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    Title Page
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    Preface
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    Table of Contents
        Page v
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    Abstract and introduction
        Page 1
        Page 2
        Page 3
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        Page 5
        Page 6
    Occurrence of surface water
        Page 7
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        Page 9
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    Storage considerations
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    Conclusions
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        Copyright
            Main

STATE OF FLORIDA
STATE BOARD OF CONSERVATION
Ernest Mitts, Director

FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director





INFORMATION CIRCULAR NO. 20


INTERIM REPORT
ON
SURFACE WATER RESOURCES
OF
BAKER COUNTY, FLORIDA


By
R. W. Pride, Hydraulic Engineer
U. S. Geological Survey


Prepared by the U. S. Geological Survey
in cooperation with the Florida Geological Survey


Tallahassee, Florida
1958









PREFACE


This report was prepared in the Ocala office of the U. S.
Geological Survey under the supervision of A. 0. Patterson,
District Engineer, as part of a cooperative agreement with
the Florida Geological Survey. Flood and basic streamflow
data utilized in the study were collected under provisions of
the same and other financial cooperative agreements. Clima-
tological data and other information are from technical
reports or publications of the U.S. Weather Bureau and the
Florida Department of Agriculture.










TABLE OF CONTENTS

Page

Abstract............. ........ .... ............. 1
Introduction........................ .. ......... 1
Purpose and scope of investigation, ............ 1
Description of area ................ ......... 2
Topography and drainage ................... 2
Climate........................ ........... 4
Industry.................................. 4
Definition of terms ............................. 4
Occurrence of surface water ..................... 6
Sources of water ............. ............... 6
Areal distribution of surface water ............ 7
Gaging-station records .......................... 8
Flow characteristics ............... ........... 8
Low flow s.................................. 17
Flow-duration curves...................... 20
Flood flows ................................. 22
Flood-frequency relations................... 22
Storage considerations ......................... 23
Evaporation from water surfaces .............. 23
Seepage and transpiration..................... 25
Potential reservoir sizes .................... 27
Conclusions ..................................... 31


ILLUSTRATIONS

Figure
1 Map of Baker County, Florida, showing
surface-water features and location of
gaging stations .......................... 3
2 Climatological data for Glen St. Mary...... 5
3 Discharge available without storage, St.
Marys River near Macclenny, 1926-57..... 19
4 Flow-duration curves for gaged streams in
Baker County, for the 31-year period,
1926-57................................. 21
5 Variations of flood discharge with drainage
area for streams in Baker County ......... 24







Figure Page
6 Mass curves for flow at three gaging
stations in Baker County and diagram
showing rate of evaporation loss from
various reservoir areas .................. 28
7 Mass curve for flow of South Prong St.
Marys River at Glen St. Mary and diagram
showing rate of evaporation loss from
various reservoir areas ................. 29


TABLES

Table
1 Gaging-station records and drainage areas
at selected locations in Baker County ...... 9
St. Marys River basin
North Prong St. Marys River at Moniac,
Georgia ............................... 10
Middle Prong St. Marys River at Taylor,
Florida ......... ...................... 11
South Prong St. Marys River near
Sanderson, Florida .................... 12
Turkey Creek at Macclenny, Florida ..... 13
South Prong St. Marys River at Glen St.
Mary, Florida.......................... 14
St. Marys River near Macclenny, Florida 15
2 Summary of monthly average evaporation
and rainfall in Baker County .............. 26












INTERIM REPORT ON SURFACE WATER RESOURCES

OF BAKER COUNTY, FLORIDA

By
R. W. Pride


ABSTRACT

The principal sources of surface-water supplies inBaker
County are the St. Marys River and its tributaries. However,
the flow of many of the small tributaries is intermittent, and
without storage they are not dependable sources of supply
during sustained periods of deficient rainfall.

Of the six stream-gaging stations in Baker County for
which complete records are available, one has been in oper-
ation for 31 years and provides a long-term record upon which
to base correlative estimates for extending the short-term
records at the other stations. All available streamflow data
to 1957 have been summarized in graphic or tabular form.

The hydrologic balance between minimum streamflows
and increased evaporation losses afforded by potential shallow
reservoirs provides design criteria for determining the max-
imum surface area of effective reservoir that can be created
at a selected site within Baker County. This information has
been presented in graphic and tabular form in the report.


INTRODUCTION

Purpose and Scope of Investigation

This report summarizes available dataonthe surface-
water resources of Baker County and evaluates the present






FLORIDA GEOLOGICAL SURVEY


and potential use of these resources. The county needs the
hydrologic data for the design of shallow reservoirs on small
streams to impound water for recreational uses. The report
provides data which will be useful not only for the specific
purpose of planning small artificial lakes but also for the
formulation of plans for the future development and economic
growth of the county.


Description of Area

Topography and Drainage

Baker County is in the Central Highlands topographic
region in the northeastern part of Florida and extends about
25 miles southward from the Georgia-Florida line. The
total area of the county is 585 square miles. The topography
of the county is gently rolling, with the elevation of most of
the area varying between 100 and 150 feet above mean sea
level. The entire land surface of Baker County is covered
with a mantle of loose gray sand ranging in thickness from
a few feet to more than 50 feet.

The St. Marys River forms the northeastern boundary
of Baker County and drains most of the county area. The
drainage from small areas in the southernpart of the county
flows into tributaries of the Suwannee River. Pinhook Swamp
in the northwesternpart of the county is a continuation of the
Okefenokee Swamp which occupies a large area in southern
Georgia. The drainage from Pinhook Swamp is to the east
into the St. Marys River basin and to the west into the Suwannee
River basin. Because of the flat surface of the PinhookSwamp
area and absence of well defined ridge lines, the drainage
divide between the St. Marys and the Suwannee River basins
is indefinite. The drainage divide between the headwaters
of several tributaries in the southwestern part of the county
is also indefinite and, in places, the basins are intercon-
nected. However, most of the drainage of the county follows
the basin divides as shown in figure 1.






INFORMATION CIRCULAR NO. 20


GEORGIA
(WARE CO)


swame--

-4t,


s,,,.-~ -,
LPinhoO~

'R* -i v er

?c-~2 Ri~ver


EXPLANATION

02 River goge, stage
and discharge

---- River basin boundary

-.- Interconnection of
Drainage basins; arrom
indicates direction
of occasional flow
across boundary.


Figure 1. Map of Baker County, Florida, showing surface-
water features and location of gaging stations.





FLORIDA GEOLOGICAL SURVEY


Climate

The average temperature, based on 58 years of record
at Glen St. Mary, is 68. 6*, with an average high of 81. 9"
in July and an average low of 55.4 in December. The aver-
age annual rainfall at Glen St. Mary for a 61-year record
since 1896 is 52. 2 inches, with the heaviest rainfall in the
months of June, July, August, and September. Figure 2
shows the variations in temperature and rainfall.


Industry

Baker County is primarily rural, with lumber, pulpwood,
and naval stores operations representing a large portion of
the revenue. Two of the largest nurseries in the State are
located near Macclenny. In addition, small and diversified
farming and the raising of poultry for the commercial market
make up a considerable part of the local economy. About
half of the Osceola National Forest is located in the western
part of the county.. The type of industry in the county at pres-
ent does not require large quantities of water.


Definition of Terms

Some of the terms of streamflow and other hydrologic
data, as used in this report, are defined as follows:

Precipitation. As used in meteorology includes all moisture
that reaches the earth,-whatever its form rain, snow,
sleet, hail, dew, or frost.

Evapotranspiration. The process whereby water leaves a
drainage area as vapor, including transpiration from
plants and evaporation from free surfaces.

Drainage area. The size of the area drained by a stream
above a given location, usually expressed in square
miles (sq mi).

Discharge. Rate of flow at a given instant in terms of volume
per unit of time; usually expressed in cubic feet per sec-
ond, gallons per minute, or millions of gallons per day.






INFORMATION CIRCULAR NO. 20


o r M J Ab U A N U
MONTHLY PRECIPITATION
61-yeor record




80so
Average 61years(18S
1957) 52.2 in
60


40


20


JF MAM J JA S ON
AIR TEMPERATURE
58-yeor record


Climatological data for Glen St. Mary.


r- NUAL PR P


ANNUAL PRECIPITATION


Figure 2.






FLORIDA GEOLOGICAL SURVEY


Cubic foot per second (cfs). The rate of discharge of a stream
whose channel is one square foot in cross-sectional area
and whose average velocity is one foot per second.

Cubic feet per second per square mile (cfsm). An average
number of cubic feet of water flowing per second from
each square mile of area drained, assuming that the
runoff is distributed uniformly in time and area.

Acre-foot. The quantityof water required to cover an acre
to a depth of one foot and is equivalent to 43, 560 cubic
feet.

Runoff in inches, The depth to which an area would be covered
if all the water draining from it in a given period were
uniformly distributed on its surface. The term is used
for comparing runoff with rainfall.

Water year. A 12-month period beginning October 1 and
ending the following September 30. Designated as the
year ending September 30.


OCCURRENCE OF SURFACE WATER

Sources of Water

Precipitation is the source of allof our water supplies.
In the endless cycle of water from the clouds to the earth and
back again, a part returns to the atmosphere through evap-
oration and transpiration and a part runs off the land into
natural waterways and returns to the sea. The remainder
seeps into the ground and eventually reaches the ground-water
zone, from which it is discharged later by seepage into
surface-water bodies or by evapotranspiration.

The amount of water following any of these paths depends
on many factors. Much of the precipitation falling after long
periods of dry weather will be absorbed by the soil. In areas
covered by tight, impervious clay or underlain by impervious
rocks, much of the precipitation will drain into the surface
bodies of water, but on the other hand, in areas underlain by






INFORMATION CIRCULAR NO. ZO


porous material a higher percentage will percolate into the
ground. In areas of rugged topography much of the precip-
itation will flow down the hillsides and enter the streams;
much of the water that does enter the ground will soon dis-
charge from the hillsides. In areas of relatively flat slopes
where the drainage is poor, the opportunity for evaporation
from surface pondage is increased. Thus, the amount of
surface water available in an area depends upon the amount
and the distribution of the precipitation, the topography, and
the geology of the area.

Because of its flat topography, swamp area, and porous
sandy soil, a rather low percentage of the precipitation in
Baker County emerges as runoff in surface streams.


Areal Distribution of Surface Water

The principal source of surface water in Baker County
is the St. Marys River system. The major branch of this
river system is the North Prong which heads in the Okefenokee
Swamp in southeastern Georgia and flows generally southward
along the northeasternboundary of Baker County. The main
St. Marys River is formed by the confluence of the North and
Middle Prongs 10 miles south of the northern boundary of
Baker County. From the confluence of these two streams the
St. Marys River flows southeastward about six miles, thence
eastward to a point just beyond the Baker County line. The
river then flows northward for a distance of 30 miles, thence
eastward again for 35 miles to the Atlantic Ocean. In the
reach of the St. Marys River along the boundary of Baker
County the larger tributaries enter from the Florida side.
Cedar Creek and South Prong are two of the larger tributaries.

Other sources of surface water in Baker County are the
headwaters of New River, Swift Creek, and Olustee Creek
for small areas in the southern part of the county and drain-
age from Pinhook Swamp westward to the Suwannee River
for a small area in the northwestern part of the county.

Ocean Pond, in the southwestern part of the county, is
the only lake of appreciable size within the county. Palestine





FLORIDA GEOLOGICAL SURVEY


Lakeand Swift Creek Pond are just south of the Baker County
line.


GAGING-STATION RECORDS

Records of stage and discharge for several gaging
stations in the St. Marys River basinhave been collected by
the U. S. Geological Survey for periods of from seven to 31
years. The first of these gaging stations was established
on North Prong St. Marys River between Baxter, Florida,
and Moniac, Georgia, in January 1921. This gaging station
is currently in operation but continuous records for the entire
period have not been collected as the station has been dis-
continued and reestablished several times during the inter-
vening period. The gaging station with the longest period of
continuous record is on the St. Marys River near Macclenny.
Records are available at this gaging site since October 1926.
Records for South Prong St. Marys River at Glen St. Mary
have been collected since January 1950. Other stations were
established in September 1955 as data-collection points for
this report.

No discharge records have been collected in Baker
County for the headwaters of streams that are not in the St.
Marys River basin. However, the areas drained by these
small streams have hydrologic characteristics similar to
those drained by the adjacent tributaries of the St. Marys
River and similar runoff relations may be assumed.

A list of the gaging-station records and drainage areas
at selected locations in Baker County are given in table 1.
Location of the gaging stations is shown in figure 1.


FLOW CHARACTERISTICS

The variability of streamflow creates problems of too
little water at times and too much water at other times.
Thus, an analysis of streamflow characteristics logically
falls into two parts the analysis of low flows and the analysis
of flood flows.








Table 1. Gaging-Station Records and Drainage Areas at Selected Locations in Baker County


Drainage
area
in square
miles


Stream and loca n


Records available to September 30, 1957
(Gage heights and daily discharges)


1 North Prong St. Marys River at State Highway 94,
at Moniac, Georgia


2 Middle Prong St. Marys River at State Highway 125,
at Taylor, Florida
Middle Prong St. Marys River at mouth
Cedar Creek at State Highway 125, near Glen
St. Mary, Florida
Cedar Creek at mouth

3 South Prong St. Marys River at State Highway 229,
near Sanderson, Florida

4 Turkey Creek at State Highway 23, at
Macclenny, Florida
Turkey Creek at mouth

5 South Prong St. Marys River at U.S. Highway 90,
at Glen St. Mary, Florida

6 St. Marys River near Macclenny, Florida


January 1921 to December 1923, January
1927 to June 1930, July 1932 to June 1934,
October 1950 to date


September 1955 to date


20.9
26.4

150


720


September 1955 to date



September 1955 to date


January 1950 to date


October 1926 to date


----, --- ----- ---- --------- ----- ---------


.ml es








GAOING.STATION RECORDS
St. Mary. River Basin

(1) North Prong St. Marys River at Moniac, Georgia

Location. Lat, 30'31', long. 82'14', in sec. 8, T. I N., R. 21 E., near right bank at upstream side ot bridge on State Highway 94, 950 feet
upstream from Georgia Southern & Florida Railway bridge, 0. mile west of Moniac, Charlton County, and 1. mile downstream from
Moccasin Creek.
Drainage area. About 160 iq mi, includes part of watershed in Okefenokee Swamp which is indeterminate.
age. Water-stage recorder. Datum of gage is 89.40 feet above mean sea level, datum of 1929. January 1921 to June 1934, staff gage at site
800 feet downstream at datum 3. 22 eet higher. October 1 to December 13, 1950, wire-weight gage at present site and datum.
Average discharge. 12 years (1921-23, 1927-29, 1932-33, 1950-57), 134 cas.

Extremes, 1921-23, 1927-30, 1932-34, 1950.57: Maximum discharge, about 6,060 cfs, probably September 19, 1928 (gage height, 19.9 feet,
present datum, at site then in use), from rating curve extended above 2,000 cis; no flow at times.

Monthly and Yearly Mean Discharge, in Cubic Feet Per Second
Water 4
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year

1921 --- -.. --- 108 45.9 11.0, 5.62 0.29 277 461 12.2 ...
1922 0.04 0.60 16.0 37.7 118 137 15.9 7.51 63.3 23.8 169 96.3 56.8
1923 218 92.4 44.9 252 85.1 91.2 97.1 146 341 331 172 82.4 164
1924 40.5 15.0 8.83 .- -- ... --- --- --- --- --

1927 .. --- --- .. 80.9 108 26.0 1.34 69.'3 330 249 39. 9 ---
1928 S.45 0.052 4.34 5.41 31.8 297 701 214 107 802 266 1,590 334
1929 491 58.2 48.7 305 512 455 154 307 151 413 403 491 315
1930 627 55.9 188 427 299 679 417 32.6 133 -. --- -..

1932 -- -- -- -- -- -- --- ... 323 557 --
1933 218 199 62.2 157 642 242 486 51.4 21.3 41.1 39.2 205 193
1934 1.10 1.02 .477 .187 .214 1.19 .203 1,01 141 ...
1951 914 136 55.2 37.3 30.6 32.9 30.5 1.24 1.36 1.44 7.82 20.3 107
1952 56.7 132 179 129 270 448 72.1 13.3 1.38 .10 22.7 36.9 113
1953 16.9 3.03 1.45 5.56 17.0 9.37 135 13.6 0.55 29.3 127 510 71.9
1954 662 58,0 291 247 52.9 33.3 13.0 1.86 0.04 0 .01 .02 115
1955 .003 0 .13 .73 2.26 .40 .82 .23 .05 2.39 70.9 118 16.3
1956 17.1 11.4 2.90 14.2 52.6 28.9 4.14 57.9 11.2 19.2 1.15 1.69 18.5
1957 79.1 18.3 2.00 .62 .59 25.2 71.7 23.8 775 78.5 65.-7 51.9 98.8






FLORIDA GEOLOGICAL SURVEY


Cubic foot per second (cfs). The rate of discharge of a stream
whose channel is one square foot in cross-sectional area
and whose average velocity is one foot per second.

Cubic feet per second per square mile (cfsm). An average
number of cubic feet of water flowing per second from
each square mile of area drained, assuming that the
runoff is distributed uniformly in time and area.

Acre-foot. The quantityof water required to cover an acre
to a depth of one foot and is equivalent to 43, 560 cubic
feet.

Runoff in inches, The depth to which an area would be covered
if all the water draining from it in a given period were
uniformly distributed on its surface. The term is used
for comparing runoff with rainfall.

Water year. A 12-month period beginning October 1 and
ending the following September 30. Designated as the
year ending September 30.


OCCURRENCE OF SURFACE WATER

Sources of Water

Precipitation is the source of allof our water supplies.
In the endless cycle of water from the clouds to the earth and
back again, a part returns to the atmosphere through evap-
oration and transpiration and a part runs off the land into
natural waterways and returns to the sea. The remainder
seeps into the ground and eventually reaches the ground-water
zone, from which it is discharged later by seepage into
surface-water bodies or by evapotranspiration.

The amount of water following any of these paths depends
on many factors. Much of the precipitation falling after long
periods of dry weather will be absorbed by the soil. In areas
covered by tight, impervious clay or underlain by impervious
rocks, much of the precipitation will drain into the surface
bodies of water, but on the other hand, in areas underlain by
















GAGING-STATION RECORDS
St. Marys River Basin
(2) Middle Prong St., Marys River at Taylor, Florida
Location. Let, 30'26', long. 82*17', on line between sees, 2 and 3, T. 1 S., R. 20 E., near center of span on upstream side of bridge on State
Highway 215, 0. 5 mile southeast of Taylor, Baker County, and three-quart.er of a mile upstream from Little River.
Drainage area. 127 sq mi, approximately.

gge. Water-stage recorder, Datui, of gage is 89.4 feet above mean sea level, datum of 1929.(from elevation of centerline of bridge, furnished by 0
Florida State Road Department.
Extremes. 1955-57: Maximum discharge 1, 040 cfs June 11, 1957 (gage height, 10. 51 feet); minimum daily, 0. 1 cts August 24-31, September 12-18,
23, 1956.

Monthly and Yearly Mean Discharge, in Cubic Feet Per Second
Water
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept, Year

1956 1.21 0.95 0.66 0.92 1.64 1.80 1.12 2.72 1.42 1.83 0.50 0.81 1.30 P
1957 124 64.2 6.49 1.88 1.32 7.10 14.7 13.3 361 36,9 321 100 87. 9
N
0








h)







'I.

GAGING-STATION RECORDS
St. Marys River Basin

(3) South Prong St. Marys River near Sanderson, Florida

Location. Lat. 30'12', long. 82'16', in NW* sec. 25, T. 3 S., R. 20 E., near left bank five feet downstream from bridge on State Highway 229, one
mile upstream from small tributary, and 3j miles south of Sanderson, Baker County.

Drainage area. 58 sq mi, approximately.

Gage. Staff gage read twice daily. Datum of gage is 112.67 feet above nmea. .ea level, datum of 1929 (Florida State Road Department benchmark). 0

Extremes. 1955.57: Maximum discharge, 1,060 cls June 10, 1957 (gage height, 6. 16 feet); no flow at times.

Monthly and Yearly Mean Discharge, in Cubic Feat Per Second

Water
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year

1956 0.99 0.31 0.12 0.76 8.11 1.85 0.04 2.15 0.87 6.20 0.03 0.08 1.77
1957 34.6 8.59 .31 .06 .03 2.89 13.3 24.6 201 12.4 58.5 22.4 31.5
















GAGINGOSTATIONS RECORDS

St. Marys River Basin

(4) Turkey Creek at Macclenny, Florida

Location. Lat. 30"16'05", long. 82'07'20", in NE* sec. 5, T. 3 S., R. 22 E., near left bank at downstream side of bridge on State Highway 23, 0.9
mile south of Macclenny, Baker County, and 1.8 miles upstream from mouth.

Drainage area. 20. 9 sq mi.

Gae. Staff gage and crest-stage indicator; gage read twice daily. Datum of gage is 102. 27 feet above mean sea level, datum of 1929 (Florida State
Road Department benchmark).

Extremes. 1935-57: Maximum discharge, 1,130 cfs October 17, 1957 (gage height, 6.90 feet); minimum, 0.2 cfi April 21-24, 1956 (gage height,
1. 4 teet).

Monthly and Yearly Mean Discharge, in Cubic Feet Per Second

Water
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year

1956 2.75 1.72 0.96 2.16 6.28 1.33 0.70 76.1 4.49 18.0 1.68 4.39 10.1
1957 68,9 5.05 2.05 1.77 2.30 8.54 8.18 6.13 81.0 10.2 94.9 22.2 26.1
0













GAGING-STATIONS RECORDS

St. Marys River Basin
(5) South Prong St. Marys River at Glen St. Mary, Florida
Location. Lat. 30'16'40", long. 8208a'40", in sec. 31, T. 2 S., R. 22 E., on right bank 65 feet upstream from bridge on U.S. Highway 90 and 1.0
mile east of Glen St. Mary, Baker County.

Drainage area. 150 sq mi, approximately.

Cage. Water-stage recorder. Datum of gage is 77.13 feet above mean sea level, datum of 19Z9.

Average discharge. 7 years, 81. Z cis. L
Etremea. 1950-57: Maximum discharge, 6, 00 cfs September 7, 1950 (gage height, 12.71 feet); minimum, 0.4 cfe May 23, 1950 (gage height,
1.52 3eet).

Flood in September 1947 reached a stage of 13.0 feet, from information furnished by Florida State Road Department (discharge, 6,700 cis).

Monthly and Yearly Mean Discharge, in Cubic Feet Per Second
Water '
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year CO

1950 -.. -- --. 8.88 11.7 31.6. 10.5 2.95 6.19 237 18.0 805 ---
1951 870 97.6 36.5 27.3 2. 4 20.5 13.8 3.99 2.50 2.65 3.93 5.84 93.5,
1953 4.10 10.6 17.8 16.7 107 81.9. 29.6 12.8 14.3 14.4 20.7 100 35.4
1953 57.1 6.34 5.76 28.4 62.1 37.5 319 12.1 8.86 17.4 418 496 12 2
1954 598 48.9 560 245 45.0 28.8 23.8 5.15 3.27 3.38 4.60 9.95 133
1955 8.64 3.35 7.54 18.7 36.8 7.51 6.47 3.02 2.18 119 16.5 77.4 25.6
1956 11.6 9.20 6.64 10.6 35.6 16.6 4.04 110 17.3 58.3 6.14 8.03 24.6
1957 213 39.5 8.86 7.99 8.96 33.0 53.4 138 611 32.3 323 138 134







GAGING-STATION RECORDS
St. Marys River Basin
(6) St. Marys River near Macclenny, Florida
Location. Lat. 30'21'35", long. 82*04'55", in sec. 2, T. 2 S., R. 22 E., on right bank 200 feet downstream from site of former Stokes Bridge,
one mile downstream from South Prong, and six miles northeast of Macclenny, Baker County.
Drainage area. 720 sq mi, approximately, Includes part of watershed in Okefenokee Swamp which is indeterminate,
Gape. Water-stage recorder. Datum of gage is 40. 00 feet above mean sea level (levels by Mesa and Meeas). Prior to February 21, 1939, staff
gage, and February 21, 1939 to August 15, 1948 water-stage recorder, at site of former bridge 200 feet upstream at same datum.
Average discharge. 31 years, 632 cfs.
'Extremes. 1926-57: Maxiumn discharge, 28,100 cLs September 25, 1947 (gage height, 22.29 feet)i minimum observed, 12 cfs May 22, 1932;
minmum gage height observed 0.04 feet June 4, 5, 1927,
Monthly and Yearly Mean Discharge, in Cubic Feet Per Second
'"Water
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year
1927 383 632 238 131 465 746 117 26.5 105 707 1,810 321 475
1928 54.5 27.3 37,4 38.7 104 770 2,750 1,140 523 2,180 150 5,370 1,173
1929 2,110 231 172 1,010 1,290 1,530 794 774 673 1,600 1,520 2,200 1,160
1930 2,860 170 422 1,290 1,310 3,760 1,630 161 1,190 753 211 162 1,160
1931 179 265 416 1,420 672 778 932 633 71.3 92.9 76,9 93.1 469
1932 22.7 15.9 18,0 21.7 20.6 44.7 27.7 20.4 640 245 1,140 1,720 326
1933 489 535 260 448 1,650 1,120 2,160' 240 180 624 312 1,480 781
1934 53.6 22.3 20.5 22.9 20.2 45..0 26.0 31.9 2,290 438 691 193 320
1935 145 35.7 37.5 77.7 79.9 61.1 25.7 22.5 18.8 390 830 2,931 386
1936 403 61.3 46.6 134 884 640 408 48.6 128 147 175 53.0 259
1937 410 67.5 197 206 1,252 599 1,045 262 68.8 291 785 2,044 595
1938 2,374 376 256 600 664 151 58.3 32.9 135 721 2,180 172 648
1939 1,228 593 103 113 205 262 199 121 423 1,712 1,700 539 605
1940 192 101 101 260 794 289 283 48.5 105 669 666 131 302
1941 30.1 23.3 191 257 410 321 176 30.6 81.6 974 374 384 271
1942 307 625 1,512 2,404 2,390 2,906 327 51,1 348 608 368 606 1,033
1943 74.3 31.6 39.5 50.7 44.9 76.8 30.8 31.0 92.2 165 607 180 120
1944 36.3 26.6 31.4 87.2 82.0 581 1,034 209 221 1,930 2,545 1,326 679
1945 3,149 583 367 1,332 573 165 56.8 49,0 62.6 2,135 3,296 1,291 1,099
1946 222 98.7 515 1,230 464 550 305 948 649 1,622 2,275 1,621 880


0)

0d

B)



p:
N



















GAGING-STATION RECORDS
St. Marys River Basin

(6) St. Marys River near Macclenny, Florida (continued)

Water
Year Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June July Aug. Sept. Year 0

1947 1,142 182 98.5 83. 1 378 1,223 1,359 332 243 523 538 4,467 877 r
1948 6,240 4, 15 2,470 1,198 1,309 3,913 4,883 70.6 32,3 525 2,133 446 2,285
1949 1,644 155 317 343 2,390 247 427 108 74,9 328 650 1,391 661
1950 235 231 109 69.1 51.8 237 102 40.6 31.6 887 87.6 4,115 514
1951 4,347 661 220 156 134 116 101 35.5 27.3 36.6 55.3 83.1 504
1952 141 286 296 261 768 861 212 73.2 59.3 52.5 62.8 158 268
1953 117 40.9 36.1 78.0 127 85.8 728 78.3 43.7 114 1,294 2,301 419
1954 3,416 312 1,803 1,268 258 165 112 45.7 28.4 31.3 24.9 64.3 636 01
1955 61.1 32,5 47,0 75.0 146 46.3 38.6 25.3 20.8 164 126 306 90.1
1956 82.8 51,1 37.9 65.7 177 94.7 38.2 343 80.7 245 54.2 81.5 113
1957 827 231 59.7 44.5 37.8 136 261 260 2,642 287 1,285 666 561
'.4






INFORMATION CIRCULAR NO. 20


Low Flows

During the period since October 1926, when streamflow
records were started for St. Marys River near Macclenny,
there have been outstanding droughts as well as major floods.
Particularly outstanding periods of low runoff are those of
1927-28, 1931-32, 1934-35, 1943, 1951-52, and 1954-56.
From the standpoint of the, collection of information on low-
flow conditions, it is fortunate that this project investigation
of streamflows in Baker County was conducted during part
of the period covered by the most recent drought.

Streamflow conditions of North Prong St. Marys River
are influenced by the amount of water stored in Okefenokee
Swamp. During prolonged periods of deficient rainfallthe
water levels in the Swamp are lowered by evapotranspiration
losses and runoff in surface streams ceases. At the gaging
station at the state line between Baxter, Florida, and Moniac,
Georgia, there was no flow for the period June 7 to December
1954, except for ten intermittent days in which an average
daily discharge of 0. 1 cubic foot per second occurred.

Middle Prong St. Marys River is also largely swamp
drainage and its runoff characteristics are somewhat similar
to those for North Prong. However, flows are better sus-
tained during low-water periods and at the gaging station at
Taylor the streamhas not ceased to flow during the two-year
period of record. The minimum daily discharge that has
occurred during the period of record at this station was 0. 1
cubic foot per second August 24-31 and September 12-18,
23, 1956. During longer drought periods, such as the latter six
months of 1954 (prior to the establishment of the station),
the flow at this station probably ceased.

No streamflow data have been collected for Cedar Creek
except a measurement of 2. 7 cfs at State Highway 125 on
April 18, 1956. Records for gaged streams in Baker County
indicate that streamflow was not extremely low at that time,
and that the flow of Cedar Creek at State Highway 125 would
drop to about one cfs during periods of drought.

The flow of South Prong St. Marys River has been






FLORIDA GEOLOGICAL SURVEY


determined at two gaging stations. At the station in the upper
part of the basin at State Highway 229 south of Sanderson,
the flow has ceased for long periods several times during
the two-year period of record. At the lower station on the
South Prong at U. S. Highway 90 at Glen St. Mary the flows
have diminished sharply during drought periods but were
better sustained than those at the upper station or those for
North and Middle Prongs. At the station on U.S. Highway
90 the minimum daily discharges were 0. 9 and 0. 8 cubic
foot per second for May 17 and May 23, 1950, respectively,
which are the only times during the 8-year period of
record that the flow has dropped below one cubic foot per
second.

One of the major tributaries of the SouthProngSt. Marys
River is Turkey Creek which flows into the South Prong about
one mile upstream from the gaging station at U.S. Highway
90. The flow of Turkey Creek has been determined since
September 1955 at a gaging station at State Highway 23, 0. 9
mile south of Macclenny. The minimum flow during the
period of recordwas 0. 2 cubic foot per second onApril 21-24,
1956. The low-water base flow for this stream is sustained
by flow from ground. storage which is probably enough to
prevent the streamflow from ceasing during moderate drought
conditions.

The gaging station on the main St. Marys River is located
one mile downstream from South Prong, near the eastern-
boundary of Baker County, and is called St. Marys River
near Macclenny. The discharge of the river at this gaging
station includes practically all of the surface runoff from
Baker County as well as that from about 200 square miles in
Georgia. The total drainage area of the stream above the
station is approximately 720 square miles. Minimum dis-
charge since October 1926 was 12 cubic feet per second
(0. 0167 cfs per square mile) which occurred May 22, 1932.

The maximum period of deficient discharge during the
period of record at the station on St. Marys River near
Macclenny is shown by curves in figure 3. One curve shows
the maximum period of consecutive days duringwhichthe flow
was less than a given amount, and the other shows the low-
est average discharge for periods ranging from one day to







'U

-a
W

U)
a


a
a
a
C
U)


a.
W
W

LL
U


10


a
hi
CD

C)
U,
5


L


CONSECUTIVE DAYS
CONSECUTIVE DAYS


CONSECUTIVE MONTHS


Figure 3. Discharge available without storage, St. Marys River near Macclenny, 1926-57.


0.3 3c I I I I I I I



.20

.IS- -
.15



.10

.0 Maximum period -
of deficient flow -

.05

.04-- --

.03-




-Lowest average
discharge, for
Indicated period


2 3 4 5 6 8 10 20 1 2 3 4 6 8 to 12


~II---~-.





FLORIDA GEOLOGICAL SURVEY


twelve months.

As an example, during the period 1926-57, 33 days was
the longest consecutive period that the daily runoff at this
station remained below 0.025 cubic foot per second per square
mile (18 cfs). The longest period during which the runoff
averaged as low as 0. 025 cubic foot per second per square
mile was 100 days.

Flow-Duration Curves

The flow -duration curve shows the percentage of time that
a specified discharge was equaled or exceeded during a given
period. In a strict sense the flow-duration curve applies
only to the period for which data were used to develop the
curve. However, if the period on which the flow-duration
curve is based represents long-termflow of the stream, the
curve may be considered a probability curve and used to
estimate the percent of time a specified discharge will be
equaled or exceeded in the future.

The duration curves of daily flow for six gaging stations
in Baker Countyare shown in figure 4. Records for only one
station, St. Marys River near Macclenny, are continuous for
the 31-year period, 1926-57. The curves for the other five
stations in the report area have been adjusted from their indi-
vidual short-term records to the 31-year base period. The
relationship of the duration of flows at the six stations in the
St. Marys River basin shown in figure 4 is for the common
31-year base period. In order to compare the duration curves
for each station, discharge is expressed as cubic feet per
second per square mile.

The difference in the low-flow characteristics of each
tributary is apparent from the curves shown in figure 4. As
an example, at the Turkey Creek station (drainage area,
20. 9 square miles) the flow equaled or exceeded 0. 025 cfs
per square mile for 90 percent of the time. However, at
the station on Middle Prong at Taylor (drainage area, 127
square miles) for the same durationperiod the flow was only
0.0021 cfs per square mile. Low flow at the Turkey Creek














GAGING STATION


.......... I. North Prong St. Morys
River at Monioc Go.
-- 2. Middle Prong St. Morys
River at Toylor, Flo.
-- 3. South Prong St. Marys
River near Sanderson Fla.
-.- 4. Turkey Creek at Mocclenny Fla.
-....-5. South Prong St. Morys
River at Glen St Mary Flo.
- 6. St. Marys River near
Macclenny Fla.


5 0.2 0.5 I 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995
PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN


DRAINAGE
AREA
SO. MI.

160

127


Figure 4. Flow-duration curves for gaged streams inBaker

County for the 31-year period, 1926-57.


INFORMATION CIRCULAR NO. 20


.001-
0.01






FLORIDA GEOLOGICAL SURVEY


station is fairly well sustained by ground-water inflow while
that at the Middle Prong station is poorly sustainedand flow
ceases during extended periods of deficient rainfall.


Flood Flows

The knowledge of flood-flow characteristics of the
streams in an area is required information in the economic
design of bridges, roadfills, spillways, detention dams, and
other structures placed in, across, or adjacent to flood
plains.

From a study of the magnitude and pattern of recurrence
of past floods a means of estimating with fair dependability
the expectancy of floods in the future has been developed.
Such a study of floods in Florida has been made and presented
in an earlier report. 1 Parts of the earlier report that are
applicable to Baker County have been abstracted and pre-
sented here.


Flood-Frequency Relations

This abstract summarizes and explains the use of re-
gional flood-frequency relations for streams inBaker County.

Among the many physical characteristics of drainage
basins that affect runoff, those most applicable in Florida
are size of drainage area of the basin; amount of storage
capacity in stream channels, swamps, and lakes; shape of
basin; land and stream slopes; porosity of soil; type of vegetal
cover; and land use.

From the earlier report it was determined that the size
of drainage area is the dominant factor influencing the


1Pride, R.W., Flood Frequency Relations for Florida:
U.S. Geol. Survey open-file report, extracted from an un-
published report, Floods in Florida, Magnitude and Fre-
quency, 1957.






INFORMATION CIRCULAR NO. 20


magnitude of floods on streams in Baker County. Figure 5,
whichwas prepared from flood relations in the earlier report,
shows the variation of flood discharge with drainage area for
streams in Baker County.

Flood data for only two gaging stations in this report
area (North Prong St. Marys River at Moniac and St. Marys
River at Macclenny) were available for a long enoughperiod
to be used in the development of the flood-frequency relation
shown in figure 5. However, the data were analyzed and
results summarized on a regional basis using flood data from
other long-term stations in Florida as well as southern
Georgia and Alabama. Baker County is part of a much larger
geographical area for which flood characteristics are similar.
Therefore it can be assumed that the relations as shown in
figure 5 may be applied with a fair degree of assurance in
estimating the magnitude of floods of various recurrence
intervals up to 50 years.


STORAGE CONSIDERATIONS

The primarypurpose of this report of the surface-water
resources of Baker County is to furnish data for the planning
of water-impoundment reservoirs for recreational uses. At
this time other water uses or benefits that would result from
the creation of impoundment reservoirs are secondary in
importance to the recreational requirement. There are
several hydrologic factors that must be considered in the
design of reservoirs.


Evaporation from Water Surfaces

The evaporationlosses fromlarge multipurpose reser-
voirs, such as those required for flood control, navigation,
water-power development, and water conservation, are
usually of minor importance compared to the inflows, out-
flows, and volume of storage. However, in the design of
small recreational reservoirs, such as those being consid-
ered by Baker County on streams with poorly sustained low
flows, the evaporation losses have an appreciable effect.






FLORIDA GEOLOGICAL SURVEY


By the construction of a reservoir an enlarged area of
water surface is exposed and the evaporation opportunity is
increased. Total evaporation losses from a reservoir are
proportional to the area of the water surface. Thus, the
losses from a shallow, wide reservoir are considerably
higher, percentagewise, than those from a deep, narrow
reservoir.

Most investigations of evaporation have been confined to
measurements from small areas, suchas the Class A evap-
oration pans used by the U. S. Weather Bureau. The yearly
evaporation from pans is greater than from natural water
bodies. The ratio of evaporation from a pan to that from a
large body of water is known as the "pan coefficient. The
results of experiments to determine the pan coefficient indi-
cate seasonal as well as geographical variations in the




o
40,000 1


Ssooo---------
0 i


S20,000






a-




o
,.- 10,000- -



a 500 --
0
0
-I
j" 300
10 20 30 40 60 100 200 400 600 10(
DRAINAGE AREA, IN SQUARE MILES

Figure 5. Variation of flood discharge with drainage area
for streams in Baker County.






INFORMATION CIRCULAR NO. 20


coefficients. Monthly pan-to-lake coefficients have been com-
puted from records collected at Lake Okeechobee, Florida,
for the period 1940-46. These coefficients range from 0. 96
for February to 0. 91 for July and August.

Records of evaporation from a ClassA pan at Gainesville,
Florida, are available for the years 1954-57. These evap-
oration records have been used with the pan coefficients,
derived fromthe Lake-Okeechobee investigation, to compute
the approximate evaporation loss thatwouldbe expected from
small reservoirs in Baker County.

Rainfall is probably more variable seasonally and geo-
graphically in Florida than evaporation. Fortunately, a 61-
year rainfall recordat Glen St. Mary is available. The aver-
age monthly rainfall based on this 61-year record has been
used to indicate the rainfall that would occur on the lake
surface.

The net water losses resulting from evaporation are
shown for each month' in table 2.


Seepage and Transpiration

As previously discussed under OCCURRENCE OF SUR-
FACE WATER, part of the. water falling as precipitation
seeps into the ground and part is used in transpiration by
plant life. In considering the availability of surface supplies
the amounts of water removed by these processes are con-
sidered to be losses.

In Baker County the seepage losses probably would be
increased to some extent by impoundment of water in shallow
reservoirs. On the other hand, in some areas in the eastern
part of the countythere is some indication of upward leakage
or flow from ground storage to the surface by artesian pres-
sure. The evaluation of seepage losses or gains is beyond
the scope of this investigation. The additional seepage that
would result from the construction of a small low-head reser-
voir has been assumed to be negligible.

Transpiration losses also would be increased by the






FLORIDA GEOLOGICAL SURVEY


Table 2. Summary of Monthly Average Evaporation
and Rainfall in Baker County


Evaporation (inches) Rainfall3 Net evap-
(inches) oration loss
Month Class A Pan1 Pan Lake from lake
Coefficient2 (inches)

January 3.38 0.77 2.60 2.73 ---
February 4. 24 .69 2. 92 3. 53 ---
March 5.96 .73 4.35 3.81 0.54
April 6.70 .84 5.63 2.97 2.66
May 8.21 .82 6.74 3.79 2.95
June 8.37 .85 7.11 6.55 .56
July 7.67 .91 6.98 7.83 ---
August 7.71 .91 7.01 6.71 .30
September 5.72 .85 4.85 5.68 ---
October 4.93 .76 3.75 3.61 .14
november 3.92 .71 2.78 1.81 .97
december 3.13 .83 2.60 3.14 ---

IMonthly average of records for 1954-57 from U.S. Weather
Bureau evaporation station at Gainesville, Florida.
Computed evaporation data for Lake Okeechobee, Florida.
Kohler, M.A., 1954, Lake and pan evaporation, in Water-loss
investigations Lake Hefner studies, technical report: U.S. Geol.
Survey Prof. Paper 269, p. 128, based on a study by Langbein,
W.B., "Research on Evaporation from Lakes and Reservoirs,"
Paper presented at Brussels Assembly, 1951, and U.S. Weather
Bureau records .
3Monthlyaverage of records for 1896-1957 from U.S. Weather
Bureau rainfall station at Glen St. Mary, Florida.






INFORMATION CIRCULAR NO. 20


construction of a shallow reservoir if vegetation around the
edges of the pool was permitted to flourish. The possible
small losses from this cause have likewise been considered
as negligible in the computations that follow.


Potential Reservoir Sizes

The relatively flat topography and shallow stream valleys
indicate that the only feasible type of surface reservoir for
Baker County is one with low-head dam and shallow pool.

The flow records at gaging stations in Baker County
indicate that the minimum flows during droughts would not
equal the increased evaporation losses that would result from
the additional surface of shallow reservoirs of large areal
extent. This would result in a decrease in the water level
in the reservoir from evaporation losses alone. However,
the minimum flows would be sufficient to balance the evap-
oration losses from small reservoirs. An analysis of the
flow records was made to determine the surface area of the
largest reservoir that could be created in the basin of each
of the gaged tributaries in Baker County to balance evapor-
ation losses against minimum inflow so as to maintain a full
reservoir.

Mass curves were plotted as shown in figures 6 and 7,
using discharge records from four of the gaging stations at
sites of potential small reservoirs. The slope of the mass
curve is a measure of the rate of flow of the stream. The
minimum slope occurs when the monthly flow is small and
is the critical condition of inflow for design of recreation
reservoirs.

The maximum rate of net evaporation loss is represented
by the right-hand curves in figures 6 and 7. Table 2 shows
the monthly evaporation losses in inches from a free water
surface, based on average conditions of pan evaporation and
rainfall. The maximum amount was 2. 95 inches, or 0. 25
foot, for May. For months when the rainfall on the reservoir
pool occurred at less than average amounts, the net evapor-
ation loss would be correspondingly higher. Greater than














S1400
18,000 12,000 1

10.000 12 00-
1 ,000. a 0 -,- / 9- .

14,000 ,000g0
24- goo
12,000 ,0
*-.?' --Go r *o o
4.000 400 00
I I 25,000 3
10,000 4000 -- BO O

8,000 20 00

M
6,000 11 I 1 I I II-II I I II0 II t
0 6 I 12 24 30 3 6
4,000 --s- ACCUMULATED MONTHS

2,000 -- -- NOTE.- SLOPE OF LINE REPRESENTS MAXIMUM MONTHLY AVERAGE
gg tv00a,6- RATE OF NET EVAPORATION LOSS IN ACRE-FEET FOo VARIOUS
o 1 1T5li 9 5 1 1 i RESERVOIR AREAS. NET EVAPORATION LOSS BASED ON NET
05 S S 196 1957T 1985 1956 1957 1955 1986 1957 RATE OF 0.25 FT PER MONTH FOR 36-MONTH PERIOD. NO
MIDDLE PRONG ST. MARYS SOUTH PRONG ST. MARYS TURKEY CREEK ALLOWANCE MA(E FOR TRANSPIRATION AND SEPAGE LOSSES.
RIVER AT TAYLOR RIVER NEAR SANDERSON AT MACCLENNY
NOTE.-FOR PERIODS OF MINIMUM FLOW SHOWN ABOVE, EVAPORATION LOSSES FROM A RESERVOIR
OF INDICATED SURFACE AREA WOULD HAVE EQUALED THE INFLOW TO THE RESERVOIR.

Figure 6. Mass curves for flow at three gaging stations in Baker County and diagram show-
ing rate of evaporation loss from various reservoir areas.










350 -- .. ----
ZINST NSET
346

300






_S_ 4 .-
344

42





30 II -j' -
IN14 INSET A

o 2,0001400
















1 || |I |9 ACCUMULATED MONTHS
1954 19551 1 INS? 1 1203



















NOTE.- SLOPE OF LINE RIEPRESENTS MAXIMUM MONTHLY AVERAGE
NOTE.-FOR PERIODS OF MINIMUM FLOW SHOWN A80VE,EVAPORATKIN RATE CF NET EVAPORATION LOSS IN ACRE-FEET FOR VARIOUS
LOSSES FROM A RESERVOIR OF INDICATED SURFACE AREA RESERVOIR AREAS NET EVAPR-ATION LOSS BASED ON NET
WOULD HAVE ALED TH INFLOW T RESER FT PER MOTH M PR NO






ALLOWANCE MAE FOR TRANSPIRATION AND SE0EPAE LOSSES

Figure 7. Mass curve for flow of South Prong St. Marys River at Glen St. Mary and dia-

gram showing rate of evaporation loss from various reservoir areas. o
so 130 A


ISET T 02 ACCUMULATED MONlTHS


NOTE.- SLOPE OP LINE REPRESENTS MAXIMUM MONTHLY AVERAGE
NOTE-FOR P25100 SF MINIMUM PLOW SWE ABS VEEVNPORION RATE OP ET EVAPORATION LOSS IN ICRE-FEET F0R VARIOUS
LOSSES PROM A RESERVOIR OP INDICATED SURFACE AREA RESERVOIR AREAS NET EVAPORATION LOSS BASED ON NET
rWULD HAVE SEALED THE INFLOW To THE RESERVOIR. RATE OF 055 FT PER MONTH FOR 36-MONTH PERID0 NO
ALLOWANCE MUM FOR TRANSPIRATION AND SEEPAGE LOSSES

Figure 7. Mass curve for flow of South Prong St. Marys River at Glen St. Mary and dia-

gram showing rate of evaporation loss from various reservoir areas. N






FLORIDA GEOLOGICAL SURVEY


average rates of rainfall would result in more discharge over
the spillway.

Using 0. 25 foot per month as a design rate of evapora-
tion, the volumes of water loss in acre-feetper month were
computed for selected pool areas in constructing figures 6
and 7. The minimum slope of the mass curve for each station
was transferred to the evaporation loss diagram. The size of
surface area of the reservoir thus obtained represents the
maximum for which inflow would have balanced evaporation
losses, during the dry months in 1955-57, assuming no other
draft or consumptive use of the impoundedwater and assuming
that the reservoir was full at the beginning of that drought.
If a larger reservoir should be created, the gap between the
supply and loss curves would represent the amount of water
in acre-feet that would be lost for evaporation in excess of
the replacement by inflow. In such case, this would result
in a reservoir less than full for a time, depending on the
size of the reservoir.

The surface areas of the largest reservoirs that could
be kept filled by the base flows at each of the four stations
shown below were determined from figures 6 and 7, which
were based on a monthly net evaporation rate of 0. 25 foot
(from table 2) and on streamflow experience during the period
of record at each station. The areas are shown in the follow-
ing table.

Surface area
Drainage area, of reservoir,
Gaging station in square miles in acres

Middle Prong St. Marys River
at Taylor 127 300
South Prong St. Marys River
near Sanderson 58 30
South Prong St. Marys River
at Glen St. Mary 150 640
Turkey Creek at Macclenny 20. 9 200


Although there are longer periods of streamflow records
for North Prong St. Marys River at Moniac and St. Marys






INFORMATION CIRCULAR NO. 20


magnitude of floods on streams in Baker County. Figure 5,
whichwas prepared from flood relations in the earlier report,
shows the variation of flood discharge with drainage area for
streams in Baker County.

Flood data for only two gaging stations in this report
area (North Prong St. Marys River at Moniac and St. Marys
River at Macclenny) were available for a long enoughperiod
to be used in the development of the flood-frequency relation
shown in figure 5. However, the data were analyzed and
results summarized on a regional basis using flood data from
other long-term stations in Florida as well as southern
Georgia and Alabama. Baker County is part of a much larger
geographical area for which flood characteristics are similar.
Therefore it can be assumed that the relations as shown in
figure 5 may be applied with a fair degree of assurance in
estimating the magnitude of floods of various recurrence
intervals up to 50 years.


STORAGE CONSIDERATIONS

The primarypurpose of this report of the surface-water
resources of Baker County is to furnish data for the planning
of water-impoundment reservoirs for recreational uses. At
this time other water uses or benefits that would result from
the creation of impoundment reservoirs are secondary in
importance to the recreational requirement. There are
several hydrologic factors that must be considered in the
design of reservoirs.


Evaporation from Water Surfaces

The evaporationlosses fromlarge multipurpose reser-
voirs, such as those required for flood control, navigation,
water-power development, and water conservation, are
usually of minor importance compared to the inflows, out-
flows, and volume of storage. However, in the design of
small recreational reservoirs, such as those being consid-
ered by Baker County on streams with poorly sustained low
flows, the evaporation losses have an appreciable effect.






INFORMATION CIRCULAR NO. 20


River near Macclenny, the sizes of potential reservoirs at
these gaging stations have not been determined as these
streams border Baker County and only part of their drainage
area is within the county.

CONCLUSIONS

Surface-water supplies in Baker County vary seasonally
as well as geographically. The highest runoff usually occurs
during the summer and early fall and the lowest during the
winter and early spring, corresponding to the same rainfall
distribution pattern.

Streamflows of the St. Marys River basin are influenced
by the large swampland areas in Baker County and southern
Georgia. During prolonged periods of deficient rainfall,
much of the surface water stored in the swamps is lost by
evaporation and transpiration and the surface streams drain-
ing from these swamps cease to flow. Long periods of little
or no flow have occurred at points on North Prong, Middle
Prong, and the upper reaches of South Prong of the St. Marys
River. Low flows in Turkey Creek and in the lower reach of
South Prong St. Marys River are fairly well sustained by
ground-water inflow.

During periods of drought, the yield of the streams in
Baker County varies from less than 0. 001 to 0.01 cfs per
square mile, depending on the location. The median runoff
varies from 0. 045 to 0. 3 cfs per square mile. The mean
annual peak flow varies from 38 cfs per square mile from a
drainage area of 10 square miles to 10.4 cfs per square mile
from 720 square miles. The ratios of the 10-, 25-, and 50-
year flood to the mean annual floods are 2. 22, 3.05, and
3. 72, respectively.

Evaporation from the water surface would account for
most of the natural water losses from proposed recreation
reservoirs in Baker County; however, streamflow even in dry
periods would sustain reservoirs in sizes of from 30 to 640
acres in certain stream basins. Larger reservoirs could be
builtat the risk of having them less than full during periods
of drought.










FLRD GEOLOSk ( IC SUfRiW


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