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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY




FLORIDA GEOLOGICAL SURVEY Robert 0. Vernon, Director




REPORT OF INVESTIGATIONS NO. 41




WATER RESOURCES
OF THE
ECONFINA CREEK BASIN AREA
IN
NORTHWESTERN FLORIDA
By
R. H. Musgrove, J. B. Foster, and L. G. Toler


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
FLORIDA GEOLOGICAL SURVEY

TALLAHASSEE
1965










FLORIDA STATE BOARD

OF

CONSERVATION


HAYDON BURNS
Governor


TOM ADAMS
Secretary of State




BROWARD WILLIAMS
Treasurer




FLOYD T. CHRISTIAN
Superintendent of Public Instruction


EARL FAIRCLOTH
Attorney General




FRED 0. DICKINSON, JR.
Comptroller




DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director






LETTER OF TRANSMITTAL


91oria Ojeologica! Qlirvey

TALLAHASSEE

July 20, 1965

Honorable Haydon Burns, Chairman Florida State Board of Conservation Tallahassee, Florida

Dear Governor Burns:

The Florida Geological Survey will publish, as Report of Investigations No. 41, a comprehensive report on the water resources of the Econfina Creek Basin area in northwestern Florida. This report was prepared by the members of the U. S. Geological Survey in cooperation with the Florida Geological Survey, as a part of its water resources study program.
The Econfina Creek is one of the largest discharging streams of the State, and its potential for meeting water resources needs is great. The publication of the total resources study, to be accomplished in a series of papers, will contribute toward the stabilization of the economic development of the Panhandle area, and will provide a basis upon which a large water-using economy can be based.

Respectfully yours,
Robert 0. Vernon,
Director and State Geologist




























Completed manuscript received
April 30, 1965
Published for the Florida Geological Survey By The St. Petersburg Printing Co., Inc.
St- Petersburg, Florida 1965





PREFACE


In the planning and preparation of this report we have tried to present the essential information that would provide a brief, concise description of the water resources of the Econfina Creek basin area. The report was designed to supply answers to general questions of the many people interested in the water resources of the basin. Other reports on particular aspects of the water resources of the basin will present more detailed information about a phase of the hydrology or geology of the basin. This report is intended to furnish the background from which the reader may refer to the phase reports for more. definitive treatments of a particular subject.
Special phases of the water resources of the basin will be featured in reports on: Deer Point Lake; The Deadening area of southeastern Washington County; geology and aquifers of Bay County; and a quantitative study of ground water in the Panama City area. In addition, the basic data available through the period of investigation will be published in the information circular series of the Florida Geological Survey.
This report was prepared by the Water Resources Division of the U. S. Geological Survey in cooperation with the Florida Geological Survey. The investigation was under the general supervision of Robert 0. Vernon, Director, Division of Geology, State Board of Conservation; A. 0. Patterson, district engineer, Surface Water Branch; C. S. Conover, district engineer, Ground Water Branch; and K. A. Mac Kichan, district engineer, Quality of Water Branch, of the U. S. Geological Survey.
A number of individuals and organizations have been most generous in supplying information, equipment, and time in the process of collecting data for this report. The courtesies extended by the following persons are most appreciated: W. C. Cooper of W. C. Cooper Plumbing and Heating Co.; H. L. Berkstresser and W. H. Galloway of the Water and Sewage Department of Panama City; G. Layman, construction engineer for Gulf Power Co.; W. H. Toske and M. G. Southall of the U. S. Navy Mine Defense Laboratory; R. B. Nixon and J. L. Gore of the Tyndall Air Force Base water department; J. M. Lowery and T. M. Jones of the International Paper Co.; A. G. Symons and R. H. Brown of the Layne-Central Co.; W. Brown of the Brown Well and Pump Co.; and J. W. Spiva of Modem Water Inc.
Data on the chloride content in water from Deer Point Lake during the period of freshening were furnished by the Florida State Board of Health.







PREFACE


We would like to express special appreciation to Judge Ira A. Hutchison who through his interest in water resources and in particular the geology of this area has been most helpful. Claude I-Ecks has volunteered invaluable assistance in the collection of water-level information in the Deadening lakes area.
We would like to thank the numerous citizens in the basin who gave us access to their wells and who furnished us with information on their water supplies.







CONTENTS

Page
Preface ------------------------------------------------------------------------------------------------------------------------ v

Abstract ------------------------------------------------------------------------------------------------------------------------ 1

Introduction ---------------------------------------------------------------------------------------------------------------- 2

T he hydrologic environm ent ------------------------------------------------------------------------------------ 4

General statem ent ---------------------------------------------------------------------------------------------- 4

Physical m ake-up of the basin ------------------------------------------------------------------------ 4

W ater m ovem ent ---------------------------------------------------------------------------------------------- 7

W ater availability ------------------------------------------------------------------------------------------------------- 8

R ainfall ---------------------------------------------------------------------------------------------------------------- 8

W ater quality characteristics -------------------------------------------------------------------------- 9

Contam ination by saline water ------------------------------------------------------------------------ 11

Stream flow ---------------------------------------------------------------------------------------------------------- 15

Storage ---------------------------------------------------------------------------------------------------------------- 18

Lakes ------------------------------------------------------------------------------------------------------------ 18

A quifers ------------------------------------------------------------------------------------------------------ 19

A quifer characteristics ------------------------------------------------------------------------------------ 20

H ydraulics of aquifers -------------------------------------------------------------------------------------- 22

A quifer tests ------------------------------------------------------------------------------------------------------ 24

W ater use -------------------------------------------------------------------------------------------------------------------- 27

W ater high lights of the basin -------------------------------------------------------------------------------- 29

Decline of water levels in the Panama City area -------------------------------------- 29

G eneral statem ent ------------------------------------------------------------------------------------ 29

H istory of ground-w ater developm ent -------------------------------------------------- 31

1 Vii







Page

The D eadening lakes ---------------------------------------------------------------------------------------- 35

Geologic and hydrologic setting ------------------------------------------------------------- 37

W ater levels ------------------------------------------------------------------------------------------------ - 37

Flow of Econfina Creek ---------------------------------------------------------------------------- 40

Springs ---------------------------------------------------------------------------------------------------------------- 41

D eer Point Lake ------------------------------------------------------------------------------------------------ 45

Sum m ary -------------------------------------------------------------------------------------------------------------------- 45

R eferences ------------------------------------------------------------------------------------------------------------------ 51





































viii








ILLUSTRATIONS

Figure Page
1 Map of Econfina Creek basin area ---------------------------------------------- 3

2 Map of Econfina Creek basin showing physiographic divisions and surface runoff------------------------------------------------------------ Facing p. 4

3 Geohydrologic sections of Econfina Creek basin area -------------------------6

4 Bar graphs of maximum, mnimium, and average monthly rainfall, and annual rainfall, at Panama City from 1935 to 1963 ------------------------- 9

5 Map of Econfina Creek basin area showing location of data-collection points referenced in report-------------------------------------------------------- 12

6 Scatter diagram showing relation of chloride to total mineral content of water from the Floridan aquifer in the Econfina. Creek basin area ---13

7 Block diagram of Econfina Creek basin showing areal distribution of mineral content and chloride concentration in water from selected wells
in the Floridan aquifer ----------------------------------- ;-------------------------- 14

8 Graphs of chloride concentration in water from selected wells in the Floridan aquifer ---------------------------------------------------------------------- 15

9 Flow chart of streams in the Econfina Creek basin --------------------------- 17

10 Graphs of water level in the water-table aquifer and rainfall near
Bennett for part of 1962 and 1963 ----------------------------------------------- 19

11 Graph of streamfiow of Econfina Creek near Compass Lake for the
period April 1 to May 7, 1963 ----------------------------------------- ---------- 20

12 Sketch showing similarity of an artesian pressure system and water
pressure developed by an elevated tank ----------------------------------------- 21

13 Map showing the piezometric surface of the Floridan aquifer in the
Econfina. Creek basin area, October 1962---------------------------------------- 23

14 Graphs showing theoretical drawdowns in the vicinity of wells being
pumped at a constant rate for selected periods------------------------------ 26

15 Theoretical drawdowns along a line of 10 wells after 100 days of
pumping at a rate of 200 gallons per minute at each well--------------- 27

16 Graphs of water use and population in the Panama City area ---------- 30 17 Map of the Panama City area showing the location of water wells for
each water system and the area supplied by these systems ---------------- 31

18 Map showing the approximate piezometric surface of the Floridan aquifer in the Panama City area in 1908--------------------------------------- 32

ix.








Figure Page

19 Graph of water levels in observation well 008-537-332 near the center
of the International Paper Company well field for the period 1951
to 1963--------------------------------------------------------------------------------- 33

20 Map showing the piezometric surface of the Floridan aquifer in the
Painana. City area in April 1947 --------------------------------------------------- 35

21 Map of White Oak Creek basin in southeastern Washington County
showing The Deadening area ------------------------------------------------------ 36

22 Geohydrologic sections through the White Oak Creek basin, southeastern Washington County-------------------------------------------------------- 38

23 Graphs of water levels and rainfall in the vicinity of the Deadening
lakes ------------------------------------------------------------------------------------ 39

24 Flow chart of Econfina Creek during the low-water period of May 1963
showing the effect on strearnfiow if 30 mgd were diverted at the proposed
dam site -------------------------------------------------------------------------------- 42

25 Flow chart of Econfina Creek showing spring flow --------------------------- 43

26 Graphs of streamflow, spring flow, and specific conductance for Econfina
Creek near Bennett for 1963 ------------------------------------------------------ 44

27 Graph showing the relation of chloride in water in Deer Point Lake to
fresh water inflow--------------------------------------------------------------------- 46

28 Graphs showing the rise of water levels and change in chloride content
of ground water after construction of Deer Point Dam ------------------47



TABLES

Table Page

I Drainage areas, average flows, and low flows of subbasins within the Econfina Creek basin --------- ------------------------------------------------------ 16

2 Record of water supply systems in the Econfina Creek Basin area------.28








WATER RESOURCES


OF THE
ECONFINA CREEK BASIN AREA IN
NORTHWESTERN FLORIDA

By
R. H. Musgrove, J. B. Foster, and L. G. Toler

ABSTRACT
The Econfina Creek basin area of about 1,000 square miles is located in northwestern Florida. Water use in the basin in 1963 averaged about 25.2 mgd (million gallons per day). The major uses of water were for the manufacture of paper products, public and domestic supplies, and recreation. Of the 25.2 mgd, 22.7 were pumped from the artesian Floridan aquifer, mostly in the Panama City area. In February 1964 use of lake water was started at the rate of about 30 mgd and ground-water withdrawal was reduced to about 11 mgd. Since February 1964 the total use of water in the area has been about 41 mgd.
The basin receives most of its water from rainfall which averages 58.0 inches per year. Highly porous, unconsolidated sands form the water-table aquifer and absorb much of the rainfall. Seepage from this aquifer is to the streams an d to the underlying artesian aquifers. The productive artesian Floridan aquifer underlies the entire basin and is the aquifer from which the most water is pumped. A secondary artesian aquifer is present in the southern part of the basin and is intermediate in depth to the water-table and Floridan aquifers. Movement of water through these aquifers is generally southwestward.
By 1963, water levels in the Floridan aquifer near Panama City had been lowered 200 feet by pumping since the first deep wen was drilled in 1908. The large drawdowns resulted from heavy pumping of closely spaced wells in this aquifer which has a low transmissibility (1,300 to 31,000 gallons per day per foot) - In January 1964, pumpage from a field of 21 wells was stopped and water levels in this field recovered 163 feet within 51 days.
Water from the water-table aquifer generally had a mineral conItent from 10 to 50 ppm. (parts per million) and that from the sec-







FLORIDA GEOLOGICAL SURVEY


ondary artesian aquifer from 80 to 150 ppm. Water from the Floridan aquifer increased in mineral content from 70 ppm in the northern part to about 700 ppm in the southern part of the basin. Mineral content of water from streams and lakes, exclusive of those receiving artesian spring flow, was from 6 to 25 ppm. Water from springs had a mineral content from 50 to 68 ppm and was similar to water from the Floridan aquifer in the upper part of the basin.
Streamfiow into the coastal bays is at an average of about 960 mgd. Flow to North Bay is about 680 mgd, of which about 650 mgd flows through Deer Point Lake. East Bay receives about 210 mgd, and West Bay about 70 mgd. Runoff from the lower half of the drainage of Econfina Creek is 90 inches per year. This is about three times the runoff from the upper half of the basin and is a result of artesian spring flow.
There are about 80 named lakes in the basin, some of which have a wide range in stage. A plan has been proposed to divert water from Econlina Creek to a group of these lakes in southeastern Washington County to stabilize their levels. At the proposed point of diversion, Econfina Creek has a minimum flow of 30 mgd, which would supply about 0.5 of a foot of water per month on the proposed lake area.

INTRODUCTION
This report describes and evaluates the water resources of the Econfina. Creek basin area located in northwestern Florida. The area encompasses about 1,000 square miles and includes most of Bay County and parts of Calhoun, Gulf, Jackson, and Washington counties, as shown in figure 1. As considered in this report, the Econfina, Creek basin area includes all basins that drain into the bay system within Bay County.
Over 90 percent of the 70,000 people in the basin are located near the coast and are centered in the Panama City area. In 1963, water use in the basin was at the rate of 25.2 mgd. The three largest water users were the International Paper Company, Panama City, and Tyndall Air Force Base.
Ground-water levels were known to be below sea level in well fields supplying the major users. Information was needed to determine the extent of the low water levels and their effect on the water resources of the area.
More than 80 fresh-water lakes are situated in the higher parts of the area, mostly in southeastern Washington County. Included is a group of lakes locally known as The Deadening. Considerable







REPORT OF INVESTIGATIONS No. 41


Figure 1. Map of Econfina Creek basin area.


interest has been expressed concerning the development of The Deadening lakes into a water-oriented recreational area. Widely fluctuating lake levels rendered this recreation plan infeasible without lake controls. The Washington County Development Authority has a plan to stabilize these lakes by water diverted from Econfina Creek. Data were collected during the investigation to evaluate this plan.
No formal reports on the water resources of the area were available before this investigation. Some data were available on groundwater levels, streamflow, and the chemistry of ground water. This report is based on a 2-year investigation which began in January 1962. The investigation was designed to provide a basis for an evaluation of the water resources of the Econfina Creek basin.






FLORIDA GEOLOGICAL SURVEY


THE HYDROLOGIC ENVIRONMENT

GENERAL STATEMENT

Water in the natural state continually moves due to many forces acting upon it. Gravity acts on water in streams and underground to keep it moving downward toward the level of the ocean. The sun and wind evaporate water from open water bodies and plants'transpire water to the atmosphere. Gravity again moves the water earthward when the atmospheric moisture meets conditions favorable for rain. This never ending'movement of water is known as the hydrologgic cycle.
The water resources of any area depend upon this hydrologic cycle. When the rate of water movement out of an area exceeds the rate of water movement into the area, water shortages Will develop. Water shortages may also develop if the quality of water is significantly altered within its natural environment to make it unfit for its intended use. Variations in the rate of movement in any phase of the hydrologic cycle, such as rainfall, may also affect an area by resulting in floods and droughts. Proper development of the water resources of an area requires a thorough knowledge of water movement and the factors controlling it. This knowledge will enable the best prediction of where to obtain water and what provisions are required to control water movement.
In general, the system through which water moves in the Econfina Creek basin is similar to most river basins in Florida. Like most other basins, (1) rainfall is the source of all the water even though some falls outside the basin and moves into the basin underground;
(2) the surface materials are highly porous, unconsolidated sands;
(3) the basin is underlain by the artesian Floridan aquifer; and
(4) water leaves the basin by streamflow, evaporation, transpiration, underground flow to the ocean and other basins, and by consumptive use.

PHYSICAL MAKEUP OF THE BASIN

Four physiographic divisions within the basin affect the surface drainage and the-water storage. These are the sand hills, sinks and lakes, the flat-woods forest, and the coastal beach sand dunes and wave-cut bluffs, shown in figure 2. The physiographic divisions have developed on a series of stair-step marine terraces which were carved into the surface sands during the ice age by the successive levels of







8600' 5 50' 4 30 25 20 IS'80


ECONFINA CREEK BASIN AREA


3(J'35 SeventeenmIle 30033'
Pond



30 GREENHEA0

I.
TAIN

1 0 1 2 3 4 5 Miles

25 '-25'




2d20



15r A ,15'





0A 10,

EXPLANATION


PHYSIOGRAPHIC DIVISIONS 5'

Sand hills A,
~ Sinks and lakes
Flat- woods forest
3 0W - - Beach dunes and wave-cut bluffs

37 Numbers represent average annual
runoff in inches from areas outlined by dashed lines,
II I I !I
860O' 55' 50' 45' 40' 35' 30' 25 20' 15' 850o'

Figure 2. Map of Econfina Creek basin showing physiographic divisions and surface runoff.


30' 25'


20' 15' 83910


86�00 55' 50d


4d







REPORT OF INVESTIGATIONS No. 41


the ocean. Low swampy areas occur throughout each of these divisions but are more prevalent in the flat-woods forest.
The sand hills in the northern part of the basin are erosional remnants of the higher marine terraces which were between 100 feet and 270 feet above the present sea level.
The sinks and lakes occur in the section of the basin west of Econfina Creek where they have developed within the sand hills. This area is typified by irregular sand bills and numerous sink holes and sink-hole lakes. The sink holes range in diameter from a few feet to broad flat areas such as those in The Deadening lakes area (see p. 73). This physiographic division was developed by the solution of the underlying limestone and the subsequent collapse of the overlying material into the solution chambers. Most of the lakes have no surface outlets.
The flat-woods forest is the largest physiographic division of the basin. It is slightly rolling to flat land lying on the terraces below an elevation of 70 feet. Most of this division is covered with pines except for a few small areas cleared for agriculture. The flat-woods forest is well drained except for some low areas around the bays on the 0 to 10 and 10 to 25 foot terraces. During rainy weather these low areas of the flat woods become quite wet. A few small perennial swamps occur at various locations throughout the flat-woods forest. The largest is Bearthick Swamp southeast of Youngstown which covers an area of about 2,000 acres (fig. 2).
The fourth physiographic division occurs adjacent to the gulf coast and is characterized by beach dune deposits and wave-cut bluffs. The beach dune deposits are the youngest sediments in the basin and are the most rapidly changing physiographic feature.
The surface materials in the basin, on which the physiographic features have developed, are generally very porous, permeable sands. The sands form the water-table aquifer which is thicker in the sand hills (80 to 100 feet) than in the lower elevations of the flat-woods forest (10 to 30 feet) and thickens again along the coast (65 to 140 feet). The sands are missing only in stream channels and in some parts of the broad depressions of the sinks and lakes division.
The sands of the water-table aquifer cover a relatively impermeable layer of sandy clay and clayey shell material which forms an aquiclude (a formation that confines water to aquifers above and below it) between the water-table aquifer and the artesian aquifers below it, as shown in figure 3. This aquiclude is present throughout the basin except where it has been breached by a collapse into solution chambers or by erosion along Econfina Creek.














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REPORT OF INVESTIGATIONs No. 41


In the bay area and along the gulf coast in the basin, two artesian aquifers are associated with the aquiclude. Here the aquiclude is thicker than it is to the north and is overlain and in part underlain by some shell-hash beds which contain water. The sandy clay material which forms the base of the water-table aquifer is sufficiently impermeable to confine water in the shell-hash beds under artesian pressure. Water producing zones in the shell-hash beds above the aquiclude are termed the secondary artesian aquifer. The water producing zones in the shell-hash beds below the aquiclude are considered part of the Floridan aquifer.
The Floridan aquifer underlies the entire basin below the aquidlude. It is composed of limestone formations that are as much as 1,200 feet thick. However, the usable part of the aquifer, the part producing potable water, is the upper 500 to 700 feet.

WATER MOVEMENT
Rain, falling on the basin, is readily absorbed by the porous surface sands. The portion that runs off directly to the streams depends on the amount and intensity of the rainfall. The rain water and the surface water are relatively pure but contain some salts carried in the evaporate from the ocean and some gases dissolved from the atmosphere. The surface water becomes colored after contact with decayed organic matter but the mineral content changes very little.
The water absorbed by the sands seeps downward to the water table, the level below which the sand is saturated. The sands are not very soluble in the rain water and consequently the mineral concentration in water from the water-table aquifer is low.
Some of the water then moves from the water-table aquifer into the streams and maintains flow during periods of no rainfall. In the northern part of the basin where the sand and clay are breached by sinkholes, some of the runoff and seepage from the sands is temporarily ponded in lakes and then moves into the Floridan aquifer. In other areas the water from the sands may seep slowly into the limestone through the clay layer.
The amount of water moving from the water-table aquifer to the Floridan aquifer diminishes toward the southwest because the aqmidlude is thicker. Water that moves downward into the limestone of the Floridan aquifer then moves in the down gradient direction shown by the piezometric map (see p. 23). The gases acquired from the at-miosphere and from the soil zone form a weak acid solution which disolves the limestone and thereby causes an increase in the mineral






FLORIDA GEOLOGICAL SURVEY


content of the water. The mineral content of the water increases in the down gradient direction as more limestone is dissolved.
In areas along Econfina Creek where the artesian pressure surface is above the land surface and the sand and clay are missing, springs have developed. Most of the flow of Econfina Creek is derived from these springs.
In the southern hal of the basin, water may percolate downward from the water-table aquifer into the secondary artesian aquifer. The sandy clay material at the base of the water-table aquifer and at the top of the secondary artesian aquifer acts as a semi-confining layer which maintains the water in this aquifer under artesian conditions.
The secondary artesian aquifer is composed of shell-hash with interlayered sand and limestone lenses. Water that moves into this aquifer from the water-table aquifer is slightly acid. This water dissolves the limestone and shell giving the water a calcium bicarbonate character.
The water withdrawn from wells in the Floridan aquifer in the Panama City area entered the aquifer through the sinks in the northern part of the basin and in areas farther north where the limestone formations are at ground surface. By the time the water reaches Panama City the mineral concentration is five to six times that of water in the northern part of the basin. Part of the increase is caused by solution of the limestone and part is caused by mixing with older water in the rocks. The pressure gradient shows that the water is being flushed into the ocean at some point where the rocks are exposed to or hydraulically connected to the ocean bottom.

WATER AVAILABILITY
The amount of water moving through each part of the hydrologic system must be known to properly evaluate a water resource. A knowledge of the environment is necessary to determine the chemical and physical properties of the water and to predict any changes in these properties that may result from withdrawal of water from the system-. Some of the parameters that affect the am ount and quality of water available are rainfall, strearnflow, water levels, rock composition, and the ability of aquifers to store and transmit water. These hydrologic features can be measured either by direct or indirect methods.
RAINFALL
The Econfina, Creek basin receives an average rainfall of 58 inches per year, based on records collected at Panama City by the U. S.





REPORT OF INVESTIGATIONS No. 41


Weather Panama showing


Bureau. During the past 29 years the annual rainfall at City has varied from 37.6 inches to 85.0 inches. Graphs variations in rainfall are given in figure 4. Short periods


M) 0) ) a) M) 0) (D


Figure 4. Bar graphs of maximum, minimum, and average monthly rainfall,
and annual rainfall, at Panama City from 1935 to 1963.

of low rainfall and short periods of high rainfall have little- direct effect on the water resources; that is,.the amount of water in storage. Extended periods of below-average rainfall, or droughts, cause reduction in storage. The most severe drought of record ended in 1956 with a 7-year deficiency in rainfall of 50.2 inches. Within 'this 7-year period, 1953 was a single year of above-average rainfall but did not bring about a complete recovery of water lost from storage duri ng the preceding years of low rainfall. The 6-year period from 1944 to 1949 was the wettest of record. Records of water levels indicate that storage was near an all-time high during this wet period.


WATER QUALITY CHARACTERISTICS
The water in the lakes and streams of the area has about -the same mineral concentration as rain water. Samples of rain water contained as much as 13 ppm of dissolved mineral matter; the water in the streams and lakes ranged from about 6 to 25 ppm. The mineral concentration of the surface water differs little from rainwater because of the r,4ative insolubility of the surface materials. During periods of low flow, high mineral concentrations are normally expected in stream water because a large part of the flow is seepage from the


25,


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z

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_j
z






FLORIDA GEOLOGICAL SURVEY


water-table aquifer. No difference in the chemistry of surface water in the basin was noted between high and low flow except for the color and pH. High color immediately following a rain is attributed to the flushing of the decayed organic material from the swampy, poorly drained areas adjacent to the streams. This same colored water tends to be acid due to the solution of carbon dioxide released from the decaying plants. The pH of the streams is lower (more acid) during high flow when the flushing of the swampy areas occurs. The pH normally ranges from 6.0 to 7.0 units but falls below 6.0 during these times.
Two areas of exception to the normal low mineral concentration in stream water occur in the Econfina Creek basin. One of the areas is alona, Econfina Creek downstream from a point about due east of Porter Lake, where the creek receives flow from artesian spr ' ings. These springs emanate from limestones of the Floridan aquifer and the chemistry and relative solubility of the rocks are reflected in the mineral constituents found in the water. The mineral concentration in water from the springs ranged from 50 to 68 ppm and all but about 10 to 12 ppm were calcium and magnesium carbonate, the constituents of limestone. The mineral content of the water in Econfina Creek, downstream from where spring water enters, is higher than that in other stream in the basin, and varies with the ratio of spring flow to surface runoff. Calculations, based on chemical analyses, (see p- 84), show that 70 to 75 percent of the base flow of Econfina Creek at the Bennett gaging station is from springs.
The other area of exception to normal low mineral concentrations in stream water is near the mouth of the streams which empty into salt-water bays. Salt water moves up the streams a distance that is dependent upon the elevation of the streambeds, the stage of the streams, and tides. This encroachment of saline water occurs in the mouths of allStTeams except those emptying into Deer Point Lake, which is a fresh water body.
That part of the rainwater that replenishes the aquifers continues to move in the hydrologic cycle but at a slower rate than the water moving, as surface flow. This slow rate of movement allows a state of chemical equilibrium to be approached and normally results in ground water having a higher concentration of mineral constituents than does the surface water in an area. The highly insoluble nature of the sandswhich form the water-table aquifer in the Econfina Creek basin results in low mineral concentration of water in this aquifer. Generally, the concentration of total mineral constituents in water from this aquifer ranged from 10 ppm (about equal to that of rainwater)






REPORT OF INVESTIGATioNs No. 41


to about 50 ppm. In areas near the coast -these sands are in contact with salt water. All water from the water-table aquifer which contained more than 50 ppm dissolved minerals was from wells located vAthin a few hundred feet of salt-water bodies.
Water in the secondary artesian aquifer is slightly more mineralized than water in the water-table aquifer. In some areas near the coast the water from this aquifer may be saline. Where there is no contamination by saline water, the water generally contains from 80 to 150 ppm dissolved minerals and is principally a calcium bicarbonate water. Most of the water samples contained hydrogen sulfide and some samples contained sulfate.
The mineral concentration of water from the Floridan aquifer is higher than that from the secondary artesian or the water-table aquifers. In the northern part of the basin the higher mineral content is due entirely to higher concentrations of calcium and bicarbonate resulting from solution of the limestone. There are definite trends in mineral concentrations in water in the Floridan aquifer. These trends have been mapped (Toler and Shampine, 1964) and generally show increases in all constituents toward the southwest. An adaptation of the map of dissolved solids is shown on page 14 and indicates the trend of all the constituents. Sulfate, sodium, and hydrogen sulfide show little trend, but are found in significant quantities in. the southern half of the basin. In this area, sulfate ranged from 0 to 81 ppm, sodium from 2 to 164 ppm, and the odor of hydrogen sulfide was detected in water from most wells.

CONTAMINATION BY SALINE WATER
The large bays in the southern half of the Econfina Creek basin provide an access for salt water. several miles inland. Along the shoreline of these bays and along the Gulf, the salt water is in contact with the sands which form the water-table aquifer. During droughts, when the water levels in the sands are low, salt water may enter the aquifer and be pumped from shallow wells near the shore. Salt water is more dense than fresh water and it moves into the aquifer in the form of a wedge below a lens of fresh water. Fresh water will generally suppress the salt water about 40 feet below sea, level for every foot of elevation of fresh water above sea level. If the water level in the aquifer is lowered by pumping, the saline wedge adjusts to the new water levels and salt water may rise to contaminate a well. An interzone of water of intermediate composition is normally present instead of a sharp fresh-water salt-water interface.







FLORIDA GEOLOGICAL SURVEY


Salt water may enter the secondary artesian aquifer from the bays or from the water-table aquifer, when the pressure surface of the secondary artesian aquifer is below the water level of either source. Highly saline water from the secondary artesian aquifer was observed in samples from two wells. One well (007-535-334a), shown in figure 5


Figure 5. Map of Econffna basin area showing location of data-collection points referenced in report.

is 76 feet deep and the water contained 1280 ppm chloride. The other well (008-545-224, fig. 5) is 101 feet deep and the water contained





REPORT OF INVESTIGATIONS No. 41 13

1090 ppm chloride. Both of these are adjacent to saline surface-water bodies. Wells penetrating the -underlying Floridan aquifer, at and near these locations, produce water low in chloride. The saline water is presumed, therefore, to have leaked from the bays through the water-table aquifer.
Apparently, the aquiclude overlying the Floridan aquifer (fig. 3). in the coastal and bay area is sufficiently impermeable to prevent leakage of water from the overlying aquifers. The occurrence of chloride in water in the Floridan aquifer does not appear to be related to areas of high chlori 'de in water in the overlying sediments or to the bays. Water levels in the Floridan aquifer have been lowered below water levels in both the water-table aquifer and the secondary artesian aquifer, by pumping in the major well fields. Extended periods of low water levels in the Floridan aquifer have not resulted in an increase in the chloride concentration of water from this aquifer as would be expected if the aquiclude were leaking.
The chloride content of the water increases southwestward, the general direction of water movement. The fresh water apparently mixes with saline water in the aquifer to account for the increase in chloride. Figure 6 shows the relation of the increase in total mineral


z
-J

W


0


400


300
Only those samples containing greater
than 5 ppmn chloride included 200


100 _ _ _ __ _ _'. __________ _ _ _ _


O 100 200 300 400 O 500 60 00 80 o
MINERAL CONTENT, IN PARTS PER MILLION
Figure 6. Scatter diagram showing relation of chloride to total mineral content
of water from the Floridan aquifer in the Econfina Creek basin area.

concentration of the water to the increase in chloride for all samples containing more than 5 ppm. chloride.
Figure 7 is a block diagram of a section along the coast showing chloride concentrations and water producing intervals of wells pene-









FLORIDA GEOLOGICAL SURVEY


Chloride, in ppm


_ - --Top of the Floridan Aquifer


.,250-Dissolvtd solids in parts per million
(ao Ped rom Toler and Shampine, 1964)


Well (number indicates dissolved solids in ppm)

Figure 7. Block diagram of Econfina Creek basin showing areal distribution of mineral content and chloride concentration in water from selected wells in the Floridan aquifer.


-J
lAJ
-J
411 LJ c2'
z
4




LUS M54

W 6( U.
IaJ





o.8






REPORT OF INVESTIGATIONs No. 41


trating the Floridan aquifer. The chloride concentration generally increases with depth into the aquifer. No chloride mineral is present in the rock-forming materials and if water is not leaking from the overlying rocks, then this saline water must be residual water that remains in the rocks from a time when they were in contact with the sea. The geologic history (Foster, in preparation) indicates this may have happened many times. The residual water in the rocks would be from sea water and chemically would probably differ little from present sea water.
Records of chloride content in water from four wells, from 1950 to 1963, are given in figure 8. Although there is considerable variation

400-r -4


Figure 8. Graphs of chloride


concentration in water from selected wells in the Floridan aquifer.


in the chloride concentration, there appears to be no long-term trends due to pumping.

STREAMFLOW
In using a stream, two quantitative aspects to be considered are channel storage and the rate of flow. Channel storage is important in considering uses such as boating, fishing, and other recreational activities. The rate of flow must be considered when determining the quantities of water that can be withdrawn from the stream at any time. Only the larger streams in the Econfina Creek basin have enough


3001-


195 195 195 195 195 125 195 195 190 15 90 19 9






FLORIDA GEOLOGICAL SURVEY


channel storage during periods of low water to be used for boating. Most of the streams have sufficient flow to be a potential water supply. During periods of miumflows there is more than 10 times as much fresh water flowing into the bays than is being withdrawn from all sources in the Panama City area.
Streaniflow in the basin comes from several sources. During and immediately following rains water flows directly into the streams as overland flow. Between rains the streams receive only water that seeps from the shallow sands and from artesian spring flow from the limestone formations. Every stream receives seepage from the shallow sands.
Streamflow to the bays is at an average rate of about 960 mgd which amounts to 40 percent of the average rainfall. About 650 mgd flows through Deer Point Lake into North Bay from Econfina Creek, Bear Creek, Big Cedar Creek, and Bayou George Creek. Another 30 mgd flows into North Bay below Deer Point Dam from smaller streams.- West Bay receives a flow of about 70 mgd from Burnt Mill Creek, Big Crooked Creek and smaller tributaries. East Bay gets about 210 mgd from Wetappo Creek, Sandy Creek, Calloway Creek, and smaller streams.
Figure 2 shows values of runoff from areas within the Econfina Creek basin. It can be seen from this map that the physiographic features affect runoff. The low runoff in the southern half of the basin results from the poor drainage of the flat-woods forest. Drainage in the sinks and lakes division is mostly internal and there is almost no surface runoff. High base flow due to seepage from the porous sands causes the high runoff in the sand hills division. The extremely high runoff of 90 inches from the lower half of Econfina Creek is a result of the artesian spring flow.


TABLE 1. Drainage areas, average flows, and low flows
of subbasins within the Econfina Creek basin.

Drainage area Average flow Low flow
Creek basin sq. ni. nxgd rngd


Econfina C rek----e------------------ -- 129 355
Bear Cr ee-------------k---------- . 128 226
W etappo Creek -----------_---------_ 78
Sandy Creek - ------ --_-------- 60 70
Bayou George Creek ------------51 26
Burnt MMllCreek - --------------- 45 23
Big Crooked Creek --------_------------ 22 17
Big Cedar Creek -------- ----------------- 62 12
Calloway Creek -------------- --- 13 9
All others.--------------------.-- --- 142


226 52.
6 10
3
8
6
4 .6






REPORT OF INVESTIGATIONS No. 41


Stream data are given in table 1. The values of streamflow, except those for Econfina Creek, are estimated from short-term continuous discharge records or from periodic discharge measurements. The low flow of a stream without storage reservoirs limits its use. Much more water can be taken from streams if storage reservoirs are available from which to draw during periods of extreme low flows.
The flow chart in figure 9 shows the streamflow pattern of the basin. The average flow of Econfina Creek is 355 mgd, by far the largest of all the streams. This is a runoff of 58 inches per year and is


Figure 9. Flow chart of streams in the Econfina Creek basin.






FLORIDA GEOLOGICAL. SURVEY


about equal to the annual rainfall on the drainage area of 129 square miles. Streaniflow records have been collected since 1936 at Porter Bridge near Bennett at a point where the drainage area is 122 square miles.
The average flow of Econfina Creek from the upper half of the basin is 90 mgd, only one-fourth of the flow from the entire basin. Upstream from Tenmile Creek (fig. 1) the flow during dry periods is seepage from the shallow sands. Downstream from Tenmile Creek artesian springs contribute most of the dry-weather flow. The minimum flow from the entire drainage area of Econfina Creek is about 210 mg-d, or seven times the minimum flow of about 30 mgd from the upper half of the drainage area.
Floods occur on Econfina Creek almost every year. The creek has overflowed its banks at least once each year in all but six of the last 28 years. The longest period that it has stayed within its banks is the 3-year period August 1950 to September 1953.
Bear Creek is the second largest creek in the basin and has an average flow of 226 mgd. It drains almost entirely from the sand hills and flow is supported by seepage from these sands.
The average total surface flow into the bays was estimated as 960 mgd. Econfina Creek and Bear Creek contribute 581 mgd of this flow. The remainder of the average flow (379 mgd) comes from the smaller streams in the basin. The larger streams are listed in table 1.


STORAGE
Rainfall, although it varies, supplies an adequate amount of water to the basin. Water held in storage in lakes and aquifers eliminates frequent shortages which would result from the inconsistent rainfall.

LAKES
There are about 80 named lakes in the basin. Most of the lakes are in southeastern Washington County. Deer Point Lake (see p. 87), a fresh-water reservoir covering 4,700 acres in Bay County, is the largest. Porter Lake in Washington County has a surface area of 930 acres and is the largest natural lake.
The natural lakes have not been developed for water use to any great extent although they offer considerable potential as recreational facilities. Wide fluctuations in most lake levels, caused by seepage losses to the ground and variations in rainfall, discourage their development. The Washington County Development Authority has pro-






REPORT OF INVESTIGATIONs No. 41


posed a plan to divert water from Econfina Creek to a group of lakes known as The Deadening (see p. 73) and thereby stabilize their levels. This plan, if executed, would add about 4,000 acres to the normal size of this group of lakes.

AQUIFERS
The three aquifers - the water-table aquifer, the secondary artesian aquifer, and the Floridan aquifer - store large quantities of water. The portion of rainfall that enters these aquifers through downward percolation is stored temporarily.
Water contained in the water-table aquifer discharges slowly by downward percolation to the underlying aquifers and to the streams and lakes through seepage and small springs. The water-table aquifer, in the basin, is composed of fine to coarse sand and contains a volume of water approximately one-fourth the volume of the saturated section. The fluctuation of water levels in the water-table aquifer is an indication of the change in storage, shown in figure 10. During dry periods the water levels decline as the aquifer discharges the water from storage. In wet periods water levels rise as more water is received by the aquifer than is discharged.
Exclusive of flow from the artesian aquifer, the low flows of the streams are maintained by seepage from the water-table aquifer and
'-7ii



-U





I 3~14 ainfll tatin 2mile wet ao Bennett


<96 19632

u)14-Ran Bennettifor parls'wt o 192 nn1963







FLORIDA GEOLOGICAL SURVEY


are indications of the size and ability of the water-table aquifer to store and transmit water. Figure 11 is a graph of streainllow of Econfina Creek near Compass Lake for the period April 1 to May 7, 1963.




30


40
0


5 10 Is 20 25 30 5
APRIL 1963 MAY
Figure 11. Graph of streaxnflow of Econfina Creek near Compass Lake for the period April 1 to May 7, 1963.
The low-flow portion of this graph represents seepage from the watertable aquifer. The nearly flat slope of the low-flow portion of this graph, such as that immediately preceding the rise of April 30, shows that storage of water in the aquifer is sufficient to maintain the low flow for long periods of no rainfall.
The secondary artesian aquifer which is present along the Gulf coast also provides for storage of water in the basin. This aquifer is saturated at all times, therefore the volume of water stored in it does not change. Water discharges from this aquifer to the Gulf and to wells. There is some exchange of water between this secondary artesian aquifer and the aquifers above and below.
The Floridan aquifer is the most extensive aquifer in the basin and the one from which most water is obtained. A more detailed study was made of the characteristic of this aquifer.
AQUIFER CHARACTERISTICS
Certain hydraulic features of aquifers are of prime importance to water-supply planners and developers. These hydraulic features, ob-






REPORT OF INVESTIGATioNs No. 41


tamned from well data, should be determined before the first well field is developed. A thorough knowledge of the hydraulics of an aquifer will enable the planners to predict how much water the aquifer will supply. In the design of a well field the planner should know how much water he can expect to pump from each well without overdrawing the aquifer; what the optimum spacing of wells should be to keep pumping interference between wells to a minimum; what the design of each well should be as to the diameter, depth of casing, length and setting for screens or depths of open hole in a consolidated rock aquifer; and the required pump specifications.
The water in an artesian aquifer is under pressure much the same as water in a pipe leading from an elevated water tank, as shown in figure 12. The piezometric (pressure) surface in an artesian aquifer


Co
200
LU
S150

00
-j
wi


Figure '12. Sketch showing similarity of an artesian pressure system and water
pressure developed by an elevated tank.







FLORIDA GEOLOGICAL SURVEY


is the level to which water will rise in cased wells drilled into the aquifer, and is likened to the level of water in a vertical pipe that taps a city water main. Water can be taken from an artesian aquifer and the piezometric surface lowered without dewatering the aquifer. Only when the piezometric surface is lowered below the top of the aquifer is the aquifer dewatered. The quantity of water that can be withdrawn without dewatering the aquifer depends upon the ability of the aquifer to transmit water and the rate of recharge to the aquifer.

HYDRAULICS OF AQUIFERS
When a well that taps the Floridan aquifer begins to discharge water, the piezometric surface surrounding the well is lowered. A cone, centered at the discharging well, describes the shape of the lowered pressure surface in the vicinity of the well. This lowered pressure surface near a well or a group of wells in a producing field is referred to as the cone of depression or cone of influence. This cone of depression is graphically portrayed by the cones developed in the piezometric surface of the Floridan aquifer in the vicinity of the well fields in the Panama City area, as shown in figure 13.
In the initial stages of development the cone of depression is small in diameter and depth. As discharge from the well continues the cone spreads out. The lowering or drawdown of the pressure surface at the well continues until the amount of water being discharged is balanced by an equal amount being transmitted through the aquifer to the well. This balance can be achieved by a decrease in natural discharge or an increase in natural recharge.
When pumping stops the pressure surface begins to recover, rapidly at first, then at a progressively slower rate. With no further pumpnC, in the vicinity the pressure surface will eventually recover to the initial level.
The response of an aquifer to pumping from one well or a group of neighboring wells in terms of the rate and extent of drawdown in the pressure surface, and the quantity of water that the aquifer will produce is related to the hydraulics of the aquifer at that location. The principal hydraulic properties of an aquifer are its ability to transmit and to store water.
An artesian aquifer, such as the Floridan aquifer in the Econfina Creek basin, functions as a conduit through which water moves from the areas of recharge to the areas of discharge. The aquifer's ability to transmit water is expressed in terms of its coefficient of transmissibility. It is the quantity of water, in gallons per day, that will flow






REPORT OF INVESTIGATIONS No. 41


Figure 13. Map showing the piezometric surface of the Floridan aquifer in the
Econfina Creek basin area, October 1962.

through a vertical section of the aquifer one foot wide and extending the full height of the aquifer, under a unit hydraulic gradient, at the prevailing temperature of the water.
The coefficient of storage of an aquifer is the volume of water released from or taken into storage per unit surface area of the aquifer







FLORIDA GEOLOGICAL SURVEY


per unit change in head normal to that surface. This storage coefficient for an artesian aquifer is a measure of the small amount of water released or taken into storage when the aquifer compresses or expands due to changes in water pressure.


AQUIFER TESTS
The coefficients of transmissibility and storage are determined by the analysis of data obtained by aquifer tests or pumping tests. Three aquifer tests were carried out during the field investigation of the Econfina Creek basin utilizing available wells in the Floridan aquifer. In each of the three tests conducted, a well was pumped at a constant rate while water levels were measured in the pumped well and in one observation well.
A test of short duration was run at Bid-a-wee (fig. 5) using a standby supply well and an observation well belonging to the city of West Panama City Beach. The pump was operated for a period of 6 hours at a rate of 55 gpm (gallons per minute). The rate of drawdown and the rate of recovery of the water level were measured in the observation well'. 49 feet from the pumped well.
A similar test was made at Long Beach (fig. 5) in which one well was pumped for a period of 5 hours at a rate of 328 gpm. In this test the observation well was 1,800 feet from the pumped well.
The third test was made at the Lansing Smith Steam Plant (fig. 5) northwest of Lynn Haven. In this test one well was pumped at a rate of 504 gpmi for a period of 50 hours. The observation well was 1,195 feet away.
The Theis graphical method (Theis, 1935) was used to compute values of T (coefficient of transmissibility) and S (coefficient of stora ge) from the test data. The following values of T and S were computed:
Bid-a-wee test T=2,000 gpd/ft
S=1.2X 10-4
Long Beach test T = 4,000 gpd/ft
S=5 X10-4
Lansing Smith Steam Plant test T =30,000 gpd/ft
S=3X10-4
These computations are based on the assumptions that the aquifer is (1) of uniform thickness; (2) of infinite areal extent; and (3) homogeneous and isotropic (transmits water equally in all directions). Determinations of T and S from data collected during these three tests give a wide range of values and show considerable change in the hy-






REPORT OF INVESTIGATIONS No. 41


draulic character of that part of the aquifer penetrated by the wells at each of the test site locations. The wells used in the tests penetrated the upper 330 feet of the aquifer at Bid-a-wee, 245 feet at Long Beach and about 250 feet at the Lansing Smith Steam Plant. None of the wells used in these tests penetrated the full thickness of the aquifer. Deeper wells would draw water from a greater thickness of the aquifer and would, consequently, give higher values.
The values of the coefficient of storage from these tests are* consistent with values for the Floridan aquifer in other areas. The coefficient of transmissibility of the aquifer at the Lansing Smith Steam Plant is higher than at the other test sites. This may indicate vertical leakage into the aquifer from the overlying formations. Because the tests show considerable differences in the coefficient of transmissibility of the aquifer within the bay area, the coefficient of transmissibility determined from pumping tests nearest a proposed well field should be used. Additional tests should be made at distant locations before a well field is designed.
In order to predict the amount and areal extent of drawdowns that will result from different rates of pumping and different well spacings, computations were -made using the Theis formula (Theis, 1935) and the coefficients of transmissibility and storage determined at the Lansing Smith Steam Plant, at Bid-a-wee, and at Long Beach. Figure 14 shows theoretical drawdowns in the vicinity of a well discharging at a constant rate for different lengths of time at the Lansing Smith Steam Plant, the Long Beach, and the Bid-a-wee locations. These drawdowns represent the conditions that would result from continuous pumping at this rate. Because drawdowns vary directly with discharge, drawdowns for greater or lesser rates of discharge can be computed from these curves. For example, the drawdown 100 feet from a well at the Lansing Smith Steam Plant discharging at 500 gpm. would be 24 feet after 100 days of pumping. If the well had discharged at 100 gpm for the same length of time, the drawdown at the same distance would have been only one-fifth as much, or about 5 feet.
The graph of drawdowns along a line of 10 wells, spaced 2,000 feet apart, at a rate of 200 gpm, are shown in figure 15. The values used to determine this profile were obtained by summing the overlapping drawdowns for each well in the line as read from the 100-day curve for the Long Beach test (fig. 14). Similar graphs can be computed to determine the drawdown that would result from different pumping rates or different well spacings (Lang, 1961, Theis, 1957).
The cone of depression in the vicinity of a well or a well field being pumped at a constant rate will eventually stabilize if a balance







FLORIDA GEOLOGICAL SURVEY DISTANCE, IN FEET, FROM DISCHARGING WELL


Figur-e 14- Graphs showing theoretical drawdowns; in the vicinity of wells being
pumped at a constant rate for selected periods.






REPORT OF INVESTIGATIONS No. 41


THOUSANDS OF FEET
25 20 15 10 5 0 5 o 0 15 20 25


50

W
W 00- _ _50 Computations based onA

S200 T= 4OOgpd/ft. _
S = .0005

250 _ __ _ __ __
Figure 15. Theoretical drawdowns along a line of 10 wells after 100 days of
pumping at a rate of 200 gallons per minute at each well.

is established between the amount being pumped and the amount moving to the well, either through a decrease in natural discharge or an increase in natural recharge. Water-level records (p. 33) in the well field of the International Paper Company show that the cone of depression in that well field had stabilized by 1951 -as a result of controlled pumping.
WATER USE
Water planners should know how much of the available water is being used and the areas from which it is taken. Oftentimes, the amount of water available in an aquifer is ascertained by determining how much is being withdrawn and by measuring the effects of this withdrawal on the water levels in the aquifer. For example, the low water levels in the Floridan aquifer prior to February 1964 were near the level where dewatering of the aquifer would begin near the centers of heavy pumping.
The major uses of water within the Econfina Creek basin are recreation, manufacture of paper products, and public and domestic supplies. An undetermined though relatively small amount is used for irrigation. More than 80 named lakes, inland bays that cover over 100 square miles, and the larger streams are used for recreation.
Information was collected on the various municipal and industrial uses of water within the basin, except recreation, in order to estimate the total amount being withdrawn. Data on principal water-supply systems are given in table 2.











'I'AInlx 2. Jltwiirl of wathr NiIl)ly syhsti$ in tiwa I(-cjflna ('rek Basin area.


Aquifer: F, Floridan; W, wattsr table. Treatment: A, aeration; C, coagulation; C1, chlorination;


F, floculation; 11, recarlonation; S, softening; St, stabilization,


Well.pump
Aquifer capacity
(Kpm)


Ground storage
(gallons)


Eleva ted storage (gallons)


Treatment


Capacity of stands by
well pump
(gpm)


Yearly pumpage
(million. of
gallons)


Panama City: St. Andrew Plant


a F 285 to 500 1,00(,000 300,000


A, St, Cl, 8


866.8 Ground storage - 2 tanks
500,000 each,
Elevated storage for
Panama City system - 3 tanks - 100,000 gal, sa.


Millvile Plant

Lynn Haven

West Panama City Beach Long Beach Tyndall Air Force Base


U. S. Navy Mine Def. Lab. Woodlawn Subdivision Hathaway Water System Mexico Beach Water System Gulf Power Co. Water Plant International Paper Co.


21 F
Io W


430 to 500 e175 7&) 700
500 328
30O to 600


300
e350
60 to 100 735 r)0
350 to 776


400,000

100,000 1 reservoir


240,000
125,000 84,000 45,000 20,000 100,000
2150,M)


100,000

250,000 100,000 500,00 160,000 50,000



100,000
400,000


A St. Cl, S A, St. C1, S A, CI

A, Cl
Cl
A, C, R, Cl, F, S
St

A, CI, St
A, C1
Cl
A, Cl


600


360
500
328 1,500


630 e350


735


660.2 95.5 84.9
76.1
1,017


78
31.6 12.7
24.4


2 tanks - 350 each



2 tanks - 250,000 each 2 tanks - 42,000 each


4 tanks - 5,000 each


- Not in operation
5,478.5 As of Jan. 31, 1964
5,478.5 began receiving water
from Deer Point Lake


e - Estimated


Location


Number of wells


Remarks





REPORT OF INVESTIGATIONs No. 41


Prior to February 1964, no surface water was being withdrawn and ground water was being used at the rate of 25.2 mgd. Of this amount, 22.7 mgd came from the Floridan aquifer. In February 1964, when the International Paper Company began using surface water, groundwater use in the basin was reduced to about 11 mgd.
The International Paper Company, the major industry in the area, is the largest user of water. Prior to February 1964, the water used by this company was supplied by wells. About 13.5 of 15 mgd was pumped from the Floridan aquifer and the remainder was pumped from the watertable aquifer. Water used by this industry prior to 1964 is shown by graph in figure 16. In February 1964, this company started receiving water from Deer Point Lake at the rate of about 30 mgd.
There are nine public water-supply systems in the area. All water produced by public water-supply systems is pumped from the ground. The rate of pumping varies from 6.7 mgd during low demand periods of fall and winter to 12.9 mgd during peak demand periods of spring and summer. Areas served by these systems and locations of the wells are shown in figure 17.
Water use has increased with population (fig. 16). Also the per capita consumption in Panama City has increased from 70 gpd (gallons per day) to 80 gpd during the 10-year period, 1950-60. This figure is based on the average daily pumpage of the Panama City water system and4the population of the area supplied by this system. Only a small part of the water pumped by the city is supplied to industry and other non-domestic users. Also, there are a number of private irrigation wells in the city. Partly for these reasons the per capita consumption is below the more normal rate of about 150 gpd per person that is reported in other areas.
Nearly 18,000 persons live in areas not served by public water systems. At a per capita consumption of 80 gpd this would amount to about 1.4 mgd used for rural domestic purposes.

WATER HIGH LIGHTS OF THE BASIN
DECLINE OF WATER LEVELS IN THE PANAMA CITY AREA GENERAL STATEMENT
From 1908 to 1964 water levels in the Floridan aquifer near Panama City were lowered about 200 feet in the centers of major well fields. This decline represents the difference between the reported static water level of 16 feet above mean sea level in the first well drilled in 1908 and the pumping water levels in the major well fields







POPULATION

i ,_


ANNUAL PUMPING, IN MILLIONS OF GALLONS


I


I


-II











------t


I-- n~ . I I I
' - -. : --Q 2 .
- - - - - - - - - -0k

01





L---U

! . - - - - - - --ir)NN


l






REPORT OF INVESTIGATIONS No. 41


Figure 17. Map of the Panama City area showing the location of water wells
for each water system and the area supplied by these systems.

in early 1964. In January 1964 one well field consisting of 21 wells was shut down. The water levels in this well field recovered 163 feet within 51 days. Figure 18 shows the approximate piezometric surface in 1908 under natural water conditions. The piezometric surface in 1962 (fig. 13) shows the lowered water levels caused by pumping since 1908.

HISTORY OF GROUND-WATER DEVELOPMENT
The first deep well reported in the Econfina Creek basin was completed in 1908 for an ice plant in downtown Panama City (Sellards, 1912). In 1909 Panama City drilled a city supply well at the location of the old National Guard Armory. In the same year. another well was drilled near. the 'present water tank on Eleventh Street to supply St. Andrew.






FLORIDA GEOLOGICAL SURVEY


Figure 18. Map showing the approximate piezometric surface of the Floridan
aquifer in the Panama City area in 1908.

From 1908 to 1930 there was not enough water withdrawn by pumping to noticeably affect water levels in the Floridan aquifer. However, in 1930 the International Paper Company developed a well field in the Millville area, consisting of seven wells in the Floridan aquifer and three wells in the water-table aquifer. Three of these wells in the Floridan aquifer flowed at the time of drilling and the static levels in the others were about 20 feet above mean sea level (from 8 to 20 feet below land surface). The original test well for this supply reportedly flowed at a rate of 60 gpm, and, when pumped at a rate of 700 gpm, the water level dropped to 55 feet below land surface. A cone of depression developed in the piezometric surface of the Floridan aquifer as water was withdrawn. Static water levels in wells drilled in 1935 were more than 50 feet lower than in the original wells drilled in 1930. By 1937 the water level near the center of the well field reportedly was 104 feet below mean sea level, a decline of 124 feet from the time pumping began. This cone of depression expanded. as the paper company extended their well field eastward and northward.
A program was initiated by the paper company to protect their water supply. Four wells near the original center of pumping were





REPORT OF INVESTIGATIONS No. 41


abandoned to decentralize pumping and to thus prevent excessive drawdowns which were limiting production of water. The control of water levels was considered necessary also as a precaution against salt-water encroachment. Pumping from each of the other wells in the field was regulated for the most efficient production from the aquifer within the cone of influence. Water-level records, shown in figure 19, of an abandoned well about one mile from the center of pumping show the effectiveness of this program.

-J
W 75
bi Water level affected by
80so near-by pumping wells
- 85
w90
S95
M 100*
I
w 105 I
ZU- 0
LU 115

120
1~ 125
< 1951 11952 1953 1954 [1955T1956 1957 1958 1959 1960 11961 1'962 1963

Figure 19. Graph of water levels in observation well 008-537-332 near the center
of the International Paper Company well field for the period 1951 to 1963.

In January 1964 the paper company was producing water from 21 wells in the Floridan aquifer and 10 wells in the water-table aquifer. These wells were pumping an average of 15 mgd, of which about 13.5 mgd were from the Floridan aquifer. At this time the water level in the Floridan aquifer under pumping conditions was about 184 feet below mean sea level at the center of pumping and 100 feet below mean sea level on the east edge of the field. These represent drawdowns of about 200 to 120 feet since pumping began in 1930. Although this is a considerable drawdown, the pumping level in the field was essentially stabilized at this level. Minor fluctuations (fig. 19) were caused in part by seasonal variations. in pumping from neighboring well fields. The major recoveries shown on this graph indicate periods when pumping from wells near the observation well was stopped temporarily or wen pumping from the entire field was stopped.







FLORIDA GEOLOGICAL SURVEY


At the end of January 1964 when the paper company began using water from Deer Point Lake, all of the wells that had been pumping from the Floridan aquifer were shut down. In four days water levels in the aquifer recovered from about 200 to 83 feet below mean sea level near the old center of pumping and from 105 to 58 feet below mean sea level on the east edge of the field. After 51 days, water levels had recovered to 21 feet below mean sea level near the center and to about mean sea level on the east edge of the field.
in 1936 Panama City built a water plant in the Millville area. This plant was initially supplied by wells in the water-table aquifer, but later supplied by wells drilled into the Floridan aquifer. In 1955 a well drilled into the Floridan aquifer bad a water level of 63 feet below mean sea level. In October 1962, after all pumps were shut off for a period of 6 hours, the water level in this well was 72 feet below mean sea level, a net decline of 9 feet from 1955 when the wen was drilled- The decline in water levels is attributed to pumping from this well field and from the nearby paper company well field.
Another public water-supply system for Panama City was constructed in the St. Andrew section during late 1942 and 1943. When the fixst of the original seven wells were drilled the water level in the Floridan aquifer stood at about mean sea level. By mid-1943, when the last of the seven wells was drilled, pumping from the first wells had lowered the water level in the vicinity about -20 feet. In October 1954, when an eighth well was added to the well field, the pumping level had been lowered to 67 feet below mean sea level. This drawdown of 67 feet resulted from pumping at an average rate of 1.6 mgd.
Measurements of water-level in the St. Andrew well field in October 1962, after a 6-hour recovery from pumping, showed the water level to be 87 feet below mean sea level near the center of the field. The additional drawdown of 20 feet in the center of the field during the 9-year period from 1954 to 1962 represents the effect of pumping at 2.0 mgd, an increase of 0.4 mgd in the average daily pumping rate.
A well field consisting of four gravel-packed, screened wells in the water-table aquifer was constructed at Tyndall Air Force Base in 1941 to supply water for the base, then under construction. It was found that this aquifer would not supply sufficient water so it became necessary to develop a supply from the Floridan aquifer. Wh en the wells were drilled in the Floridan aquifer the water level stood about 8 feet above mean sea level. By 1946 the water level had lowered to about 10 feet below mean sea level. In 1961 pumping levels in the Floridan aquifer were as much as 82 feet below mean sea level near






REPORT OF INVESTIGATIONs No. 41


the center of the well field. The cone of depression which had been developing in this field was clearly established by 1961.
The maps of the Panama City area showing the piezometric surface of the Floridan aquifer, figures 13, 18, and 20, illustrate the effect of development of water from this aquifer. The piezometric surface in 1908 (fig. 18) is indicative of the general conditions in the area up to about 1930. By 1947 the 4 principal well fields were producing enough water to develop sizeable cones of depression in the piezometric sur-


Figure 20. Map showing the piezometric surface of the Floridan aquifer in the Panama City area in April 1947.

face (fig. 20). A comparison 6f piezometric surfaces in figures 13 and 20 clearly shows that increased pumping from expanded well fields has extended the cones of depression and has lowered water levels generally throughout the Panama City area during the period from 1947 to 1962.
THE DEADENING LAKES
The Deadening is a group of lakes in the lower end of a closed creek basin 'in the southeastern corner of Washington County, as shown in figure 21. These lakes receive the surface drainage from the







FLORIDA GEOLOGICAL. SURVEY


38 3 35, 35 is 32r 3V 0530


Figure 21. Map of White Oak Creek basin in southeastern Washington County showing The Deadening area.

White Oak Creek basin of 44 square miles and seepage from the watertable aquifer which underlies the surrounding sand hills. They lose water only by evapotranspiration and percolation to the underlying limestone formation. Gully Pond, Wages Pond, Hamilini Pond, Still Pond, and Hammock Lake are joined at an elevation of 70 feet and their combined surfaces cover 3,640 acres. Porter Lake is connected to the other lakes at high water through Swindle Swamp and Black Slough. At an elevation of 70 feet, Porter Lake covers 930 acres. The






REPORT OF INVESTIGATIONs No. 41


area of these lakes and Swindle Swamp is about 5,000 acres at an elevation of 70 feet.
The variances in the supply of water and the constant drain through the ground cause wide fluctuations in stages of The Deadening lakes. In 1950, as a result of flood waters, the lakes reached an elevation of about 70 feet. Due to the dry weather for a period of several years (fig. 4) some of the lakes were dry and others had receded to elevations as low as 40 feet by 1956. Above average rains in the late 1950's caused some of the lakes to recover to normal levels. Since 1960 lake levels have again receded.
The Deadening lakes have a considerable recreation potential. However, the wide ranges in lake levels prevent the potential from being realized.
The Washington County Development Authority has proposed a plan to divert water from Econfina Creek to these lakes at the rate necessary to stabilize them at an elevation of 70 feet above mean sea level. The diversion from Econfina Creek would be at a point just downstream from Tenmile Creek, by way of a diversion canal to Porter Lake. After Porter Lake is filled, water would overflow through Swindle Swomp and Black Slouth to The Deadening lakes.

GEOLOGIC AND HYDROLOGIC SETTING
The Deadening lakes are located in the sinks and lake physiographic division (fig. 2). They originated by the collapse of the overlying sands and clays into cavities caused by solution of the limestone of the Floridan aquifer. Where solution and collapse activity has breached the confining layer, figure 22, there is a loss of water from the lakes to the Floridan aquifer.

WATER LEVELS
Levels of the Deadening lakes have been as high as 70 feet and as low as about 40 feet above mean sea level. A topographic map made in 1950 shows an elevation of 70 feet for Porter Lake) and shows the Deadening lakes to be completely covered with water at an elevation of 69 feet. Based on flood marks, about 70 feet is the highest elevation that the lakes have reached. The bottoms of Hammock Lake and Porter Lake are at an elevation of about 40 feet. Hammock Lake was reported to have been dry in 1956.
Figure 23 shows that lake levels have varied from a high of 68.3 feet in Porter Lake to a low of 44.2 feet in Gully Pond during the period frow 1961 to 1963. Lake levels declined throughout most of that period. In mid-1963 the lakes began responding to rainfall as






FLORIDA GEOLOGICAL SURVEY


A
-- 20-.1-:.=





L � *t' lS I Of l1Ib* Flonidos omit.,l
I 2 3 UIko
30
2W

o0z"r 0, 100


- -Co-,. *, : .




Figuare 22 Geohydrologic sections through the WVhite Oak Creek basin,
southeastern Washington County.

shown by the graphs in figure 23. The similarity of the graphs of lake and ground-water levels indicates hydrologic continuity between the lakes and the aquifer.
Flow from White Oak Creek enters Swindle Swamp and separates, part going to Porter Lake and parL going to Still Pond through Black Slough (fig. 21). The flow from Still Pond is to Hamlin Pond by way of subsurface channels. These subsurface channels are evidenced by sink holes through which movement of water can be seen. Hanilin Pond overflows to Hammock Lake. Wages Pond receives surface drainage from Howard Swamp and overflows to Gully Pond. Hammock Lake and Gully Pond are at a lower stage than the other lakes because they receive surface flow only when the other lakes overflow.
A comparison of the recessions of lake levels to the expected evaporational losses indicates the lakes lose water to the underlying Floridan aquifer. The level of Clarks Hole, an arm of Hamlin Pond, receded seven feet from August to December 1962. Below a stage of 55 feet, Clarks Hole is separated from Hamlin Pond and the shore line is below the line of vegetation, which eliminates most transpirational losses. The major water losses from Clarks Hole below a stage of 55 feet are evaporation and downward leakage. During the 5-month period that water levels in Clarks Hole declined seven feet, the evaporational loss was about 2 feet, based on pan evaporation records







REPORT OF INVESTIGATIONS No. 41


1961
JIFIMIAIMJJIAISOIN D
A I I I I .I II I I I


~Cn W12zI0
8

6
j 40-


1962


1963


AIMIJIJIAISIOINIDIJIF IMIAIMIJ T FN J I SO~ D
I I . . . . I . . . . . . . . . . .
(2 milesI not1f1otrhae
(2 mites north of Porter Lake)


70

-J
W 68

-/
66



CO 64


Z 62



60

w

0 58



56
I-
W
W "- 54


1961


1962


1963


Figure 23. Graphs of water levels and rainfall in the vicinity of the Deadening lakes.


Well 030-555-422b ,
Porter Lake Late .,,able aquifer) '--0/



100

Well 031-535-233 Still Pond Floridan aquifer









(HSmlin Pond) eli q ufe3



Pond Pond

II I I es

J ~ ~ ~ ~ Cak Fol M A NDJFMAM 0JFMAMJ


52

-J
W 50


J
48






FLORIDA GEOLOGICAL. SURVEY


collected at Woodruff Dam by the U. S. Weather Bureau. The remnaining five feet represents leakage to the ground. Clarks Hole receive no inflow during this period. Some of the other lakes did, which minimizes the apparent losses shown by graphs in figure 23.
The Deadening area received about 11 inches of rain in July 1963, of which 8 inches fell during the last 10 days of the month. These heavv rains caused moderate rises in the lake levels and the piezometric surface of the Floridan aquifer. The ground-water level and lake levels, in general, showed about the same amount of rise, from 2 to 5 feet. The water level in Clarks Hole rose about 12 feet as a result of overflow from Hamlin Pond.
Water in the Floridan aquifer moves in the general direction of the slope of the piezometric surface (fig. 13). Water moves to the center of The Deadening area from the northeast, and moves radially from The Deadening area toward Econfina Creek to the southeast, the Gulf of Mexico to the south, and Pine Log Creek to the southwest.
Wells in The Deadening area showed larger gains during the rise of July 1963 than wells outside the area. This indicated that the Floridan aquifer gains water indirectly from rainfall more rapidly in The Deadening, area than in the surrounding area.
Water diverted to The Deadening lakes would move from the lakes to the Floridan aquifer at a rate proportional to the head between the lake surfaces and the piezometric surface of the aquifer. Raised lake levels could increase this head and cause more water to enter the aquifer. If the lake levels are maintained at a constant elevation. the head that will be established depends on the ability of the Floridan aquifer to transmit water away from the area.

FLOW OF ECONFINA CREEK
Information on the flow of Econfina Creek was obtained to determnine the amount of water available at the proposed point of diversion and to determine what effect diversion would have on streamfiow.
The proposed point of diversion is just east of the north end of Porter Lake, about midway of the basin. The drainage area of Econfina Creek above the proposed point of diversion is about 67 square miles. The average flow at this point was estimated to be 90 mgd.
Minimum flow at the point of diversion is the important criterion in determining the available flow. The greatest amount of water will be needed in the lakes when the creek flow is lowest. A minimum flow of 30 mgd was estimated on the basis of three discharge measurements and the relation of these measurements to the long-term flow record at the Bennett gaging station. This minimum flow probably will






REPORT OF INVESTIGATioNS No. 41


not occur more often than once every 15 to 20 years, and then probably will not persist for more than a few months. A flow of 36 mgd was measured at the point of diversion on May 27, 1963, during a period of extreme low flow.
A dlam to create a retention reservoir along Econfina Creek is being considered. The main purpose of this reservoir would be to raise the water level in the creek and make gravity flow to Porter Lake possible. There would be a usable storage in this reservoir between elevations 80 and 95 feet of about 4,000 acre-feet. This amount of storage would provide 10 mgd for a period of four months. This, added to the natural flow of the creek, would assure a minimum flow of about 40 mgd. A flow of 40 mgd would supply about 0.7 of a foot of water per month on the 5,000-acre lake area.
If diversion from Econfina Creek is at a rate of 30 mgd, the streamflow just downstream from the point of diversion would be almost depleted during periods of low flow. This effect will diminish downstream. Diversion of 30 mgd would reduce the flow below Gainer Springs about 15 percent. The width of the stream at this point would not be affected, and the depth would be reduced from a usual 4.5 feet to about 4 feet. Figure 24 shows, pictorially, the effect on streamflow if 30 mgd were taken from the creek during low flow. A diversion of this amount is a negligible part of the total flow into Deer Point Lake and would have no adverse effect on this water supply.
Some of the diverted water would be returned to Econfina Creek by an increase in the flow of artesian springs. The higher spring flow would result from an increase in the piezometric slope caused by recharge to the Floridan aquifer from the lakes.

SPRINGS
The artesian springs along Econfina Creek are located downstream from a point just east of Porter Lake. Spring flow to the creek increases downstream to a maximum near the Washington-Bay County line. Below Gainer Springs it diminishes and there is little, if any, spring flow to the creek below the gaging station near Bennett, as shown on the flow chart in figure 25.
Spring water flows into Econfina Creek directly through the stream bed, from the base of rock bluffs, and from short spring runs about a quarter of a mile in length. The spring water emanates from the Floridan aquifer where Econfina Creek has breached the overlying, confining clay layer. Figure 22 illustrates the hydrologic relationship of the aquifer with the creek. Figure 13 shows the pattern. of flow towards the springs.






FLORIDA GEOLOGICAL SURVEY


0 2 4 Was


NO S WPU S L"REAM FRN NM



FLOW CHART
Tftol wiTh of stream represets flow with no diversion.
U 30 m d diverted
streoamflow ofter 30 rigd diverted
4 Flow-meowig Poi t
0 400 mgd
Flow cole


Figure 24. Flow chart of Econfina Creek during the low-water period of May 1963 showing the effect on streamflow if 30 mgd were diverted at the proposed dam site.

It was possible to make direct measurements of the flow from Blue Springs and Williford Springs. Flow from Gainer Springs was determined by the difference in streamflow measurements above and below the group. Other spring flow, which could not be measured, enters the creek along its bed and banks.
The amount of flow attributable to spring flow was calculated at the Bennett gaging station utilizing electrical conductivity measurements of the water. Pure water is a poor conductor of electricity but mineral matter dissolved in water consists of charged particles which will conduct an electrical current. The amount of current that a water will conduct is an indicator of the amount of dissolved minerals in the water. The measurement of the electrical current conducted by






REPORT OF INVESTIGATIONS No. 41


FLOW CHART M Spring flow E3 Non-spring flow o 300mgd
Flow scale


1 0 I 2 3 4 5mi.

Figure 25. Flow chart of Econfina Creek showing spring flow.


water is expressed as specific conductance in units of micromhos.
The specific conductance of the water from the springs along Econfina Creek ranged from 95 to 150 micromhos. Water in the creek above the area of spring flow ranged from 14 to 26 micromhos. Average specific conductance values of 114 micromhos for spring water and 20 micromhos for non-spring water were used in the calculation of spring flow.






FLORIDA GEOLOGICAL SURVEY


Water at the Bennett gaging station was considered to be a thoroughly mixed combination of spring water and non-spring water. Flow at the Bennett gaging station, attributable to springs, was calculated from the formula:
K-K
QS= K -KW Qb
s n
where: QS is spring flow.
Qb is streamfiow at Bennett
K is specific conductance of spring water
K is specific conductance of non-spring water
Kb is specific conductance of the mixture

Figure 26 shows the flow of Econfina Creek during non-flood periods and that portion attributable to springs for 1963. Spring flow contributes about two-thirds of the total flow of Econfina Creek.


9OC! 800



ri+TOTAL FLOW 600

-500

400 400
300 - 300
0




3i
0~CALC E DA l SPTIN FL60





SECIFI CreekCTMI nerBnnt5n093
:IL

,0
"M 'n A M"JUNE J" M SPT OT M DE


Fire 26. Graphs of streamflow, spring flow, and specific conductance for
Econfina Creek near Bennett in 1963-






REPORT OF INVESTIGATioNs No. 41


DEER POINT LAKE
Deer Point Lake (fig. 1) was formed on November 17, 1961, by construction of a salt-water barrier across North Bay at Deer Point. The lake was planned to serve as a source of fresh water and to provide recreational facilities. It covers 4,700 acres, most of which was formerly a part of North Bay, and stores approximately 32,000 acrefeet of water at a level of 4.5 feet above mean sea level, the elevation of the dam.
The lake is stabilized at an elevation of 5.0 feet above mean sea level. The potential fresh water supply is approximately 650 mgd, the average flow through the lake to North Bay. In February 1964 the only withdrawal from Deer Point Lake was the 30 mgd by the International Paper Company.
A study of the lake hydrology in the period immediately before and for several months after the dam was constructed (Toler, Musgrove, and Foster, 1964) was made to determine the rate of freshening and the effect the lake would have on the water-table aquifer.
Figure 27 shows the rate of freshening of the lake in terms of the number of times the inflow of fresh water would have filled the lake. Plotted in this manner, the graph enables a prediction of the rate of freshening of any similar lake if the volume and concentration of lake water and inflowing water are known (Toler, Musgrove, and Foster, 1964). When the barrier was completed on November 17, 1961, the lake was about half full and the chloride concentration was about 7,400 ppm. Flow over the spillway began on November 29, 1961, and the chloride concentration had been reduced to 3,700 ppm. In midFebruary 1962 the chloride concentration was about 200 ppm.
When the barrier was completed, water levels in the lake and in the water-table aquifer adjacent to the lake rose rapidly, as shown in figure 28. An immediate effect of the rise in the lake level was to reverse the water-table gradient near the lake so that water moved from the lake into the aquifer. This is evidenced by the rise in chloride content in water from well 015-535-232, 45 feet from the lake. Water in wells 100 feet or more from the lake showed no change in chloride content. When the water table adjusted to the new lake level, the water movement was again toward the lake and the high chloride water was flushed from the aquifer.

SUMNL4-RY
In general, the hydrologic system through which'water moves in the Econfina Creek basin is similar to most basins in northwest I ?








46 FLORIDA GEOLOGICAL SURVEY


1961 j 1962 D 1963
DEC JAN FED MAR PR JIJ JL AUG SE" OCT NOV DEC JAN



4500:




4000



3500

z
2
._ 300 Vis volume of fresh water thot has flowed Into Joke
.since spillway overflow began

. V- vokme of the lake at spillway elevation
2500


z
.2(00 '



U 1500




1000



500



I -- : t. " I = .
1 2 3 4 5 6 7 8 .9 10 II 12 13 14 15 16 17 18 19 20 21 v,/V0

Figure 27. Graph showing the relation of chloride in water in Deer Point Lake to fresh water inflow.


Florida. That is: (1) rainfall is the source of all the water even though some falls outside the basin and moves into the basin underground;
(2) the surface materials are highly porous, unconsolidated sands;
(3) it is underlain by the artesian Floridan aquifer; and (4) water leaves the basin by streanflow, evaporation, transpiration, underground flow to the ocean and other basins, and by consumptive use.
There are four physiographic divisions within the basin that affect the surface drainage and the water storage, both above and






REPORT OF INVESTIGATIONS No. 41


4.0 i Well 016-535-342b Z
0 _j~0
Wole( level
I- -30 I.'

524
0
I.0% 3000 _Z
:Chloride
VMl 015-535-232
1.0 2000

0 1000

0
NOV. DEC. JAN. FEB. MAR. APR. MAY JUNE JULY AU. SEP. OCT. NOV. DEC. JAN. FEB, MAR. APR. MAY aLINE
961 1962 1963
Figure 28. Graphs showing the rise of water levels and change in chloride
content of ground water after construction of Deer Point Dam.

below the ground. These are the sand hills, sinks and lakes, the flatwoods forest, and the coastal sand dunes and wave-cut bluffs.
The surface materials on which the physiographic features have developed are generally very porous, permeable sands which are from 0 to 140 feet thick. These sands form the water-table aquifer. A confining layer, or aquiclude, of sandy clay and clayey shell material separates the water-table aquifer and the Floridan aquifer.
In the bay area and along the gulf coast there are two artesian aquifers. Here the formation that forms the aquiclude is thicker than it is to the north and is overlain and in part underlain by some shellhash beds which contain water under artesian pressure. Water producing zones in the shell-hash beds above the aquiclude are termed the secondary artesian aquifer.
The Floridan aquifer underlies the entire basin below the aquielude. It is composed of limestone formations that include the lower units of the shell-hash beds and are as much as 1,200 feet thick.
The basin receives an average of 58 inches of rainfall per year. A part~of the rainfall is absorbed by the porous surface sands and a part moves directly into the streams. Some water from the sands moves to the streams and maintains flow during periods of no rain-






FLORIDA GEOLOGICAL SURVEY


fall- Water also moves from the sands downward to the Floridan aquifer but the amount diminishes toward the southwest because the aquiclude becomes thicker. Movement within the Floridan aquifer is generally southward with some water flowing into the channel of Econfina Creek by way of artesian springs.
The transmissibility of the Floridan aquifer varies within the basin, and is lower than the transmissibility of this aquifer in most other areas in Florida. Coefficients of transmissibility range from
9.000 to 30,000 gpd/ft.
The water in the lakes and streams differs little in mineral concentration from rain water because of the relative insolubility of the surface materials. Two areas of exception are where Econfina Creek receives artesian spring flow and near the mouth of streams that empty into salt-water bays.
The mineral content of water from the water-table aquifer generally ranges from 10 to 50 ppm, and that of water from the secondary artesian aquifer from 80 to 150 ppm. The mineral content of water from the Floridan aquifer is higher than that from the other two aquifers. Mineral concentrations in water from this aquifer show increases in all constituents from the northern part of the basin to the southwest.
Some salt-water intrusion was detected in the water-table and the secondary artesian aquifers adjacent to the bays and Gulf. The confining clay layer overlying the Floridan aquifer in the coastal and bay area is sufficiently impermeable to prevent leakage of water from the overlying aquifers. Water in the Floridan aquifer in the southern part of the basin is apparently a mixture of fresh water and residual saline water.
Streamflow to the bays is at an average rate of about 960 mgd which for a vear would amount to 40 percent of the average annual rainfall of 58 inches. About 650 mgd flows through Deer Point Lake into North Bay, and another 30 mgd flows into North Bay below Deer Point Dam. East Bay receives a flow of about 210 mgd and West Bay about 70 mgd. Most of the streams have sufficient flow to be a potential water supply. During periods of minimum flows there is more than 10 times as much fresh water flowing into the-bays than is being withdrawn in the basin. Econfina Creek, by far the largest stream in the basin, has an average flow of 355 mgd.
Low runoff from the southern part of the basin results from poor drainage features of the flat-woods forest. Drainage in the sinks and lakes division is mostly internal. High base flow due to seepage from the porous sands causes high runoff in the sand hills division.







REPORT OF INVESTIGATIONS No. 41


There are about 80 named lakes in the basin, most of which are in southeastern Washington County. Deer Point Lake, a fresh-water reservoir covering 4,700 acres, is the largest. Porter Lake has a surface area of 930 acres and is the largest natural lake.
The major uses of water within the basin are for the manufacture of paper products, for public and domestic supplies, and for recreation. Prior to February 1964 no surface water was being withdrawn and ground water was being used at the rate of 25.2 mgd. Of this amount, 22.7 mgd came from the Floridan aquifer. The International Paper Company was the largest user of water, using about 13.5 mgd from the Floridan aquifer and about 1.5 mgd from the water-table aquifer. In February 1964 this company started receiving water from Deer Point Lake at the rate of about 30 mgd. Ground-water use in the Panama City area was reduced to about 11 mgd.
The first well in the Floridan aquifer was drilled in 1908. Later, as the demand for water increased, more wells and well fields were developed and water levels were lowered. By the end of 1963, when water was being withdrawn at the rate of about 25.2 mgd, pumping levels had been lowered as much as 200 feet near the centers of major well fields. Pumping from the paper company well field, consisting of 21 wells, was discontinued in February 1964 and water levels in this field recovered 163 feet within 51 days.
The Deadening lakes in southeastern Washington County offer considerable recreation potential. However, they lose water to the ground at a high rate causing wide fluctuations in stage and this prevents their full potential from being realized. The Washington County Development Authority has proposed a plan to divert water from Econfina Creek to stabilize these lakes at an elevation of 70 feet. The diversion from Econfina Creek would be at a point just downstream from Tenmile Creek where the minimum flow was estimated to be 30 mgd. The proposed plan calls for a detention reservoir on Econfina Creek to raise the water level and make gravity flow through a diversion canal possible. The storage in this reservoir, added to the natural flow of the creek, would provide a minimum flow of 40 mgd which would supply about 0.7 of a foot of water per month on the 5,000-acre lake area.
Water leaks from the lakes to the Floridan aquifer at a rate proportional to the head between the lake surfaces and the piezometric surface of the aquifer. If the lake levels are maintained at a constant elevation, the head that will be established depends on the ability of the Floridan aquifer to transmit water away from the area.
If diversion from Econfina Creek is at a rate of 30 mgd, the stream






FLORiDA GEOLOGICAL SURVEY


just downstream from the point of diversion would be almost depleted during periods of low flow. This effect will diminish downstream and become almost negligible below Gainer Springs, a group of large artesian springs just downstream from the Washington-Bay County line-. A diversion of 30 mgd is a negligible part of the total flow of 650 mgd into Deer Point Lake and would have no adverse effect on this water supply. A part of the water diverted to the lakes would be merely re-routed through the lakes into the ground and back to the Econfina. Creek through the artesian springs below the dam.
Deer Point Lake is a fresh-water lake formed November 17, 1961, by a salt-water barrier across North Bay. It covers 4,700 acres and stores about 32,000 acre-feet of water. The lake elevation is 5.0 feet above mean sea level and fluctuates very little.
Artesian spring water flows from the Floridan aquifer into Econfina Creek directly through the streambed, from the base of rock bluffs and from short runs about a quarter of a mile in length. These springs occur from a point just east of Porter Lake downstream to a point near the Bennett gaging station. Springs contribute about twothirds of the flow of Econfina. Creek.







REPORT OF INVESTIGATIONS No. 41


REFERENCES

Foster, J. B. (also see Toler, L. G.)
In Preparation Geology and ground-water hydrology of Bay County,
Florida.
Gunter, Herman (see Sellards, E. H.)
Hantush, M. S.
1955 (and Jacob, C. E.) Non-steady radial flow in an infinite leaky
aquifer: Am. Geophys. Union Trans., V-37, No. 6, p. 702-714.


Lang, S. M.
1961


Methods for determining the proper spacing of wells in artesian aquifers: U.S. Geol. Survey Water-Supply Paper 1545-B.


Musgrove, R. H. (see Toler, L. G.)


Sellards, E.
1912


H.
(and Gunter, Herman) The underground water supply of westcentral and west Florida: Florida GZol. Survey 4th Ann. Rept., p. 116.


Shampine, W. J. (see Toler, L. G.)
Theis, C. B.
1935 The relation of the lowering of the
rate and duration of discharge of storage: Am. Geophys. Union Trans.
1964 The spacing of pumped wells: U.S.
Paper 1545-C, p. 113.


Toler, L. G.
1964


piezometric surface and the a well using ground-water p. 519-524, August. Geol. Survey Water-Supply


(and Musgrove, R. H., and Foster, J. B.) Freshening of Deer Point Lake, Bay County, Florida: Am. Water Works Assoc. Journal, V. 56, No. 8, p. 984-990.


1965 (and Shampine, W. J.) Quality of water from the Floridan aquifer
of the Econfina Creek basin area, Florida: Florida Geol. Survey
Map Series No. 10.

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STATE OF FLORIDA STATE BOARD OF CONSERVATION DIVISION OF GEOLOGY FLORIDA GEOLOGICAL SURVEY Robert O. Vernon, Director REPORT OF INVESTIGATIONS NO. 41 WATER RESOURCES OF THE ECONFINA CREEK BASIN AREA IN NORTHWESTERN FLORIDA By R. H. Musgrove, J. B. Foster, and L. G. Toler Prepared by the UNITED STATES GEOLOGICAL SURVEY in cooperation with the FLORIDA GEOLOGICAL SURVEY TALLAHASSEE 1965

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FLORIDA STATE BOARD OF CONSERVATION HAYDON BURNS Governor TOM ADAMS EARL FAIRCLOTH Secretary of State Attorney General BROWARD WILLIAMS FRED O. DICKINSON, JR. Treasurer Comptroller FLOYD T. CHRISTIAN DOYLE CONNER Superintendent of Public Instruction Commissioner of Agriculture W. RANDOLPH HODGES Director

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LETTER OF TRANSMITTAL 01D WE 11' 97orida jeological Qlurvey TALLAHASSEE July 20, 1965 Honorable Haydon Burns, Chairman Florida State Board of Conservation Tallahassee, Florida Dear Governor Burns: The Florida Geological Survey will publish, as Report of Investigations No. 41, a comprehensive report on the water resources of the Econfina Creek Basin area in northwestern Florida. This report was prepared by the members of the U. S. Geological Survey in cooperation with the Florida Geological Survey, as a part of its water resources study program. The Econfina Creek is one of the largest discharging streams of the State, and its potential for meeting water resources needs is great. The publication of the total resources study, to be accomplished in a series of papers, will contribute toward the stabilization of the economic development of the Panhandle area, and will provide a basis upon which a large water-using economy can be based. Respectfully yours, Robert O. Vernon, Director and State Geologist

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Completed manuscript received April 30, 1965 Published for the Florida Geological Survey By The St. Petersburg Printing Co., Inc. St. Petersburg, Florida 1965

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PREFACE In the planning and preparation of this report we have tried to present the essential information that would provide a brief, concise description of the water resources of the Econfina Creek basin area. The report was designed to supply answers to general questions of the many people interested in the water resources of the basin. Other reports on particular aspects of the water resources of the basin will present more detailed information about a phase of the hydrology or geology of the basin. This report is intended to furnish the background from which the reader may refer to the phase reports for more definitive treatments of a particular subject. Special phases of the water resources of the basin will be featured in reports on: Deer Point Lake; The Deadening area of southeastern Washington County; geology and aquifers of Bay County; and a quantitative study of ground water in the Panama City area. In addition, the basic data available through the period of investigation will be published in the information circular series of the Florida SGeological Survey. This report was prepared by the Water Resources Division of the U. S. Geological Survey in cooperation with the Florida Geological Survey. The investigation was under the general supervision of Robert O. Vernon, Director, Division of Geology, State Board of Conservation; A. O. Patterson, district engineer, Surface Water Branch; C. S. Conover, district engineer, Ground Water Branch; and K. A. Mac Kichan, district engineer, Quality of Water Branch, of the U. S. Geological Survey. A number of individuals and organizations have been most generous in supplying information, equipment, and time in the process of collecting data for this report. The courtesies extended by the following persons are most appreciated: W. C. Cooper of W. C. Cooper Plumbing and Heating Co.; H. L. Berkstresser and W. H. Galloway of the Water and Sewage Department of Panama City; G. Layman, construction engineer for Gulf Power Co.; W. H. Toske and M. G. Southall of the U. S. Navy Mine Defense Laboratory; R. B. Nixon and J. L. Gore of the Tyndall Air Force Base water department; J. M. Lowery and T. M. Jones of the International Paper Co.; A. G. Symons and R. H. Brown of the Layne-Central Co.; W. Brown of the Brown Well and Pump Co.; and J. W. Spiva of Modern Water Inc. Data on the chloride content in water from Deer Point Lake during the period of freshening were furnished by the Florida State Board of Health. V

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PREFACE We would like to express special appreciation to Judge Ira A. Hutchison who through his interest in water resources and in particular the geology of this area has been most helpful. Claude Hicks has volunteered invaluable assistance in the collection of water-level information in the Deadening lakes area. We would like to thank the numerous citizens in the basin who gave us access to their wells and who furnished us with information on their water supplies. vi

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CONTENTS Page Preface .............. ---... ---...-----......--.. .-----..-..-.---v Abstract ...-....................... .---------------------------............-........... 1 [ntroduction ---...........---..-................ ..... ---. ---.. .........---2 The hydrologic environment ---..--............-..-..------------------4 General statement ..........................-------------------4 Physical make-up of the basin ...........-............--------..-..----... 4 Water movement .-.....---....--------------------------7 Water availability .........--....................-------------------8 Rainfall ...................... ........ ..... ..-------------------------8 Water quality characteristics .--..-...-....-........-------.--------9 Contamination by saline water .-......-...............----.........------11 Streamflow ..-.......-...--------..........---------------------15 Storage .-..~.......---.......-.....-.--.----------------------18 Lakes ..--............ .. -------.---. ---------------18 Aquifers ......-...........--..---------------------19 Aquifer characteristics ................---------------------------20 Hydraulics of aquifers ......-........-.....--.-----------------22 Aquifer tests ....-...................-..-------------------24 Water use ......................------------------------------------27 Water high lights of the basin .--.............-... --------------------29 Decline of water levels in the Panama City area ...---...---...--...--..-.......----.. 29 General statement .........-........---------------------29 History of ground-water development ..--------................. .............31 vii

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Page The Deadening lakes ...................................... ...............---35 Geologic and hydrologic setting ..--......--..-..........---------------37 Water levels ...--............---.......--------------------37 Flow of Econfina Creek .......-.................-------------------40 Springs ---..........-...--..--..-...------------------------41 Deer Point Lake .........--.....------------------------45 Summary -..-----.----------------------------.----45 References .......-..---........----------------------------51 viii

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ILLUSTRATIONS Figure Page 1 Map of Econfina Creek basin area ........--......................---............. 3 2 Map of Econfina Creek basin showing physiographic divisions and surface runoff --................. ....-.-..-..--.......--.......-....--.................. Facing p. 4 3 Geohydrologic sections of Econfina Creek basin area --...-..-.......----...-...--. 6 4 Bar graphs of maximum, minimum, and average monthly rainfall, and annual rainfall, at Panama City from 1935 to 1963 ....-........-.....-....---..---9 5 Map of Econfina Creek basin area showing location of data-collection points referenced in report -....--.......-...-..----.....--.....---------------...............-.... 12 6 Scatter diagram showing relation of chloride to total mineral content of water from the Floridan aquifer in the Econfina Creek basin area .... 13 7 Block diagram of Econfina Creek basin showing areal distribution of mineral content and chloride concentration in water from selected wells in the Floridan aquifer -....--...--........................................ -......... .......-14 8 Graphs of chloride concentration in water from selected wells in the Floridan aquifer .............------..--.......-....-........--......-.. ....------------.---15 9 Flow chart of streams in the Econfina Creek basin -..-....--...---........-....-... -17 10 Graphs of water level in the water-table aquifer and rainfall near Bennett for part of 1962 and 1963 ..----.......----......................--.......-.-.19 11 Graph of streamflow of Econfina Creek near Compass Lake for the period April 1 to May 7, 1963 ......-..-...-........--------..-..-.------. -----. 20 12 Sketch showing similarity of an artesian pressure system and water pressure developed by an elevated tank .--..........---.................-----..-----21 13 Map showing the piezometric surface of the Floridan aquifer in the Econfina Creek basin area, October 1962 ...----.........-..---...--...-...----.-23 14 Graphs showing theoretical drawdowns in the vicinity of wells being pumped at a constant rate for selected periods .....-...-.....-...........-...-...... 26 15 Theoretical drawdowns along a line of 10 wells after 100 days of pumping at a rate of 200 gallons per minute at each well -..--.....-..--.... 27 16 Graphs of water use and population in the Panama City area -...-....-.... 30 17 Map of the Panama City area showing the location of water wells for each water system and the area supplied by these systems -..--..-..........--.. 31 18 Map showing the approximate piezometric surface of the Floridan aquifer in the Panama City area in 1908 ---.........---..-.--... -~.. ------. 32 ix

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Figure Page 19 Graph of water levels in observation well 008-537-332 near the center of the International Paper Company well field for the period 1951 to 1963 .-..-..-..........................................-........-..............................----........... .33 20 Map showing the piezometric surface of the Floridan aquifer in the Panama City area in April 1947 ....-......--.......-...................--...-..................... -35 21 Map of White Oak Creek basin in southeastern Washington County showing The Deadening area ..-..-.........-................. .... ...-------........................ 36 22 Geohydrologic sections through the White Oak Creek basin, southeastern W ashington County .............................-.............. .......-......-----....... 38 23 Graphs of water levels and rainfall in the vicinity of the Deadening lakes .....----------------------.. ....... .... .............. ....................... ................. ........ 39 24 Flow chart of Econfina Creek during the low-water period of May 1963 showing the effect on streamflow if 30 mgd were diverted at the proposed dam site ..--.......-..-...-...-..... ---------------------------------.................................. 42 25 Flow chart of Econfina Creek showing spring flow ......-............................... 43 26 Graphs of streamflow, spring flow, and specific conductance for Econfina Creek near Bennett for 1963 ..----.......................... ...................................... 44 27 Graph showing the relation of chloride in water in Deer Point Lake to fresh water inflow --...-----.. .... ...........-----------------.......................... 46 28 Graphs showing the rise of water levels and change in chloride content of ground water after construction of Deer Point Dam ...............--.....-..-.. 47 TABLES Table Page 1 Drainage areas, average flows, and low flows of subbasins within the Econfina Creek basin ----------............-------------------.................................. 16 2 Record of water supply systems in the Econfina Creek Basin area .......... 28 x

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WATER RESOURCES OF THE ECONFINA CREEK BASIN AREA IN NORTHWESTERN FLORIDA By R. H. Musgrove, J. B. Foster, and L. G. Toler ABSTRACT The Econfina Creek basin area of about 1,000 square miles is located in northwestern Florida. Water use in the basin in 1963 averaged about 25.2 mgd (million gallons per day). The major uses of water were for the manufacture of paper products, public and domestic supplies, and recreation. Of the 25.2 mgd, 22.7 were pumped from the artesian Floridan aquifer, mostly in the Panama City area. In February 1964 use of lake water was started at the rate of about 30 mgd and ground-water withdrawal was reduced to about 11 mgd. Since February 1964 the total use of water in the area has been about 41 mgd. The basin receives most of its water from rainfall which averages 58.0 inches per year. Highly porous, unconsolidated sands form the water-table aquifer and absorb much of the rainfall. Seepage from this aquifer is to the streams and to the underlying artesian aquifers. The productive artesian Floridan aquifer underlies the entire basin and is the aquifer from which the most water is pumped. A secondary artesian aquifer is present in the southern part of the basin and is intermediate in depth to the water-table and Floridan aquifers. Movement of water through these aquifers is generally southwestward. By 1963, water levels in the Floridan aquifer near Panama City had been lowered 200 feet by pumping since the first deep well was drilled in 1908. The large drawdowns resulted from heavy pumping of closely spaced wells in this aquifer which has a low transmissibility (1,300 to 31,000 gallons per day per foot). In January 1964, pumpage from a field of 21 wells was stopped and water levels in this field recovered 163 feet within 51 days. Water from the water-table aquifer generally had a mineral content from 10 to 50 ppm (parts per million) and that from the sec1

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2 FLORIDA GEOLOGICAL SURVEY ondary artesian aquifer from 80 to 150 ppm. Water from the Floridan aquifer increased in mineral content from 70 ppm in the northern part to about 700 ppm in the southern part of the basin. Mineral content of water from streams and lakes, exclusive of those receiving artesian spring flow, was from 6 to 25 ppm. Water from springs had a mineral content from 50 to 68 ppm and was similar to water from the Floridan aquifer in the upper part of the basin. Streamflow into the coastal bays is at an average of about 960 mgd. Flow to North Bay is about 680 mgd, of which about 650 mgd flows through Deer Point Lake. East Bay receives about 210 mgd, and West Bay about 70 mgd. Runoff from the lower half of the drainage of Econfina Creek is 90 inches per year. This is about three times the runoff from the upper half of the basin and is a result of artesian spring flow. There are about 80 named lakes in the basin, some of which have a wide range in stage. A plan has been proposed to divert water from Econfina Creek to a group of these lakes in southeastern Washington County to stabilize their levels. At the proposed point of diversion, Econfina Creek has a minimum flow of 30 mgd, which would supply about 0.5 of a foot of water per month on the proposed lake area. INTRODUCTION This report describes and evaluates the water resources of the Econfina Creek basin area located in northwestern Florida. The area encompasses about 1,000 square miles and includes most of Bay County and parts of Calhoun, Gulf, Jackson, and Washington counties, as shown in figure 1. As considered in this report, the Econfina Creek basin area includes all basins that drain into the bay system within Bay County. Over 90 percent of the 70,000 people in the basin are located near the coast and are centered in the Panama City area. In 1963, water use in the basin was at the rate of 25.2 mgd. The three largest water users were the International Paper Company, Panama City, and Tyndall Air Force Base. Ground-water levels were known to be below sea level in well fields supplying the major users. Information was needed to determine the extent of the low water levels and their effect on the water resources of the area. More than 80 fresh-water lakes are situated in the higher parts of the area, mostly in southeastern Washington County. Included is a group of lakes locally known as The Deadening. Considerable

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REPORT OF INVESTIGATIONS No. 41 3 486Od 5e 50 45 4d 3 3 2 2'd 1 aSid WID r, 2 0 1 2; 4 25 Ml WNW 5.IV N -1 -5 N52 0 d -o2 5 Figure 1. Map of Econfina Creek basin area. interest has been expressed concerning the development of The Deadening lakes into a water-oriented recreational area. Widely fluctuating lake levels rendered this recreation plan infeasible without lake controls. The Washington County Development Authority has a plan to stabilize these lakes by water diverted from Econfina Creek. Data were collected during the investigation to evaluate this plan. No formal reports on the water resources of the area were available before this investigation. Some data were available on groundwater levels, streamflow, and the chemistry of ground water. This report is based on a 2-year investigation which began in January 1962. The investigation was designed to provide a basis for an evaluation of the water resources of the Econfina Creek basin.

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4 FLORIDA GEOLOGICAL SURVEY THE HYDROLOGIC ENVIRONMENT GENERAL STATEMENT Water in the natural state continually moves due to many forces acting upon it. Gravity acts on water in streams and underground to keep it moving downward toward the level of the ocean. The sun and wind evaporate water from open water bodies and plants transpire water to the atmosphere. Gravity again moves the water earthward when the atmospheric moisture meets conditions favorable for rain. This never ending movement of water is known as the hydrologic cycle. The water resources of any area depend upon this hydrologic cycle. When the rate of water movement out of an area exceeds the rate of water movement into the area, water shortages will develop. Water shortages may also develop if the quality of water is significantly altered within its natural environment to make it unfit for its intended use. Variations in the rate of movement in any phase of the hydrologic cycle, such as rainfall, may also affect an area by resulting in floods and droughts. Proper development of the water resources of an area requires a thorough knowledge of water movement and the factors controlling it. This knowledge will enable the best prediction of where to obtain water and what provisions are required to control water movement. In general, the system through which water moves in the Econfina Creek basin is similar to most river basins in Florida. Like most other basins, (1) rainfall is the source of all the water even though some falls outside the basin and moves into the basin underground; (2) the surface materials are highly porous, unconsolidated sands; (3) the basin is underlain by the artesian Floridan aquifer; and (4) water leaves the basin by streamflow, evaporation, transpiration, underground flow to the ocean and other basins, and by consumptive use. PHYSICAL MAKEUP OF THE BASIN Four physiographic divisions within the basin affect the surface drainage and the water storage. These are the sand hills, sinks and lakes, the flat-woods forest, and the coastal beach sand dunes and wave-cut bluffs, shown in figure 2. The physiographic divisions have developed on a series of stair-step marine terraces which were carved into the surface sands during the ice age by the successive levels of

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86"00' 55 50' 45 40 35 30 25' 20 15' 83*10 ECONFINA CREEK BASIN AREA E 30035ý 30'33 3 GREENHEA i II0 TAIN 1 0 1 2 3 4 5 Miles Esr ! 2d IO CIT EXPLANATION PHYSIOGRAPHIC DIVISIONS 5 al Sand hills A, C 0 ,: Sinks and lakes a IiMaia Flatwoods forest S30WBeach dunes and wave-cut bluffs 37 Numbers represent average annual runoff in inches from areas outTr-EWAy lined by dashed lines, 8o0 55' 50 45' 40' 35' 30' 25' 20' 15' 8510' Figure 2. Map of Econfina Creek basin showing physiographic divisions and surface runoff.

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REPORT OF INVESTIGATIONS No. 41 5 the ocean. Low swampy areas occur throughout each of these divisions but are more prevalent in the flat-woods forest. The sand hills in the northern part of the basin are erosional remnants of the higher marine terraces which were between 100 feet and 270 feet above the present sea level. The sinks and lakes occur in the section of the basin west of Econfina Creek where they have developed within the sand hills. This area is typified by irregular sand hills and numerous sink holes and sink-hole lakes. The sink holes range in diameter from a few feet to broad flat areas such as those in The Deadening lakes area (see p. 73). This physiographic division was developed by the solution of the underlying limestone and the subsequent collapse of the overlying material into the solution chambers. Most of the lakes have no surface outlets. The flat-woods forest is the largest physiographic division of the basin. It is slightly rolling to flat land lying on the terraces below an elevation of 70 feet. Most of this division is covered with pines except for a few small areas cleared for agriculture. The flat-woods forest is well drained except for some low areas around the bays on the 0 to 10 and 10 to 25 foot terraces. During rainy weather these low areas of the flat woods become quite wet. A few small perennial swamps occur at various locations throughout the flat-woods forest. The largest is Bearthick Swamp southeast of Youngstown which covers an area of about 2,000 acres (fig. 2). The fourth physiographic division occurs adjacent to the gulf coast and is characterized by beach dune deposits and wave-cut bluffs. The beach dune deposits are the youngest sediments in the basin and are the most rapidly changing physiographic feature. The surface materials in the basin, on which the physiographic features have developed, are generally very porous, permeable sands. The sands form the water-table aquifer which is thicker in the sand hills (80 to 100 feet) than in the lower elevations of the flat-woods forest (10 to 30 feet) and thickens again along the coast (65 to 140 feet). The sands are missing only in stream channels and in some parts of the broad depressions of the sinks and lakes division. The sands of the water-table aquifer cover a relatively impermeable layer of sandy clay and clayey shell material which forms an aquiclude (a formation that confines water to aquifers above and below it) between the water-table aquifer and the artesian aquifers below it, as shown in figure 3. This aquiclude is present throughout the basin except where it has been breached by a collapse into solution chambers or by erosion along Econfina Creek.

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240 -I -240 10 -0 160 Sso So level 0 ------0 Seatle F I D AN AQU IFER EXPLANATIONL T ! I "T -0 So1 i w 80-.4 ... r. 1 .r. -.60 240 Sond 240 SShells -320 400 Clay -400 , ;, .. Limestone j" .,--49 0 so .I A AE : : : jo , S _ I T ., e., -----AQUICLUDE g. -" ." ..." E !-,',.. -16 A --uu .. " ----AQUICLUDE -UICL1 LUDE 01 1 1 l 320 400 -400 FLORIDAN AQUIFER .640 1 1 -i .640 0 1 2 3 4i 5 10 miles Figure 3. Geohydrologic sections of Econfina Creek basin area.

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REPORT OF INVESTIGATIONS NO. 41 7 In the bay area and along the gulf coast in the basin, two artesian aquifers are associated with the aquiclude. Here the aquiclude is thicker than it is to the north and is overlain and in part underlain by some shell-hash beds which contain water. The sandy clay material which forms the base of the water-table aquifer is sufficiently impermeable to confine water in the shell-hash beds under artesian pressure. Water producing zones in the shell-hash beds above the aquiclude are termed the secondary artesian aquifer. The water producing zones in the shell-hash beds below the aquiclude are considered part of the Floridan aquifer. The Floridan aquifer underlies the entire basin below the aquiclude. It is composed of limestone formations that are as much as 1,200 feet thick. However, the usable part of the aquifer, the part producing potable water, is the upper 500 to 700 feet. WATER MOVEMENT Rain, falling on the basin, is readily absorbed by the porous surface sands. The portion that runs off directly to the streams depends on the amount and intensity of the rainfall. The rain water and the surface water are relatively pure but contain some salts carried in the evaporate from the ocean and some gases dissolved from the atmosphere. The surface water becomes colored after contact with decayed organic matter but the mineral content changes very little. The water absorbed by the sands seeps downward to the water table, the level below which the sand is saturated. The sands are not very soluble in the rain water and consequently the mineral concentration in water from the water-table aquifer is low. Some of the water then moves from the water-table aquifer into the streams and maintains flow during periods of no rainfall. In the northern part of the basin where the sand and clay are breached by sinkholes, some of the runoff and seepage from the sands is temporarily ponded in lakes and then moves into the Floridan aquifer. In other areas the water from the sands may seep slowly into the limestone through the clay layer. The amount of water moving from the water-table aquifer to the Floridan aquifer diminishes toward the southwest because the aquiclude is thicker. Water that moves downward into the limestone of the Floridan aquifer then moves in the down gradient direction shown by the piezometric map (see p. 23). The gases acquired from the atmosphere and from the soil zone form a weak acid solution which dissolves the limestone and thereby causes an increase in the mineral I

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8 FLORIDA GEOLOGICAL SURVEY content of the water. The mineral content of the water increases in the down gradient direction as more limestone is dissolved. In areas along Econfina Creek where the artesian pressure surface is above the land surface and the sand and clay are missing, springs have developed. Most of the flow of Econfina Creek is derived from these springs. In the southern half of the basin, water may percolate downward from the water-table aquifer into the secondary artesian aquifer. The sandy clay material at the base of the water-table aquifer and at the top of the secondary artesian aquifer acts as a semi-confining layer which maintains the water in this aquifer under artesian conditions. The secondary artesian aquifer is composed of shell-hash with interlayered sand and limestone lenses. Water that moves into this aquifer from the water-table aquifer is slightly acid. This water dissolves the limestone and shell giving the water a calcium bicarbonate character. The water withdrawn from wells in the Floridan aquifer in the Panama City area entered the aquifer through the sinks in the northern part of the basin and in areas farther north where the limestone formations are at ground surface. By the time the water reaches Panama City the mineral concentration is five to six times that of water in the northern part of the basin. Part of the increase is caused by solution of the limestone and part is caused by mixing with older water in the rocks. The pressure gradient shows that the water is being flushed into the ocean at some point where the rocks are exposed to or hydraulically connected to the ocean bottom. WATER AVAILABILITY The amount of water moving through each part of the hydrologic system must be known to properly evaluate a water resource. A knowledge of the environment is necessary to determine the chemical and physical properties of the water and to predict any changes in these properties that may result from withdrawal of water from the system. Some of the parameters that affect the amount and quality of water available are rainfall, streamflow, water levels, rock composition, and the ability of aquifers to store and transmit water. These hydrologic features can be measured either by direct or indirect methods. RAINFALL The Econfina Creek basin receives an average rainfall of 58 inches per year, based on records collected at Panama City by the U. S.

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REPORT OF INVESTIGATIONS No. 41 9 Weather Bureau. During the past 29 years the annual rainfall at Panama City has varied from 37.6 inches to 85.0 inches. Graphs showing variations in rainfall are given in figure 4. Short periods 25 100 W 20 -80 iAVERAGE 57.98 Z MAXIMUM 95 60 F, 10 40 ZLAG AVER G S5 20 0 0 JIFMIAIMIJ IJIA SIOINID to o 0 o 0 o I q I It 9) (0 I I Figure 4. Bar graphs of maximum, minimum, and average monthly rainfall, and annual rainfall, at Panama City from 1935 to 1963. of low rainfall and short periods of high rainfall have little direct effect on the water resources; that is, the amount of water in storage. Extended periods of below-average rainfall, or droughts, cause reduction in storage. The most severe drought of record ended in 1956 with a 7-year deficiency in rainfall of 50.2 inches. Within this 7-year period, 1953 was a single year of above-average rainfall but did not bring about a complete recovery of water lost from storage during Sthe preceding years of low rainfall. The 6-year period from 1944 to 1949 was the wettest of record. Records of water levels indicate that storage was near an all-time high during this wet period. WATER QUALITY CHARACTERISTICS The water in the lakes and streams of the area has about the same mineral concentration as rain water. Samples of rain water contained as much as 13 ppm of dissolved mineral matter; the water in the streams and lakes ranged from about 6 to 25 ppm. The mineral concentration of the surface water differs little from rainwater because of the relative insolubility of the surface materials. During periods of low flow, high mineral concentrations are normally expected in stream water because a large part of the flow is seepage from the

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10 FLORIDA GEOLOGICAL SURVEY water-table aquifer. No difference in the chemistry of surface water in the basin was noted between high and low flow except for the color and pH. High color immediately following a rain is attributed to the flushing of the decayed organic material from the swampy, poorly drained areas adjacent to the streams. This same colored water tends to be acid due to the solution of carbon dioxide released from the decaying plants. The pH of the streams is lower (more acid) during high flow when the flushing of the swampy areas occurs. The pH normally ranges from 6.0 to 7.0 units but falls below 6.0 during these times. Two areas of exception to the normal low mineral concentration in stream water occur in the Econfina Creek basin. One of the areas is along Econfina Creek downstream from a point about due east of Porter Lake, where the creek receives flow from artesian springs. These springs emanate from limestones of the Floridan aquifer and the chemistry and relative solubility of the rocks are reflected in the mineral constituents found in the water. The mineral concentration in water from the springs ranged from 50 to 68 ppm and all but about 10 to 12 ppm were calcium and magnesium carbonate, the constituents of limestone. The mineral content of the water in Econfina Creek, downstream from where spring water enters, is higher than that in other streams in the basin, and varies with the ratio of spring flow to surface runoff. Calculations, based on chemical analyses, (see p. 84), show that 70 to 75 percent of the base flow of Econfina Creek at the Bennett gaging station is from springs. The other area of exception to normal low mineral concentrations in stream water is near the mouth of the streams which empty into salt-water bays. Salt water moves up the streams a distance that is dependent upon the elevation of the streambeds, the stage of the streams, and tides. This encroachment of saline water occurs in the mouths of all streams except those emptying into Deer Point Lake, which is a fresh water body. That part of the rainwater that replenishes the aquifers continues to move in the hydrologic cycle but at a slower rate than the water moving as surface flow. This slow rate of movement allows a state of chemical equilibrium to be approached and normally results in ground water having a higher concentration of mineral constituents than does the surface water in an area. The highly insoluble nature of the sands which form the water-table aquifer in the Econfina Creek basin results in low mineral concentration of water in this aquifer. Generally, the concentration of total mineral constituents in water from this aquifer ranged from 10 ppm (about equal to that of rainwater)

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REPORT OF INVESTIGATIONS NO. 41 11 ,o about 50 ppm. In areas near the coast these sands are in contact vith salt water. All water from the water-table aquifer which contained more than 50 ppm dissolved minerals was from wells located within a few hundred feet of salt-water bodies. Water in the secondary artesian aquifer is slightly more mineralized than water in the water-table aquifer. In some areas near the coast the water from this aquifer may be saline. Where there is no contamination by saline water, the water generally contains from 80 to 150 ppm dissolved minerals and is principally a calcium bicarbonate water. Most of the water samples contained hydrogen sulfide and some samples contained sulfate. The mineral concentration of water from the Floridan aquifer is higher than that from the secondary artesian or the water-table aquifers. In the northern part of the basin the higher mineral content is due entirely to higher concentrations of calcium and bicarbonate resulting from solution of the limestone. There are definite trends in mineral concentrations in water in the Floridan aquifer. These trends have been mapped (Toler and Shampine, 1964) and generally show increases in all constituents toward the southwest. An adaptation of the map of dissolved solids is shown on page 14 and indicates the trend of all the constituents. Sulfate, sodium, and hydrogen sulfide show little trend, but are found in significant quantities in the southern half of the basin. In this area, sulfate ranged from 0 to 81 ppm, sodium from 2 to 164 ppm, and the odor of hydrogen sulfide was detected in water from most wells. CONTAMINATION BY SALINE WATER The large bays in the southern half of the Econfina Creek basin provide an access for salt water several miles inland. Along the shoreline of these bays and along the Gulf, the salt water is in contact with the sands which form the water-table aquifer. During droughts, when the water levels in the sands are low, salt water may enter the aquifer and be pumped from shallow wells near the shore. Salt water is more dense than fresh water and it moves into the aquifer in the form of a wedge below a lens of fresh water. Fresh water will generally suppress the salt water about 40 feet below sea level for every foot of elevation of fresh water above sea level. If the water level in the aquifer is lowered by pumping, the saline wedge adjusts to the new water levels and salt water may rise to contaminate a well. An interzone of water of intermediate composition is normally present instead of a sharp fresh-water salt-water interface.

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12 FLORIDA GEOLOGICAL SURVEY Salt water may enter the secondary artesian aquifer from the bays or from the water-table aquifer, when the pressure surface of the secondary artesian aquifer is below the water level of either source. Highly saline water from the secondary artesian aquifer was observed in samples from two wells. One well (007-535-334a), shown in figure 5 es a d 5d 4d d 3d sd 2a 2d I ad 30/ --45 4d Figure 5. Map of Econffna basin area showing location of data-collection points referenced in report. is 76 feet deep and the water contained 1280 ppm chloride. The other well (008-545-224, fig. 5) is 101 feet deep and the water contained W 2du IS-LUMM A 32 well (008-545-224, fig. 5) is 101 feet deep and the water contained

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REPORT OF INVESTIGATIONS No. 41 13 1090 ppm chloride. Both of these are adjacent to saline surface-water bodies. Wells penetrating the underlying Floridan aquifer, at and near these locations, produce water low in chloride. The saline water is presumed, therefore, to have leaked from the bays through the water-table aquifer. Apparently, the aquiclude overlying the Floridan aquifer (fig. 3) in the coastal and bay area is sufficiently impermeable to prevent leakage of water from the overlying aquifers. The occurrence of chloride in water in the Floridan aquifer does not appear to be related to areas of high chloride in water in the overlying sediments or to the bays. Water levels in the Floridan aquifer have been lowered below water levels in both the water-table aquifer and the secondary artesian aquifer, by pumping in the major well fields. Extended periods of low water levels in the Floridan aquifer have not resulted in an increase in the chloride concentration of water from this aquifer as would be expected if the aquiclude were leaking. The chloride content of the water increases southwestward, the general direction of water movement. The fresh water apparently mixes with saline water in the aquifer to account for the increase in chloride. Figure 6 shows the relation of the increase in total mineral 400 30 -J·S 3 00 --------------_---_----_----_----_________ .Only those samples containing greater than 5 ppm chloride included **' 200 S00_____ _____ _____ _____ 0 100 200 300 400 500 600 700 800 900 MINERAL CONTENT, IN PARTS PER MILLION Figure 6. Scatter diagram showing relation of chloride to total mineral content of water from the Floridan aquifer in the Econfina Creek basin area. concentration of the water to the increase in chloride for all samples containing more than 5 ppm chloride. Figure 7 is a block diagram of a section along the coast showing chloride concentrations and water producing intervals of wells pene-

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14 FLORIDA GEOLOGICAL SURVEY I-C 20 Ch loide, in pm S* Tap o hi Flaridan Aquifer--„. 250Oissolved solidi in parts per million s ' (Btfapt~id It Tolwe anid Shmples, 1904) 275 Well (number indicotes dissolved solids in ppm) Figure 7. Block diagram of Econfina Creek basin showing areal distribution of mineral content and chloride concentration in water from selected wells in the Floridan aquif r.

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REPORT OF INVESTIGATIONS No. 41 15 trating the Floridan aquifer. The chloride concentration generally increases with depth into the aquifer. No chloride mineral is present in the rock-forming materials and if water is not leaking from the overlying rocks, then this saline water must be residual water that remains in the rocks from a time when they were in contact with the sea. The geologic history (Foster, in preparation) indicates this may have happened many times. The residual water in the rocks would be from sea water and chemically would probably differ little from present sea water. Records of chloride content in water from four wells, from 1950 to 1963, are given in figure 8. Although there is considerable variation 350 -350 004-55\-333 3004»7ff. d.ee -300 S010-43-42--. 2 -00 0 537-332 * 0'3o0 5 00.. 1e e \ l 1'\ /\ /V .V.. .' 0-333-121 . S" -\ ft. d o" \ Pf 2 3"'.'\ .l\ !. 0\' \ / \ I o o .1»« I I . 3010 a 130 1951 1953Z 1I9 1934 155 1933 6 I23 2 203 19523 2160 2002 2062 0iri0 Figure 8. Graphs of chloride concentration in water from selected wells in the Floridan aquifer. in the chloride concentration, there appears to be no long-term trends due to pumping. STREAMFLOW In using a stream, two quantitative aspects to be considered are channel storage and the rate of flow. Channel storage is important in considering uses such as boating, fishing, and other recreational activities. The rate of flow must be considered when determining the quantities of water that can be withdrawn from the stream at any time. Only the larger streams in the Econfina Creek basin have enough

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16 FLORIDA GEOLOGICAL SURVEY channel storage during periods of low water to be used for boating. Most of the streams have sufficient flow to be a potential water supply. During periods of minimum flows there is more than 10 times as much fresh water flowing into the bays than is being withdrawn from all sources in the Panama City area. Streamflow in the basin comes from several sources. During and immediately following rains water flows directly into the streams as overland flow. Between rains the streams receive only water that seeps from the shallow sands and from artesian spring flow from the limestone formations. Every stream receives seepage from the shallow sands. Streamflow to the bays is at an average rate of about 960 mgd which amounts to 40 percent of the average rainfall. About 650 mgd flows through Deer Point Lake into North Bay from Econfina Creek, Bear Creek, Big Cedar Creek, and Bayou George Creek. Another 30 mgd flows into North Bay below Deer Point Dam from smaller streams. West Bay receives a flow of about 70 mgd from Burnt Mill Creek, Big Crooked Creek and smaller tributaries. East Bay gets about 210 mgd from Wetappo Creek, Sandy Creek, Calloway Creek, and smaller streams. Figure 2 shows values of runoff from areas within the Econfina Creek basin. It can be seen from this map that the physiographic features affect runoff. The low runoff in the southern half of the basin results from the poor drainage of the flat-woods forest. Drainage in the sinks and lakes division is mostly internal and there is almost no surface runoff. High base flow due to seepage from the porous sands causes the high runoff in the sand hills division. The extremely high runoff of 90 inches from the lower half of Econfina Creek is a result of the artesian spring flow. TABLE 1. Drainage areas, average flows, and low flows of subbasins within the Econfina Creek basin. Drainage area Average flow Low flow Creek basin sq. mi. mgd mgd Econfina Creek --.....--..........................-.... 129 355 226 Bear Creek .-------------.......... ........... ............... 128 226 52. Wetappo Creek ---...-.....-..................... ... --77 80 6 Sandy Creek ----------........ ................ .... 60 70 10 Bayou George Creek ..---.......---...-... 51 26 3 Burnt Mill Creek ---......... ................. 45 23 8 Big Crooked Creek .....--........---..-....-----.. 22 17 6 Big Cedar Creek -....... .. ....----.....-. .62 12 4 Calloway Creek ...................._.. __._.._. .13 9 .6 All others .....................-.......... -........ -142

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REPORT OF INVESTIGATIONS NO. 41 17 Stream data are given in table 1. The values of streamflow, except those for Econfina Creek, are estimated from short-term continuous discharge records or from periodic discharge measurements. The low flow of a stream without storage reservoirs limits its use. Much more water can be taken from streams if storage reservoirs are available from which to draw during periods of extreme low flows. The flow chart in figure 9 shows the streamflow pattern of the basin. The average flow of Econfina Creek is 355 mgd, by far the largest of all the streams. This is a runoff of 58 inches per year and is FLOW CHART Width of stream represents average flow in million gallonsper day. EI b Flow Scale fm e L,° { A'SHINGTON .COUNTY. cBi N a T COUNTY i e 9Loke 1 0 FY 9. F hw George Creek Figure 9. Flow chart of streams in the Econfina Creek basin.

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18 FLORIDA GEOLOGICAL SURVEY about equal to the annual rainfall on the drainage area of 129 square miles. Streamflow records have been collected since 1936 at Porter Bridge near Bennett at a point where the drainage area is 122 square miles. The average flow of Econfina Creek from the upper half of the basin is 90 mgd, only one-fourth of the flow from the entire basin. Upstream from Tenmile Creek (fig. 1) the flow during dry periods is seepage from the shallow sands. Downstream from Tenmile Creek artesian springs contribute most of the dry-weather flow. The minimum flow from the entire drainage area of Econfina Creek is about 210 mgd, or seven times the minimum flow of about 30 mgd from the upper half of the drainage area. Floods occur on Econfina Creek almost every year. The creek has overflowed its banks at least once each year in all but six of the last 28 years. The longest period that it has stayed within its banks is the 3-year period August 1950 to September 1953. Bear Creek is the second largest creek in the basin and has an average flow of 226 mgd. It drains almost entirely from the sand hills and flow is supported by seepage from these sands. The average total surface flow into the bays was estimated as 960 mgd. Econfina Creek and Bear Creek contribute 581 mgd of this flow. The remainder of the average flow (379 mgd) comes from the smaller streams in the basin. The larger streams are listed in table 1. STORAGE Rainfall, although it varies, supplies an adequate amount of water to the basin. Water held in storage in lakes and aquifers eliminates frequent shortages which would result from the inconsistent rainfall. LAKES There are about 80 named lakes in the basin. Most of the lakes are in southeastern Washington County. Deer Point Lake (see p. 87), a fresh-water reservoir covering 4,700 acres in Bay County, is the largest. Porter Lake in Washington County has a surface area of 930 acres and is the largest natural lake. The natural lakes have not been developed for water use to any great extent although they offer considerable potential as recreational facilities. Wide fluctuations in most lake levels, caused by seepage losses to the ground and variations in rainfall, discourage their development. The Washington County Development Authority has pro-

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REPORT OF INVESTIGATIONS No. 41 19 posed a plan to divert water from Econfina Creek to a group of lakes known as The Deadening (see p. 73) and thereby stabilize their levels. This plan, if executed, would add about 4,000 acres to the normal size of this group of lakes. AQUIFERS The three aquifers -the water-table aquifer, the secondary artesian aquifer, and the Floridan aquifer -store large quantities of water. The portion of rainfall that enters these aquifers through downward percolation is stored temporarily. Water contained in the water-table aquifer discharges slowly by downward percolation to the underlying aquifers and to the streams and lakes through seepage and small springs. The water-table aquifer, in the basin, is composed of fine to coarse sand and contains a volume of water approximately one-fourth the volume of the saturated section. The fluctuation of water levels in the water-table aquifer is an indication of the change in storage, shown in figure 10. During dry periods the water levels decline as the aquifer discharges the water from storage. In wet periods water levels rise as more water is received by the aquifer than is discharged. Exclusive of flow from the artesian aquifer, the low flows of the streams are maintained by seepage from the water-table aquifer and jU) --.in 0 lo \/ Well 023-532=124, a 12 -at Bennett
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20 FLORIDA GEOLOGICAL SURVEY are indications of the size and ability of the water-table aquifer to store and transmit water. Figure 11 is a graph of streamflow of Econfina Creek near Compass Lake for the period April 1 to May 7, 1963. 30 I8 I I 1 1 1i lili I I I I I I III I i i i i i II 0 °I I 5 10 15 20 25 30 5 APRIL 1963 MAY Figure 11. Graph of streamflow of Econfina Creek near Compass Lake for the period April 1 to May 7, 1963. The low-flow portion of this graph represents seepage from the watertable aquifer. The nearly flat slope of the low-flow portion of this graph, such as that immediately preceding the rise of April 30, shows that storage of water in the aquifer is sufficient to maintain the low flow for long periods of no rainfall. The secondary artesian aquifer which is present along the Gulf coast also provides for storage of water in the basin. This aquifer is saturated at all times, therefore the volume of water stored in it does not change. Water discharges from this aquifer to the Gulf and to wells. There is some exchange of water between this secondary artesian aquifer and the aquifers above and below. The Floridan aquifer is the most extensive aquifer in the basin and the one from which most water is obtained. A more detailed study was made of the characteristics of this aquifer. AQUIFER CHARACTERISTICS Certain hydraulic features of aquifers are of prime importance to water-supply planners and developers. These hydraulic features, ob-

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REPORT OF INVESTIGATIONS No. 41 21 tained from well data, should be determined before the first well field is developed. A thorough knowledge of the hydraulics of an aquifer will enable the planners to predict how much water the aquifer will supply. In the design of a well field the planner should know how much water he can expect to pump from each well without overdrawing the aquifer; what the optimum spacing of wells should be to keep pumping interference between wells to a minimum; what the design of each well should be as to the diameter, depth of casing, length and setting for screens or depths of open hole in a consolidated rock aquifer; and the required pump specifications. The water in an artesian aquifer is under pressure much the same as water in a pipe leading from an elevated water tank, as shown in figure 12. The piezometric (pressure) surface in an artesian aquifer Elevoted Tak Level to which'water would rise in standpipes with no discharge 10-------------------. --------------------100 Level to which water would rise in _a standpipe when water is 75 -discharging CO c .50 a JV l \ wl w ^^^SSQ^^' ^ ^£r\^ -L^~Pierometric Surface cJ Ioo. 5 0 --. , L Figure '12. Sketch showing similarity of an artesian pressure system and water pressure developed by an elevated tank. -j 0pressure developed by an elevated tank.

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22 FLORIDA GEOLOGICAL SURVEY is the level to which water will rise in cased wells drilled into the aquifer, and is likened to the level of water in a vertical pipe that taps a city water main. Water can be taken from an artesian aquifer and the piezometric surface lowered without dewatering the aquifer. Only when the piezometric surface is lowered below the top of the aquifer is the aquifer dewatered. The quantity of water that can be withdrawn without dewatering the aquifer depends upon the ability of the aquifer to transmit water and the rate of recharge to the aquifer. HYDRAULICS OF AQUIFERS When a well that taps the Floridan aquifer begins to discharge water, the piezometric surface surrounding the well is lowered. A cone, centered at the discharging well, describes the shape of the lowered pressure surface in the vicinity of the well. This lowered pressure surface near a well or a group of wells in a producing field is referred to as the cone of depression or cone of influence. This cone of depression is graphically portrayed by the cones developed in the piezometric surface of the Floridan aquifer in the vicinity of the well fields in the Panama City area, as shown in figure 13. In the initial stages of development the cone of depression is small in diameter and depth. As discharge from the well continues the cone spreads out. The lowering or drawdown of the pressure surface at the well continues until the amount of water being discharged is balanced by an equal amount being transmitted through the aquifer to the well. This balance can be achieved by a decrease in natural discharge or an increase in natural recharge. When pumping stops the pressure surface begins to recover, rapidly at first, then at a progressively slower rate. With no further pumping in the vicinity the pressure surface will eventually recover to the initial level. The response of an aquifer to pumping from one well or a group of neighboring wells in terms of the rate and extent of drawdown in the pressure surface, and the quantity of water that the aquifer will produce is related to the hydraulics of the aquifer at that location. The principal hydraulic properties of an aquifer are its ability to transmit and to store water. An artesian aquifer, such as the Floridan aquifer in the Econfina Creek basin, functions as a conduit through which water moves from the areas of recharge to the areas of discharge. The aquifer's ability to transmit water is expressed in terms of its coefficient of transmissibility. It is the quantity of water, in gallons per day, that will flow

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REPORT OF INVESTIGATIONS No. 41 23 .Ad,' d As' A Ad 30 25' 20i 8o' asd H ,0 L -E' U w I J A C K S 0d .L .. SWI N N I j^ -c^ ^ ^ ^ ^L --------------r ^ A "" 2 .1 Figure 13. Map showing the piezometric surface of the Floridan aquifer in the Econfina Creek basin area, October 192. through a vertical section of the aquifer one foot wide and extending the full height of the aquifer, under a unit hydraulic gradient, at the ", O .AN L 0 ; prevailing temperature of the water. o o i/ The coefficient of storage of an aquifer is the volume of water released from or taken into storage per unit surface area of the aquifer

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24 FLORIDA GEOLOGICAL SURVEY per unit change in head normal to that surface. This storage coefficient for an artesian aquifer is a measure of the small amount of water released or taken into storage when the aquifer compresses or expands due to changes in water pressure. AQUIFER TESTS The coefficients of transmissibility and storage are determined by the analysis of data obtained by aquifer tests or pumping tests. Three aquifer tests were carried out during the field investigation of the Econfina Creek basin utilizing available wells in the Floridan aquifer. In each of the three tests conducted, a well was pumped at a constant rate while water levels were measured in the pumped well and in one observation well. A test of short duration was run at Bid-a-wee (fig. 5) using a standby supply well and an observation well belonging to the city of West Panama City Beach. The pump was operated for a period of 6 hours at a rate of 55 gpm (gallons per minute). The rate of drawdown and the rate of recovery of the water level were measured in the observation well, 49 feet from the pumped well. A similar test was made at Long Beach (fig. 5) in which one well was pumped for a period of 5 hours at a rate of 328 gpm. In this test the observation well was 1,800 feet from the pumped well. The third test was made at the Lansing Smith Steam Plant (fig. 5) northwest of Lynn Haven. In this test one well was pumped at a rate of 504 gpm for a period of 50 hours. The observation well was 1,195 feet away. The Theis graphical method (Theis, 1935) was used to compute values of T (coefficient of transmissibility) and S (coefficient of storage) from the test data. The following values of T and S were computed: Bid-a-wee test T= 2,000 gpd/ft S=1.2X 10-4 Long Beach test T= 4,000 gpd/ft S=5 X10-4 Lansing Smith Steam Plant test T=30,000 gpd/ft S=3X10-4 These computations are based on the assumptions that the aquifer is (1) of uniform thickness; (2) of infinite areal extent; and (3) homogeneous and isotropic (transmits water equally in all directions). Determinations of T and S from data collected during these three tests give a wide range of values and show considerable change in the hy-

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REPORT OF INVESTIGATIONS NO. 41 25 draulic character of that part of the aquifer penetrated by the wells at each of the test site locations. The wells used in the tests penetrated the upper 330 feet of the aquifer at Bid-a-wee, 245 feet at Long Beach and about 250 feet at the Lansing Smith Steam Plant. None of the wells used in these tests penetrated the full thickness of the aquifer. Deeper wells would draw water from a greater thickness of the aquifer and would, consequently, give higher values. The values of the coefficient of storage from these tests are consistent with values for the Floridan aquifer in other areas. The coefficient of transmissibility of the aquifer at the Lansing Smith Steam Plant is higher than at the other test sites. This may indicate vertical leakage into the aquifer from the overlying formations. Because the tests show considerable differences in the coefficient of transmissibility of the aquifer within the bay area, the coefficient of transmissibility determined from pumping tests nearest a proposed well field should be used. Additional tests should be made at distant locations before a well field is designed. In order to predict the amount and areal extent of drawdowns that will result from different rates of pumping and different well spacings, computations were made using the Theis formula (Theis, 1935) and the coefficients of transmissibility and storage determined at the Lansing Smith Steam Plant, at Bid-a-wee, and at Long Beach. Figure 14 shows theoretical drawdowns in the vicinity of a well discharging at a constant rate for different lengths of time at the Lansing Smith Steam Plant, the Long Beach, and the Bid-a-wee locations. These drawdowns represent the conditions that would result from continuous pumping at this rate. Because drawdowns vary directly with discharge, drawdowns for greater or lesser rates of discharge can be computed from these curves. For example, the drawdown 100 feet from a well at the Lansing Smith Steam Plant discharging at 500 gpm would be 24 feet after 100 days of pumping. If the well had discharged at 100 gpm for the same length of time, the drawdown at the same distance would have been only one-fifth as much, or about 5 feet. The graph of drawdowns along a line of 10 wells, spaced 2,000 feet apart, at a rate of 200 gpm, are shown in figure 15. The values used to determine this profile were obtained by summing the overlapping drawdowns for each well in the line as read from the 100-day curve for the Long Beach test (fig. 14). Similar graphs can be computed to determine the drawdown that would result from different pumping rates or different well spacings (Lang, 1961, Theis, 1957). The cone of depression in the vicinity of a well or a well field being pumped at a constant rate will eventually stabilize if a balance

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26 FLORIDA GEOLOGICAL SURVEY DISTANCE, IN FEET, FROM DISCHARGING WELL !0 100 1000 10o00 100,000 ..z 300 gp rn T = 2,000 gpd/ft 0 t. S 0.00012 3CC 4C I I I I I I III I I BID-A-WEE TEST Io 100 1000 10,000 100,000 %: \ v .Computations based on: Q=500gpm T= 4,000 gpd/ft. SI S= 0.0005 Ct I it I 1I LCNG BEACH TEST 0 )00 1000 10,p00 100 00 20 , -Computations based on: SWOO C3 0:500 gpm ST =30,000 gpd/ft S= 0.0003 I40 ---I-! I ! i I l t i lI I I l l ifit LANSING SMITH STEAM PLANT TEST Figr-e 14. Graphs showing theoretical drawdowns in the vicinity of wells being pumped at a constant rate for selected periods.

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REPORT OF INVESTIGATIONS NO. 41 27 THOUSANDS OF FEET 25 20 15 10 5 0 5 10 15 20 25 150--IComputations based or 200 T= 4,OOgpd/ft. S= .0005 250 __ Figure 15. Theoretical drawdowns along a line of 10 wells after 100 days of pumping at a rate of 200 gallons per minute at each well. is established between the amount being pumped and the amount moving to the well, either through a decrease in natural discharge or an increase in natural recharge. Water-level records (p. 33) in the well field of the International Paper Company show that the cone of depression in that well field had stabilized by 1951 as a result of controlled pumping. WATER USE Water planners should know how much of the available water is being used and the areas from which it is taken. Oftentimes, the amount of water available in an aquifer is ascertained by determining how much is being withdrawn and by measuring the effects of this withdrawal on the water levels in the aquifer. For example, the low water levels in the Floridan aquifer prior to February 1964 were near the level where dewatering of the aquifer would begin near the centers of heavy pumping. The major uses of water within the Econfina Creek basin are recreation, manufacture of paper products, and public and domestic supplies. An undetermined though relatively small amount is used for irrigation. More than 80 named lakes, inland bays that cover over 100 square miles, and the larger streams are used for recreation. Information was collected on the various municipal and industrial uses of water within the basin, except recreation, in order to estimate the total amount being withdrawn. Data on principal water-supply systems are given in table 2.

PAGE 39

T'I'AIj 2. Itwclirl of watcr Uilpply s f.yst'rs in tli IKc'onflna (rrtk lasin urea. o Aquifer: F, Floridan; W, wator table. F, floculation; I, recarbonation; Treatment: A, aeration; C, coagulation; CI, chlorination; S, softening; St, stabilization, Capacity of Number Well-pump Ground Elevated stand by Yearly pumpaeg Location of wells Aquifer capacity storage storage Treatment well pump (millonH of Remarks (gpm) (gallons) (gallons) (gpm) gallons) Panama City: St. Andrew Plant 8 F 285 to 500 1,000,000 300,000 A, St, CI, 8 800 866.8 Ground storage -2 tanks 500,000 each, Elevated storage for Panama City system -3 tanks -100,000 gal, ea. Millville Plant 3 F 430 to 500 400,000 -A, St, Cl, S 600 660.2 4 W e175 --A, St,CI, S -Lynn Haven 2 F 750 100,000 100,000 A, Cl -95.5 --700 30 -2 tanks -350 each West Panama City Beach 2 F 500 1 reservoir 250,000 A, Cl 500. 84.9 Long Beach 2 F 328 -100,000 Cl 328 76.1 Tyndall Air Force Base 0 F 300 to 600 240,000 500,000 A, C, R, CI, F, S 1,500 1,017 2 tanks -250,000 each St ---125,000 160,000 U. S. Navy Mine Def. Lab. 2 F 300 84,000 50,000 A, CI, St 630 78 2 tanks -42,000 each Woodlawn Subdivision 1 F e350 45,000 -A, Cl e350 31.6 Hathaway Water System 4 F 60 to 100 20,000 -Cl -12.7 4 tanks -5,000 each Mexico Beach Water System 1 F 735 100,000 100,000 A, Cl 735 24.4 Gulf Power Co. Water Plant 2 F rw)0 250,000 400,000 ---Not in operation International Paper Co. 21 F n)5 to 776 --5,478.5 As of Jan. 31, 1964 10 W -----,478.5 began receiving water from Deer Point Lake e -Estimated

PAGE 40

REPORT OF INVESTIGATIONS No. 41 29 Prior to February 1964, no surface water was being withdrawn and ground water was being used at the rate of 25.2 mgd. Of this amount, 22.7 mgd came from the Floridan aquifer. In February 1964, when the International Paper Company began using surface water, groundwater use in the basin was reduced to about 11 mgd. The International Paper Company, the major industry in the area, is the largest user of water. Prior to February 1964, the water used by this company was supplied by wells. About 13.5 of 15 mgd was pumped from the Floridan aquifer and the remainder was pumped from the watertable aquifer. Water used by this industry prior to 1964 is shown by graph in figure 16. In February 1964, this company started receiving water from Deer Point Lake at the rate of about 30 mgd. There are nine public water-supply systems in the area. All water produced by public water-supply systems is pumped from the ground. The rate of pumping varies from 6.7 mgd during low demand periods of fall and winter to 12.9 mgd during peak demand periods of spring and summer. Areas served by these systems and locations of the wells are shown in figure 17. Water use has increased with population (fig. 16). Also the per capita consumption in Panama City has increased from 70 gpd (gallons per day) to 80 gpd during the 10-year period, 1950-60. This figure is based on the average daily pumpage of the Panama City water system and the population of the area supplied by this system. Only a small part of the water pumped by the city is supplied to industry and other non-domestic users. Also, there are a number of private irrigation wells in the city. Partly for these reasons the per capita consumption is below the more normal rate of about 150 gpd per person that is reported in other areas. Nearly 18,000 persons live in areas not served by public water systems. At a per capita consumption of 80 gpd this would amount to about 1.4 mgd used for rural domestic purposes. WATER HIGH LIGHTS OF THE BASIN DECLINE OF WATER LEVELS IN THE PANAMA CITY AREA GENERAL STATEMENT From 1908 to 1964 water levels in the Floridan aquifer near Panama City were lowered about 200 feet in the centers of major well fields. This decline represents the difference between the reported static water level of 16 feet above mean sea level in the first well drilled in 1908 and the pumping water levels in the major well fields

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30 FLORIDA GEOLOGICAL SURVEY a "O O " i I a " i I I i i ' I I I i i. I \ 6POOI I I I I I I I I I S I a I I I I I I I I I .I'I 1 I. II I INTERNATIONAL ' PAPER COMPANY 5000 SI * , I a l \ I II II I , r I I I I 11 I II " I i .: ' ; I I t I I I I i I I j j l I I | V I i ' I I i l 000 I ' , i I J 4,i 5 i .9 I .r I I _ r 6 r ', , n o aion i t ' , , '. i I ,1 1 11I I TN IA AI R, I IFR g000 igIBA O r in i P i I aa Cl I , aFigure 16. Graphs of water use and population in the Panama CitY area. Figur 1.Gphofwtrl us an ppltoi heP aaCI tar.

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REPORT OF INVESTIGATIONS No. 41 31 7-TO < 5 * 4 0 ' 3S 1 t i sli l t s 5V --' ., Figure 17. Map of the Panama City area showing the location of water wells for each water system and the area supplied by these systems. in early 1964. In January 1964 one well field consisting of 21 wells was shut down. The water levels in this well field recovered 163 feet within 51 days. Figure 18 shows the approximate piezometric surface in 1908 under natural water conditions. The piezometric surface in 1962 (fig. 13) shows the lowered water levels caused by pumping since 1908. HISTORY OF GROUND-WATER DEVELOPMENT The first deep well reported in the Econfina Creek basin was completed in 1908 for an ice plant in downtown Panama City (Sellards, 1912). In 1909 Panama City drilled a city supply well at the location of the old National Guard Armory. In the same year another well was drilled near, the present water tank on Eleventh Street to supply St. Andrew.

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32 FLORIDA GEOLOGICAL SURVEY SS 55y 45 40 35 d 25 20 85' 36-... 55' 50' 45" S 2S 2 0 • Figure 18. Map showing the approximate piezometric surface of the Floridan aquifer in the Panama City area in 1908. From 1908 to 1930 there was not enough water withdrawn by pumping to noticeably affect water levels in the Floridan aquifer. However, in 1930 the International Paper Company developed a well field in the Millville area, consisting of seven wells in the Floridan aquifer and three wells in the water-table aquifer. Three of these wells in the Floridan aquifer flowed at the time of drilling and the static levels in the others were about 20 feet above mean sea level (from 8 to 20 feet below land surface). The original test well for this supply reportedly flowed at a rate of 60 gpm and, when pumped at a rate of 700 gpm, the water level dropped to 55 feet below land surface. A cone of depression developed in the piezometric surface of the Floridan aquifer as water was withdrawn. Static water levels in wells drilled in 1935 were more than 50 feet lower than in the original wells drilled in 1930. By 1937 the water level near the center of the well field reportedly was 104 feet below mean sea level, a decline of 124 feet from the time pumping began. This cone of depression expanded as the paper company extended their well field eastward and northward. A program was initiated by the paper company to protect their water supply. Four wells near the original center of pumping were

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REPORT OF INVESTIGATIONS No. 41 33 abandoned to decentralize pumping and to thus prevent excessive drawdowns which were limiting production of water. The control of water levels was considered necessary also as a precaution against salt-water encroachment. Pumping from each of the other wells in the field was regulated for the most efficient production from the aquifer within the cone of influence. Water-level records, shown in figure 19, of an abandoned well about one mile from the center of pumping show the effectiveness of this program. -J W 75 Water level affected by 80near-by pumping wells J -8590S95 M 100U I w 105 5 1951 1952 1953 1954 1955 1956 1957 1958 1959 11960 1961 1962 1963 Figure 19. Graph of water levels in observation well 008-537-332 near the center of the International Paper Company well field for the period 1951 to 1963. In January 1964 the paper company was producing water from 21 wells in the Floridan aquifer and 10 wells in the water-table aquifer. These wells were pumping an average of 15 mgd, of which about 13.5 mgd were from the Floridan aquifer. At this time the water level in the Floridan aquifer under pumping conditions was about 184 feet below mean sea level at the center of pumping and 100 feet below mean sea level on the east edge of the field. These represent drawdowns of about 200 to 120 feet since pumping began in 1930. Although this is a considerable drawdown, the pumping level in the field was essentially stabilized at this level. Minor fluctuations (fig. 19) were caused in part by seasonal variations in pumping from neighboring well fields. The major recoveries shown on this graph indicate periods when pumping from wells near the observation well was stopped temporarily or when pumping from the entire field was stopped.

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34 FLORIDA GEOLOGICAL SURVEY At the end of January 1964 when the paper company began using water from Deer Point Lake, all of the wells that had been pumping from the Floridan aquifer were shut down. In four days water levels in the aquifer recovered from about 200 to 83 feet below mean sea level near the old center of pumping and from 105 to 58 feet below mean sea level on the east edge of the field. After 51 days, water levels had recovered to 21 feet below mean sea level near the center and to about mean sea level on the east edge of the field. In 1936 Panama City built a water plant in the Millville area. This plant was initially supplied by wells in the water-table aquifer, but later supplied by wells drilled into the Floridan aquifer. In 1955 a well drilled into the Floridan aquifer had a water level of 63 feet below mean sea level. In October 1962, after all pumps were shut off for a period of 6 hours, the water level in this well was 72 feet below mean sea level, a net decline of 9 feet from 1955 when the well was drilled. The decline in water levels is attributed to pumping from this well field and from the nearby paper company well field. Another public water-supply system for Panama City was constructed in the St. Andrew section during late 1942 and 1943. When the first of the original seven wells were drilled the water level in the Floridan aquifer stood at about mean sea level. By mid-1943, when the last of the seven wells was drilled, pumping from the first wells had lowered the water level in the vicinity about 20 feet. In October 1954, when an eighth well was added to the well field, the pumping level had been lowered to 67 feet below mean sea level. This drawdown of 67 feet resulted from pumping at an average rate of 1.6 mgd. Measurements of water-level in the St. Andrew well field in October 1962, after a 6-hour recovery from pumping, showed the water level to be 87 feet below mean sea level near the center of the field. The additional drawdown of 20 feet in the center of the field during the 9-year period from 1954 to 1962 represents the effect of pumping at 2.0 mgd, an increase of 0.4 mgd in the average daily pumping rate. A well field consisting of four gravel-packed, screened wells in the water-table aquifer was constructed at Tyndall Air Force Base in 1941 to supply water for the base, then under construction. It was found that this aquifer would not supply sufficient water so it became necessary to develop a supply from the Floridan aquifer. When the wells were drilled in the Floridan aquifer the water level stood about 8 feet above mean sea level. By 1946 the water level had lowered to about 10 feet below mean sea level. In 1961 pumping levels in the Floridan aquifer were as much as 82 feet below mean sea level near

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REPORT OF INVESTIGATIONS No. 41 35 the center of the well field. The cone of depression which had been developing in this field was clearly established by 1961. The maps of the Panama City area showing the piezometric surface of the Floridan aquifer, figures 13, 18, and 20, illustrate the effect of development of water from this aquifer. The piezometric surface in 1908 (fig. 18) is indicative of the general conditions in the area up to about 1930. By 1947 the 4 principal well fields were producing enough water to develop sizeable cones of depression in the piezometric sur86sW0 55' 56 45' 40' 35 3Y' 25' 2d 8515' iur 0 oi io r face (fig. 20). .A comparison 6f piezometric surfaces in figures 13 and 20 clearly shows that increased pumping from expanded well fields has extended the cones of depression and has lowered water levels generally throughout the Panama City area during the period from 1947 to 1962. THE DEADENING LAKES The Deadening is a group of lakes in the lower end of a closed 1-ut A -,woe 0 1 2 3 4 5 10 " .;1., 86W0' 55' 50' 45' 4d 35 R 25 2 8" Figure 20. Map showing the piezometric surface of the Floridan aquifer in the Panama City area in April 1947. face (fig. 20). A comparison 6f piezometric surfaces in figures 13 and 20 clearly shows that increased pumping from expanded well fields has extended the cones of depression and has lowered water levels generally throughout the Panama City area during the period from 1947 to 1962. THE DEADENING LAKES The Deadening is a group of lakes in the lower end of a closed creek basin-'in the southeastern corner of Washington County, as shown in figure 21. These lakes receive the surface drainage from the

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36 FLORIDA GEOLOGICAL SURVEY 6* c« 3W' s3 as 34 33W a32W 31 85 30' * ~ ~ -I :-J ,.. :--!----/^.WHITE OAK CREEK BASIN / 1___-_ \_ \I t -/' -Seci tA*A ond --i cre given is figure 2 showing The Deadening area. table aquifer which underlies the surrounding sand hills. They lose / 1\ '2 ( / / 29 } limestone formation. Gully Pond, Wages Pond, Hamlin Pond, Still Pond, and Hammock Lake are joined at an elevation of 70 feet and 52323 39' \ 3' M 3their combined surfaces cover 3,640 acres. Porter Lake is connected to the other lakes at high water through Swindle Swamp and Black Slough. At an elevation of 70 feet, Porter Lake covers 930 acres. The Slough, At an elevation of 70 feet, Porter Lake covers 930 acres. The·

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REPORT OF INVESTIGATIONS No. 41 37 area of these lakes and Swindle Swamp is about 5,000 acres at an elevation of 70 feet. The variances in the supply of water and the constant drain through the ground cause wide fluctuations in stages of The Deadening lakes. In 1950, as a result of flood waters, the lakes reached an elevation of about 70 feet. Due to the dry weather for a period of several years (fig. 4) some of the lakes were dry and others had receded to elevations as low as 40 feet by 1956. Above average rains in the late 1950's caused some of the lakes to recover to normal levels. Since 1960 lake levels have again receded. The Deadening lakes have a considerable recreation potential. However, the wide ranges in lake levels prevent the potential from being realized. The Washington County Development Authority has proposed a plan to divert water from Econfina Creek to these lakes at the rate necessary to stabilize them at an elevation of 70 feet above mean sea level. The diversion from Econfina Creek would be at a point just downstream from Tenmile Creek, by way of a diversion canal to Porter Lake. After Porter Lake is filled, water would overflow through Swindle Swamp and Black Slouth to The Deadening lakes. GEOLOGIC AND HYDROLOGIC SETTING The Deadening lakes are located in the sinks and lake physiographic division (fig. 2). They originated by the collapse of the overlying sands and clays into cavities caused by solution of the limestone of the Floridan aquifer. Where solution and collapse activity has breached the confining layer, figure 22, there is a loss of water from the lakes to the Floridan aquifer. WATER LEVELS Levels of the Deadening lakes have been as high as 70 feet and as low as about 40 feet above mean sea level. A topographic map made in 1950 shows an elevation of 70 feet for Porter Lake, and shows the Deadening lakes to be completely covered with water at an elevation of 69 feet. Based on flood marks, about 70 feet is the highest elevation that the lakes have reached. The bottoms of Hammock Lake and Porter Lake are at an elevation of about 40 feet. Hammock Lake was reported to have been dry in 1956. Figure 23 shows that lake levels have varied from a high of 68.3 feet in Porter Lake to a low of 44.2 feet in Gully Pond during the period from'1961 to 1963. Lake levels declined throughout most of that period. In mid-1963 the lakes began responding to rainfall as

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38 FLORIDA GEOLOGICAL SURVEY A A -----3642 "11 S 1 2 3 1I00 Figure 22 Geohydrologic sections through the White Oak Creek basin, southeastern Washington County. shown by the graphs in figure 23. The similarity of the graphs of lake and ground-water levels indicates hydrologic continuity between the lakes and the aquifers. Flow from White Oak Creek enters Swindle Swamp and separates, part going to Porter Lake and part going to Still Pond through Black Slough (fig. 21). The flow from Still Pond is to Hamlin Pond by way of subsurface channels. These subsurface channels are evidenced by sink holes through which movement of water can be seen. Hamlin Pond overflows to Hammock Lake. Wages Pond receives surface drainage from Howard Swamp and overflows to Gully Pond. Hammock Lake and Gully Pond are at a lower stage than the other lakes because they receive surface flow only when the other lakes overflow. A comparison of the recessions of lake levels to the expected evaporational losses indicates the lakes lose water to the underlying Floridan aquifer. The level of Clarks Hole, an arm of Hamlin Pond, receded seven feet from August to December 1962. Below a stage of 55 feet, Clarks Hole is separated from Hamlin Pond and the shore line is below the line of vegetation, which eliminates most transpirational losses. The major water losses from Clarks Hole below a stage of 55 feet are evaporation and downward leakage. During the 5-month period that water levels in Clarks Hole declined seven feet, the evaporational loss was about 2 feet, based on pan evaporation records

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REPORT OF INVESTIGATIONS NO. 41 39 1961 1962 1963 JIFIMIA MIJIJIAISI INDAIMIJ IJ IAISIOINIDIJIF IMIAIMIJIJ IAJS(O(NID 70 12 I -8 (2 miles north of Porter Lake) W 68 z'-> 6w -JJ 66 < \ 0W 6 Well 030-535-422b SPorter Lake \ateAtable aquifer) '-S62 w---0 w Io 60 -, wJ Well 031-535-233 (HPmlin Pond) n eld 030-53'-47a 52 Floridan aquifer) 0 58 Still Pondo 50 4 o \\Pond Clarks Hole z 52 (Hamlin Pond) \ Well 030-53w-4 4a 521961 196 1963loridon SHammk Lake _I £l Gully l'46 Pond -44 j|F|MIA|MIJ J AISiO|NiD J|F|M|AiMIJIJIAsoiNSIDJ |D FIMIAIMI IJ IAI A oi"Do 1961 1962 1963 Figure 23. Graphs of water levels and rainfall in the vicinity of the Deadening lakes.

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40 FLORIDA GEOLOGICAL SURVEY collected at Woodruff Dam by the U. S. Weather Bureau. The remaining five feet represents leakage to the ground. Clarks Hole received no inflow during this period. Some of the other lakes did, which minimizes the apparent losses shown by graphs in figure 23. The Deadening area received about 11 inches of rain in July 1963, of which 8 inches fell during the last 10 days of the month. These heavy rains caused moderate rises in the lake levels and the piezometric surface of the Floridan aquifer. The ground-water level and lake levels, in general, showed about the same amount of rise, from 2 to 5 feet. The water level in Clarks Hole rose about 12 feet as a result of overflow from Hamlin Pond. Water in the Floridan aquifer moves in the general direction of the slope of the piezometric surface (fig. 13). Water moves to the center of The Deadening area from the northeast, and moves radially from The Deadening area toward Econfina Creek to the southeast, the Gulf of Mexico to the south, and Pine Log Creek to the southwest. Wells in The Deadening area showed larger gains during the rise of July 1963 than wells outside the area. This indicated that the Floridan aquifer gains water indirectly from rainfall more rapidly in The Deadening area than in the surrounding area. Water diverted to The Deadening lakes would move from the lakes to the Floridan aquifer at a rate proportional to the head between the lake surfaces and the piezometric surface of the aquifer. Raised lake levels could increase this head and cause more water to enter the aquifer. If the lake levels are maintained at a constant elevation, the head that will be established depends on the ability of the Floridan aquifer to transmit water away from the area. FLOW OF ECONFINA CREEK Information on the flow of Econfina Creek was obtained to determine the amount of water available at the proposed point of diversion and to determine what effect diversion would have on streamflow. The proposed point of diversion is just east of the north end of Porter Lake, about midway of the basin. The drainage area of Econfina Creek above the proposed point of diversion is about 67 square miles. The average flow at this point was estimated to be 90 mgd. Minimum flow at the point of diversion is the important criterion in determining the available flow. The greatest amount of water will be needed in the lakes when the creek flow is lowest. A minimum flow of 30 mgd was estimated on the basis of three discharge measurements and the relation of these measurements to the long-term flow record at the Bennett gaging station. This minimum flow probably will

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REPORT OF INVESTIGATIONS No. 41 41 not occur more often than once every 15 to 20 years, and then probably will not persist for more than a few months. A flow of 36 mgd was measured at the point of diversion on May 27, 1963, during a period of extreme low flow. A dam to create a retention reservoir along Econfina Creek is being considered. The main purpose of this reservoir would be to raise the water level in the creek and make gravity flow to Porter Lake possible. There would be a usable storage in this reservoir between elevations 80 and 95 feet of about 4,000 acre-feet. This amount of storage would provide 10 mgd for a period of four months. This, added to the natural flow of the creek, would assure a minimum flow of about 40 mgd. A flow of 40 mgd would supply about 0.7 of a foot of water per month on the 5,000-acre lake area. If diversion from Econfina Creek is at a rate of 30 mgd, the streamflow just downstream from the point of diversion would be almost depleted during periods of low flow. This effect will diminish downstream. Diversion of 30 mgd would reduce the flow below Gainer Springs about 15 percent. The width of the stream at this point would not be affected, and the depth would be reduced from a usual 4.5 feet to about 4 feet. Figure 24 shows, pictorially, the effect on streamflow if 30 mgd were taken from the creek during low flow. A diversion of this amount is a negligible part of the total flow into Deer Point Lake and would have no adverse effect on this water supply. Some of the diverted water would be returned to Econfina Creek by an increase in the flow of artesian springs. The higher spring flow would result from an increase in the piezometric slope caused by recharge to the Floridan aquifer from the lakes. SPRINGS The artesian springs along Econfina Creek are located downstream from a point just east of Porter Lake. Spring flow to the creek increases downstream to a maximum near the Washington-Bay County line. Below Gainer Springs it diminishes and there is little, if any, spring flow to the creek below the gaging station near Bennett, as shown on the flow chart in figure 25. Spring water flows into Econfina Creek directly through the stream bed, from the base of rock bluffs, and from short spring runs about a quarter of a mile in length. The spring water emanates from the Floridan aquifer where Econfina Creek has breached the overlying, confining clay layer. Figure 22 illustrates the hydrologic relationship of the aquifer with the creek. Figure 13 shows the pattern of flow towards the springs.

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42 FLORIDA GEOLOGICAL SURVEY 0 2 4 W as id JACKSON COUNTY -( FLOW CHART S229 "mgd Tm to width of stream represe»ts flow with no diversion. S 30 mgd diverted Figure 24. Flow chart of Econfina Creek during the low-water period of May 1963 showing the effect on streamflow if 30 amgd were diverted at the proposed 4 Flow-measuring poiWt Figure 24Flow chart of Econfina Creek during the low-water period of May 1963 showing the effect on streamflow if 30 mgd were diverted at the proposed dam site. It was possible to make direct measurements of the flow from Blue Springs and Williford Springs. Flow from Gainer Springs was determined by the difference in streamflow measurements above and below the group. Other spring flow, which could not be measured, enters the creek along its bed and banks. The amount of flow attributable to spring flow was calculated at the Bennett gaging station utilizing electrical conductivity measurements of the water. Pure water is a poor conductor of electricity but mineral matter dissolved in water consists of charged particles which will conduct an electrical current. The amount of current that a water will conduct is an indicator of the amount of dissolved minerals in the water. The measurement of the electrical current conducted by

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REPORT OF INVESTIGATIONS NO. 41 43 A S tt FLOW CHART M Spring flow E Non-spring flow 0 300mgd Flow scale 1 0 1 2 3 4 5mi. Figure 25. Flow chart of Econfina Creek showing spring flow. water is expressed as specific conductance in units of micromhos. The specific conductance of the water from the springs along Econfina Creek ranged from 95 to 150 micromhos. Water in the creek above the area of spring flow ranged from 14 to 26 micromhos. Average specific conductance values of 114 micromhos for spring water and 20 micromhos for non-spring water were used in the calculation of spring flow.

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44 FLORIDA GEOLOGICAL SURVEY Water at the Bennett gaging station was considered to be a thoroughly mixed combination of spring water and non-spring water. Flow at the Bennett gaging station, attributable to springs, was calculated from the formula: Kb -K s K -K Qb s n where: Q is spring flow Qb is streamflow at Bennett K is specific conductance of spring water K is specific conductance of non-spring water Kb is specific conductance of the mixture Figure 26 shows the flow of Econfina Creek during non-flood periods and that portion attributable to springs for 1963. Spring flow contributes about two-thirds of the total flow of Econfina Creek. 90C G800 7070T 600 TOTAL FLOW 600 00-500 3 i S400 -400 300 00 Z SEF CALULATED SPRI FLOW5 Is .oo -s o b0 0 *' YSPEanc COW~UCTAMC V ' V ~ so ^ JA" FE"B MU AR A MX JUNE I I AU6 SEPT OCT MOV DEC Figure 26. Graphs of streamflow, spring flow, and specific conductance for Econfina Creek near Bennett in 1963.

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REPORT OF INVESTIGATIONS No. 41 45 DEER POINT LAKE Deer Point Lake (fig. 1) was formed on November 17, 1961, by construction of a salt-water barrier across North Bay at Deer Point. The lake was planned to serve as a source of fresh water and to provide recreational facilities. It covers 4,700 acres, most of which was formerly a part of North Bay, and stores approximately 32,000 acrefeet of water at a level of 4.5 feet above mean sea level, the elevation of the dam. The lake is stabilized at an elevation of 5.0 feet above mean sea level. The potential fresh water supply is approximately 650 mgd, the average flow through the lake to North Bay. In February 1964 the only withdrawal from Deer Point Lake was the 30 mgd by the International Paper Company. A study of the lake hydrology in the period immediately before and for several months after the dam was constructed (Toler, Musgrove, and Foster, 1964) was made to determine the rate of freshening and the effect the lake would have on the water-table aquifer. Figure 27 shows the rate of freshening of the lake in terms of the number of times the inflow of fresh water would have filled the lake. Plotted in this manner, the graph enables a prediction of the rate of freshening of any similar lake if the volume and concentration of lake water and inflowing water are known (Toler, Musgrove, and Foster, 1964). When the barrier was completed on November 17, 1961, the lake was about half full and the chloride concentration was about 7,400 ppm. Flow over the spillway began on November 29, 1961, and the chloride concentration had been reduced to 3,700 ppm. In midFebruary 1962 the chloride concentration was about 200 ppm. When the barrier was completed, water levels in the lake and in the water-table aquifer adjacent to the lake rose rapidly, as shown in figure 28. An immediate effect of the rise in the lake level was to reverse the water-table gradient near the lake so that water moved from the lake into the aquifer. This is evidenced by the rise in chloride content in water from well 015-535-232, 45 feet from the lake. Water in wells 100 feet or more from the lake showed no change in chloride content. When the water table adjusted to the new lake level, the water movement was again toward the lake and the high chloride water was flushed from the aquifer. SUMMARY In general, the hydrologic system through which water moves in the Econfina Creek basin is similar to most basins in northwest I,

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46 FLORIDA GEOLOGICAL SURVEY 1961 1962 1963 O( I pC JAN FEB MAI APR J' JUL AUG SP OCT NOV DEC JAN 4500 4000 3500 z 2 S3000 Vivolume of fresh woltr that has flowed into lake I:slince spillway overflow begon a" V volume of the lake at spillway elevotion a 2500 I.2000 1 ! 500 1000 . 500 -I 2 3 4 5 6 7 8 9 10 II 12 13 14 15 16 17 18 19 20 21 V, /V0 Figure 27. Graph showing the relation of chloride in water in Deer Point Lake to fresh water inflow. Florida. That is: (1) rainfall is the source of all the water even though some falls outside the basin and moves into the basin underground; (2) the surface materials are highly porous, unconsolidated sands; (3) it is underlain by the artesian Floridan aquifer; and (4) water leaves the basin by streamflow, evaporation, transpiration, underground flow to the ocean and other basins, and by consumptive use. There are four physiographic divisions within the basin that affect the surface drainage and the water storage, both above and

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REPORT OF INVESTIGATIONS No. 41 47 4.0 * Well 016-535-342b 30 3 2.0 -3000 SChloride SWill 015-535-232 1.0 ** 2000 0o -oo1000 NOV. DEC. JAN. FEr MAR APR. MAY JUNE JULY AUG SEP. OCT. NOV. DEC. JAN. FE. MAR. APR. MAY JUNE 961 1962 1963 Figure 28. Graphs showing the rise of water levels and change in chloride content of ground water after construction of Deer Point Dam. below the ground. These are the sand hills, sinks and lakes, the flatwoods forest, and the coastal sand dunes and wave-cut bluffs. The surface materials on which the physiographic features have developed are generally very porous, permeable sands which are from 0 to 140 feet thick. These sands form the water-table aquifer. A confining layer, or aquiclude, of sandy clay and clayey shell material separates the water-table aquifer and the Floridan aquifer. In the bay area and along the gulf coast there are two artesian aquifers. Here the formation that forms the aquiclude is thicker than it is to the north and is overlain and in part underlain by some shellhash beds which contain water under artesian pressure. Water producing zones in the shell-hash beds above the aquiclude are termed the secondary artesian aquifer. The Floridan aquifer underlies the entire basin below the aquiclude. It is composed of limestone formations that include the lower units of the shell-hash beds and are as much as 1,200 feet thick. The basin receives an average of 58 inches of rainfall per year. A partof the rainfall is absorbed by the porous surface sands and a part moves directly into the streams. Some water from the sands moves to the streams and maintains flow during periods of no rainEl

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48 FLORIDA GEOLOGICAL SURVEY fall. Water also moves from the sands downward to the Floridan aquifer but the amount diminishes toward the southwest because the aquiclude becomes thicker. Movement within the Floridan aquifer is generally southward with some water flowing into the channel of Econfina Creek by way of artesian springs. The transmissibility of the Floridan aquifer varies within the basin, and is lower than the transmissibility of this aquifer in most other areas in Florida. Coefficients of transmissibility range from 2,000 to 30,000 gpd/ft. The water in the lakes and streams differs little in mineral concentration from rain water because of the relative insolubility of the surface materials. Two areas of exception are where Econfina Creek receives artesian spring flow and near the mouth of streams that empty into salt-water bays. The mineral content of water from the water-table aquifer generally ranges from 10 to 50 ppm, and that of water from the secondary artesian aquifer from 80 to 150 ppm. The mineral content of water from the Floridan aquifer is higher than that from the other two aquifers. Mineral concentrations in water from this aquifer show increases in all constituents from the northern part of the basin to the southwest. Some salt-water intrusion was detected in the water-table and the secondary artesian aquifers adjacent to the bays and Gulf. The confining clay layer overlying the Floridan aquifer in the coastal and bay area is sufficiently impermeable to prevent leakage of water from the overlying aquifers. Water in the Floridan aquifer in the southern part of the basin is apparently a mixture of fresh water and residual saline water. Streamflow to the bays is at an average rate of about 960 mgd which for a year would amount to 40 percent of the average annual rainfall of 58 inches. About 650 mgd flows through Deer Point Lake into North Bay, and another 30 mgd flows into North Bay below Deer Point Dam. East Bay receives a flow of about 210 mgd and West Bay about 70 mgd. Most of the streams have sufficient flow to be a potential water supply. During periods of minimum flows there is more than 10 times as much fresh water flowing into the bays than is being withdrawn in the basin. Econfina Creek, by far the largest stream in the basin, has an average flow of 355 mgd. Low runoff from the southern part of the basin results from poor drainage features of the flat-woods forest. Drainage in the sinks and lakes division is mostly internal. High base flow due to seepage from the porous sands causes high runoff in the sand hills division.

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REPORT OF INVESTIGATIONS No. 41 49 There are about 80 named lakes in the basin, most of which are in southeastern Washington County. Deer Point Lake, a fresh-water reservoir covering 4,700 acres, is the largest. Porter Lake has a surface area of 930 acres and is the largest natural lake. The major uses of water within the basin are for the manufacture of paper products, for public and domestic supplies, and for recreation. Prior to February 1964 no surface water was being withdrawn and ground water was being used at the rate of 25.2 mgd. Of this amount, 22.7 mgd came from the Floridan aquifer. The International Paper Company was the largest user of water, using about 13.5 mgd from the Floridan aquifer and about 1.5 mgd from the water-table aquifer. In February 1964 this company started receiving water from Deer Point Lake at the rate of about 30 mgd. Ground-water use in the Panama City area was reduced to about 11 mgd. The first well in the Floridan aquifer was drilled in 1908. Later, as the demand for water increased, more wells and well fields were developed and water levels were lowered. By the end of 1963, when water was being withdrawn at the rate of about 25.2 mgd, pumping levels had been lowered as much as 200 feet near the centers of major well fields. Pumping from the paper company well field, consisting of 21 wells, was discontinued in February 1964 and water levels in this field recovered 163 feet within 51 days. The Deadening lakes in southeastern Washington County offer considerable recreation potential. However, they lose water to the ground at a high rate causing wide fluctuations in stage and this prevents their full potential from being realized. The Washington County Development Authority has proposed a plan to divert water from Econfina Creek to stabilize these lakes at an elevation of 70 feet. The diversion from Econfina Creek would be at a point just downstream from Tenmile Creek where the minimum flow was estimated to be 30 mgd. The proposed plan calls for a detention reservoir on Econfina Creek to raise the water level and make gravity flow through a diversion canal possible. The storage in this reservoir, added to the natural flow of the creek, would provide a minimum flow of 40 mgd which would supply about 0.7 of a foot of water per month on the 5,000-acre lake area. Water leaks from the lakes to the Floridan aquifer at a rate proportional to the head between the lake surfaces and the piezometric surface of the aquifer. If the lake levels are maintained at a constant elevation, the head that will be established depends on the ability of the Floridan aquifer to transmit water away from the area. If diversion from Econfina Creek is at a rate of 30 mgd, the stream

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50 FLORIDA GEOLOGICAL SURVEY just downstream from the point of diversion would be almost depleted during periods of low flow. This effect will diminish downstream and become almost negligible below Gainer Springs, a group of large artesian springs just downstream from the Washington-Bay County line. A diversion of 30 mgd is a negligible part of the total flow of 650 mgd into Deer Point Lake and would have no adverse effect on this water supply. A part of the water diverted to the lakes would be merely re-routed through the lakes into the ground and back to the Econfina Creek through the artesian springs below the dam. Deer Point Lake is a fresh-water lake formed November 17, 1961, by a salt-water barrier across North Bay. It covers 4,700 acres and stores about 32,000 acre-feet of water. The lake elevation is 5.0 feet above mean sea level and fluctuates very little. Artesian spring water flows from the Floridan aquifer into Econfina Creek directly through the streambed, from the base of rock bluffs and from short runs about a quarter of a mile in length. These springs occur from a point just east of Porter Lake downstream to a point near the Bennett gaging station. Springs contribute about twothirds of the flow of Econfina Creek.

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REPORT OF INVESTIGATIONS No. 41 51 REFERENCES Foster, J. B. (also see Toler, L. G.) In Preparation Geology and ground-water hydrology of Bay County, Florida. Gunter, Herman (see Sellards, E. H.) Hantush, M. S. 1955 (and Jacob, C. E.) Non-steady radial flow in an infinite leaky aquifer: Am. Geophys. Union Trans., V-37, No. 6, p. 702-714. Lang, S. M. 1961 Methods for determining the proper spacing of wells in artesian aquifers: U.S. Geol. Survey Water-Supply Paper 1545-B. Musgrove, R. H. (see Toler, L. G.) Sellards, E. H. 1912 (and Gunter, Herman) The underground water supply of westcentral and west Florida: Florida Gzol. Survey 4th Ann. Rept., p. 116. Shampine, W. J. (see Toler, L. G.) Theis, C. B. 1935 The relation of the lowering of the piezometric surface and the rate and duration of discharge of a well using ground-water storage: Am. Geophys. Union Trans. p. 519-524, August. 1964 The spacing of pumped wells: U.S. Geol. Survey Water-Supply Paper 1545-C, p. 113. Toler, L. G. 1964 • (and Musgrove, R. H., and Foster, J. B.) Freshening of Deer Point Lake, Bay County, Florida: Am. Water Works Assoc. Journal, V. 56, No. 8, p. 984-990. 1965 (and Shampine, W. J.) Quality of water from the Floridan aquifer of the Econfina Creek basin area, Florida: Florida Geol. Survey Map Series No. 10.