Interim report on the water resources of Escambia and Santa Rosa Counties, Fla. ( FGS: Information circular 30 )

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY

FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director

INFORMATION CIRCULAR NO. 30

INTERIM REPORT
ON
THE WATER RESOURCES
OF
ESCAMBIA AND SANTA ROSA COUNTIES, FLORIDA

By
R. H. Musgrove, J. T. Barraclough, and O. T. Marsh
U. S. Geological Survey

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
In cooperation with the
FLORIDA GEOLOGICAL SURVEY,
ESCAMBIA COUNTY, SANTA ROSA COUNTY
and the
CITY OF PENSACOLA

TALLAHASSEE
1961

AGRI.
CULTURAL
LIBRAP y

Completed manuscript received
April 14, 1961
Printed by the Florida Geological Survey
Tallahas see

PREFACE

An investigation, currently in progress, deals with
the water resources of Escambia and Santa Rosa counties,
Florida. The mild climate and excellent water supplies are
prime reasons for a trend of industrial development in this
section of Florida. Information on the water resources of
the area prior to this investigation was sketchy and based
on a minimum of documented data. The purpose of this
investigation is to collect water data and combine it with
data previously collected into an interpretative report that
will be beneficial to water users.

In 1958 the U. S. Geological Survey, in cooperationwith
the Florida Geological Survey, began a detailed investigation
of the surface-water and ground-water resources of Escambia
and Santa Rosa counties, Florida. Half of this work was
financed by the Federal Government and the remainder by
the State, Escambia and Santa Rosa counties, and the city
of Pensacola.

This is a preliminary report that summarizes progress
on the investigation up to January 1, 1960. The purpose of
this report is to present detailed factual and interpretative
information on the occurrence, quality, quantity, and other
.aspects of the area's water resources for the guidance of
present and future water users. A final and more compre-
hensive report will be prepared after two additional years
of field work.

The interim investigation was made by personnel of
the Water Resources Division of the U.S. Geological Survey.
Rufus H. Musgrove, hydraulic engineer, Surface Water
Branch, worked parttime onthe project. Jack T. Barraclough,
hydraulic engineer, and Owen T. Marsh, geologist, Ground
Water Branch, spent full time onthe investigation. The work
was supervised by A. 0. Patterson, district engineer, Sur-
face Water Branch; M. I. Rorabaugh, district engineer,
Ground Water Branch; and J. W. Geurin, district chemist,

Quality of Water Branch. The study was suggested by
Robert 0. Vernon, director, Florida Geological Survey,
and the Survey has provided the State matching funds for
the project.

Appreciation is expressed to the following individuals
for providing information and extending courtesies which
greatly facilitated the investigation:

Clarence G. Menke, Quality of Water Branch,
U. S. Geological Survey;
M. E. Batz, Chemstrand Corporation;
D. W. Young, C. E. Adams, and J. A. Hamm, Jr.
St. Regis Paper Company;
E. L. Russell, W. E. Moore, H. E. Province, and
J. F. Schindler, the California Company;
R. C. Howard and M. F. Kirby, Gulf Oil
Corporation;
S. Sweeney, Water Department, city of
Pensacola;
J. J. Pinke and C. G. Mauriello, American
Cyanamid Company;
J. Ivie, Columbia National Corporation.

CONTENTS
Page
Abstract....................................... 1
Introduction ............... ..................... 3
Purpose and scope ........................... 3
Previous work .............................. 4
Description of the area ....................... 6
Rainfall .............. .. .................... 8
Temperature... ............................ 10
Geology ......... ............................. 11
Introduction ................................. 11
General statement ......................... 11
Test drilling ............................... 11
Stratigraphy............... ........ ......... 13
Aquifers ................... ..... ........ 13
Sand-and-gravel aquifer ................ 13
Floridan aquifer ....................... 17
Aquicludes ................... ........... 19
Aquicludes within the sand-and-gravel
aquifer .............................. 19
Aquiclude between the two aquifers ....... 20
Aquicludes within the Floridan aquifer .... 21
Aquiclude below the Floridan aquifer...... 22
Regional dip. ...... ......... ................. 22
Relationship of geology to ground water ........ 22
Movement of water...................... 22
Relationship of geology to quality of water ... 23
Zones of fresh and salty water ........... 23
Mineralization and hardness of ground
water ................................. 23
Relation of quality of water to geologic
history of the gulf coast .............. 24
Surface water................................. 24
The collection of data ........................ 25
Occurrence and quality..................... 28
Perdido River basin..................... .. 29
Escambia River basin ..................... 37
Blackwater River basin.................. 46
Yellow River basin...................... 51
Ground water ................................. 51
Principles of occurrence ..................... 51

Hydrologic properties of the aquifers........... 52
Sand-and-gravel aquifer.................... 53
Floridan aquifer ........................... 53
Movement of water ........................... .54
Ground-water velocities ................... 56
Areas of artesian flow ..................... 57
Storage of water ............................... 57
Fluctuation of the water level.................. 58
Temperature of ground water ................. 66
Wells .............. ... ...... .............. 67
Quantitative studies ......................... 68
Chemical quality of ground water ............. 70
Use of water .................. ............... 74
Surface water............................... 74
Ground water................................ 75
Sand-and-gravel aquifer.................... 75
Use by industries ....................... 75
Use by municipalities ................... 76
Use by agriculture ....................... 76
Supplies for domestic use................ 76
Floridan aquifer ............................. 77
Water problems ............................... 77
Problems from natural causes................ 77
Periods of low rainfall................... .. 78
Decline of water levels .................. 78
Salt-water encroachment ................ 78
Periods of high rainfall .................... 79
Manrnade problems. .......................... 80
Large drawdowns ...................... 80
Salt-water encroachment................... 80
Industrial waste disposal................... 82
Potential water supplies ......................... 83
Surface water ............................... 83
Ground water............................... 84
Sand-and-gravel aquifer................... 84
Areas of abundant fresh ground water..... 84
Factors limiting availability of fresh
ground water ........................ 85
Floridan aquifer............... ..... ....... 86
References ................................. ... 87

ILLUSTRATIONS

Figure Page
1 Location map of Escambia and Santa Rosa
counties, Florida. ..................... 7
2 Bar graph of rainfall at Pensacola, Florida,
and Brewton, Alabama, showing monthly
averages, maximums and minimums, and
yearly rainfall for the period 1926-58..... 9
3 Geologic sequence in Escambia and Santa
Rosa counties, Florida, as shown byrepre-
sentative log of oil test well near Pensacola 12
4 Geologic section across Escambia and Santa
Rosa counties showing aquifers and aqui-
cludes along section A-A' in figure 7...... 14
5 Geologic section showing facies changes
and zones of relative permeability and im-
permeability in the upper part of the sand-
and-gravel aquifer along the Perdido River,
Escambia County, Florida ............... 15
6 Map of Escambia and Santa Rosa counties
showing contours on top of Miocene clay
unit .................................. facing 20
7 Map of Escambia and Santa Rosa counties
showing contours on top of Bucatunna clay
member of Byram formation ............facing 22
8 Basin map of thePerdido, Escambia, Black-
water, and Yellow rivers ................ 25
9 Bar graph showing duration and types of
surface-water records in Escambia and
Santa Rosa counties, Florida ............. 27
10 Map of Escambia and Santa Rosa counties,
Florida, showing surface drainage and data-
collection points.............. .............facing 28
11 Chloride content of the Escambia River taken
daily at Chemstrand Corporation's cooling-
water intake and monthlyflows of Escambia
River at State Highway 4. near Century,
Florida, 1957, 1958..... ............ .facing 30
12 Regional flood frequency curves for the
Perdido, Escambia -Blackwater, and Yellow

river basins ....... ................... 32
13 Low-flow frequency curves for Perdido
River at Barrineau Park, Florida, 1941-58 34
14 Bar graph of the minimum, average, and
maximum monthly discharge of the Perdido
River at Barrineau Park, Florida, 1942-59 35
15 Flow-duration curves ................... 36
16 Channel-bottom profile of Pine Barren
Creek................................ 40
17 Discharge available without storage, Pine
Barren Creek near Barth, Florida, 1952-58 41
18 Mas s-flow curve for Pine Barren Creek near
Barth, Florida, 1952-58 ................. 42
19 Bar graph of the minimum, average, and
maximum monthly discharge of the Es-
cambia River near Century, Florida, 1935-58 45
20 Channel-bottom profile of Pond Creek ..... 47
21 Low-flow frequency curves for Big Cold-
water River near Milton, Florida, 1938-58 48
22 Bar graph of the minimum, average, and
maximum monthly discharge of Big Cold-
water River near Milton, Florida, 1939-58 50
23 Water levels in an artesian well and a
nonartesian well drilled into the sand-and-
gravel aquifer in northern Escambia County,
Florida ................................ 55
24 Hydrographs of wells SR 8 and SR 10...... 59
25 Hydrographs of wells E 46, E 45, and E 74
and graph of yearly rainfall at Pensacola.. 61
26 Hydrographs of wells E 62, E 62-A, and
E 39.................................... 63
27 Hydrographs of well SR 102............. 65
28 Graph showing theoretical drawdowns inthe
vicinity of a well being pumped at a rate of
700 gpm (about 1 mgd) for selected periods
of time .............................. 71
29 Map of Escambia.and Santa Rosa counties
showing the daily consumptive use of ground
water by industries and municipalities dur-
ing 1958................... ... ....facing 76
30 Cross section showing the decline of water
levels inthe vicinity of Cantonment, Florida 81

viii

Table Page
1 Range in mineral content for seven streams
in Escambia and Santa Rosa counties...... 30

ii

INTERIM REPORT
ON
THE WATER RESOURCES
OF
ESCAMBIA AND SANTA ROSA COUNTIES, FLORIDA

By
R.H. Musgrove, J.T. Barraclough,
and O.T. Marsh

ABSTRACT

An investigation, currently in progress, deals with
the water resources of Escambia and Santa Rosa counties,
Florida. The mild climate and excellent water supplies are
prime reasons for a trend of industrial development in this
section of Florida. Information on the water resources of
the area prior to this investigation was sketchy and based
on a minimum of documented data. The purpose of this
investigation is to collect water data and combine it with data
previously collected into an interpretative report that will
be beneficial to water users.

Escambia and Santa Rosa counties, the westernmost
counties in Florida, have an abundant supply of both ground
and surface water of excellent quality. The streams and
underground formations are major sources of supplies.

Over 7- bgd (billion gallons per day) of fresh water
flow into the 200 square miles of estuarine bays from four
major rivers. The Escambia River, the fifth largest in the
State, has an average flow of over 4 bgd. Many smaller
streams within the' area produce large quantities of water.

The ground water occurs in two major aquifers; the
sand-and-gravel aquifer and the Floridan aquifer. Almost

FLORIDA GEOLOGICAL SURVEY

all the 86 million gallons of water taken from the ground
each day comes from the sand-and-gravel aquifer. This
aquifer extends from the water table down to various depths
ranging from 350to 1,000 feet. Water inparts of this aquifer
is confined by numerous layers of clay or hardpan and is
under artesianpressure. The sand-and-gravel aquifer con-
tains a large supply of exceptionally soft and unmineralized
ground water. Dissolved solids generally range from 20 to
80 ppm (parts per million).

The Floridan aquifer, consisting of limestones which
underlie the sand-and-gravel aquifer, contains a large supply
of harder, more mineralized artesian water that is virtually
untapped.

An extensive clay bed the Bucatunna clay member
of the Byram formation lies near the top of the Floridan
aquifer. Water in the upper part of the Floridan aquifer
above the Bucatunna clay member is fresh except in the
extreme southernparts of both counties. Water in the lower
part of this aquifer below the Bucatunna clay member is
fresh in the northern half of both counties. In places this
clay bed retards upward or downward movement of ground
water and separates saltwater below fromfreshwater above.

Recharge of the sand-and-gravel aquifer is mostly by
local rainfall. The Floridan aquifer is recharged by rain
falling in southern Alabama, 10to 35 miles north of the area,
and by downward leakagefrom the sand-and-gravel aquifer.

The main water problems considered thus far in this
investigation are: decline of the water table and salt-water
encroachment. Below-normal rainfall causes the water
table to drop throughout the area. However, locally the
greatest lowering of the water is caused by heavy pumping of
closely spaced wells. The possibility of salt-water encroach-
ment is especially greatwhere pumping near salty bays and
rivers lowers the water table below sea level. Evidence of
upward movement of salt water has not been found. Flooding
of residential areas following heavy local rains causes incon-
venience where the watertable intersects the ground surface
or where layers of clay or hardpan permit rainwater to collect

INFORMATION CIRCULAR NO. 30

in ponds. In addition, some flooding occurs along streams
after heavy rains.

The major uses of water in the area are for industrial
processes, recreation, and municipal requirements. Indus-
tries use about 70 percent of the ground water withdrawn
from the area, the largest single user being the St. Regis
Paper Company which pumps 35 mgd (million gallons per
day). The large amount of water being used by industries
and municipalities, however, is only a small part of the
area's usable supply.

INTRODUCTION

Purpose and Scope

An immediate need of community and industrial plan-
ners in Escambia and Santa Rosa counties is information on
the water resources of the area. It is presently known that
the area has a large supply of water that is low in mineral
content. However, because the water needs of this fast
growing section of Florida arebecoming greater, information
about other characteristics of the water must be made avail-
able so that the area may realize its full industrial potential
without creating problems caused by permanently lowered
water levels, salt-water encroachment, and pollution.

An investigation of the water resources of Escambia
and Santa Rosa counties was started in January 1958 by the
U. S. Geological Survey in cooperation with the Florida
Geological Survey, Escambia and Santa Rosa counties, and
the city of Pensacola. This investigation was designed to
obtain, over a 4-year period, data on the occurrence, quality,
and quantity of surface and ground water. The information
collected during the investigation will serve two major
purposes: (1) It will provide an inventory of the area's water;
and (2) it will provide a sound basis for planning development
and use of the area's water resources.

The purpose of this report is to make available, to
community and industrial planners, information collected

FLORIDA GEOLOGICAL SURVEY

prior to 1960 on the quantity and quality of water in the area
and on certain characteristics such as fluctuations in supplies
because of uneven distribution of rainfall. It contains a brief
discussion of climate, a geologic description of the area,
information on streamflow and strearflow characteristics,
principles of the occurrence and movement of groundwater,
properties of the ground-water aquifers, and chemical
characteristics of the area's water resources. It discusses
present use of water, some existing problems associated
with water, and potential water supplies of the area.

Previous Work

The earliest published report that describes the water
resources of Escambia and Santa Rosa counties was by
Sellards and Gunter (1912); it discusses the water supply of
west-central and west Florida. This report describes the
physiography, drainage, water wells, and soils of Escambia
and Santa Rosa counties. It contains information on wells
in Santa Rosa County at Bagdad, Blackman, Cobb, Milligan,
Milton, Mulat, Pace, and Robinson Point. Data are supplied
for wells in Escambia County at Cantonment, Bohemia,
Molino, Muscogee, Pine Barren, McDavid, and Pensacola,
including chemical analyses of water from several of these
wells. The report also contains a map(p. 95 ) showing areas
of artesian flow in the two counties.

The following year (1913) Matson and Sanford published
a report on the geology and ground water of the entire State.
They briefly describe the physiography, geology, and water
supply of Escambia and Santa Rosa counties (p. 301-304;
401-403). Data on typical wells and general information on
water resources of selected towns are tabulated for each of
the two counties. The wells discussed range from 30 to
1,620 feet in depth and draw water from beds of Oligocene,
Miocene, Pliocene (?), and Pleistocene age. Two geologic
logs are given, one of a 1,435-foot well at Cantonment and
the other of a 1,101 -foot well south of Pensacola.

Streamflow records have been collected on the Es-
cambia River since 1934, on Big Coldwater River since 1938,

INFORMATION CIRCULAR NO. 30

and on the Perdido River since 1941. Daily records of flow
for these rivers are published by the U. S. Geological Survey
in an annual series of water-supply papers.

The first detailed investigation of ground water in the
area was made by Jacob and Cooper (1940, U. S. Geological
Survey, open-file report on the ground-water resources of
the Pensacola area). The report contained a section on
geology by Sidney A. Stubbs. The study included pumping
tests of both the drawdown type and the recovery type to
obtain coefficients of transmissibility and storage for the
aquifer in the vicinity of Pensacola. Since 1940, continuous
and periodic measurements have been made of the water
level in wells as far north as Cantonment to determine the
effect of rainfall, pumping, barometric pressure, and tides.
Jacob and Cooper also had chemical analyses made of water
from several wells and studied the encroachment of salt
water from Bayou Chico into wells of the Newport Industries
and of the U. S. Navy.

The mineral spring at Chumuckla in Santa Rosa County
is briefly described by Ferguson, Lingham, Love, and Vernon
(1947) in their report on the springs of Florida.

In 1951, Heath and Clark made a detailed investigation
of the potential yield of ground water in the vicinity of Gulf
Breeze onFair Point Peninsula, Santa Rosa County. Twenty
test wells were drilled across the peninsula, and periodic
water-level measurements were made to obtain profiles of
the water table. Heath and Clark conducted quantitative
studies to determine the effect of pumping in relationto salt-
water encroachment and to determine how much ground water
could be pumped from wells. They give a brief but adequate
discussion on the geology and cover such topics as use and
quality of ground water.

Chemical analyses of ground water in the two counties
have been published by the U. S. Geological Survey (Collins
and Howard, 1928) and by the Florida State Board of Conser-
vation (Black and Brown, 1951). Black, Brown, and Pearce
(1953) give a short description of the intrusion of salt water
into wells of the Newport Industries and of the U. S. Navy

FLORIDA GEOLOGICAL SURVEY

near Pensacola. Chemical analysis of water fromPensacola
city wells appears in a report by Collins (1923, p. 33). An-
other analysis of water from these wells was published by
the U.S. Geological Survey (Lohr and Love, 1954, p. 111).

No detailed study of the geology of Escambia and Santa
Rosa counties has been published. Stubbs (in Jacob and
Cooper, 1940, p. 5-12) describes the upper 300 feet of the
Pleistocene, Pliocene (?), and Miocene deposits in the
southern half of Escambia County. Heath and Clark (1951,
p. 12-15) describe the same stratigraphic interval at the
western end of Fair Point Peninsula in Santa Rosa County.
Cooke (1945, p. 232-233) describes a short measured section
of the upper 70 feet of the Pleistocene and Pliocene (?)beds
that are exposed in the bluffs on the west side of Escambia
Bay. He also noted the presence of several Pleistocene
marine terraces in Escambia and Santa Rosa counties.
MacNeil (1949) and Carlston (1950) likewise recognize the
existence of several marine terraces in the area, but they
differ as to the number of such terraces. Calver's report
on Florida kaolins and clays (1949, p. 24-28, 41-42) gives
information on clays in Escambia and Santa Rosa counties
and indicates which clays he believes have commercial value.

Description of the Area

Escambia and Santa Rosa counties are located in the
extreme northwest corner of Florida (fig. 1). Escambia
County is the westernmost county in the State and is bordered
by Alabama on the west. Both counties border on Alabama
to the north and on the Gulf of Mexico to the south. Water
courses serve as boundarylines on three sides of Escambia
County and two sides of Santa Rosa County. The Perdido
River is the boundary line between Florida and Alabama on
the west and the Escambia River separates the two counties.
Santa Rosa County is the larger, but less populous, with
1,151 squaremiles and a 1950 population density of 23 persons
per square mile. Escambia County covers 759 square miles
and had a 1957 population density of 245 persons per square
mile. '

INFORMATION CIRCULAR NO. 30

Figure 1. Location map of Escambia and Santa Rosa
counties, Florida.

The two major cities in the area are Pensacola and
Milton. Pensacola, located in southern Escambia County
on Pensacola Bay, had a population of over 57, 000 in 1957.
Greater Pensacola includes several small suburban commu-
nities and thus has a much greater population than Pensacola
proper. Milton is the largest town in Santa Rosa County,
with a population of 2, 040 in 1950.

Much of the land in the southern part of the area is
less than 30 feet above sea level. Bays, low marshy areas,
peninsulas, and islands with long shorelines characterize
this section. Estuarine bays extend inland some 20 miles
and cover over 200 square miles. Santa Rosa Island is about
half a mile wide and 55 miles long and extends from the
mouth of the Pensacola Bay eastward with sand dunes standing
as much as 30 feet above sea level. North of Pensacola the

FLORIDA GEOLOGICAL SURVEY

land is hilly and well dissected with streams that draintoward
the Pensacola area. The elevations of the streambeds are
near sea level for a distance of 30 to 40 miles inland from
the coast. The hills 20 miles inland are about 150 feet above
sea level, becoming higher to the north. The highest eleva-
tions are 290 feet alongthe northernboundary of the counties.

Agricultural activities predominate in the northern
half of the area. Much of the area is devoted to forest.
The Blackwater River State Forest takes in the northeast
quarter of Santa Rosa County. Row-crop farming is preva-
lent throughout the northern half of the area. Industrial
operations predominate in the section south of Cantonment
and Milton. Chemicals, synthetic fibers, and paper are the
major products of the local industries. Raw materials from
many parts of the State are shipped to the industrial area
around Pensacola for processing and manufacturing. Fishing,
shipping, military operations, and tourists also contribute
to the economy of the area.

Rainfall

To evaluate the effect of rainfall on the area's water
resources, a study was made of records collected by the
U. S. Weather Bureau at two stations during the 33-year
period, 1926-58. Data for these two stations are presented
in graphical form infigure 2. The rainfall data at Pensacola
were selected to represent the rainfall in the southern part
of the area along the coast, and data fromthe Brewton station,
located in Alabama about 10 miles north of the State line,
were selected to represent the rainfall farther inland. Within
the two-county areathere seems to be onlyminor long-term
variations in amounts of rainfall.

All points in the area receive approximatelythe same
amount of rainfall over a long period of time. The difference
between the Pensacola and Brewton averages for the 33-year
period was only 0. 43 inch. The shorter the period of time
for which rainfall is measured at any two points, the greater
the difference may be. A 1-year period can show uneven
distributions. For example, in 1953 Pensacola received

INFORMATION CIRCULAR NO. 30

PENSACOLA, FLA.

25

to
Il
K0

Figure 2.

Bar graph of rainfall at Pensacola, Florida, and
Brewton, Alabama, showing monthly averages,
maximums and minimums, and yearly rainfall
for the period 1926-58.

one-third more rainfall than Brewton. The pattern was re-
versed in 1929 when Brewton had 87.18 inches and Pensacola
had a below-average rainfall of 60. 79 inches. The average
rainfall, based on the 33 years of record at the Brewton and
Pensacola stations, is 62 inches per year. The year-to-year
variation can be great at any one point. For example, the
highest and lowest annual rainfall occurred in successive
years at Pensacola 90.41 inches in 1953 and 28. 66 inches
in 1954.

to
BO= _-- ----------- _------ -I-- ... -- -----L- ------

BREWTON, ALA.

10

200 l -l--------- --
80 | ------------- ,----------
| -.- 33ft Dn

FLORIDA GEOLOGICAL SURVEY

The pattern of seasonal distribution is the same over
the entire area, the wettest periods occurring in early spring
and late summer and the driest in October and November.
Except during October and November, rainfall of at least
4 inches each month can be expected, on the average.
October and November have an average rainfall of about
2.9 inches and 3. 8 inches, respectively. An average rain-
fall of over 6.0 inches occurs during March, July, August,
and September. July has the highest average, with 7.4 inches.
There is always the possibility, however, of having a dry
month during normally wet seasons or a wet month during
seasons which are usually dry. For example, rainfall in
October has varied from zero to a maximum of 20. 5 inches
at Pensacola and March, normally a wet month, has experi-
enced as little as 0. 9 inch of rainfall.

Another interesting aspect of the area's rainfall is the
high intensity as much as 0.6 inch has been measured
during a 5-minute period. Rainfalls of 3. 5 inches during a
I-hour period and daily rainfalls in excess of 6.0 inches are
not uncommon.

Temperature

Temperatures in the area are mild. The average
annual temperature at Pensacola is 68" F. Average monthly
temperatures vary from a high of 81 F. in July and August
to a low of 54* F. in December and January. The extreme
temperatures recorded at Pensacola have been as high as
103* F. and as low as 7 F.; however, they seldom rise
above 100 F. or drop below 20 F. On the average, 275
frost-free days occur annually. Along the coast, winter
temperatures may be as much as 100 F. higher than in the
northern part of the area.

INFORMATION CIRCULAR NO. 30

GEOLOGY1

Introduction

General Statement

In Escambia and Santa Rosa counties, the top of the
Floridan aquifer (fig. 3) lies at depths ranging from about
400 to 1,200 feet below the land surface and is virtually
untapped by water wells. Above the limestones of the Floridan
aquifer lies a thick sequence of sand, gravel, and clay;
nearly all the wells in the area tap permeable sediments
within this sequence referred to in this report as the
sand-and-gravel aquifer. In the northern half of the area,
the Floridan aquifer and the sand-and-gravel aquifer are in
contact with each other, but in the southern part they are
separated by a thick clay unit that serves to confine the water
that is present in the upper part of the Floridan aquifer. An
extensive clay bed, the Bucatunna clay member of the Byram
formation, underlies the upper limestone of the Floridan
aquifer (fig. 3) and forms an aquiclude throughout the area
(Marsh, 1961). The limestones of the Floridan aquifer rest
upon relatively impermeable clay and shale.

Test Drilling

In 1959 the U. S. Geological Survey contracted to have
six test wells in Escambia County and five test wells in Santa
Rosa County drilled by the rotary method. There were two
main purposes for these test wells. First, they helped to
delineate aquifers and aquicludes inparts of the area where
little or no geologic information was available. Geologic
logs of the wells were compiled from an examination of rock

1The stratigraphic nomenclature used herein is that of the Florida Geological
Survey and does not necessarily conform to that of the U. S. Geological Survey.

FLORIDA GEOLOGICAL SURVEY

Figure 3. Geologic sequence in Escambia and Santa Rosa
counties, Florida, as shown by representative
log of oil test well near Pensacola.

INFORMATION CIRCULAR NO. 30

cuttings that were collected at intervals of 5 or 10 feet.
Fossils were picked fromthe rock cuttings and will be iden-
tified to determine the age of the sand-and-gravel aquifer.
Electric logs of the two deepest wells were made to determine
accurately the position of clay layers and permeable zones.
Second, these test wells made itpossibleto install recording
gages in areas where information on water levels was needed.
A total footage of 2, 800 feet was drilled, and the depths of
the wells ranged from 60 to 750 feet.

Stratigraphy

Aquifers

Sand-and-gravel aquifer: Virtually all the wells in
Escambia and Santa Rosa counties draw their water from the
sand-and-gravel aquifer. This aquifer extends from the
ground surface to various depths, ranging from 350 feet in
the northeast corner of Santa Rosa County to 1,000 feet in
the center of the area (fig. 4). In the northern half of the
area the sand-and-gravel aquifer overlies a thin limestone
of late Oligocene age (uppermost part of the Floridan aquifer),
but inthe southern half of the area the sand-and-gravel aquifer
rests upon a thick clay of Miocene age.

Abrupt facies changes are characteristic of the sand-
and-gravel aquifer. Although composed predominantly of
sand, the aquifer contains numerous lenses and layers of
clay and gravel that are as much as 60 feet thick. The dis-
continuityof the sediments inthe sand-and-gravel aquifer is
shown in figure 5. This is a detailed geologic section of the
uppermost 100 feet of the aquifer along the Perdido River
in west-central Escambia County. The cross section is
based on rock cuttings and electric logs of 20 test wells.
These wells were drilled for the St. Regis Paper Company
to test the infiltration characteristics of the groundalongthe
Perdido River. The logs were made by the firm of Leggette,
Brashears, and Graham, consulting ground-water geologists.
As can be seen from the cross section, irregular lenses of
gravel and clay extend for short horizontal distances. For
example, one gravel lens that is 20 feet thick is only about

O SAND' AND |ORl AVEL AQUIFER o.

0-0 0 0
. SHA [ EXPLANATiON
a 5 6 as asse

Figure 4. Geologic sectionacross Escambia and Santa Rosa counties showing aquifers
and aquicludes along section A-A' in figure 7.

B B'
South I .h
S" .0 .

40 -40

os y Cr menti0O lefed on eleidt lopge and simple loe of oolAA
D ^ S ^wells s drilled by t Me St ShRh POr Co pan 9 in 5 il t In.
..< 3-:D *L w eiltrolln ch ristdei of tNo ground aln 00
'400 :aq I d th Pee R ivdo Logs weie mode by Loggelne,
I3 Y d ge log, New IYor) and carroeled by Owenon I g SMah

4 6 1mn I
'14 0 o "t .14 0

-- -- -,--
s,, ... ....0

O .. .....

ReleIly y meobe zone
100* .100
(cSoy r sond and cloy II

140 140

Figure 5. Geologic section showing faces changes and zones of relative permeability
and impermeability in the upper part of the sand-and-gravel aquifer along
the Perdido River, Escambia County, Florida.

FLORIDA GEOLOGICAL SURVEY

200 feet long. Well logs of the sand-and-gravel aquifer else-
where indicate that this cross section is fairly representative
of the aquifer throughout the area.

The uppermost 5-20 feet of the sand-and-gravel aquifer
differs markedlyfrom the underlying beds. This upper part
consists of light tan fine to coarse sand that is soft and loose
in contrast to the hard reddish brownpebbly sand that under-
lies it. In many places, the light tan sand has been removed
by erosion, leaving the hard reddish sand exposed as a flat
surface.

The sand-and-gravel aquifer consists predominantly
of quartz sand, ranging from white tolight brown or reddish
brown. Although some of the sandis moderately well sorted,
it is generally rather poorly sorted. The grains range from
very- fine to very coarse and are commonly mixed with
granules and small pebbles of quartz and chert. The sand
grades locally into stringers and lenses of gravelwhich are
made up chiefly of pea-sized or slightly larger pebbles. In
addition to the large lenses of clay within the aquifer, small
amounts of white to gray clay are scattered throughout.
Fragments and layers of black lignite are found occasionally,
and at many places throughout both counties layers of black
carbonaceous sand and gravel, containing twigs and bits of
coal, are exposed at the surface. These layers range in
thickness from a few inches to more than 2 feet.

It seems likely that the materials in the upper part of
the sand-and-gravel aquifer were deposited in an environ-
ment similar to that of the present day Mississippi River
delta. This is suggested by the rapid facies changes, the
absence of fossils, and the abundance of sand and gravel.
These sediments were probably deposited by a network of
streams whose channels were constantly shifting back and
forth across the surface of the delta. In this environment,
clay was deposited in quiet pools or abandoned channels while
gravel was beinglaid down by swiftly flowing streams nearby.

The sand-and-gravel aquifer has a rather high average
porosity and permeability and is thus an excellent reservoir

INFORMATION CIRCULAR NO. 30

for ground water. The fact that the aquifer consists princi-
pally of relatively insoluble quartz grains accounts for the
remarkably low mineral content and softness of this water.
In contrast tothe rest of Florida, the ground-water conditions
inEscambia and Santa Rosa counties are complicated by the
great lithologic variability of the aquifer. Ground water is
under artesian pressure where lenses and layers of clay or
hardpan overlie a saturated, permeable bed. Ground water
is under nonartesian conditions where such clays and hardpan
are absent. It is notuncommonfor well totapboth artesian
and nonartesian water. It was not considered feasible to
construct a piezometric map because of the unpredictable
differences in'head throughout the area. Groundwater inthe
sand-and-gravel aquifer is derived largelyfrom rain falling
in the area.

Floridan aquifer: In the northern half of the area, the
sand-and-gravel aquifer is underlain by a thick sequence of
limestones known collectively as the Floridan aquifer. In
the southern half of the area the two aquifers are separated
by a thick clay unit of Miocene age (fig. 4). The Floridan
aquifer in Escambia and Santa Rosa counties is divided into
two parts by athick clay bed (Bucatunna clay member of the
Byram formation) near the top of the aquifer. The part that
lies above this clay bedwill be referred to in this report as
the upper limestone and the part below the clay as the lower
limestone.

The upper limestone is chiefly the Chickasawhay lime-
stone of late Oligocene age. Within the area, this formation
ranges in thickness from approximately 40 to 160 feet. Its
upper surface is an erosional unconformity of low relief
which dips gently toward the southwest. In the northern
part of Escambia County, the Chickasawhay apparently inter-
fingers with beds of sand and gravel. The Chickasawhay is
typically a brown to light gray hard dolomitic limestone or
dolomite with a distinctive spongy-looking texture. It contains
abundant shell fragments. Several wells in the area obtain
water from this limestone.

In the southern part of the area, the Chickasawhay
limestone is overlain unconformably by a remnant of the

FLORIDA GEOLOGICAL SURVEY

Tampa limestone of early Miocene age. This is a cream-
colored to light gray soft to hard sandy limestone which
contains shell fragments and abundant foraminifers. A few
wells in the southern part of the area obtain water fromthis
limestone.

The upper limestone is recharged partly by downward
leakage of water fromthe sand-and-gravel aquifer in northern
Escambia and Santa Rosa counties, Florida. Additional
recharge comes from rain that falls north of the area in
Escambia County, Alabama, and percolates southward or
southwestward through the upper limestone, which is under-
lain by the Bucatunna clay member of the Byram formation.

The lower limestone of the Floridan aquifer in this
area consists of the Ocala group of late Eocene age. The
top of the lower limestone, although an erosional uncon-
formity, is a relatively flat surface that dips gently toward
the southwest. The lower limestone rests unconformably
upon shale and clay of middle Eocene age. The lower lime-
stone ranges in thickness from about 300 feet in central
Escambia County to as much as 1,200 feet in the northern part
of Santa Rosa County (fig. 4). Thus, unlike most sedimentary
units along the gulf coast, this limestone thins rather than
thickens downdip. The lower limestone is white to grayish
cream and is rather soft and chalky. Well samples contain
as much as 30 percent very fine to very coarse sand, but
some of this probably caved from above during drilling.
Samples also contain some gray clay. Lenses of hard light
gray shale occur within the limestone, but these appear to
be randomly distributed and cannot be correlated from well
to well over any great distance. Much of this limestone
consists of foraminifers, corals, bryozoans, ostracods,
fragments of echinoids and mollusks, and other fossils.
Black phosphatic grains are locally plentiful.

Much of the Floridan aquifer in Escambia and Santa
Rosa counties is composed of highly porous and permeable
coquina consisting of fossil fragments. This aquifer contains
great quantities of ground water. Most of the water in both
the upper and lower limestones of the Floridan aquifer is
confined above and below by beds of relatively impermeable

INFORMATION CIRCULAR NO. 30

clay. Groundwater in the lower limestone, which constitutes
most of the Floridan aquifer, is derived mainly from precipi-
tation 15 miles or so north of the area in Escambia County,
Alabama. In the northern part of Escambia and Santa Rosa
counties some recharge may occur by leakage of water
through the Bucatunna clay member of the Byram formation
which overlies the lower limestone.

Aquicludes

Aquicludes within the sand-and-gravel aquifer: As
shown by the geologic section along the Perdido River in
Escambia County (fig. 5), the sand-and-gravel aquifer con-
tains discontinuous layers and lenses of clay and sandy clay.
The clay strata range in thickness from a few inches to
several tens of feet. For example, the Taylor Brick Company
of Molino in Escambia County mines clay from a bed that is
about 50 feet thick. The available data suggest that the clay
and sandy clay strata may range in length from a few feet to
several miles.

Another type of relatively impermeable layer within
the sand-and-gravel aquifer is hardpan. This rock, formed
by cementation of sand by iron oxides precipitated from
ground water, occurs extensively throughout westernmost
Florida and southern Alabama. This rock ranges inthickness
from a fraction of an inch to 4 feet. Little is known con-
cerning the lateral extent of these hardpan layers, but it is
unlikely that any layer extends for more than a few thousand
yards. Although the rock is dense, these layers are com-
monly filled with many curiously shaped cavities of uncertain
origin. The rockis rustbrownandis generally hard, although
some of it is soft. It is composed of iron oxides in the form
of limonite and goethite. Most "rock" on local drillers'
logs is hardpan. It is the only consolidated rock near the
surface in westernmost Florida, and it is widely used in the
construction of stone walls and occasionally inthe construc-
tion of buildings.

The relatively impermeable layers of clay and hardpan
affect ground water in several ways. First, they reduce the

FLORIDA GEOLOGICAL SURVEY

average permeability of the aquifer. Second, although ground
water in the sand-and-gravel aquifer probably is hydraulically
connected, owing to the discontinuity of the impermeable
beds, these layers (assisted by the hydraulic gradient) cause
the water beneath them to be under artesian pressure.
Third, where theselayers lie at or near the ground surface,
they decrease rechargeto the aquifer by reducing infiltration
rates and causing water tobe retained in depressions, where
it is evaporated. Several hundred ponds, large enough to
be shown on topographic maps, dot Escambia and Santa Rosa,
counties. Inconvenience is causedin some residential areas
by ponding of water above clay or hardpanlayers after heavy
rains. In some areas these layers underlie perched water
bodies and thus make small or moderate supplies of ground
water available at relatively shallow depths. Finally, these
layers are responsible for countless springs, which are
typically found at the heads of gullies and small box canyons
called steepheads. These canyons are notched into the
plateau-like areas that are remnants of marine terraces of
Pleistocene age. Excellent examples of such steepheads
are found on the Eglin Air Force Base, south of the Yellow
River. Here numerous small streams originate as springs
that discharge along clay or hardpan layers at the steepheads
of the gullies. As most of these springs occur at about the
same elevation, 50 feet or so above sea level, it seems likely
that they are emerging along the same relatively imper-
meable layer. The gullies wereformed by headward erosion
from the edges of the terraces.

Aquiclude between the two aquifers: A thick clay unit
of Miocene age (fig. 4, 6) lies between the sand-and-gravel
aquifer and the Floridan aquifer in the southern part of the
area. The observed thickness of this clay ranges from about
600 feet 1 miles southwest of Pensacola to about 240 feet
5 miles east of Milton. As shown by the structure-contour
map (fig. 6), the upper surface of the clayforms a westward-
trending trough which is more than 600 feet deep beneath
the upper part of Perdido Bay. This results in a corres-
pondingly greater thickness of the sand-and-gravel aquifer
above the trough.

UNITED STATES DEPARTMENT OF TIHE INTERIOfl
GfPJLOGICAI. W U Y
8Y40' st t' h' PW It' 10' O5' 7.l0oo' 56s' bo' 85065'

E S C A M R A COUNT T Y, AL A M A

ES CAMB I CO NT SANTAI ROSAL CO UN

5, 5--

50' 50,

S (ASSENT) (ABSENT) 45'
45 NIT

9A MIOCENE ?--

40 ] 4'

335, 5

30ro

20 0 4'o q0
is below oon coo2les l

080100- t f o
n92 Fn 0o

Bo. oml c U Geoo

hon top of Miocene clay unit.
/s 00a ov aiept to0 tI V
20",- q-500 I *

0 Well shown g ueprh to the top of
n Miocne clay unit, in feetyo

mean Soo level.
Contour interval 100 fet

87*40 35' 30' 25' 217 1010 67100' 55' 50 W45'
se compiled from US Geological
Survey topographic quadrongles

Figure 6. Map of Escambia and Santa Rosa counties showing contours
on top of Miocene clay unit.

INFORMATION CIRCULAR NO. 30

A few miles north of Cantonment, the clay interfingers
with beds of sand and gravel (fig. 4). Southward from Ensley,
the clay unit splits into two beds the upper about 100 feet
thick, the lower about 230 feet thick within the area -
separated by as much as 140 feet of sand.

The clay that makes up this unit is gray to dark gray
and contains much silt, very fine to coarse sand, and some
gravel. It is dated as Miocene on the basis of mollusks and
foraminifers. Apparently, this is the unit that local drillers
call the "Blue Marl. "

Aquicludes within the Floridan aquifer: The Bucatunna
clay member of the Byram formation of middle Oligocene
age (Marsh, 1961), which separates the upper and lower
limestones of the Floridan aquifer, underlies all of western-
most Florida and parts of Louisiana, Mississippi, and
Alabama. Withinthe area, the Bucatunna ranges inthickness
from about 45 feet in the northwest corner of Santa Rosa
Countyto 215 feet just north of Escambia Bay. The Bucatunna
rests unconformably upon the eroded surface of the lower
limestone of the Floridan aquifer and is overlain conformably
bytheflat, evenbase of the upperlimestone. The Bucatunna
consists of gray soft siltyto sandy clay containing foramini-
fers, ostracods, and a few mollusks. The unit crops out
along a belt that lies about 10 to 35 miles north of the area
in Alabama.

Although much of the Floridan aquifer is highly porous,
it contains zones of dense rock which were probably caused
by solution and re-precipitation of calcite. These dense
layers serve toprevent or retardupward movement of water
and thus may be classed as aquicludes.

The lower part of the Floridan aquifer contains thick
but irregular zones of gray hard slightly calcareous silty
clay-shale as much as 300 feet thick. As these zones are
near the base of the aquifer and are discontinuous, they
probably have little effect on the water in the limestone.
However, they reduce the average transmissibility (see p.68 )
of the aquifer.

INFORMATION CIRCULAR NO. 30

Aquiclude below the Floridan aquifer:. The Floridan
aquifer is underlain everywhere in the:area by gray shale
and clay of middle Eocene age. The. top of the shale and
clay although sloping generally southwestward, undulates
broadly, implying that these rocks were eroded before
deposition of the overlying limestone (fig. 4).

Regional Dip

The lack of exposures and observable bedding within
the sand-and-gravel aquifer makes it impossible to obtain
the strike and dip of this unit. However, the top of the
Bucatunna clay member presents a generally uniform, easily
identifiable surface whose attitude can be computed readily
(fig. 7). This surface strikes about N. 65* W. and dips about
30 feet per mile toward the southwest. Probably the sand-
and-gravel aquifer has a gentler dip. Although thetop of the
Floridan aquifer has not been contoured, it is safe to assume
that it also dips southwestward.

Relationship of Geology to Ground Water

Movement of Water

The direction of ground-water flow is determined
primarily by the pressure head from point to point. The
head, inturn, is determined by the hydrologic, geologic, and
topographic conditions between the recharge and discharge
areas. The relative position of rock layers of greatly dif-
fering permeabilities may have an important influence on the
direction of ground-water flow. Owing to the relatively
impermeable Miocene clay unit and the Bucatunna clay
member, which dip gently toward the southwest, ground
water in the Floridan aquifer probably is moving generally
southwestward in the area. On the other hand, the dip of
strata inthe sand-and-gravelaquifer is so slight that ground-
water flow in this aquifer is probably controlled principally
by differences in head resulting from local topographic
irregularities.

UNITED STATES DEPARTMENT OF THE INTERIOR
87*LOGICAL SUIJFY
87,0 30' HW''

ESCA MBIA

COUNTY,

A L A A M A

well EX PLAN
845 Number indickne depth to he top of
the Bucotunno clay member in fet
below mean io fal

0 I 2 3 4 5 6 7 8 9 0 Wih

TrON
A-

-A' Line of creos-soetn *Iie in file 3.

Re^" ribled di of the tp of tte
Bucetunno clay menma .

Contlou line represents the eonfil of He4 top of
the uCunno clay member in loM below wme
We iml. Contour internol 100 feet

Bose compiled from, S. G.osolcal
Srvey Wpog~ro quoadro n

Figure 7. Map of Escambia and Santa Rosa counties showing contours

on top of Bucatunna clay member of Byram formation.

31DO'

1oo00'

55'

INFORMATION CIRCULAR NO. 30

Just how faults affect flow of the ground water is not
known, but different resistivity readings on opposite sides
of faults, shown by electric logs, suggest that some salt
water may move upward along faults in the lower part of the
Floridan aquifer.

Relationship of Geology to Quality of Water

Zones of fresh and salty water: Most of the water in
the sand-and-gravel aquifer is fresh. The Floridan aquifer,
however, contains large quantities of both fresh and salt
water. In the northern half of the area, the uppermost few
hundred feet of the limestone beneath the Bucatunna clay
member (lower limestone of the Floridan aquifer) contains
fresh water. At depths greater than 1,200 feet, the lime-
stone contains salt water. In the southern part of the area,
the lower limestone contains only salt water. Here the
relatively impermeable Bucatunna clay member serves to
retard the vertical movement of water and thus to prevent
salt water in the lower limestone from moving upward and
contaminating the fresh water in the upper limestone. The
water in the upper limestone becomes salty downdip, a few
miles from where section A-A' (fig. 4) crosses the Perdido
River. The same is true of the water inthe sand-and-gravel
tongue that lies within the thick Miocene clay unit (fig. 4).
Although no samples of water from these salt-water zones
are available for analysis, zones of fresh and salty water
may be distinguished on electric logs. An analysis of more
than 40 electric logs was made for this purpose in the course
of the present study.

Mineralization and hardness of ground water: In addi-
tionto differences in salinity, groundwater inthe sand-and-
gravel aquifer and the Floridan aquifer differs in amount of
dissolved solids and hardness (see p. 71) because of differ-
ences inlithologyof the two aquifers. As might be expected,
water in the Floridan aquifer (composed mostly of limestone)
is harder and more mineralized than water inthe sand-and-
gravel aquifer, which is composed principally of relatively
insoluble quartz sand. As ground water percolates through
the sand-and-gravel aquifer, it encounters verylittle soluble

FLORIDA GEOLOGICAL SURVEY

material and consequently remains soft and virtually unmin-
eralized. The abundance of ground water remarkably low
in mineral content has influenced several large industries
to locate in Escambia and Santa Rosa counties.

Relation of quality of water to geologic history of the
Gulf Coast: For millions of years the Gulf coastal area has
been slowly subsiding, forming a vast sinking trough, or
geosyncline. As the trough sank, streams emptying into the
Gulf of Mexico kept the trough nearly full by dumping into it
huge quantities of mud, sand, and gravel. According to Howe
(1936, p. 82), "These sediments have been concentrated along
a narrow zone paralleling the present shore, and, since the
beginning of the Eocene, have accumulated to a thickness
which probably exceeds 30,000 feet [south of the Mississippi
River] the region of the present coastline has been
depressedunder the weight of these deposits to almost three
times the present maximum depth of the Gulf of Mexico.
The major axis of the gulf coast geosyncline approximately
parallels the Louisiana coastline .. "

Ground water in the Floridan aquifer in the Florida
peninsula is more or less mineralized because it moves
through soluble limestones. In Escambia and Santa Rosa
counties, however, these limestones have been depressed
hundreds of feet bythe sinking of the gulf coast geosyncline.
This circumstance made it possible for rivers and streams
to deposit the deltaic sand and gravel which make up the
principal ground-water aquifer in westernmost Florida.
Apparently the main area of subsidence did not extend far
enough to the east to depress greatly the limestones of
peninsular Florida.

SURFACE WATER

Escambia and Santa Rosa counties have an abundant
supply of surface water. More than 71 bgd flow into the
bays along the southern ends of the counties from the four
major rivers, the Perdido, the Escambia, the Blackwater,
and the Yellow. This adequate supply of surface water
allows many varied activities to be carried on within the
area.

INFORMATION CIRCULAR NO. 30

The following discussion on surface water describes
briefly the scope of the data-collection program and gives
interpretations of streamflow data, stream characteristics,
and chemical analyses by river basins. These basins are
outlined in figure 8.

The Collection of Data

The early streamflow data in Escambia and Santa Rosa
counties were collected at three stations one in each of
three major river basins. The collection of data began in

Figure 8. Basin map of the Perdido, Escambia,
Blackwater, and Yellow rivers.

.~L~-L---'L'~

FLORIDA GEOLOGICAL SURVEY

the Escambia River basin in 1934; 'in the Blackwater River
basin in 1938; and in the Perdido River basin in 1941. Data
at other points in these basins and also in the Yellow River
basin have been collected in Alabama and Okaloosa County,,
Florida. To meet the demand for more information about
surface water, the collection of streamflow data was started
on Pine Barren Creek in the Escambia River basin in 1952,
while prior to this, the collection of stage data on the lower
Escambia River, in the vicinity of the Chemstrand nylon
plant, was started in 1951. Chemical'analyses at two stations,
one on Pine Barren Creek and one on Escambia River, have
been obtained on a systematic basis since 1952.

The present program of investigation was started in
early 1958. This program will define the streamflow condi-
tions in the area and determine the water supply available.
Prior to the present investigation, stream gaging was limited
to the larger streams. The three earliest stations gaged
flow from drainage areas of 237, 394, and 3,817 square
miles. Gaged flow from smaller areas helps to define the
component characteristics of the larger basins and provides
a basis for computing, more accurately, flow from ungaged
areas. Also, as the economy of an area expands, more
importance is placed on the smaller streams. For example,
at Pensacola, the upper 11 square miles of the Bayou Marcus
Creek basin are being developed to provide storage reser-
voirs that will enhance the value of the land for residential
purposes. The present investigation collects data on drainage
areas as small as 11.2 square miles.

Nineteen data-collection sites were established as
part of the present program of investigation. Also, field
reconnaissances are being made throughout the area to relate
the characteristics of ungaged areas to gaged areas, to deter-
mine existing surface-water problems, and to determine
future demands on surface-water supplies.

The duration of surface water records is given in
figure 9, and the locations of data-collection sites are shown
on the map in figure 10.

INFORMATION CIRCULAR NO. 30

I 3byou trau.s Cn..k n.ar Pn...ool., rf. 11.

9 Dig Coldat.r Ivtr na.r Milton, 1a. 237

3 Big Juniper Craek n. r .arold, I. 142

4 six JIunlp Crank 6ear Mune on, 7la. 3

6 M1.k6anftr River iner Holt. Fla. 0 6

0 Bgruhy Crank n-r l.nut ll111, Fla. 40

7 Cano Crank Mr .lluff D Spring., 1Fa. -

8 X.6t Fark Coldnater Crmk near un.on, 1.a. 84

9 1lvn11le Cra0 k nar In.lty, 1Fl. -

10 X6Da1blI Cra.k At Flaouton. Al.. 335

11 .c..bl. b Ivr nMar Cetury, Fl. .117

14 IsJnan. arh ur Oh0onaul.., 1.
is I-.13 Rivr e n. r srllan, Ift. .

1< Jlk. n-h ...l Wkrogen, Fl, W.2

21 MooD,.ri Crek near urrimu P1rk, rf1 B.0

17 Prldoid R1vlr at Darrin7.u Park, Fla. 30

1S Perdido liver near o0ol6. Alm. -

19 Pinn Barren Craek nar barth., Fa. 75.3

0 Poad Crank near Milton. 6 i6a. 0.7

21 1wt.r1 Crie k -ar 1Munon, 1fa. 4

Is 3wnt Fork Coldlater Crmk t Cobbto0n, 71. 31.0B

as Tll. *Iver 6ne6r lolt, F1A. 1, 0

61r6t asn, 606.. Cheste11 6a6fl7e

Figure 9. Bar graph showing duration and types of

surface-water records in Escambia and

Santa Rosa counties, Florida.

FLORIDA GEOLOGICAL SURVEY

Occurrence and Quality

Surface water occurs in the area as streams, many
small natural ponds, a few manmade ponds, and estuarine
bays- Streams are the main source of fresh water. The
area has an abundance of streams carrying great quantities
of water of excellent quality. Small reservoirs created by
dams are, at present, few in number. .However, much of
theterrainlends itself well to smallreservoirs, and a larger
number will probably be built as the economy of the area
expands. The bays along the coast cover over 200 square
miles and provide excellent facilities for boating, fishing,
swimming, and shipping.

Tides from the Gulf of Mexico push salt water into the
bays and intothe lower reaches of the rivers. The salt-water
front extends farther upstream during periods of low stream-
flow, and it extends even farther upstream during periods
when low streamflow coincides with seasonal high tides.
The chloride content and flow of Escambia River are shown
on figure 11. This illustration shows that a high chloride.
content can be expected at the Chemstrand nylon plant,
7 miles upstreamfromthe mouth, whenthe flow of Escambia
River is low.

The presence of salt in the lower reaches of rivers
limits the usefulness of the water for some purposes. It is
also a potential source of contaminant to the adjacent supply
of ground water.

The quality of the area's surface-water is exceedingly
good. Fresh water in the streams above tide effect is ex-
tremely low in mineral content, is soft, and has very little
color. The small streams originating in the area have a
maximum mineral content of about 50 ppm. The Escambia
River, entering the" area from Alabama, has a maximum
mineral content of about 100 ppm. Minerals most prevalent
inthe streams are silica, calcium, sodium, iron, bicarbonate
and chlorides. Except for color imparted ,to the water by
flood runoff, the smaller streams are almost crystal clear.

87'3I

S-EXA1 TIN

-EXPLANATION-

UIrl mten rfew

sIr*mlf lwd i rew 1

NL olf "ll in

Na of oll In

osem s wpm ft
111 fig. 9

MEXICO

SULF

Figure 10.

Map of Escambia and Santa Rosa counties, Florida,
showing surface drainage and data-collection points.

1957

Figure 11.

1958

Chloride content of the Escambia River taken daily at
Chemstrand Corporation's cooling-water intake and
monthly flows of Escambia River at State Highway 4,
near Century, Florida, 1957, 1958.

INFORMATION CIRCULAR NO. 30

The ranges in mineral content for seven streams are
given in table 1. The most noteworthy characteristics of the
water are the low mineral content and the narrow range in
concentration. The latter indicates that seasonal fluctuations
are minor.

The quantity and quality of available surface water in
the area varies from place to place and from time to time.
The seasonal fluctuations follow very closely the pattern of
rainfall. The discussion that follows is concerned with the
availability and quality of surface water within the two- county
area.

Perdido River Basin

The Perdido River, the westernmost stream in Florida,
forms the north- south boundary between Florida and Alabama.
The part of the basin in Florida lies in a narrow band along
the eastern side of the main channel. Thefour major tribu-
tary streams on the Florida side of the river are Brushy
Creek, Boggy Creek, McDavid Creek, and Jacks Branch.
Elevenmile Creek and Bayou Marcus Creek, which flow into
Perdido Bay, are included in the discussion of the Perdido
River basin.

The basin, outlined on the map in figure 8, covers
925 square miles. Of this area, 238 square miles are in
Florida. Streams in the basin drain very hilly country.
The hills rise 100 tol50 feet above the stream valleys. The
fall of the Perdido River streambed from the northwestern
corner of the State to the town of Muscogee is 150 feet, and
fromMuscogee to Perdido Bay the fall is 15 feet (taken from
topographic maps).

Tidal fluctuations occur in the lower reach of the river.
The distance upstream from the mouth to the upper limit of
tide fluctuation depends on the elevation and slope of the
streambed and magnitude of the river flow. Tidal effect
will extend the greatest distance upstream during periods
whenthe riverflowis low and thetides are at seasonal highs.
During periods of low flow, tidal effects extend upstream to

Table 1. Range in Mineral Content for Seven Streams in Escambia and Santa Rosa Counties

Range in Iarts per million
Total
Number of dissolved Bicar-
Stream analysis solids Silica Calcium bonates Sodium Chlorides Iron *Color

Big Coldwater River
near Milton 13 11 21 2 11 0.6 2 2- 4 1 2 3 4 0.01 -0.4 5- 10

Big iuniper Creek
near.Harold 14 13- 24 6- 8 .6- 2 2- 7 1 2 2- 4 .02- .3 4- 25

Blackwater River
:nearHolt 13 14- 26 2- 10 .8- 1 1- 4 1 2 2- 4 .02- .6 4- .45

Escambia River
S near Century 127 47-101 5 21 1 -17 8-51 1 -10 3-22 .04- .7 4t- 120,

Perdido.River
iat BarrineauPark 44 17 52 5 15 .6- 3 1 -13 2 4 3 5 .03 .8 3- 60

Pie 'Barren Creek :
,, near Barth 49 11- 38. 2- 9 .4- 2 1- 6 .8- 2 1- 6 .01-1. 0,- 72

Fellow River- : '
nearMiligan 17 27- 53 4- 9 2 11 8-42 2 3 2 4 .00-.7 5-60

*Expressed in platinum-cobalt scale unite.

III

CA'

i
'',:? ''' i
1

11,1- .,

INFORMATION CIRCULAR NO. 30

the reach of the river between the U. S. Highway 90 crossing
and the town of Muscogee, 15 miles above the mouth. The
salt front, however, does not extend as far upstream as the
tidal effect. The upstream movement of the salt front can
be retarded or stopped by low-head dams serving as salt
barriers.

Throughout its length the Perdido River channel is
tortuous. The low-water channel inthe vicinity of Barrineau
Park is about 150 feet wide and winds through a thickly wooded
flood plain that is half a mile wide. The streambed is com-
posed of sand and gravel and is characterized by sandbars
and deep holes.

The steep hill and channel slopes cause high rates of
direct runoff. Consequently, floods in this basin are usually
of short duration. A rise in water level of 15 feet is not
uncommon at Barrineau Park. The highest flood of record
reached an elevation of 51. 5 feet above mean sea level in
March 1929. This is in comparison to a usual low-water
level of 28 feet above mean sea level. During the flood of
April 1955, which was the highest inthe 17-year period ending
in 1958, the river reached a peak flow of 39,000 cubic feet
per second at an elevation of 49.7 feet above sea level at the
Barrineau Park gaging station.

The consideration of floods and their effects on the
area is an essential item in planning developments adjacent
to the stream channel. The probability of future floods can
be predicted on the basis of floods that have occurred in the
past. From a study of the magnitude and frequency of past
floods, a means of estimating the frequency of floods has
been developed for Florida (Pride, 1957). Regional flood
frequency curves applicable tothis areahavebeen developed
from this report and are presented in figure 12.

Other items to be examined in considering an area for
development are data on the quantity and quality of water
available. If the minimumflow of a streamduring a reason-
ably long period of time is known to be above the anticipated
demand, the supply is adequate without storage. However,
if the minimum flow falls below the anticipated demand,

FLORIDA GEOLOGICAL SURVEY '

200,000

Figure 12.

DRAINAGE AREA, IN SQUARE MILES

Regional flood frequency curves for the Perdido,
Escambia, Blackwater, and Yellow River basins.

either of two measures can be undertaken. Storage reser-
voirs can be built to store water during periods of excess
flow for use during periods of deficient flow; or, if the
deficient flow is of short duration and occurs infrequently,
the use of water might be geared to the available supply.

Data collected at Barrineau Park (see table 1) show
the river water to be of very desirable quality. The mineral
content ranges from 17 to 52 ppm, with silica being the most
prominent mineral, having a range from 5 to 15 ppm. The
color of the water ranges from 3 to 60 units. A color of
20 units is considered the upper limit for drinking water.
Results of analyses from samples collected farther up-
stream, near the town of Nokomis, Alabama, indicate the
water there to be essentialythe same as at Barrineau Park.

INFORMATION CIRCULAR NO. 30

The low-flowfrequency curves given in figure 13 show
the frequency of average flows for the indicated periods.
For example, a discharge of 250 cfs will occur as a 1-day
average once in 2.6 years, or as a 30-day average once in
every 6 years.

The Perdido River basin yields copious quantities of
water. The average runoff at Barrineau Park is 25.9 inches
per year. That is, the average flow of 752 cfs (cubic feet
per second) for 1 year would cover the drainage area of 394
square miles to a depth of 25.9 inches. This is in comparison
withthe State average runoff that is estimated tobe 14 inches
per year (Patterson, 1955). The high yield of the Perdido
River basin can be attributed to twofactors: (1) a high annual
rainfall this area receives about 62 inches per year; and
(2)the coarse sand and gravel covering the area that release
water to the streams as seepage from the water table or as
artesian flow from local aquifers.

The pattern of variation of flow with respect totime is
similar to the rainfall pattern. March and April are by far
the months of highest runoff, and October stands out as the
month of lowest runoff. The bar graph in figure 14 shows
the average, maximum, and minimum monthly discharges
for the Perdido River at Barrineau Park for the 18-year
period 1942-59.

The flow-duration curve for Perdido River in figure 15
shows some other flow characteristics at Barrineau Park.
The slope of this curve indicates the variability of flow. This
stream has high flood flows, as well as relatively stable
flows during medium and low-water periods. The flow of
Perdido River is comparatively stable because of ground-
water seepage into the stream. The period of lowest flow
was caused by a prolonged period of deficient rainfall in
1954-56. The runoff at the Barrineau Park gaging station
reflects the average of all contributing areas above the
station.

Records of flow are being collected on four tributaries
in this basin. A cursory analysis of the low-water records

FLORIDA GEOLOGICAL SURVEY

1200

1100

1.5 2 3 4 b b tO
RECURRENCE INTERVAL, IN YEARS

I.U0 1.1

2U 30

Figure 13. Low-flow frequency curves for Perdido River
at Barrineau Park, Florida, 1941-58.

S-- Drainage area: 394 sq. mi
Average flow: 752

LOW-FLOW FREQUENCY
Example: For o 10-year recur-
rence Interval the I-day minimum
flow is 220 cfs and the 12-month-
minimum flow is 460 cfs

_\ I -,

r _-__

--\ .-^ -^- ^ -

1000

900

600

700

600

500

400

300

200

A

INFORMATION CIRCULAR NO. 30

2600
o
0
o
o 2400
w
U2200

W 2000
a.

S1800
w
LUJ

" 1600

1(400

1200

Figure 14.

Bar graph of the minimum, average, and maxi-
mum monthly discharge of the Perdido River at
Barrineau Park, Florida, 1942-59.

MAXIMUM

AVER AGE

JFMAMJA--SON

MINIMUM

J F M A M J J A S O N D

1000

800

600

400

200

0

FLORIDA GEOLOGICAL SURVEY

100o000
00,000
60.000
40,000

20,000
10.,000
8,000
6,000
4.000

2,000
1,000
goo

PERCENT OF TIME INDIATED DISOHIAROE
WAS EQUALED OR EXOEEDED

Figure 15. Flow-duration curves.

collected during the 2-year period, 1958-59, is included.
The purpose of this analysis is to give an indication of the
average yield from these gaged areas.

Brushy Creek drains 75 square miles 53 square
miles in the extreme northwest corner of Florida and 22
square miles in southern Alabama. The flowfromthis creek
enters the Perdido River 13 miles above Barrineau Park.
The low-water yield during the gaged period from the upper
49 square miles of this basin was at the rate of 20 inches per
year (47 mgd). The low-water yield of the Perdido River
at Barrineau Park during the same period was 10 inches per
year from 394 square miles. Based on the ratio of the low-
water yield to the average yield of the Perdido River, the
average yield of Brushy Creek would be 50 inches per year.
This yield ranks among the highest in the State.' The water
in this creek has a mineral content of about 25 ppm.

INFORMATION CIRCULAR NO. 30

McDavid Creek joins the Perdido River a mile above
Barrineau Park and has a low-water flow of about 20 cfs
(13 mgd) from a drainage area of 26.5 square miles. The
low-wateryield of this basin is estimated tobe 10 inches per
year, which is equal to the low-water yield of the Perdido
River above Barrineau Park. The mineral content of this
water is about 20 ppm.

Jacks Branch drains 24.2 square miles north of Canton-
ment and has an extremely low yield compared to other
streams in the area. A low flow of 4 cfs (2.6 mgd) was
measured from the upper 23. 2 square miles of this basin.
Converted to runoff in inches, this equals 2. 3 inches per
year. The mineral content of Jacks Branch is about 25 ppm.

Elevenmile Creek drains into the north end of Perdido
Bay and is used for industrial waste disposal. The water in
this stream has a mineral content of 400 to 900 ppm and is
extremely high in color.

Bayou Marcus Creek is the most downstreamtributary
in the Perdido River basin. It drains 25.9 square miles along
the northwestern outskirts of Pensacola and empties into
Perdido Bay. The lowest base flow recorded during the
2-year period, 1958-59, was 25 cfs (16 mgd). This flow is
from 11.2 square miles and equals 30 inches per year, which
is an extremely high base flow. The upper part of this basin
above U. S. Highway 90, is being developed for storage reser-
voirs to enhance the value of land for residential purposes.
Bayou Marcus Creek has a mineral content of about 30 ppm.

Escambia River Basin

The Escambia River is the largest source of surface
water within the study area and the fifthlargest in the State.
The basin as outlined in figure 8 covers 4,233 square miles,
of which413 square miles are in Florida. The main channel
starts near Union Springs, Alabama, as the Conecuh River
and flows in a southwesterly direction to the Florida-Alabama
State line near Century, Florida. Near the State line the
name changes to Escambia River. The Escambia River flows

FLORIDA GEOLOGICAL SURVEY

in a southerly direction and empties into Escambia Bay north
of Pensacola.

The Escambia River water at Century is not quite as
low in mineral content, 47 to 101 ppm, as water in the nearby
smaller streams. However, a mineral content. of 100 ppm is
not objectionable for many uses. The minerals present in
the largest quantities are silica (5 to 21 ppm), bicarbonates
(8 to 51 ppm), and chlorides (3 to 22 ppm). Other quality
data is given in table 1.

Foz purposes of discussion the basin is divided into
two parts, the lower and upper basins, with the divide being
at Pine Barren Creek. The lower part of the river exerts a
major influence on the area, not only because it serves as a
source of water supply but also because of its physical size
and location with respect to the fast developing industrial
area at Pensacola. The upper basin has many tributaries.
The lower basin is about 9 miles wide. The river channel
is tortuous and winds through a low, swampy flood plain
about 3 miles wide. Several estuarine channels extend into
the flood plain from Escambia Bay. Farther upstream two
islands within the flood plain are exposed during periods of
low river stages.

Flow in the lower river basin is affected by tide to a
point north of Brosnaham Island. The change in stage due
totide effect at the north end of the island was 1.8 feet during
a series of flow measurements made August 24, 1954, The
direction of flow does not reverse at that point. A tide range
of 2. 5 feet is not uncommon near the nylon plant of the
Chemstrand Corporation. An observation of flow conditions
made near the Chemstrand plant on October 22, 1952, showed
the flow to reverse at that point.

Below Pine Barren Creek the tributaries are short and
drain small areas. The ridges forming the drainage divides
vary in elevation from 150 to 200 feet above sea level. The
flood plain is about 15 feet above sea level near Pine Barren
Creek and slopes to sea level at Escambia Bay.

INFORMATION CIRCULAR NO. 30

The larger streams in the Escambia River basin with
watersheds in Florida are Pine Barren Creek, Canoe Creek,
and Moore Creek. Above Pine Barren Creek the basin
spreads out and larger tributaries join the main channel.

Pine Barren Creek drains an area of 98.1 square miles,
most of which is in Escambia County, Florida. The creek's
headwaters are near the town of Atmore, Alabama, 2 miles
north of the State line. The average yield of Pine Barren
Creek is 22 inches per year, about one-third of the rainfall
on the basin. A very substantial base flow of 60 cfs (39.9
mgd) has been measured from an area of 75. 3 square miles
above the gaging station. The magnitude of flow will be
different at any other point in the basin. Based on a flow
measurement of a tributary entering just below the gaging
station, it is reasonable to assume that the magnitude of flow
at any point in the basin is proportional to the size of the
area drained above that point.

The flow-duration curve for Pine Barren Creek in
figure 15 shows some of the streamflow characteristics at
the gaging station during the 6-year period, 1953-58.

The upper end of this curve, where it is almost vertical
represents short periods of exceedingly high flows. These
periods of high flow are a result of rainfall and basin physio-
graphy. As pointed out in an earlier section of this report,
the area receives large amounts of rainfall. The basin has
an elongated shape about six times longer than it is wide,
with steep hills and valley slopes. These factors give rise
to a short "time of concentration" of runoff. Rain anywhere
on the basin has to move only a short distance before reaching
the main channel. The steep valley slope of the main channel
allows this water toflow at high velocities to the next channel,
the Escambia River. The channel-bottom profile of Pine
Barren Creek is givenin figure 16. This channel has a slope
of more than 10 feet per mile.

The fast-changing rates of flow during floods in this
basin can be visualized more clearlyby comparing an aver-
age flowfor a day with the momentary peak flow. The mean

FLORIDA GEOLOGICAL SURVEY

too

,__
N1

.00_ _i ---i- -- -

NOTE. o I-- -- -

S a 4 4 I 3 I 14 1 2o0 1 24 al
CHANNEL DSTANCC AVA MOUTH. IN MILES

Figure 16. Channel-bottom profile of Pine Barren Creek.

daily flow for April 4, 1955, was 9,460 cfs and the peak flow
on the same day was 24, 800 cfs over 2 times greater.

The flow-duration curve for Pine Barren Creek,
figure 15, shows the percent of time a specified discharge
has been equalled or exceeded during a 6-year period. For
example, the mean daily flows at the gaging station were
greater than 62 cfs (40 mgd) for 97 percent of the time. If
an industry needs a water supply of 40 mgd, a deficiency
3 percent of the time might be tolerated if it were uniformly
distributed with only a few days of deficient flow in any con-
tinuous period. A deficient flow 3 percent of the time,
on the other hand, could prove disastrous if it came in a
continuous period of two months' duration. The data given
in figure 17 are helpful in determining probability of length

INFORMATION CIRCULAR NO. 30

of periods of deficient flow. The lowest average flow for a
specified period can be determined from the lower curve in
figure 17. For example, the lowest average flow for a
1-month period was 60 cfs (38. 8 mgd). The upper curve
shows the longest period of time that a specified flow was
deficient. The curve shows, for example, the longest period
that the flow was 60 cfs or less was 10 consecutive days.

10,000
8,000
6,000
5,000

o 3,000

n 2,000

S1000
BOO
600

L. 400
300
o
, 200
0

c 100
80
s 60
G 50

I 2 3 4 6 8 10 20 1 2 3 4 56 8 12
Consecutive Days Consecutive Months

24 48 72

Figure 17.

Discharge available without storage, Pine
Barren Creek near Barth, Florida, 1952-58.

Fromthis studyit canbe determinedif the flow is suf-
ficient for a particular use without storage. If storage is
needed to maintain a higher flow than the stream will produce
naturally, the amount of storage required can be determined
from the mass-flow curve given in figure 18. The volume

.

FLORIDA GEOLOGICAL SURVEY

o / -
2to

240

220

200
Storage required
12,000 cfs--days

NOTE- No allowance made for f
evaporation ond seepoge
losses.
z 160

140

S120

SStorg500 requireday

-so
80

60

40

0
0 1I 1 III U J.llll ll ll l l lll UIll ll ll I I II ll Illll lll IIIII lIlII
1952 1953 1954 195 195 1957 1956

Figure 18. Mass-flow curve for Pine Barren Creek
near Barth, Florida, 1952-58.

INFORMATION CIRCULAR NO. 30

of water required n a reservoir canbe determined by super-
imposing a line representing the flow required onto the mass
curve at such a position as to give the maximum distance
between mass curve and the flow-required line. The maxi-
mum distance represents the amount of storage required,
excluding losses by evaporation and seepage.

The Pine Barren Creek water is of excellent quality.
The mineral content did not exceed 38 ppm during the
period 1953-59. Silica is the predominant constituent with
a maximum measured content of 9 ppm. The iron content
has not exceeded 1.2 ppm. The water is almost colorless
most of the time.

The Moore Creek watershed lies within Santa Rosa
County. Theflowfromthis creek enters the Escambia River
just above Pine Barren Creek. Three discharge measure-
ments indicate the yield from this basin to be approximately
the same as Pine Barren Creek basin, about 22 inches per
year. Pine Barren Creek was flowing at about average rate
when the Moore Creek measurements were made. The
average flow from the upper 22.0 square miles of the Moore
Creek basin, based on these measurements, is about 35 cfs
(22.6 mgd). The mineral content of the water is about 20 ppm
and it has little or no color.

Canoe Creek lies mostly within Escambia County,
Florida, with its headwaters in Alabama. The channel bed
is lined with sand and gravel, and the banks are steep and
heavily wooded. Based on afield observation of the physical
characteristics of Canoe Creek basin, it appears that the
flow characteristics are similar to those of Pine Barren
Creek. The water is almost crystal clear and has a mineral
content of about 25 ppm.

The drainage area of the Escambia River at the Century
gaging station is 3, 817 square miles. The basin above the
Century gaging station is slightly elongated in shape, with
the longer axis lying in a northeast-southwest direction.
The Conecuh River is located along the southern edge of the
basin above Century. All the large tributaries have their

FLORIDA GEOLOGICAL SURVEY

headwaters along the northern edge of the basin and flow
south to the Conecuh River.

The seasonal distribution of flow at the Century gaging
station, although from a large area located in Alabama,
shows a pattern similar tothat of the smaller nearby streams
in Florida. The bar graph in figure 19 shows the seasonal
distribution of flows at the gaging station located on State
Highway 4 near Century for a 24-year period. The highest
flows occur in March and April while September, October,
and November flows are the lowest. The variation of flows
for any month canbe great. January, although not the month
of highest flow, has the greatest variation of flows with the
average monthly flows varying from a low of 1, 900 cfs to a
maximum of 31,500 cfs. The averageflows for October, the
month of lowest flow, have varied from 666 cfs to 6,520 cfs.

Some streamflow characteristics for the 24-year
period of record at State Highway 4 are expressed by the
flow-duration curve shown in figure 15. Based on the flow-
duration curve, the flow has been below 1,000 cfs (646 mgd)
for only 4 percent of the time. The maximum flow during
the 24-year period ending in 1958 was 73,900 cfs, and the
minimum flow recorded was 600 cfs (388 mgd). The com-
puted peak discharge for the flood of March 1929, which
reached an elevation of 66. 1 feet above sea level and rose
4. 5 feet above the floor of the bridge, was 315,000 cfs.
Regional flood-frequency curves for the Escambia River
basin are given in figure 12.

The average yield per unit area from the Escambia
River basin appears to be evenly distributed. Based on
records of the eight gaging stations that are located throughout
the basin, the average yield is about 20 inches per year,
ranging from a low of 18. 3 inches to a high of 21.5 inches.
The flows measured at these stations came from drainage
areas ranging in size from 75.3 to 3,817 square miles. The
average yield at the Century gaging station at State Highway 4
was 21.5 inches per year.

INFORMATION CIRCULAR NO. 30

I I I" l" I l I .1

Figure 19.

I 5 Il IN I

Bar graph of the minimum, av-
erage, and maximum monthly
discharge of the Escambia
River near Century, Florida,
1935-58.

FLORIDA GEOLOGICAL SURVEY

Blackwater River Basin

The headwaters of Blackwater River are in southern
Alabama, north of Bradley. The river enters Florida north
of Baker, flows across the northwestern corner of Okaloosa
County, and winds southward along the Santa Rosa-Okaloosa
county line for a distance of about 4 miles. At Bryant Bridge,
about 3 miles west of Holt, it turnstothe southwest and flows
toward Milton, receiving the flow from Big Coldwater River
and Big Juniper Creek on its way. At Milton it turns south-
ward and flows into Blackwater Bay.

The shape of the Blackwater River basin and the pattern
of drainage are similar to those of the Escambia River basin,
in that the main channel parallels the eastern and southern
edge of the basin and all major tributaries enter from the
north. The basin is well dissected by tortuous stream
channels that wind their way through a thick forest of pine
and juniper trees. Except during floods, the water is clear
and almost colorless and flows in clean channels of sand and
gravel. The quality of the water throughout the basin is
excellent, the mineral content ranging from only 11 to 26
ppm. Most of the land within the basin is covered by pine
forests, but some is used for row-crop farming.

The following discussion of streamflow is bytributary
basins, proceeding upstream in the following order: Pond
Creek, Big Coldwater River, Big Juniper Creek, and upper
Blackwater River.

Pond Creek's entire drainage area of 92 square miles
lies within Santa Rosa County. The creekflows in a southerly
direction and empties into the Blackwater River just south of
Milton. The basin has an elongated shape with relatively
short tributaries that drain directly from the steep hills that
slope toward the main channel. The land along the basin
divide is flat and is from 1 to 2 miles wide. From the flat
divide, however, the land slopes steeply to the stream
channel.

There are two channels within the lower three-fourths
of the Pond Creek flood plain. One of these is the natural

INFORMATION CIRCULAR NO. 30

channel which is very crooked and winding while the other is
a channel dug many years ago for transporting logs. The
valley slope is steep (fig. 20) with a total fall of about 200
feet from the headwaters to the mouth, a distance of 24 miles.

Pond Creek has large quantities of water that is low
in mineral content. The minimum flow from the upper 58. 7
square miles of drainage area during the 20 months ending
September 1959 was 43 cfs (27. 8 mgd). A flow of 43 cfs for
a year would cover the drainage area of 58. 7 square miles
to a depth of 10 inches; however, the average yield of this
stream is much greater- estimated to be 25 inches per
year. Rainfall on the area is about 62 inches per year.

Big Coldwater River is the largest tributary feeding
the Blackwater River. The total area drained by this tribu-
tary is 241 square miles, of which 230 square miles are in
Santa Rosa County, Florida. All except the smallest streams
in the Big Coldwater River basin have perennial flows, the
magnitude of flow generally being proportional to the area

22 ---- --- --

125

eo1
0 ------------------

0 I2 4 6 a 12 1 I Is 20 22 24 2
VALLEY DISTANCE AVE MOUTH, IN MILE

Figure 20. Channel-bottom profile of Pond Creek.
Figure 20. Channel-bottom profile of Pond Creek.

s

FLORIDA GEOLOGICAL SURVEY

drained. The average flow,from the entire basin of 518 cfs
is Z. 1 cfs (1.4 mgd) per square mile of drainage area.

Streamflow records have been collected for the past
20 years on Big Coldwater River. The gaging station near
Milton is located at State Highway 191 and measures flow
from 237 square miles. The flow-duration curve for Big
Coldwater River infigure 15 shows some streamflow charac-
teristics at this point. Other than the peaks caused by flood
waters that run off at a rapid rate, there are only minor
fluctuations inflow, because a large amount of water, seeping
into the streambed from the ground keeps the flow fairly
constant.

A useful arrangement of data is the group of low-flow
frequency curves given in figure 21. They show not only
what the lowest daily flow is likely to be but also how often

200

Drainage area: 237 sq. mi.
Avera e flow: 518 cfs

S LOW-FLOW FREQUNFCY
Example: For a 20 year recurrnce
Interval the 1-day minimum-
N flow Is 155 ofs and the 12-
Smonh minimum flow is

it monhe
9 moh -

120 days
--------- a a ^ ^l..^
a deas
30 days

day
I.051.1 1.5 5 3 4 a 10 20 30 40 50

RECURRENCE INTERVAL, IN

YEARS

Figure 21.

Low-flow frequency curves for Big Coldwater
River near Milton, Florida, 1938-58.

INFORMATION CIRCULAR NO. 30

it is likely to occur. For example, the minimum daily flow
of 200 cfs (129 mgd)for Big Coldwater River on the average
has a recurrence interval of about 5 years.

The seasonal distribution of runoff in Big Coldwater
River basin follows very closely the pattern of rainfall. The
distribution of monthly flows is given in figure 22. Heavy
spring rains cause high runoff, thus March and April have
the highest average flows. High-intensity rainstorms in
JulyandAugust cause highpeak flows. October is the month
of lowest flow.

Big Juniper Creek, which enters Blackwater River
5 miles above Big Coldwater River, drains 146 square miles,
of which 136 square miles are in Florida. The streambeds
in this basin are composed of loosely packed sand and gravel,
whereas the banks are steep and heavily wooded.

Four discharge measurements have been made on Big
Juniper Creek near Harold, 3 miles upstreamfromthe mouth.
The lowest of these measurements, made August 28, 1959,
was 175 cfs (113 mgd). Measurements were also made where
State Highway 4 crosses Big Juniper Creek and where it
crosses Sweetwater Creek. A flow of 42 cfs (27.1 mgd) was
measured at the State Highway 4 crossing of Sweetwater
Creek (drainage area, 45 square miles) onthe same daythat
Big Juniper Creek at State Highway 4 (drainage area, 36
square miles) was flowing at a rate of 35 cfs (22. 6 mgd).
The lowest flow of Big Juniper Creek at State Highway 4 for
the 20 months ending September 1959 was 25 cfs (16. 2 mgd).

The Blackwater River drains 276 square miles above
the Santa Rosa-Okaloosa county line and brings about 250
million gallons of water per day into Santa Rosa County. The
flow-duration curve in figure 15 is based on 8- years of rec-
ord collected at State Highway 4 in Okaloosa County. The
drainage area above this point is 205 square miles. The
daily flow varied during the period of record from a low of
60 cfs (39 mgd) to a high of 10, 300 cfs (6, 650 mgd). The
average flow was 245 cfs (190 mgd). The flood of December 4,
1953, reached a crest elevation of 81.3 feet above sea level
and a peak flow of 17, 200 cfs.

FLORIDA GEOLOGICAL SURVEY

2000
o
2O
0
w 1800
0n

1600

1400

1200

1000

800

600

400

200

0

Figure 22.

MAXIMUM

i 1 ,

-- AVERAGE

MINIMUM -

SJ F I M I A I M I J JJ IAI IS IN I D

Bar graph of the minimum, average, and maxi-
mum monthly discharge of Big Coldwater River
near Milton, Florida, 1939-58.

INFORMATION CIRCULAR NO. 30

Yellow River Basin

The headwaters of the Yellow River are in southern
Alabama, north of Andalusia and Opp. The river flows in a
southerly direction, entering Okaloosa County, Florida,
north of Crestview. South of Crestview, it receives the flow
from Shoal River, its largest tributary, turns southwestward,
and enters Santa Rosa County near Holt. From Holt it flows
southwestward and into Blackwater Bay.

The Yellow River drains 1,365 square miles, of which
only 115 are in Santa Rosa County. Although the percentage
of the basin in Santa Rosa County is small, the river exerts
a major influence on the area. The average flow entering
Blackwater Bay from the Yellow River basin is about 2,500 cfs.
This is the second largest flow in the two-county area; the
flow of Escambia River is the largest. Tides from the Gulf
of Mexico affect the flow in a large part of the 19-mile reach
of channel in Santa Rosa County. The main channel winds
through a heavily wooded, swampy, flood plain about 2 miles
wide. Several estuarine channels extend into the flood plain
from Blackwater Bay. From the Okaloosa County line to the
mouth there are several cutoff channels that leave the main
channel and re-enter farther downstream.

The tributary streams located in Santa Rosa County
are small and have exceedingly steepbanks. Their channels
have the appearance of gullies that were cut back into the
land by water flowing in from the upper end. Some of the
channels have been cut down as much as 80 feet below the
adjacent land surface. Most of the flow in these streams is
from springs.

GROUND WATER

Principles of Occurrence

Ground water is the subsurface water in the zone of
saturation, the zone in which all pore spaces are filled with
water under pressure greater than atmospheric. Ground
water is derived almost entirelyfrom precipitation. Part of

FLORIDA GEOLOGICAL SURVEY

the precipitation returns to the atmosphere by evaporation
and transpiration, part drains from the land surface into the
lakes and streams, and part reaches the zone of saturation
to become ground water. In addition, a small amount is
suspended in the zone of aeration as capillary water. Ground
water moves laterally under the influence of gravity toward
places of discharge such as wells, springs, streams, lakes,
or larger bodies of water.

Ground water may occur under either nonartesian or
artesian conditions. Where it is not confined, its surface is
free to rise and fall, and it is said to be under nonartesian
conditions. The upper water surface is called the water
table. Where the water is confined in a permeable bed that
is overlain by a less permeable bed, so that its water sur-
face is not free to rise and fall, it is said to be under artesian
conditions and the upper water surface in wells is called the
artesian pressure surface. The term "artesian" is applied
to ground water that is confined and under sufficient pressure
to rise above the top of the permeable bed that contains it,
though not necessarily to or above the land surface. The
height to which water will rise in an artesian well is called
the artesian pressure head.

An aquifer is a formation, group of formations, or
part of a formation in the zone of saturation that is
permeable enough to transmit usable quantities of water.
Places where aquifers are replenished are called recharge
areas, and places where water is lost from aquifers are
called discharge areas.

Hydrologic Properties of the Aquifers

Ground water in Escambia and Santa Rosa counties
occurs in two major aquifers a shallow aquifer, which is
both artesian and nonartesian(the sand-and-gravel aquifer),
and a deep artesian aquifer (the Floridan, aquifer). In the
southern half of the area, the aquifers are separated by a
thick section of relatively impermeable clay; but in the nor-
thern half the aquifers are in contact with one another.

INFORMATION CIRCULAR NO. 30

Sand-and-Gravel Aquifer

The sand-and-gravel aquifer is composed of sand but
has numerous lenses and layers of clay and gravel in it. In
the northeast corner of Santa Rosa County, the aquifer ex-
tends from the first saturated beds (near the land surface)
to a depth of about 350 feet. In the center of the area,
however, it extends to a depth of about 1,000 feet. This
aquifer lies at the surface in Escambia and Santa Rosa
counties.

The shallow saturated permeable beds in the sand-and-
gravel aquifer contain ground water under nonartesian con-
ditions, and the deep permeable beds contain ground water
under artesian pressure. The artesian water is confined by
lenses of clay and sandy clay. Most of the water inthe sand-
and-gravel aquifer is under artesian pressure.

The sand-and-gravel aquifer is recharged by local
rainfall, which infiltrates to the water table. The aquifer is
discharged by pumping; evapotranspiration; and seepage into
streams, swamps, bays, and the Gulf of Mexico.

Floridan Aquifer

In Escambia and Santa Rosa counties, the Floridan
aquifer is composed of two sections of limestone separated
by a thick clay bed. In the northeast corner of Santa Rosa
County, the upper surface of the Floridan aquifer is only
about 350 feet below the land surface, whereas in the south-
west corner of Escambia County the upper surface is more
than 1, 500 feet below the land surface, owing to the south-
westward dip of the aquifer.

The Floridan aquifer is thickest, 1,300 feet, in north-
central Santa Rosa County and thinnest, 600 feet, near the
Escambia River northeast of Cantonment (fig. 4). The thick-
ness of the Bucatunna clay member has not been included in
the above figures.

FLORIDA GEOLOGICAL SURVEY

The water in the Floridan aquifer is under high artesian
pressure. The artesian pressure head in wells drilled into
the upper part of the aquifer in southeastern Santa Rosa
County is from 30 to 70 feet above sea level (fig. 24). At
low land-surface elevations, large flows are obtained from
this aquifer; but the water is more mineralized than that
from the sand-and-gravel aquifer. Because suitable water
of low mineral content usually is available near the surface,
little use is made of the water from the Floridan aquifer in
this area.

The Floridan aquifer is recharged by rain in areas of
outcrop. The Floridan aquifer probably is recharged also
by percolationfrom the sand-and-gravel aquifer inthe north-
ern half of the area. The aquifer is discharged by seepage
into the gulf, upward or downward leakage, and pumping.

Movement of Water

Ground water in the sand-and-gravel aquifer moves
from higher toward lower elevations. Ground-water levels
usually correlate with land-surface elevations. Thus, inthe
two counties, the general areas of ground-water recharge
are indicated by topographic maps. Recharge is greatest
where the land is relatively flat. Water percolates downward
to the watertable and then moves laterally toward the places
of discharge.

The lower permeable beds in the sand-and-gravel
aquifer are recharged by percolation of water from upper
permeable beds through and around beds of clay or sandy
clay. The percolation results from differences in the hydro-
static heads within the permeable beds.

Water levels in an artesian well and a nonartesian well,
drilled into the sand-and-gravel aquifer, are illustrated by
figure 23. The wells are at OakGrovein northern Escambia
County,and are about 6 feet apart. Relatively permeable
and impermeable beds, as indicated by drill cuttings, and
changes in the water levels caused by the high rainfall in
1959 are shown in figure 23.

Sketch showing location of
wells I anid 2
Screen In
well 2
EXPLANATION

Relotlve jamoble
Relatlvel armeoble

Gravel
Sr^ In

71 I I I I I I I -

Depth, oft 1.. .. ,--.-' ..---. .

1
72----^-----

/

71
/

75 -- I I ,I I I -I I

Well I (Artesian)
Depth- 206 feet

/ C

89

0 MAY JUNE JULY AUG SPT OCT V DEC JAN F I AR
1959 1960

Figure 23.

Water levels in an artesian well and a nonartesian well drilled
into the sand-and-gravel aquifer in northern Escambia County,
Florida.

FLORIDA GEOLOGICAL SURVEY

Well 1 was drilled to a depth of 206 feet and is screened
from 201 to 206 feet in a permeable sand bed. Although the
top of the bed is 190 feet below the surface, the water in the
well rose to within 90 feet of the land surface. The artesian
pressure head gradually increased about 2 feet during the
period of record.

Well 2 was drilled to a depth of 107 feet and is screened
from 102 to 107 feet in a permeable sand bed. The water in
this bed is not under artesian pressure, and its upper sur-
face is free to rise and fall. The water level ranged from
about 71 to 75 feet below the land surface during the period
of record. The water level had a rapid rise during June-
September 1959, a slight rise from October to the end of the
year, and a slow decline in the first part of 1960.

The water level in well 2 generally stands from 14 to
16 feet above the water level in well 1, and, thus, water in
the upper permeable sands has the head potential to recharge
the lower permeable sands. The water level in the upper
sands shows more response to high rainfall than that in the
lower sands.

Ground-Water Velocities

The rate of ground-water flow under natural conditions
depends upon the slope of the water surface, the permeability
of the aquifer, and the temperature of the water. Jacob and
Cooper (1940, p. 50-51) calculated ground-water velocities
in the sand-and-gravel aquifer in the Pensacola area. The
average ground-water velocity between Cantonment and
Warrington, 16 miles apart, was computed by Jacob and
Cooper to be 0. 21 foot per day, or 77 feet per year. Using
the earliest water-level data available, Jacob and Cooper
computed the average velocity in the sands near Pensacola
Baytobe 0.37 foot per day, or 135feet per year. Thefigures
given represent the velocityunder natural, undisturbed con-
ditions. In the vicinity of discharging wells, the velocities
would, of course, be higher.

INFORMATION CIRCULAR NO. 30

Areas of Artesian Flow

Water will flow from artesian wells whenthe artesian
pressure head is higher than the land surface. The water
from rainfallpercolates into the ground in the higher, rela-
tively level land and moves downward and laterally toward
places of discharge. Some of this water is confined by
impermeable beds below which the water is under artesian
pressure. The areas of flow in the two counties are usually
relatively low lands along streams.

One area of artesian flow is at Molino, near the
Escambia River, where the artesian pressure head is more
than 20 feet above the land surface in places. At Pine Barren,
the artesian pressure head is as much as 30 feet above the
land surface.

Water from the Floridan aquifer is under sufficient
artesian pressure to rise to more than 30 feet above sea
level in the southeastern part of the area (fig. 24, well SR 8).
Thus, the areas of flow from wells that tap the Floridan
aquifer are generally at elevations less than 30 feet above
sea level. Examples of areas of artesianflow of water from
the Floridan aquifer are at Holley, Navarre, and Pensacola
Beach.

Storage of Water

The amount of water that may be stored in a rock or
soil is limited by the porosity of the material. The amount
Sof water that a saturated rock will yield when allowed to drain
is somewhat less thanthe porosity because some of the stored
Water will be held by capillarity.

The amount of water stored by an aquifer also depends
on whether the aquifer is artesian or nonartesian, for all
aquifers serve as both conduits and reservoirs. An artesian
aquifer functions primarily as a conduit, transmitting water
from places of recharge to places of discharge; however, it

FLORIDA GEOLOGICAL SURVEY

is capable of storing water by expansion, or releasing water
by compression. A nonartesian aquifer functions primarily
as a reservoir and can store a much larger quantity of water
for a given rise in the water level than can be stored in an
artesian aquifer.

Fluctuation of the Water Level

Water-level records show that the water surface is not
stationary but fluctuates almost continuously. Water-level
fluctuations result from variations in rainfall, evaporation
and transpiration, natural discharge, and pumping. Long-
term periodic measurements of water levels are used to
determine significant changes in the water level, to correlate
water levels and rainfall, and to show the influence of pumping
on the water level. These long-term records are needed to
distinguish between short-term fluctuations and progressive
trends.

Over most of the area, changes in the water level
correlate with rainfall. In the heavily pumped areas, water
levels reflect both the influence of the pumping and rainfall.

Figure 24 compares changes in the artesian pressure
head in a well drilled into the Floridan aquifer with changes
of the water level in a well drilled into the sand-and-gravel
aquifer. Well SR 8 at Holley is 1, 063 feet deep and obtains
water from the upper part of the Floridan aquifer from 716
to 1.063 feet below the land surface. Well SR 10, 8 miles
northeast of Holley, is 197 feet deep and obtains water from
the sand-and-gravel aquifer from about 140 to 197 feet below
the land surface.

The hydrograph for well SR 10 shows the water-level
changes during the last 12 years in an area where there is
not much withdrawal of ground water. The graph shows
close correlation with rainfall and reflects a very wet period
from 1944-49, a dry period from 1950-55, and a wet period
from 1956-59. The effect of 90.41 inches of rainfall in 1953,
the highest recorded in 80 years at Pensacola, is shown by
the rise in water levels during 1953 and the first part of
1954. However, this rise in the water level was canceled

INFORMATION CIRCULAR NO. 30 59

7 5 -1 I 1-1-I I 1 1 1
Well SR 8, at Holley(in the
Floridan aquifer)
Depth: 1,063 feet

70
-J

LII

u 65

SANTA ROSA CO
SSR IO
5 Holley

r 55
wSR 8

6-

I,
<50
?. U R Al

Figure 24. Hydrographs of wells SR 8 and SR 10.

FLORIDA GEOLOGICAL SURVEY

by the effect of the lowest rainfall on record, 28. 68 inches,
in 1954. Declining water levels during 1954 and the first
half of 1955 reflect this low rainfall. The maximum change
observed during the period of record was 13feet. The water
levelwas highest, 56feet above sea level, in1949and lowest,
43 feet above sea level, in 1955.

The hydrograph for well SR 8, which penetrates the
Floridan aquifer, shows similar fluctuations. The hydro-
graph shows the high artesian pressure head during 1947-49
and the sharp decline from 1950 through early 1956. Just
after the artesian pressure started to recover, the well
collapsed, and accurate measurements were no longer ob-
tainable. The hydrograph shows a maximum fluctuation of
21 feet. Artesian pressure was highest, 75 feet above sea
level, in 1949 and lowest, 54 feet above sea level, in 1956.
The artesian pressure head stood above the water level in
the sand-and-gravel aquifer during the entire period of record.

Well SR 8 is the only well in this area that taps the
Floridan aquifer and also has a long-term record. The
hydrographis included to showthe relationbetween artesian
pressure changes and rainfall, to illustrate the fluctuations
in artesian pressure inthe Floridan aquifer, and to compare
these fluctuations withthose in the sand-and-gravel aquifer.

Figure 25 contrasts changes of the water level in an
area little affected by pumping, as shown by well E 46 at
Ensley, with changes of the water level in areas of heavy
pumping, as shown by well E 45 at Cantonment and well E 74,
3 miles east of Cantonment. All three wells are in the sand-
and-gravel aquifer. In 1948 the water table at Ensley reached
its highest level during the period of record (75 feet above
sea level), and in 1956 the lowest level was recorded (49 feet
above sea level). From 1940 to 1959, the water level at
Ensley fluctuated 26 feet. Well E 46 is 239 feet deep. The
rise and fall of the watertable in this area, as shown by the
graph, closely parallels variations in rainfall. In general,
whenever the annual rainfall was less than 60 inches, the
water level declined; and whenever the annual rainfall ex-
ceeded 60 inches, the water level rose.

INFORMATION CIRCULAR NO. 30

Conlonment G AtA O SA
CO.
45
N C

SCAMIIA C O.
Pesncola

0 2 4 t 8 lOmlis

EXPLANATION

Water level, n feet
above mean sea level

Continuous record
AhI
Periodic record

20-- ----____

Well E 74, 3 miles
ealt of Cantonment
Depth 352 feel
\ i I I- I -

Will E46, fl Entity
Depth 239 fee

50
1 1-- 1- I I I frli i

Figure 25. Hydrographs of wells E46, E45, andE 74
and graph of yearly rainfall at Pensacola.

s I I I I

' I

I

1 v

FLORIDA GEOLOGICAL SURVEY

Figure 25 shows changes of water level in well E 45
(152 feet deep) at Cantonment. This hydrograph shows the
decline usually associated with continued, concentrated
pumping in an area. During 20 years of record, the water
level fluctuated 42 feet. The highest water levelwas 65 feet
above sea level in 1941, and the lowest was 23 feet above
sea level in 1957.

The hydrograph shows a decline in the water level of
more than 42 feet from 1941-56 due to continued and increased
pumping. The hydrograph shows the effect of the very high
rainfall in 1946-49 as a slight rise inthe water level followed
by a gentle decline during the 4-year period. The sharp
decline of the water level stopped in 1956, and late in 1957
the water level started to recover. The recovery is due
principally to the fact that several nearby wells that were
pumping water fromthe same zone were taken out of service
and also because the rainfall has been above normal in 1956,
1958. and 1959. Some of the recovery of the water level
during 1959 is due to a recharge experiment made by the St.
Regis Paper Company. During this experiment water was
pumped into a nearby well at a rate of a million gallons per
day for a year. The recharge well is located2,170 feet from
well E 45. An inspection of the hydrograph of well E 45 and
the calculated time-distance-recovery curves indicate that
this amount of recharge would cause the nonpumping water
level in well E 45 to rise from 1 to 2 feet.

The hydrograph for well E 74, about 3 miles east of
Cantonment and about 1 mile west-northwest of the Chem-
strand Corporation plant, is shown in figure 25. This well
is 352 feet deep and is screened from260-270 feet and from
340-350 feet below the land surface. The water level is prob-
ably affected by pumping at two nearby industrial plants, the
St. Regis Paper Company and the Chemstrand Corporation.
The graph shows a maximum change of 13 feet during the
8 years of record with the highest water level being 21 feet
above sea level in 1952 and the lowest water level being 8 feet
above sea level in 1959. The graph shows a rapid decline of
the water level from 1954 to 1956. The decline was due to
pumping and below-normal rainfall. The water level was

INFORMATION CIRCULAR NO. 30

nearly stable during 1957-59 owing to above-normal rainfall
and infiltration of the Escambia River into the well field of
the Chemstrand Corporation.

Figure 26 shows changes in the water level southwest
of Pensacola, as recorded in three wells. Two of the wells

Figure 26. Hydrographs of wells E 62, E 62-A, and E 39.

FLORIDA GEOLOGICAL SURVEY

(E 62 and E 62-A) are near the Newport Industries plant.
Well E 39 is in Warrington, about 2 miles southwest of the
plant. Well E 62 is 142 feet deep and is at Pensacola, 450
feet from Bayou Chico. The range of water-level fluctuation
in well E 62 was 14 feet during the 20 years of record. The
water in well E 62 was highest, 3.6 feet above sea level, in
1949 and lowest, 10. 8 feet below sea level, in 1955. The
water level in well E 62 is influenced by heavy pumping at
Newport Industries and by changes in rainfall. The water
level probably was lowered by pumping before water-level
measurements were started in 1940.

The hydrograph of wellE62 shows the water level has
been lowered by heavy pumping by Newport Industries.
Figure 26 indicates that the water level in well E 62 has been
below sea level since the summer of 195Z. As salt water in
Bayou Chico is only 450 feet from the well, the differences
in water levels could enable salty water from the bayou to
percolate into the aquifer in this area and destroy its use-
fttlness.

Figure 26 shows the graph of the water-level changes
in well E 62-A which was drilled beside well E 62. The
depth of this well is 17. 5 feet, and the recharge from rain-
fall percolates rapidly to the water table. The water level
fluctuated only 4.4 feet during the 20-year period of record.
The water level rose to 5.2 feet above sea level in 1956 and
fell to o.8 foot above sea level in 1951, 1955, 1957, and 1958.

The water level in well E 62-A has been above the water
level in well E 62 for most of the 20 years of record. The
greater head of the water in the upper permeable beds permits
some recharge to the lower permeable beds. However,
sotmeof the water from the shallow aone moves laterally into
Bayou Chico.

The water-level changes in well E 39 (247 feet deep)
at Warrington are shown in figure 26. The highest water
level was 6 feet above sea level, in 1940, and the lowest was
4 feet below sea level, in 1952. The graph shows a slight
decline of the water level during the last 20 years from 1940

INFORMATION CIRCULAR NO. 30 65

to 1959, probably owing to increased use of ground water
in the Warrington area. The water level declined below sea
level during the summer in 12 of the 20 years of record.
The years the water level dropped below sea level include
1943-45 and 1950-58. The lowering of the water level is
brought about by an increase in the use of ground water during
the summer.

The water level in well SR 102, half a mile east of the
Gulf Breere post office, is shown in figure 27. This well

10f
Well S 02

SIby i -a y pumlng
; PERIODS ol- AINIALL
iu
S10 .. .. ....... -.-. --I_ l O "-- --"- "
L(I
J Well SR 102

10 AINIALL A lTtPEN3AC na ol
o3 .. ....

$ Ig

-~j
LE 4

.rr .MAi I ML .L u I ..2. I tic Irr I C

Figure 27. Hydrographs of well SR 102 and graph of rain-
fall at Pensacola.

FLORIDA GEOLOOGIAL 8URkVEY

was drilled to a depth of 41 feet and the loWer 10 feet of the
well was equipped with a screen. During the 10=yar pe-riod
of record, the water level fluctuated 8. 6 feet. The highest
water level was 9. 8 feet above sea level, in 1959, and the
lowest was 1.2 feet above sea level1 in 1955.

Fresh ground water at Fairpoint Peninsula is derived
entirely from local rainfall. Some of the rainwater perco-
lates quickly through a few feet of sand to the water table.
Ground water then moves laterally and discharges into
Pensacola Bay or Santa Rosa Sound. The water in the sand-
and-gravel aquifer is under nonartesian conditions, and the
water level rises rapidly after intense rainfall and declines
slowly during prolonged periods without rain. The hydro-
graph of well SR 102 shows the response of the water level
to rainfall. Pumping from nearby wells alsohadan influence
on the water level in this well. Wells owned by the Santa
Rosa Island Authority pumped about 60,000 gpd during the
winter and about 120,000 gpd during the summer from 1951
to 1956. After 1956, when there was no pumping and rainfall
was above normal, the water level rose graduallytoa record
high in 1959.

The lower graph in figure 27 shows the water-level
changes in well SR 102 during 1959 and the monthly rainfall
at Pensacola. This hydrograph shows the rapid rise of the
water level that resulted from intense rainfall. The water
level changed only slightly until heavy rains in September
caused a rise of 2.5 feet. Additional heavy rains on October 10
caused another rise of 2. 5 feet. These rises brought the
water level near or above the land surface in some areas
aroung Gulf Breeze, causing some damage and considerable
inconvenience.

Temperature of Ground Water

The temperature of the earth's crust increases with
depth at the rate of about 1" F. for each 50 to 100 feet. The
temperature of ground water generally increases with depth
at approximately the same rate.

INt RMATION CIRCULAR NO. 30

Orobund-water temperatures in Escambia and Santa
iRtsa coutities from aquifers 50 to 250 feet deep usually range
ffom 66 to 73' F. This temperature range reflects the
average annual air temperature, which is about 68" F. at
Pensacola,

The temperature of water from aquifers in this area
usually increases about 16 F. for each 52 to 85 feet of depth
below 50 feet. For example, the geothermal gradient 9 miles
southwest of Pensacola, as shownby measurements made in
an oil test hole, is about 1 F. for each 81 feet of depth down
to 12, 500 feet. The temperature at the bottom of the hole
was 222 F.

Wells

Information has been collected on about 450 wells in
this area. Of these, 253 wells are in Escambia County and
202 are in Santa Rosa County. They range in depth from
about 15 feet to almost 1,400 feet, but most of them are
between 30 and 300 feet deep. They range in diameter from
14 inches to 30 inches. Most of the domestic supply wells
are 1- to 4 inches in diameter, and most of the industrial
supply wells are 10 to 24 inches in diameter. About 99
percent of the wells draw water from the sand-and-gravel
aquifer, and the rest draw water from the Floridan aquifer.

The larger diameter wells tapping the sand-and-gravel
aquifer are constructed by drilling an openhole until perme-
able strata (generally coarse sand or gravel) are penetrated.
Screens are then set in these permeable zones. Almost all
of these wells are equipped with screens.

The wells obtaining water from the Floridan aquifer
are constructed by drilling an open hole into the limestone,
then casing the well to the top of the limestone. The water
is obtained from the uncased limestone section. Sometimes
an open hole is drilled tothe top of the limestone, the casing
is firmly seated into the limestone, and drilling is continued
into the limestone below the bottom of the casing.

FLORIDA GEOLOGICAL SURVEY

Quantitative Studies

The withdrawal of water from an aquifer creates a
depression in the water table or artesian pressure surface
around the point of withdrawal. This depression generally
has the form of an inverted cone and is referred to as the
cone of depression. The amount by which the water surface
is lowered at any point withinthis cone is known as the draw-
down at that point. The size, shape, and rate of growth of
the cone of depression depend on several factors: (1) the
rate of pumping, (2) the duration of pumping, (3) the water-
transmitting and storage capacities of the aquifer, (4) the
increase in recharge resulting from the lowering of the
water surface, (5) the decrease in natural discharge from
the aquifer due to the lowering of that surface, and (6) the
hydrologic boundaries of the aquifer.

A measure of the capacity of an aquifer to transmit
water is the coefficient of transmissibility. This is the
quantity of water, in gpd (gallons per day), that will move
through a vertical section of the aquifer 1 foot wide and
extending the full saturated height of the aquifer, under a
unit hydraulic gradient, at the prevailing temperature of the
water. The coefficient of storage is a measure of the capacity
of an aquifer to store water. It is defined as the volume of
water released from or taken into storage per unit surface
area of the aquifer per unit change in the component of head
normal to that surface. These coefficients are generally
determined by means of aquifer test on wells.

Although no aquifer tests have been made during the
current investigation, many detailed tests have been made in
parts of the area. The coefficients determined bythese tests
are still applicable to the test areas and can be used for
hydrologically similar areas.

In the spring of 1940, Jacob and Cooper (1940, p. 33-49)
made several aquifer tests on wells owned by the city of
Pensacola and the U. S. Navy (at Corry Field). These wells
were drilled about 240 feet into the sand-and-gravel aquifer,

INFORMATION CIRCULAR NO. 30

and the lower half was screened. The average coefficient of
transmissibility for 120 feet of aquifer, as determined by
the tests, is 75,000 gpd per foot. This coefficient can be
used to calculate the effects of pumping on the water level
near Pensacola. The average coefficient of storage is
0. 00055. This relatively low average coefficient of storage
indicates that an effective confining layer overlies the sands
from whichthe water is withdrawn. However, this confining
layer does not extend over a large area.

The aquifer tests showthat artesian conditions existed
during thefew days of the tests and perhaps artesian condi-
tions would exist for as long as a few months after continuous
pumping started. Later, local recharge by leakage from
other parts of the sand-and-gravel aquifer would probably
occur at the edges of and through the confining layers which
would lessen the drawdown. Because of the effect of this
recharge, it has been found empiricallythat reasonably ac-
curate drawdowns can be predicted using a storage coefficient
of 0. 15 in this area. This empirical coefficient of storage
would give more reasonable time-distance-drawdown figures
than those calculated by using the average coefficient obtained
from the relatively short pumping tests.

In the fall of 1950, Heath and Clark (1951, p. 31-34)
made an aquifer test on the Fairpoint Peninsula in Santa Rosa
County. The test area was about half a mile east of the Gulf
Breeze Post Office. The wells penetrated the upper part of
the sand-and-gravel aquifer and the coefficients that were
determined apply to the upper 75 feet of the aquifer. This
part of the aquifer was found to have a coefficient of trans-
missibility of 34,000 gpdperfoot and a coefficient of storage
of 0. 23. This relatively high storage coefficient indicates
nonartesian conditions. Several curves relating pumping
rates andwell spacing to the resultant drawdowns are given
in the report by Heath and Clark (1951).

Several aquifer tests have been made during 1951-55
on some of the Chemstrand Corporation's wells, about 13
miles north of Pensacola. Each well is equipped with about
110 feet of well screen, usually made up in two sections.

FLORIDA GEOLOGICAL SURVEY

The screens are set inthe most permeable zones inthe sand-
and-gravel aquifer, between 170 and 380 feet below the land
surface. The average coefficients of transmissibility and
storage determined from these tests were 150,000 gpd per
foot and 0.001, respectively.

The coefficients of transmissibility and storage may
differ considerably from place to place; therefore, drawdowns
at one place cannot be predicted onthe basis of data collected
elsewhere. Figure 28 illustrates how water levels are af-
fected in the vicinity of a pumping well and may be used -to
predict drawdowns atvarious distances from the well. This
figure shows theoretical drawdowns in the vicinity of a well
pumping at the rate of 700 gpm (about 1 mgd) from an aquifer
having a transmissibility coefficient of 150,000 gpd per foot
and a storage coefficient of 0.15. As the drawdowns outside
the pumped well vary directly with discharge, drawdowns
for greater or lesser rates of discharge can be computed
from these curves. For example, as shown in figure 28,
under the assumed conditions, the drawdown 100 feet from
a well discharging at 700 gpm would be 4. 3 feet after 100 days
of pumping. If the well had discharged 2, 100 gpm for the
same length of time, the drawdown at the same distance
would have been three times as much, or 12. 9 feet.

Chemical Quality of Ground Water

Rain that falls on the earth's surface is practically
free of dissolved mineral matter. However, as it travels
through rocks composing the earth's crust, it gradually
dissolves them. The rock minerals constitute most of the
dissolved materials in ground water. Thus, the chemical
character of ground water is dependent in part on the type
of material through which the water flows. The quartz sand
(and gravel) of the sand-and-gravel aquifer is relatively in-
soluble; limestone and dolomite which constitute the Floridan
aquifer are among the most soluble of common rocks.

Mineralization of ground water may result from the
mixing of relatively fresh water with highly mineralized sea

INFORMATION CIRCULAR NO. 30

DISTANCE, IN FEET. FROM PUMPED WELL
IKn I

Figure 28.

rI *' ---- --- y -.-^- _.*? ^. ^^.tfi 'v

I -6

9- Computed on the basis of;
T-150,000 pd/fl
_0_ S x 0.15
Q0 700 gpm
Nofe Compulallons based on the assumption of a tightly
confined aquifer of large oerial exten without recharge.

Graph showing theoretical drawdowns in the
vicinity of a well being pumped at a rate of 700
gpm (about 1 mgd) for selected periods of time.

water that has not been completely flushed from the aquifer.
Ground water also may become mineralized as a result of
mixing industrial wastes with fresh water. Fresh ground
water also maybecome mineralized in areas near salt-water
bodies when the fresh-water table is lowered (usually by
pumping) and the salt water moves into the aquifer.

The principal mineral constituents and physical prop-
erties of the water from wells in Escambia and Santa Rosa
counties are discussed below. The concentration of mineral
constituents is given in parts per million -1 ppm is approxi-
mately equivalent to 8.34 pounds per million gallons of water.

Water containingless than 500 ppm of dissolved solids
is generally considered to be of good chemical quality al-
though, for some uses, certain constituents may be present
in objectionable quantities. The concentration of dissolved

01 nn00

01 0 0

FLORIDA GEOLOGICAL SURVEY

solids in water from the sand-and-gravel aquifer in Escambia
and Santa Rosa counties ranged from 13 to 465 ppm-generally
from 20 to 80 ppm. The concentration of dissolved solids
in water from the Floridan aquifer ranged from295 to 3,960
ppm.

Hardness of water is generally recognized because it
increases the consumption of soap and causes the formation
of scale in steam boilers or other vessels in whichthe water
is heated. Water having a hardness of less than 60 ppm is
considered soft; 60 to 120 ppm, moderately hard; 121 to200
ppm, hard; and more than200 ppm, veryhard. The hardness
of water is caused chiefly by calcium and magnesium. Ground
water from the sand-and-gravel aquifer ranged in hardness
from 3 to 379 ppm but was generally less than 25 ppm.
Ground water from the Floridan aquifer ranged in hardness
from 24 to 87 ppm.

As the chloride salts constitute about 90 percent of the
dissolved solids in sea water, the chloride content of coastal
ground water is generally a reliable index of the amount of
contamination from the sea. Water having a chloride content
of not more than 250 ppm is acceptable for a public supply,
nnd water having a chloride content of less than 500 ppm does
not taste objectionably salty to most people. The chloride
content of water from the sand-and-gravel aquifer ranged
from 1.0 to 16, 100 ppm, but most of the samples contained
from 3 to 15 ppm. The chloride content of water from the
Floridan aquifer ranged from 19 to 2,050 ppm.

The high chloride concentrations in ground water in
Escambia and Santa Rosa counties are from three sources.
The first source is salt water that entered the formation
during higher stands of the sea and has not been completely
flushed from the aquifer. Examples of this are found in the
lower part of the Floridan aquifer in the southern half of both
counties, in the upper part of the Floridan aquifer in the
southernmost part of both counties, and in the sand-and-
gravel aquifer at depths below 150 feet near Gulf Breeze.
The second source of high-chloride content in ground water
is from lateral encroachment from salt-water bodies. This

INFORMATION CIRCULAR NO. 30

encroachment occurs where pumping has lowered the water
tablebelow sea level, as near Bayou Chico. The third source
comes from industrial wastes that have high chloride con-
tent, as in northern Pensacola.

Fluoride is present in minor amounts in most ground
water. Water containing more than 1.5 ppm of fluoride may
cause mottling of children's teeth. In concentrations of about
1 ppm, fluoride is beneficial to dental health by reducing
tooth decay and is added to some public supplies for this
reason. The fluoride content of water from the sand-and-
gravel aquifer ranged from 0. 0 to 8. 5 ppm, but the water
usually contained less than 0. 1 ppm. The fluoride content
of water from the Floridan aquifer ranged from 0. 8 to 6. 5
ppm.

Iron occurs in almost all rocks, but the quantity of
iron dissolved by ground water is small in comparison with
the quantity of more soluble minerals. Water containing
more than 0.3 ppm of iron causes stains on fixtures, utensils,
and clothing; and water containing 0. 5 to 1.0 ppm or more
has objectionable taste. Iron as bicarbonate maybe removed
by aeration and filtration. The iron content of water from
the sand-and-gravel aquifer ranged from 0. 0 to 3.1 ppm.
However, the iron content of water from this aquifer is usually
less than 0. 1 ppm. The iron content of water from the
Floridan aquifer ranged from 0. 03 to 5. 0 ppm.

The pH indicates the degree of acidity or alkalinity of
a water and is an important indication of its corrosive tend-
encies. A pH below 7.0 indicates acidity, and apHabove 7.0
indicates alkalinity. The corrosiveness of water usually
increases as the pH decreases andis alsodependenton such
factors as dissolved carbon dioxide, dissolved oxygen, degree
of salinity, and temperature. The pH of the water samples
from the sand-and-gravel aquifer ranged from 4. 1 to 7. 3,
generally from 5.0 to 6.3, which indicates the water is
acid and corrosive. The pH of the water samples from the
Floridan aquifer ranged from 8.0 to 8.4, which indicates
the water is moderately alkaline and not corrosive.

FLORIDA GEOLOGICAL SURVEY

Most industries and public systems treat the ground
water to reduce its corrosiveness. Treatment includes the
addition of lime, soda ash, or some form of phosphate. This
treatment stops most of the corrosion of water pipes, water
heaters, and metals that the water contacts. Most of the
"yellow water" associated with untreated well water is a
result of the corrosion of the water upon metals.

Hydrogen sulfide is dissolved in some waters fromthe
sand-and-gravel aquifer and most waters from the Floridan
aquifer. This gas gives the water a distinctive taste and
odor. Waters containing it are usually called "sulfur water."

USE OF WATER

Surface Water

Only a small part of the area's surface waters are
being used. Recreation, shipping, cooling, and waste dis-
posal are the major uses of today (1960). These uses are
nonconsumptive in that no water is permanently removed from
the water body. Water used for cooling is removed from a
stream and returned with only a slight rise in temperature.
There are noknown major consumptive uses withinthe area,
and the full potential of the surface waters is farfrom being
realized.

Most uses of surface water are within the southern
half of the area. Principal among these are recreation and
shipping. The 200 square miles of bays are excellent for
boating, fishing, swimming, and other recreational activities.
The Intercoastal Waterway parallels the coast and allows
shipping in protected waters to and from Pensacola harbor.
The Chemstrand nylon plant and the Gulf Power plant use
water from the lower Escambia River for cooling purposes.
Elevenmile Creek is used for disposal of industrial wastes.
Small storage reservoirs are located on Bayou Marcus to
enhance the value of land.

INFORMATION CIRCULAR NO. 30

Yellow River Basin

The headwaters of the Yellow River are in southern
Alabama, north of Andalusia and Opp. The river flows in a
southerly direction, entering Okaloosa County, Florida,
north of Crestview. South of Crestview, it receives the flow
from Shoal River, its largest tributary, turns southwestward,
and enters Santa Rosa County near Holt. From Holt it flows
southwestward and into Blackwater Bay.

The Yellow River drains 1,365 square miles, of which
only 115 are in Santa Rosa County. Although the percentage
of the basin in Santa Rosa County is small, the river exerts
a major influence on the area. The average flow entering
Blackwater Bay from the Yellow River basin is about 2,500 cfs.
This is the second largest flow in the two-county area; the
flow of Escambia River is the largest. Tides from the Gulf
of Mexico affect the flow in a large part of the 19-mile reach
of channel in Santa Rosa County. The main channel winds
through a heavily wooded, swampy, flood plain about 2 miles
wide. Several estuarine channels extend into the flood plain
from Blackwater Bay. From the Okaloosa County line to the
mouth there are several cutoff channels that leave the main
channel and re-enter farther downstream.

The tributary streams located in Santa Rosa County
are small and have exceedingly steepbanks. Their channels
have the appearance of gullies that were cut back into the
land by water flowing in from the upper end. Some of the
channels have been cut down as much as 80 feet below the
adjacent land surface. Most of the flow in these streams is
from springs.

GROUND WATER

Principles of Occurrence

Ground water is the subsurface water in the zone of
saturation, the zone in which all pore spaces are filled with
water under pressure greater than atmospheric. Ground
water is derived almost entirelyfrom precipitation. Part of

INFORMATION CIRCULAR NO. 30

The surface waters within the northern half of the two
counties are virtually unused. Several small dams on the
Conecuh River in Alabama regulate slightly the flow of Es-
cambia River. The Florida Game and Fresh Water Fish
Commission operates afish hatchery in the Blackwater River
basin near the Santa Rosa-Okaloosa county line. Some of the
many small ponds in the area are used to water livestock.

Ground Water

Information was collected on the various uses of
ground water within the area in order to estimate the total
amount being withdrawn. These data are essential to show
areas of probable overdevelopment and areas of potential
development. Information on the use of ground water can
be compared with water-level graphs to estimate safe with-
drawals from an area.

Sand-and-Gravel Aquifer

Almost all the ground water used in Escambia and
Santa Rosa counties comes fromthe sand-and-gravel aquifer.
The daily consumption of ground water in both counties is
estimated to be about 86 million gallons approximately
60, 000 gpm. Figure 29 shows the approximate amount of
ground water used daily in the two counties. The quantities
of water are represented by the size of the circles. The
illustration shows that most of the water is used in southern
Escambia County and southwestern Santa Rosa County.

Use byindustries: Industries use the largest amount
of ground water in Escambia and Santa Rosa counties. The
industries use ground water at the rate of about 61 mgd.
The daily pumpage by industries is estimated as follows:

Paper and wood products .............. 45 mgd
Chemical plants...................... 15 mgd
Other uses (brewing,laundries, etc.) .... 1 mgd

FLORIDA GEOLOGICAL SURVEY

Use by municipalities:- The se.con ,-largest juse of
ground water in both counties is for public supply. Twelve
million gallons are used daily for this purpose.. .The .city
of Pensacola used an average of 10 mgd during 1959.- Other
public water supplies ar.e located at Milton, Jay, .-Century,
Warrington, Gulf Breeze, and Ferry Pass.

The city of Pensacola and other local suppliers make
a practical use of the low mineral content of the ground
water. Because the raw ground water requires little treat-
ment, the water can be treated at the well site. Therefore,
the wells can be drilled in the areas of need and the treated
water distributed from the well sites. Many public water
plants must pump the raw water to a central point where it
is treated and then distributed. Pensacola's method enables
the city to use smaller diameter distribution lines and to
space the wells farther apart. This wider spacing is good
practice because it eliminates the large cone of depression
caused by pumping closely spaced wells.

Use by agriculture: The amount of ground water used
for irrigation in both counties is small. Lawn and garden
irrigation accounts for most of the water used for irrigation.
Probably not more than 10 large-capacity wells have-b-ee
drilled in this area for irrigation. The need for irrigation
water is not great-because rainfall is fairly abundant during
the growing season. .

The amount of water available far exceeds the quantity
needed for irrigation, especially in the'northern half of the
counties. In many places, part of the water used forIrri-
gationpercolates downward to rechargethe sand-and-gravel
aquifer at the point where it was pumped.,

Supplies for domestic use: A sufficient quantity of
ground water for domestic use can be obtained by wells
almost any place in Escambia and Santa Rosa counties. Wells
in the area are usually less than. 150 feet deep;, "and many
are less than 100 feet.deep. The wells are screenedL in the
permeable sand or gravel. The pernmeble zones ,.ii- which
the screens are set, are located by inspection of the drill
cuttings while the well is being drilled.

i11 I il I I : I_ ______ '

F 5 C A M B I A C 0 U N T Y A L A B A M A

8i0 1 -_ ___ -- -_ 310Co
CE S C AMC MA CO TY IANTA ROSA r.OiJI TY
/*0' MB CANTONMENT l N.0c

F L 0cen tu I D A

55' 55,

,* 550

45' 45N

v ,

dailySt. Regis Poper O 40'i
4' company d V 0

0 MMILTON

CANTONMENT A Columbia Nalional Milton ..o
C- corporation t
S ambia Chemica
35, A'- Corporation 35
C)Amerlcon Cyanamid o -

30'30,

supply
A S I Ir A y

25'- 25'

20'

I.'. 5

U 9 5 0 million gallons per day
Diameters of circles represent total daily use of water in millions of gallons

0 I 2 3 4 5 6 7 8 9 0 miles

?740 35' I0 25'. 1 0' O' o 50' G,.!5'

Figure 29. Map of Escambia and Santa Rosa counties showing the
daily consumptive use of ground water by industries
and municipalities during 1958.

INFORMATION CIRCULAR NO. 30

The number of persons using ground water from
private wells for domestic purposes is estimated to be
60,000 in Escambia County and 20,000 inSanta Rosa County.
The water used by these people, estimated to be 9 mgd in
Escambia County and 3 mgd in Santa Rosa County, is only a
small part of the total amount available. As each well with-
draws only a small amount of water, and because the wells
are widely spaced, the effect of this pumping on the water
table is slight.

Floridan Aquifer

The quantity of water withdrawn from the Floridan
aquifer by wells in Escambia and Santa Rosa counties is
small. Probably not more than five wells obtain water from
this aquifer. The use of water from this aquifer is small
because sufficient quantities canbe obtained, generally, from
the overlying sand-and-gravel aquifer, because the water is
high in mineral content, and because deep wells are expensive.

WATER PROBLEMS

Problems concerning water resources can be divided
into those resulting from natural causes, those arising from
man's use of water, and those resulting from a combination
of both.

Problems from Natural Causes

Water problems arising from natural causes are usually
associated with too little or too much rainfall. Deficient
rainfall causes the water level in wells to decline, runoff
from streams to decrease, and pond levels to be lowered.
Excess rainfall may cause flooding of lands that are poorly
drained and lands adjacent to streams.

FLORIDA GEOLOGICAL SURVEY

Most industries and public systems treat the ground
water to reduce its corrosiveness. Treatment includes the
addition of lime, soda ash, or some form of phosphate. This
treatment stops most of the corrosion of water pipes, water
heaters, and metals that the water contacts. Most of the
"yellow water" associated with untreated well water is a
result of the corrosion of the water upon metals.

Hydrogen sulfide is dissolved in some waters fromthe
sand-and-gravel aquifer and most waters from the Floridan
aquifer. This gas gives the water a distinctive taste and
odor. Waters containing it are usually called "sulfur water."

USE OF WATER

Surface Water

Only a small part of the area's surface waters are
being used. Recreation, shipping, cooling, and waste dis-
posal are the major uses of today (1960). These uses are
nonconsumptive in that no water is permanently removed from
the water body. Water used for cooling is removed from a
stream and returned with only a slight rise in temperature.
There are noknown major consumptive uses withinthe area,
and the full potential of the surface waters is farfrom being
realized.

Most uses of surface water are within the southern
half of the area. Principal among these are recreation and
shipping. The 200 square miles of bays are excellent for
boating, fishing, swimming, and other recreational activities.
The Intercoastal Waterway parallels the coast and allows
shipping in protected waters to and from Pensacola harbor.
The Chemstrand nylon plant and the Gulf Power plant use
water from the lower Escambia River for cooling purposes.
Elevenmile Creek is used for disposal of industrial wastes.
Small storage reservoirs are located on Bayou Marcus to
enhance the value of land.

FLORIDA GEOLOGICAL SURVEY

Periods of Low Rainfall

Decline of water levels: The relationship of the change
in ground-water levels to rainfall is shown by the hydr ographs
of wells in this area. During periods of low rainfall, the
water level declines. This results in additional pumping
costs, drying up of shallow wells, and salt-water encroach-
ment. In well E 46 at Ensley, the water level dropped more
than 9 feet in 1950 and again in 1954 (fig. 25). These declines
were due to a reduction in recharge brought about bybelow-
normal rainfall.

The level of ponds drops during low rainfall periods
and some ponds dryup entirely. Streamflow decreases during
the dry periods.

Salt-water encroachment: Low ground-water levels
and below-normal streamflow, brought about by lack of rain,
allow salt-water encroachment into surface and ground-water
supplies. The streamflow decreases during periods of low
rainfall and the salt-water front moves upstream during this
period. Studies are necessary to determine salinity values
and the range of movement of the salt-water front.

Lowered ground-water levels may allow upward salt-
water encroachment or lateral encroachment. Upward
encroachment is possible where the upper aquifer contains
fresh water and the lower aquifer contains salt water and
the head in the lower aquifer is higher than, the head in the
upper aquifer. Lateral encroachment into ground water
from surface bodies of salt water is possible where the
ground-water level does not have sufficient head. The
danger of salt-water encroachment occurs during periods
of low rainfall in areas of heavy pumping.

INFORMATION CIRCULAR NO. 30

Periods of High Rainfall

Periods of moderately high rainfall are desirable
because the amount of ground water in storage is increased
and streamflow becomes greater. However, severe problems
such as floods or ponded water may result from excessive
rainfall.

Every stream in the area responds to rain falling in
its basin. It is important for local residents having property
that is subjected to flooding to know the level to which a
river will rise. The height to which a stream will rise de-
pends on the amount and distribution of rain and the physical
characteristics. of the river basin. The stages of some of
the smaller streams in the area vary as much as 15 feet
while stages of some of the larger streams vary as much
as 36 feet. The magnitude and frequency of floods are import-
ant to engineers in charge of designing river appurtenances
(bridges, dams) and other structures in the flood plain. Data
on the magnitude and frequency of floods in the area are
presented in figure 12.

Another problem associated with intense rainfalls is
ponded water. Ponded water occurs in areas where the land
is flat and drainage facilities are inadequate. Examples of
this can be found near Pensacola. Water stands inlow spots
for varying lengths of time after each intense rain. This
ponded water leaves some areas only by evaporation and
infiltration. In these areas the problem can be made worse
by developments such as paved streets, houses, and lawns
that cause an increase in the rate of runoff to the ponded
areas. The problem of ponded water can be solved by pro-
viding adequate drainage.

Ponded water can also occur where the water table
intersects the land surface. This happened near the com-
munity of Gulf Breeze during the fall of 1959 when heavy
rains caused the water table to rise rapidly (fig. 27) and low
lands were flooded. The figure shows the slow decline of
the water table following abrupt rises. Surface drainage or
pumping are the most effective methods for removing the
excess water.

FLORIDA GEOLOGICAL SURVEY

Manmade Problems

Water resources problems caused by man are usually
associated with heavywithdrawal of groundwater in an area;
the pollution of ground water or surface water by industrial
wastes; or structures that alter drainage, infiltration, or
runoff characteristics.

Large Drawdowne

Large industries usually require a continuous supply
of water. Prolonged pumping of ground water causes draw-
downs of the water level in proportion to the number of wells,
rate of pumping, and spacing of wells. Such drawdowns
increase the cost of pumping water and cause the cone of
depression to extend farther outward than is desirable,

An example of large drawdowns can be found at
Cantonment. Figure 25 shows that the water level in well E 45
declined more than 42 feet from 1941 to 1956. This decline
was mainly the result of heavy pumping although low rainfall
was a contributing factor. During the 15-year period the
water level declined at an average rate of 2.8 feet per year.

Salt- Water Encroachment

Salt-water encroachment canbe a serious "side effect"
when water levels are lowered near bodies of salt water.
If the sediments betweenthe salt-water body and the aquifer
are relatively impermeable, the rate of salt-water encroach-
ment is slow; if these sediments are relatively permeable,
the rate of encroachment is high.

An example of a slow rate of encroachment is shown
by industrial wells near Bayou Chico where several years
of heavy pumping lowered water levels, below sea level
(fig. 26). As a result of this lowering, water from wells
nearest the bayou slowly became salty, and it became
necessary to drill replacement wells farther away from the
bayou. Usually several years were required after the chloride

INFORMATION CIRCULAR NO. 30

The number of persons using ground water from
private wells for domestic purposes is estimated to be
60,000 in Escambia County and 20,000 inSanta Rosa County.
The water used by these people, estimated to be 9 mgd in
Escambia County and 3 mgd in Santa Rosa County, is only a
small part of the total amount available. As each well with-
draws only a small amount of water, and because the wells
are widely spaced, the effect of this pumping on the water
table is slight.

Floridan Aquifer

The quantity of water withdrawn from the Floridan
aquifer by wells in Escambia and Santa Rosa counties is
small. Probably not more than five wells obtain water from
this aquifer. The use of water from this aquifer is small
because sufficient quantities canbe obtained, generally, from
the overlying sand-and-gravel aquifer, because the water is
high in mineral content, and because deep wells are expensive.

WATER PROBLEMS

Problems concerning water resources can be divided
into those resulting from natural causes, those arising from
man's use of water, and those resulting from a combination
of both.

Problems from Natural Causes

Water problems arising from natural causes are usually
associated with too little or too much rainfall. Deficient
rainfall causes the water level in wells to decline, runoff
from streams to decrease, and pond levels to be lowered.
Excess rainfall may cause flooding of lands that are poorly
drained and lands adjacent to streams.

INFORMATION CIRCULAR NO. 30

content of the water from a well started increasing before
the water became too salty for use.

An example of a rapid encroachment occurred along
the Escambia River at the Chemstrand nylon plant. Nearby
pumping caused the ground-water level tofall below sea level
for the first time in 1955, and it has remained below sea
level most of the time since 1955. In 1956, there was an
increase from 10 ppm to more than ,100 ppm in the chloride
content of water from a well about 500 feet west of the
Escambia River.

Figure 11 shows the chloride content of the Escambia
River at the Chemstrand nylon plant cooling water intake.
During 1957 and 1958, the chloride content of the Escambia
River was above 25 ppm for about Z5 percent of the time.
Thus, the salt-water front can advance at least 7 miles above
the mouth of the river.

Figure 30 shows the lowering of ground-water levels
and their relation to the level of the Escambia River. The

Note Vetiicl ioggOeraoln obol l 100 limt
~ h-------15 40 mii~s -

Figure 30. Cross section showing the decline of water levels
in the vicinity of Cantonment, Florida.

FLORIDA GEOLOGICAL SURVEY

figure is a cross section from Cantonment eastward to the
Escambia River. The water table was above the river level
in 1951 and doubtless was contributing water tothe Escambia
River. Since 1955 the water table, adjacent to the river, has
usually been below river level and water from the river has
infiltrated into the well field. Ordinarily this infiltration
fromthe river would be a desirable featurebecause it would
recharge the aquifer and decrease the drawdowns. However,
because the Escambia River is salty part of the time (fig. 11),
the infiltration introduces salt water into the sand-and-gravel
aquifer adjacent to the river.

A study of electric-log resistivities indicates that the
water in a thick clay section (fig. 4) below the sand-and-gravel
aquifer at Chemstrand is salty. As this clay is virtually
impermeable, the salt-water encroachment is not believed to
comefromthis source. Also, the well nearest the Escambia
River was the first to show an increase in the chloride content
of the water. In addition, infiltration of water fromthe river
into the aquifer could explain the fact that the ground-water
level has generally stabilized. These conditions indicate
strongly that the salt water in some wells at the Chemstrand
nylon plant is coming from the Escambia River by lateral
encroachment.

Industrial Waste Disposal

The complex problem of disposing of industrial wastes
is very important because these wastes can pollute both
surface- and ground-water supplies. A thorough knowledge
of the geology and hydrology of an area is valuable in planning
for safe disposal of industrial waste. Some industries in
this area presently discharge wastes directly into streams,
bays, and infiltration ponds.

Disposing of waste into surface-water bodies may cause
objectionable odors, kill fish and plant life, discolor the
water, and cause the accumulation of solid waste materials.
A knowledge of streamflow is very helpful in determining the
dilution necessary to keep the concentration of plant wastes

MILLISECOND	CLASS.METHOD	MESSAGE
0	sobekcm_page_globals.constructor
0	sobekcm_page_globals.constructor	Application State validated or built
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.constructor	Navigation Object created from URI query string
0	sobekcm_database.verify_item_lookup_object
0	sobekcm_page_globals.display_item	Retrieving item or group information
0	sobekcm_page_globals.get_entire_collection_hierarchy	Retrieving hierarchy information
0	sobekcm_assistant.get_entire_collection_hierarchy
0	cached_data_manager.retrieve_item_aggregation
0	cached_data_manager.retrieve_item_aggregation	Found item aggregation on local cache
0	item_aggregation_builder.get_item_aggregation	Found 'all' item aggregation in cache
0	system.web.ui.page.page_load (ufdc.page_load)
0	sobekcm_page_globals.constructor.on_page_load
0	html_echo_mainwriter.add_style_references	Adding style references to HTML
0	html_echo_mainwriter.add_text_to_page	Reading the text from the file and echoing back to the output stream
73	html_echo_mainwriter.add_text_to_page	Finished reading and writing the file

	Title Page
	Preface
	Table of Contents
	Abstract
	Introduction
	Geology
	Ground water
	Use of water
	Water problems
	Potential water supplies
	References