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Pensacola area's water
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Printed by the Florida Geological Survey
LEAFLET NO. 3
THE PENSACOLA AREA'S WATER
The Pensacola area is endowed with a
vital and bountiful natural resource--WATER.
The water is available in large quantities. It
is easily obtained, is remarkably soft, and con-
tains very small amounts of dissolved minerals.
The quality of much of this water is far better
than that required for public supplies and by
To explain the occurrence of this water
we must look back into the geologic history of
the area. For millions of years part of the Gulf
coastal area has been sinking very slowly.
This lowered area has been filled to depths of
300 to 1,000 feet with sand, gravel, and clay
brought in by streams. The sand and gravel
beds form a vast, highly productive water-
bearing formation, or aquifer, that supplies al-
most all the wells and part of the streamflow in
the area. This surficial sand-and-gravel aquifer
is replenished continually by a bountiful rain-
fall, which totals more than 5 feet annually.
As the rain water seeps underground to re-
charge the aquifer, it remains almost pure be-
cause the sand and gravel is quartz, which is
not very soluble in water.
Industry, shipping, and recreation....There's plenty
of water for all
Two limestone formations of the extensive
Floridan aquifer lie beneath the sand-and-gravel
aquifer and contain large amounts of water.
For several reasons, very little water is used
from these limestones in the Pensacola area.
They are deeper than the sand-and-gravel
aquifer, the water contains more dissolved
minerals, and the southern parts of the limestone
aquifers contain salt water. However, these
limestone aquifers lie waiting as a ready
reserve of usable water.
The area receives fresh water from three
sources--rain falling directly on the area,
streams flowing in from adjacent areas, and
flow through the underground system. Escambia
and Santa Rosa counties receive an average
yearly rainfall of 62 inches, which amounts
to 5 billion gallons of water per day. Streams
bring in 62 billion gallons per day from ad-
jacent areas. About 0.1 billion gallons per day
of ground water flows underground into the
Pensacola area through the aquifers that are
fed by rain falling on the northern parts of
RAINFALL AT PENSACOLA, FLA.
In I- In
S 63.11 ich -
s 1. a5 MA z
Sol2- lfaFiwwl n 5.
ALONG THE GULF
0 15 20P25 Miles
SANTA ROSA "
8.5 BGD Flows into Boys from 4 major Rivers
Escambia and Santa Rosa counties and south
Alabama. The sand-and-gravel aquifer, recharge
by local rainfall, supplies most of the groui
water being used.
About 3 billion gallons of water per d:
that falls as rain on Escambia and Santa Ro:
counties is returned to the atmosphere throu,;.
the processes of evaporation and transpirati(
(water given off by plants and trees). T\
billion gallons of this rain water enters t
streams as overland flow or as seepage fr(
the ground and runs off into the estuaries. On
a small part of the rain water leaves the ar
as underground flow. Streams receive abc
two-thirds of their flow from the ground, result
in stable flows even during dry seasor
Although huge quantities of water are us
every day, vast amounts remain untapped. Mq
of the 87 million gallons of ground water usea
each day is taken from the sand-and-gravel
aquifer in the southern half of the area. Also,
in this area, water from streams is used for
15 1 17 IB 19 20 21 22 25 24 25
STAGE GRAPH CHANNEL CROSS SECTION
^50:- 40- 4- -----
STA10 DISCR FLG OO-FREENEY R16 LW-F- FO E
STAGE-DISCHARE LARRN-FRE PRKib LOW-FLOW FRULAENCY
CURVE CURVE FLOW- DURATION CURVES
.e120 r ~ hed Tred s PERDIDO RIVER
10 L |IIIX -AT
'Sao- -V? BARRINEAU PARK. FLA..
S 1945 195o0 15 19A 1965
TRENDS IN STREAMFLOW
THE BEHAVOIR OF A STREAM
cooling and some wastes are discharged into
ie rivers. Even so, the southern half of the
rea still has much water that may be used.
[ensacola, as do other communities, derives
|s water supply from wells developed in the
Very little water is used in the northern
alf of the area. Over a billion gallons of
ear, soft water flow from the small tributary
eams each day. Many of these streams offer
cellent possibilities for dams and reservoirs.
:eservoirs would increase the usable supply
f the streams and also would make possible
;esirable and needed recreational areas.
Reservoirs----Water can be stored
PARTS PER MILLION
MAXIMUM ALLOWABLE o 100 200oo
ACET&rF FIBR f
P PAN P P(R
'- DISSOLVED SOLIDS
Are there any problems associated with
developing and using this supply of water?
There certainly are. If this water is unwisely
developed or misused, problems will be
multiplied many times over, both in number
GULVF OF MEC
Large quantities available
Small to moderate quantities
Areas of concentrated use
THICKNESS OF SAND-AND-GRAVEL AQUIFER
IF' Fv i\CO
Less than 250 feet
250 500 feet
S500 1,000 feet
and severity. At best works of man frequently
have detrimental effects on our water resources.
Two abuses of water supply, which can
be disastrous, are excessive use and pollution.
In an ideally developed water supply there is
a balance between supply and demand. That
is, the water is not being used at a greater
rate than it is being replenished by nature.
Often times excess use brings pollution or
contamination such as that which results from
salt-water encroachment. In several areas
around Pensacola, excessive pumping has
lowered the level of fresh ground water and
allowed salty water to move in. In some areas,
ponded industrial wastes may seep underground
and contaminate water wells and streams.
Many years are required for a ground-water
supply to freshen after it has been contaminated
by salt water. It also takes many years of
diligent effort and large sums of money to
clean up a stream after it has been used as a
receiver of excessive wastes. Limestone
aquifers near the coast contain salty water;
however, they offer possibilities of being used
for disposal of industrial waste.
GROUND WATER AND RAINFALL NEAR
WATER LEVEL IN WELL
NORTH OF PENSACOLA
-NORMAL--- WET DRY WET---*
I iTREN -1 f[-- -NORMAL
M/nf^ F L 3<
HOW WAS THE WATER RESOURCE
A community must know the answers to
many questions in order to plan orderly in-
dustrial and urban expansion. What are the
sources of water? How much is available?
How does the supply fluctuate? What is the
quality of the water? What are the effects of
use on quantity and quality? There must be a
planned program of investigation to answer
these and many other questions pertaining to
Such a study was completed in 1962 by the
U.S. Geological Survey with financial cooperation
from the Florida Geological Survey, the City
of Pensacola, Escambia County, and Santa
(Parts per million)
SAND AND GRAVEL AQUIFER
USE OF GROUND WATER
IN ESCAMBIA AND SANTA ROSA COUNTIES
MILLION GALLONS PER DAY
10 ---- ------ ------
INDUSTRY CITY RURAL MILITARY
Mapping and measuring water-bearing
formations: One can only imagine the confusion
that would exist if there were no maps or plans
of Pensacola's water works showing the source
of water and the location and size of the under-
ground pipe system. Community life might go
smoothly until a break in a line occurred or an
expansion of this system was necessary to take
care of a population increase. At that time
many questions would have to be answered
before progress. could be made, some of which
are: Where are the pipes? Are they large enough
to allow for the expansion? How long has the
system been here? Do the pipes leak? From
where does the water come and in what amounts?
In the case of the natural water resource
system that serves a complex industrial society
these questions are multiplied many times. The
earth structure serves both as a storage reser-
voir and as a distribution system. This structure
is mapped by piecing together information from
many sources. The services of experienced
geologists, engineers, and chemists are necessary
Cooling towers conserve
water by re-use
288-ft well yields 1,300
gpm from sand-and-gra-
vel aquifer with 23-ft
to identify and measure the extent and water-
bearing characteristics of the materials that
make up the earth structure.
Most geologic information is obtained from
wells. Existing.wells must be studied and tested,
test wells drilled and logged, drill cuttings
examined, water samples analyzed chemically,
and water levels measured. Much information is
gained by observing the reaction of ground-water
levels to rainfall and to pumping. When a well
is pumped the water level underground lowers
TRENDS IN WATER USE
,15 ./ 150
.10 --- 100 0 I
3& ^ ^^/0 2
to form a depression, similar in shape to a cone.
The rate and amount of this lowering while
the well is being pumped at a measured rate and
the rate at which the water level recovers after
pumping ceases is a measure of the ability of
the formation to transmit and store water.
The behavior of a stream: All physical
aspects of a stream must be measured several
times during a period of years to determine how
much water it carries, to ascertain its fluc-
tuations and to determine the quality of the
water. The stage of a river is changing con-
tinually. It is either rising or falling. Infrequently
and for short periods it may be relatively
stationary. This fluctuation of a stream has to be
measured and recorded continuously for the
period of study. Flow measurements are made
throughout the range in stage to define the
stage-discharge relation. Using the continuous
record of stage and the stage-discharge relation,
a continuous record of flow is computed. From
an adequate record of basic flow data, several
essential and useful tools can be produced, such
as, flood frequency curves, low-flow frequency
curves, flow duration curves, and graphs in-
dicating long-term trends.
Variations in mineral content of water:
Samples of water taken daily or sometimes at
less frequent but regular intervals are analyzed
to determine the seasonal variations in surface
water. Ground water is studied by sampling
several wells, but often only one analysis per
well is needed. Maps showing mineral content of
the water in an aquifer may be prepared from
these analyses. In areas of suspected contam-
ination, ground water must be analyzed regularly
to determine changes in mineral content.
Additional information on the water resources
if the Pensacola area is contained in the following
reports of Florida Geological Survey, prepared
under the cooperative program with the U.S.
Interim Report on the Water Resources of Escambia
and Santa Rosa Counties, Florida: Fla. Geol.
Surv. Inf. Circ. No. 30, by R.H. Musgrove,
J.T. Barraclough, O.T. Marsh.
Aquifers and Quality of Ground Water along the
Gulf Coast of Western Florida: Fla. Geol.Surv.
Rept. of Inv. No. 29, by J. T. Barraclough and
O. T. Marsh.
Relation of Bucatunna Clay Member (Byram
Formation, Oligocene) to Geology and Ground
Water of Westernmost Florida: Geol. Soc.
America Bull., v. 73, p. 243-252, by O.T.Marsh.
These reports are available in many libraries
and the following offices:
Florida Geological Survey
P.O. Box 631
U.S. Geological Survey
244 Federal Building
U.S. Geological Survey
P.O. Box 2315
TEXT PREPARED BY:
Musgrove, R.H.; Barraclough, J.T.; and Grantham,
R.G., U.S. Geological Survey.
FLRD GEOLOSk ( IC SUfRiW
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