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MEMORANDUM July 14, 1972
TO: Donald R. Feaster, Direcfor, Water Resources Division v
William B. Smith, Chief, Hydrology Department
FROM: William D. Courser, Biologist, Environmental Department
FRE: Investigations of the effect of Pinellas County Eldridge Wilde Well Field's aquifer
cone of depression on cypress head water lIevesfi~d v tati.
It has been long suspected that cypress heads might be in some manner affected by aquifer
levels. G.G. Parker (personal communication) has noted this effect on several occasions.
W. C. Sinclair (fide W.B.Smith) has conducted studies on the recharge capabilities of a
few cypress heads in NW Hillsborough County. He found, at least in this location, that
aquifer recharge is possible through the selected cypress heads he studies.' A rigorous lit-
erature search was not conducted by the writer but personnel of the Environmental and
Hydrology Departments know of no studies that have been conducted on this subject. The
Senior Scientist concurs in this.
In order to qualitatively assess the possible effects that a well field's cone of depression
might have on cypress heads and their vegetation in the area of a well field we examined
Cypress heads within the Pinellas County's Eldridge Wilde Well Field proper and at varying
intervals away from the cone of depression's center. On 13 June 1972 (accompanied by
S Steve Rose) cypress heads, marsh areas and hardwood hammocks in the Eldridge Wilde Well
Field were investigated. The accompanying maps show the location of the sites investigated.
These sites were chosen at random and do not represent a complete survey of all such asso-
ciations within the well field. Appendix A details the observations at each site.
On the afternoon of June 22 cypress heads at 1.0, 1.5, 2.0, 2.6, and 3.0 miles east of the
well field along Lake Tarpon Road were checked. Appendix B lists the results of those
The results in Appendix A show that all cypress heads, hardwood forest floors and marsh areas
visited within the well field contained no water and, with one exception, contained dry soil.
All sites investigated were chosen at random. The one site that had moist soil might have been
receiving water from a spread irrigation system in operation nearby. Stations 4 6 showed signs
of a recent fire. The high degree of muck oxidation noted at Station 6 could have been explained
by the fire's action.
The ground cover within the sample of cypress heads was generally sparse and lacking in the
normal aquatic plants (i.e., lilies, pickerel weed, buttonbush, pipewort, etc.). At several
sites more terrestrial plants such as groundsel (Baccharis sp) dog-fennel (Eupatorium sp.) and
pokeweed (Phytolacca americana) were invading the cypress heads. Dog-fennel normally
establishes on disturbed, dry siles and is generally an "old field" type plant.. Groundsel and
pokeweedd also become esrablishecd in disturbed areas but can probably tolerate more moisture
than dog-fennel. The presence of dog-fennel in cypress heads would clearly indicate very
- OP 6l 'r.. ... I .. .
July 14, 1972
S Station 0 was revisited on July II. Dog-fennel has now become established in this cypress
head also (see photograph). In addition, brown areas observed in the crown of cypress
Streets at Station 0 would indicate stress conditions.
As we have been experiencing a prolonged drought can we blame the well field for the
conditions observed above. The question can be answered by examining a series of cypress
heads starting within the well field's cone of depression and proceeding out beyond the
cone's drawdown area. If the cypress heads are affected by the well field and not by wea-
ther, the cypress head beyond 2.0 miles from the cone of depression's center (W..B. Smith,
estimate of extent of major area of cone affect) should be different as far as water levels,
soil moisture and ground cover conditions.
As the results in Appendix B demonstrate, the area of cypress head occupied by water
progressively increased from 2.0 miles out after no water was recorded at 1.0 and 1.5 miles.
Soil moisture also increased visibly with increased distance from the well field. Qualitative
observations on vegetation revealed that as soon as soils became moist, vegetation more
characteristic of local heads was observed. A thick carpet of low vegetation was present
at each head from 1.5 miles out. ,
The results "hold even more water" when it is noted that a hurricane passed during June
17 19 leaving from 5 to 8 inches of water but at the same time not affecting the water
levels, vegetation, or soil conditions at Stations 1.0 and 1.5 miles distant from the center
of the well field. The vegetation observed in the more distant heads could not have con-
ceivably grown between the storm date and dates of examination. Further study could yield
even more valuable quantitative data if: (I) cypress heads in all four major compass headings
away from the center of the cone could be investigated; (2) each cypress head should be
transected across its diameter to record plant species diversity and density; and (3) the ecotone
vegetation examined either qualitatively or quantitatively. This type of analysis might become
a valuable tool in monitoring environmental changes caused by excessive pumping.
Cypress heads, marshes, lakes and hardwood hammocks in the Pinellas County Eldridge Wilde
Well Field are in a dry condition and undergoing invasion by more terrestrial forms of vege-
tation not commonly found within the wet cypress heads outside the well field's cone of
depression. Comparison of heads both within and outside of the well field area would indicate
direct aquifer effects on most cypress heads in this area.
The cypress head 2.0 miles distant was visited again on July II. Standing water was no longer
present but the soil was still saturated and the ground cover showed little visible change. Since
little significant precipitation has occurred since Hurricane Agnes this observation suggests
drought conditions coupled with aquifer drawdowns can cause visible changes in cypress heads.
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