the aquifer it confines (i.e., the aquifer it overlies). Intuitively, a confining unit may also be
named after the aquifer system in which it resides, especially if that unit crosses multiple
lithostratigraphic units precluding a lithostratigraphic-based name. The MFCU, which has been adopted
by the CFHUD II accordingly follows this line of reasoning.

 Any proposed changes in Florida's hydrostratigraphic nomenclature will hopefully address the
IAS/ICU, in which relative permeability is an important consideration. In the northern part of the study
area, confining to semi-confining sediments are dominant, whereas in the southern part of the study area,
distinct local to sub-regional zones of higher permeability exist. Some hydrogeologists prefer to
characterize the northern area as ICU and the southern area as IAS; however, it is noteworthy that a
system (IAS) and a unit (ICU) are not at the same hierarchical level (Aadland et al., 1995). As a result,
the ICU would be a unit of the IAS.

 The concept of a confining system should also be considered for the IAS/ICU. Jorgenson et al. (1993)
define a confining system as "two or more confining units separated at most locations by one or more
aquifers that are not in the same hydraulic system." Renken (1998) clarifies this definition by stating
"...confining units that may contain local aquifers, but which function together to retard the vertical
movement of water, are called confining systems." In consideration of these definitions, and Laney and
Davidson's (1986) suggestion on nomenclature (i.e., avoid naming based on relative position), the IAS
may be more appropriately named the Upper Floridan confining system, which would allow for presence
of hydraulically disconnected permeable zones within a system that confines the FAS. In the study area,
the northern lateral equivalent of this confining system could be named the Upper Floridan confining
unit. Alternatively, the area could simply be recognized as part of the Upper Floridan confining system.

 Naming these systems or units relative to the FAS may be more appropriate than using a
lithostratigraphic reference because the FAS, as well as its overlying confining/semi-confining sediments
are not limited to a single lithostratigraphic formation or group. For example, to name the IAS/ICU based
on association with the Hawthorn Group may lead to confusion given that part of this lithostratigraphic
package is included in the UFA.