This item has the following downloads:

( PDF )

FLRD GEOLOSk ( IC SUfRiW


COPYRIGHT NOTICE
[year of publication as printed] Florida Geological Survey [source text]


The Florida Geological Survey holds all rights to the source text of
this electronic resource on behalf of the State of Florida. The
Florida Geological Survey shall be considered the copyright holder
for the text of this publication.

Under the Statutes of the State of Florida (FS 257.05; 257.105, and
377.075), the Florida Geologic Survey (Tallahassee, FL), publisher of
the Florida Geologic Survey, as a division of state government,
makes its documents public (i.e., published) and extends to the
state's official agencies and libraries, including the University of
Florida's Smathers Libraries, rights of reproduction.

The Florida Geological Survey has made its publications available to
the University of Florida, on behalf of the State University System of
Florida, for the purpose of digitization and Internet distribution.

The Florida Geological Survey reserves all rights to its publications.
All uses, excluding those made under "fair use" provisions of U.S.
copyright legislation (U.S. Code, Title 17, Section 107), are
restricted. Contact the Florida Geological Survey for additional
information and permissions.











STATE OF FLORIDA
STATE BOARD OF CONSERVATION




DIVISION OF GEOLOGY
Robert O. Vernon, Director




REPORT OF INVESTIGATIONS NO. 53




LOW STREAMFLOW IN THE MYAKKA RIVER
BASIN AREA IN FLORIDA
By
H. N. Flippo, Jr. and B. F. Joyner
U. S. Geological Survey




Prepared by the
UNITED STATES GEOLOGICAL SURVEY
In cooperation with the
DIVISION OF GEOLOGY, FLORIDA BOARD OF CONSERVATION,
SARASOTA COUNTY
and the
CITY OF SARASOTA, FLORIDA




Tallahassee
1968










FLORIDA STATE BOARD
OF
CONSERVATION


--,



CLAUDE R. KIRK, JR.
Governor


TOM ADAMS
Secretary of State




BROWARD WILLIAMS
Treasurer




FLOYD T. CHRISTIAN
Superintendent of Public Instruction


EARL FAIRCLOTH
Attorney General



FRED O. DICKINSON, JR.
Comptroller



DOYLE CONNER
Commissioner of Agriculture


W. RANDOLPH HODGES
Director






LETTER OF TRANSMITTAL


STATE BOARD OF CONSERVATION
Division of Geology
Tallahassee
June 25, 1968


Honorable Claude R. Kirk, Jr., Chairman
State Board of Conservation
Tallahassee, Florida

Dear Governor Kirk:
The Division of Geology, Florida Board of Conservation, is
publishing as Report of Investigations No. 53, a study of the "Low
Streamflow in the Myakka River Basin Area in Florida." This
report was prepared as a part of the cooperative program between
the Division of Geology and the U. S. Geological Survey, by H. N.
Flippo, Jr., and B. F. Joyner.
The Sarasota-Manatee area is a water-short area and the study
was undertaken in 1963 in order to determine the storage capa-
bility and discharge rates of the Myakka water shed. It was found
that many of the streams of the water shed were virtually dry
during part of every year. However, the basins of the Myakka
lakes, through which the river flows offer some storage potential,
that if properly developed would provide a continuance drift of
about seven million gallons of water per day of good quality water
that would be high in color and temperature upon occasion. With
reasonable treatment some of this water could be used to meet
the present needs of the rapidly expanding coastal areas.

Respectfully yours,
Robert O. Vernon
Director and State Geologist
ROV:jkm

















































Completed manuscript received
June 25, 1968
Printed for the Florida Board of Conservation
Division of Geology
By the Douglas Printing Company
Jacksonville, Florida

iv






CONTENTS

A b stra c t ......................................... ......................................................................................... ............................................ 1

Introduction .................................................................................... ........................................ 1

Purpose and Scope .............................................................................................. 2

Description of the Area ..................................................................... ........................................... ................. 2

C lim a te ...................................................................................... ........................................................ ................. 2

Topography and Drainage ................................................................................. ................................... 2

G e o lo g y .............................. .......... ............................... ................................. .................................................. 4

Streamflow Data ............................................................................. ........................................................... 5

Dry Season Streamflow ............................................................................................................ 6

Factors Affecting Low Flows ............................................... ............................................................... 6

Low-Flow Characteristics .................................... .......................... ........................................ 14

Frequency ................................. .................................................................... ....................... 14

Duration and Magnitude ....................................................................... .................... .. 18

Low Flow Quality ................................... .............................. ............................. .. ............................ 22

Current Usage of Surface W after ..................................................... ................. ........................ 23

Draft-Storage Relations ........................................................................................................... .............. 28

C on clu sion s .................................................................................................................... ............................ .. 32

R e f e r e n c e s .......................................................................................................................................................................... 3 4






ILLUSTRATIONS


Figure Page

1 Myakka River basin area showing location of data-collection
sta tio n s ............................................ ....................................................................... ........

2 Period and type of hydrologic record for surface waters in
Myakka River basin and vicinity .... ....................... ...................................... 7

3 Duration curves of daily low flow for selected streams, stand-
ard period- 1940-64 .................................................. ............................... 21

4 Stage versus volume, Upper and Lower Myakka Lakes .................................... 29

5 Mass curve of daily volumes, Myakka River near Sarasota,
F lo rid a ......... ......................... .................. ........................................ 3 1





TABLES


Table Page

1 Selected low-flow discharge measurements made at various
g a g in g sta tio n s ........................................ ..................................................... ........................................ 8

2 Magnitude and frequency of annual low flow of Myakka River
n ea r S a ra so ta ............................................................................... ....................... ................................. 15

3 Monthly mean, median, and minimum discharges for March,
April, and May at continuous-record stations ............................ .............................. 17

4 Low-flow characteristics at short-term-continuous, partial and
m miscellaneous record stations ..................................... ......................................... ............... 19

5 Duration of daily flow at continuous-record stations in Myakka
R iv er ba sin a rea .................................................................... .......................... .............................. ..... 2 0

6 Chemical analysis of surface waters during low-flow periods .................. 24

vi







LOW STREAMFLOW IN THE MYAKKA RIVER
BASIN AREA IN FLORIDA

By
H. N. Flippo, Jr. and B. F. Joyner


ABSTRACT
Streamflow data, collected in the Myakka River basin area since
1936 and supplemented by means of a more complete network of
stream-gaging stations since 1963, indicate that all non-tidal reaches
of streams in the area ceased natural flows during at least five
droughts since 1938. Many of these non-tidal reaches go virtually dry
during the late spring of most years. Effective utilization of stream-
flow is restricted by these frequent droughts and a limited choice of
practicable storage sites. Upper and Lower Myakka Lakes, through
which the Myakka River flows, occupy two of the largest natural
depressions in the area and have a total storage capacity of approxi-
mately 8,100 acre-feet. Average discharge at a stream-gaging sta-
tion located between these lakes is 266 cfs (cubic feet per second),
or about 192,000 acre-feet per year. Draft-storage studies indicate
that these lakes will provide a continuous draft of at least 6.5 mgd
(million gallons per day), provided their storage potential is ade-
quately developed.
Surface waters that are derived from natural drainage are of
good quality, except for occasional high color and temperatures of
about 900F. during the summer months. In many channels in low
lying areas, low flows are often supplemented by waters of rela-
tively high dissolved solids content derived from irrigation wells
and domestic waste.

INTRODUCTION
A thorough knowledge of the occurrence, availability, and qual-
ity of the water resources of any area is prerequisite to the orderly
development and utilization of that resource. This report is one of
several resulting from an investigation to appraise the water re-
sources of the Myakka River basin area and to define specific prob-
lems associated with obtaining adequate supplies of fresh water in
the area. The investigation was conducted by the U.S. Geological
Survey, in cooperation with Sarasota County, the City of Sarasota,
and the Division of Geology, Florida Board of Conservation.
1






REPORT OF INVESTIGATIONS NO. 53


PURPOSE AND SCOPE
The purposes of this report are to describe briefly the climate,
topography, drainage, and geology of the area, and to explain their
influences on the low-flow characteristics of the streams; to point
out and illustrate the similarities and differences among the major
streams during periods of low flow; to present the hydrologic data
and to interpret these data for use in considering the major streams
in the area as future sources of fresh water. Data obtained at sev-
eral stream-gaging stations located outside the area of investigation
have been included and used for comparative purposes.

DESCRIPTION OF THE AREA
The area investigated includes all of Sarasota County, that part
of Charlotte County located west of Charlotte Harbor, and that part
of the Myakka River basin lying within Manatee and Hardee coun-
ties-an area of about 1,000 square miles, figure 1.

CLIMATE

The climate of the area is humid-subtropical; annual rainfall
averages 54 inches, about the same as for the State. The driest part
of the year is usually November through May. Heavy rains, gener-
ally associated with convective thunderstorms, occur during the
summer months.
Mean annual lake evaporation is approximately 52 inches, with
about 60 percent occurring from May to October (Kohler and others,
1959, pl. 2, 4). Evaporation and transpiration from shallow vegeta-
tion-filled lakes probably exceeds 60 inches per year. Overall evapo-
transpiration, excluding bays and estuaries, is estimated at 85 to
40 inches per year. Runoff, based on records for the three long-term
stations, averages about 14 inches per year; however, average an-
nual runoff from upland areas exceeds 18 inches based on records
collected in the Manatee River basin.

TOPOGRAPHY AND DRAINAGE
Land surface altitudes in the area range from sea level to about
115 feet above sea level at the headwaters of the Myakka River.
The topography is generally flat away from the streams, with a
fairly sharp break from these flats into the stream channels. Except
where deepened by man, the sloughs which serve as tributaries to
the larger streams are seldom more than a few feet deep, but they







Low STREAMFLOW-MYAKKA RIVER


2790c-


82 30'


2 00'


-27 30'



















-27"00'


e02z30 82z00'
Figure 1. Myakka River basin area showing location of data-collection stations.


may range in width from several feet to more than a mile. Numer-
ous wet-weather ponds dot the broad, flat landscape in the central
part of the area, where the water table is usually within a few feet
of the ground surface. Marsh and swamps each occupy about 5 per-
cent of the upland lying above 40 feet in altitude. This upland is
composed of the remnants of several Pleistocene marine terraces.
In a topographically low area, near the center of its basin, the
Myakka River flows through Upper and Lower Myakka Lakes.
Both lakes are entirely within the Myakka River State Park. The
combined lake area is about 1,380 acres and depths are usually be-


R..'s I lIVE I lir E I R o E 4 RIVE REOE I R E-E I a EEL
"I K Q-V-~Ht~b~~t4C
MAWAE CO.
il i B>i /- I '*
idif


EXPLANATION
SIlt,,010, It"" ltllrdl
A wi,.rnmrnIi,, # ,eq16r1.1.- yNr. W4 'W 0
AU fl, k.e.Itull 19.010OOA, oIme
-m UN,..~pet0.0" ..ol I..g
tlp ~mdy ot Uyoio ftl,tt Ma
tlo ftj bt ft"'o by h-01661-
Woklltl'.l Aw-


- I __ _- .1


n IR-lo.
I "Itol; I Rv~r i NV2 t I


I "1 r 1 0 IkIr I "ll't i r IN t l"t






REPORT OF INVESTIGATIONS NO. 53


tween 5 and 6 feet over most of this area; however, the levels of
these lakes fluctuate widely with seasonal climatic changes. Both
lakes are considerably larger than any of the other perennial lakes
in the area.
In 1941, a low concrete dam was constructed at the outlet to the
upper lake; an earthen dam had been installed several years earlier
at the outlet to the lower lake. The purpose of these controls was
to provide enough storage so that the lakes would not go completely
dry during seasonal droughts. The concrete control maintained a
minimum of 3 feet of water in the upper lake during the severe
drought of 1943-45; the lower control was in a washed-out condition
(as it is at the present time) and the lower lake dried up completely
in 1945.
The Myakka River and a tributary, Big Slough Canal, are the
two major streams whose basins lie entirely within the area of in-
vestigation. Phillippi Creek and Cow Pen Slough (Shakett Creek)
are the largest coastal streams; both have been dredged for drain-
age purposes. About 20 other small coastal streams, such as Alliga-
tor, Fox, and South Creeks, arise within several miles of the coast
and flow into bays and estuaries; each of these streams is tidal
throughout much of its reach. The long, low keys which parallel the
coast have no defined drainage channels.

GEOLOGY

The Hawthorn Formation of late Miocene age, consisting prima-
rily of phosphatic sandstones, clays, and sandy limestones, underlies
the entire area. Recent dredging in the lower reaches of Cow Pen
Slough has exposed beds of stratified shell and clay that are similar
to Hawthorn deposits which have been penetrated by wells in the
general locality. These relatively impervious beds, which are now
under study by interested parties, may represent the shallowest
occurrences of the Hawthorn Formation in the area.
In the upper Myakka River valley, generally northeast of the 60-
foot altitude contour, the clayey quartz and phosphatic sand of the
Bone Valley Formation, of Pliocene age, overlie the Hawthorn For-
mation and are unconformably overlain by Pleistocene terrace
deposits.
Exposures of the Caloosahatchee Marl composed of beds of sandy
marl and dolomite of early Pleistocene age (Dubar, 1962, p. 8) occur
in several creeks near Punta Gorda, in some canals in Port Char-
lotte, and in the Myakka River channel east of Venice. The Caloosa-






Low STREAMFLOW-MYAKKA RIVER


hatchee Marl underlies thin surficial sands on the east side of the
Myakka River, in the southeastern part of the area.
In general, the Pleistocene and Holocene deposits exert the great-
est geologic influence on the low-flow characteristics of the streams.
Driller's logs indicate that the higher marine terraces, such as in the
vicinity of Myakka Head, are underlain by deposits of fine to coarse
quartz sands, some pea gravel, and minor amounts of shell and clay.
These deposits are believed to be relatively thin beneath the
channels of deeply incised streams, but they may exceed 100 feet in
thickness beneath the ridges. The soils on the ridges have been
classified by the U.S. Department of Agriculture (Caldwell, 1958, p.
3) as "excessively to moderately well drained deep sandy soils." The
predominant soil types in this upland area are somewhat poorly
drained, because they are usually underlain by thin, but poorly per-
meable, dark-colored organic hardpans. Alluvial and organic ma-
terials (peat) that have been deposited within the Myakka River
valley and its associated marshes have a texture and composition
which produce poor drainage characteristics.
Late Pleistocene and Holocene deposits, which cover most of the
Sarasota and Charlotte County parts of the area of investigation,
are composed chiefly of quartz sand, shell, and marl. Soils which
have developed on these materials are poorly to very poorly drained.
Several Holocene deposits of peat or "muck", covering several
square miles in the Cow Pen Slough and Phillippi Creek basins, are
also very poorly drained (Wildermuth, 1959, p. 28, 36).
The relatively impermeable beds of clay and marl of Miocene,
Pliocene and early Pleistocene ages that lie relatively near the
ground surface influence the low-flow characteristics of streams
because some are perching or confining layers (aquicludes). The
influences of these aquicludes upon low flows are discussed in the
section on factors affecting low flows.

STREAMFLOW DATA
Although long-term records of daily stage and discharge are
available for sites on the three larger streams in, and adjacent to,
the area of investigation, there is a dearth of record for the numer-
ous small streams and canals in the area. Prior to 1962, practically
no quality of surface-water information was collected in this region
by the U.S. Geological Survey; however, in the past 50 years, sev-
eral analyses of water from the Myakka River and from privately
owned springs were made by both State agencies and private ana-
lysts. Records of surface water that are available for gaging sta-






REPORT OF INVESTIGATIONS NO. 53


tions in the area are shown in figure 2. The locations of surface-
water data-collection stations are shown in figure 1. Miscellaneous
stations are numbered consecutively in downstream order, excluding
Nos. 20, 21, and 22 which are in the Peace River basin. Continuous
and partial-record stations are numbered, in downstream order, with
the essential digits of the seven digit U.S. Geological Survey num-
bering system. Table 1 summarizes the results of low-flow measure-
ments made at these data-collection stations during the period of
this investigation.
Streamflow records used in this report have been collected since
1936 by the U.S. Geological Survey in cooperation with the Divi-
sion of Geology, Florida Board of Conservation, the Florida State
Road Department, Sarasota County, and the city of Sarasota.

DRY SEASON STREAMFLOW
FACTORS AFFECTING LOW FLOWS
The base flow of streams in the study area is principally influ-
enced by (1) the permeability and porosity of the surficial Pleisto-
cene and Holocene deposits; (2) the interrelations among these
deposits and older, underlying beds; (3) the relative altitudes of
the water table and the surface in the streams; (4) soil moisture
conditions and evapotranspiration rates; (5) manmade changes to
the regimens of streams, such as the dredging of sloughs, inflow of
ground water discharged from wells, and inflow of water from sew-
age disposal facilities, and (6) time distribution of precipitation.
The Pleistocene age sand and gravel deposits, which cover most
of the study area and which are the principal contributors to base
flow, are porous and permeable on the upland ridges and knolls but
less permeable over broad, flat areas. Natural streamflow in upland
areas, such as at Myakka River at Myakka City (station No. 2982),
diminishes rapidly at the end of the summer rainy season and ap-
proaches zero if there is a month or more of little or no rainfall.
Somewhat poorly drained sandy soils occupy about 100 of the 125
square miles that the Myakka River drains above this station. Al-
though the relief between the drainage divides and the river bottom
exceeds 50 feet along more than half the length of the main chan-
nel, low permeability beds that underlie these soils restrict the
downward movement of water and thus help maintain relatively
high water table. Many shallow depressions scattered among low
knolls are the sites of wet-weather ponds. The low permeabilities
of the hardpan and clay strata greatly restrict the downward per-






Period and type of record
8.o d O0--co cs.c ro z Ionr- o Wo V ro o r-w cMo o N0-0 ror W M
z Station name ao n o oto Vl V V oV oO o0 o m o n o wn 5o Wo to to 0o


2980 Horse Creek near Arcadia M1
2982 Myakka River at Myokka City
2985 Myakka River below Upper Myakka M
Lake near Sarasota
Upper Myakka Lake E, ,
2990 Myakka River near Sarasota
2995 Myakka River below Lower Myakka !
Lake near Sarasota
-- Lower Myakka Lake 7A
29955 Myakka River near Venice
2996 Big Slough Canal near Myakka City
29966 Big Slough near Murdock
2997 Cow Pen Slough near Bee Ridge
29972 Cow Pen Slough near Laurel
29975 Phillippi Creek near Sarasota
2998 Phillippi Creek at Sarasota
3000 Manatee River near Bradenton i--
SDaily stage and record E Daily stage Periodic stage and flow
m Daily chemical quality
Figure 2. Period and type of hydrologic record for surface waters in Myakka River basin and vicinity.










TABLE 1. SELECTED LOW.FLOW DISCHARGE MEASUREMENTS MADE AT VARIOUS GAGING STATIONS

Measuremaent

No. Station name Loation and drainage area Gaet
(fi. Date height Discharge
(mal) (efs)

Peace River Basin

20 Morningstar Waterway (at Port NE%4 see. 16. T. 40 S., R. 22 E,, below mouth of Dorchester Waterway and about 500 ft. below &-13.6 0.79
Charlotte) bridge on Midway Boulevard in Port Charlotte, and 2.6 miles southeast of Murdock, Charlotte 5.21-64 .82
County. 4- -5 0
3.65 ** .05
6. 4-65 ** .14

21 Fordham Waterway (at Port NWA see. 12, T. 40 S., R. 22 E., at culvert on Quesada Boulevard in Port Charlotte and 4% miles 5-1343 .22
Charlotte) east of Murdock, Charlotte County. 5.21-64 .20
4-5.64 0
5- 3.65 ** .10
6- 4-65 1.25

22 Niagara Waterway (at Port NW% see. 12 T. 40 S., R. 22 E., at culvert on Quesada Boulevard in Port Charlotte and 5 miles 5-3-63 .13
Charlotte) east of Murdock, Charlotte County. 5-21-4 .05
4- 5-65 1.40
5- 3-5 .41
6- 4-65 .34

Myakka River basin

'1 Myakka River (near Myakka City) SE% see. 4, T. 35 S., R. 22 E., at bridge on State Highway 64, 8% miles northeast of Myakka 4-1663 0
City, Manatee County. Drainage area: 11 sq mi.. approximately. 5-1964 0
4- -65 ,03
5- 345 .002
6- 165 0

2 Wingate Creek (near Myakka NEA sec. 7, T. 35 S., R. 22 E., 1% mile below State Highway 64, and 7'4 miles north of Myakka 4-24-56 ** .05
City) City, Manatee County. 4-1663 .78
5-1944 .89
4- 5-65 .97
5- 3-65 .82
6- 165 1.39

3 Ogieby Creek (near Myakka City) NWI4 sec. 5, T. 36 S., R. 21 E., at culvert on State Highway 70, 5.0 miles northwest of Myakka 5- 365 0
City, Manatee County.
2982. Myakka River at Myakka City Lat. 27*20'47", long. 82*09'17", in E% sec. 13, T. 36 S., R. 21 E., on downstream side of bridge 5-15.63 28.04 .01
on State Highway 70, 0.2 mile downstream from Owen Creek and 0.6 mile southeast of 4- 6-65 28.61 2.74
Myakka City post office, Manatee County. Drainage area: 125 sq mi. 5- 8-65 28.42 .73
6- 1-65 28.83 .02






/ 2990.



6



2 2995.5


9


10


11


12


13


14





15


16


Myakka River near Sarasota



Myakka River (at Rocky Ford
near Venice)


Myakka River near Venice


Myakka River Tributary (near
Venice)

Myakka River Tributary No. 2
(near Venice)


Myakka River Tributary No. 3
(near Venice)


Myakka River Tribuary No. 4
(near Venice)


Myakka River Tributary No. 5
(near Venice)


Deer Prairie Creek (near Venice)





Deer Prairie Creek at dam
(near Venice)

Warm Mineral (Salt) Spring
(near Murdock)


Lat. 2714'25", long. 82018'50", In sec. 21, T. 37 S., R. 20 E., on right bank, half a mile up-
stream from bridge on State Highway 72, 2 miles upstream from Lower Myakka Lake, and 14
miles southeast of Sarasota, Sarasota County. Drainage area: 235 sq mi., approximately.

NE' sec. 24, T. 38 S., R. 19 E., at Rocky Ford, 6% miles northeast of Venice, Sarasota County.



SW% see. 31, T. 38 S., R. 20 E., at bridge on county road, % mile upstream from Blackburn
Canal and 6 miles northeast of post office in Venice, Sarasota County. Drainage area: 270 sq
mi., approximately.

NE% sec. 18, T. 39 S., R. 20 E., at culvert on county road, 6% miles east of Venice, Sarasota
County.

NW4 sec. 28, T. 39 S., R. 20 E., at culvert on county road, 8.2 miles southeast of Venice, Sara-
sota County,


S sec. 28, T. 39 S., R. 20 E., at culvert on county road, 8.7 miles southeast of Venice, Sara-
sota County.


SE'4 see. 28, T. 39 S., R. 20 E., at culvert on county road, 9.1 miles southeast of Venice, Sara-
sota County.


NE4 sec. 33. T. 39 S., R. 20 E., at culvert on county road, 9.3 miles southeast of Venice, Sara-
sota County.


NE'4 sec. 14, T. 39 S., R. 20 E., at ford, 10'4 miles east of Venice, Sarasota, County.





SEI4 sec. 22, T. 39 S.. R. 20 E.. at concrete dam. 10 miles southeast of Venice, Sarasota County.


N% sec. 25, T. 39 S., R. 20 E., at head of Salt Creek, S miles northwest of Murdock, Charlotte
County.


5-15463
4- 5-65
5- 5-65
6- 2-65

3- 1462
5-14-63
4- 745
5- 5-65

6- 4-65


4- 6-65
5- 545
6- 3-45

4- 6-65
5- 5-65
6- 345

4- 6-65
5- 5-65


6- 3-65
4- 1645

5- 5-65
4- 3-65
5- 5-65
6- 3-65

S3- 1-62
5-13-63
5-21-64
4- 7-65
5- 3-65
6- 3.65

5-21.64
4- 8-S5
5- 3-65

4-24-56
6- 7-62


9.47
10.27
9.52
8.66





-0.51


0
8.09
0
0

.85
.99
9.55
.97

a


.63
.40
.21

.62
.79
.79

.01
** .15
0

.03
** .05
a-.1l

.02
** .01
a-.69

* .14
* .29
.60
.60
.56
.34

.90
.55
.55

9.53
9.25


to







TABLE 1. (Continued)

Measurements
Map
No. Station name Location and drainage area Gage
(fig. 1) Date height Discharge
(mal) (ofs)

2996. Big Slough near Myakka City On line between sees. 6 and 7, T. 38 S., R. 22 E., Sarasota County, at bridges on State Highway 6- 4-62 27.31 .24
72, 11 miles south of Myakka City. Manatee County. Drainage area: 36.5 sq ml. 5-15-63 27.26 .07
4- 5-65 27.40 .43
5- 5-65 27.26 .07
6- 2-65 27.09 0

17 Big Slough (near Murdock) SE'A see. 4, T, 39 S., R. 21 E., Sarasota County, 5 miles north of U. S. Highway 41 and 7% 6- 5.62 .15
miles northwest of Murdock, Charlotte County. 5.13-63 .12
4- 6-65 1.16
5- 8-65 .39
6- 4-65 .09

2996.5 Big Slough near Murdock Lat. 2704'15", long. 82*13'05", in N'W' see. 21, T. 39 S., R. 21 E., Sarasota County, near left 6- 5-62 5.37 .48
bank, 3 miles upstream from bridge on U. S. Highway 41 and 5%i miles northwest of Mur- 5-13-63 6.48 .32
dock, Charlotte County. Drainage area: 87.5 sq mi. 4- 6-65 6.59 1.53
5- 3-65 6.54 1.11
6- 4-65 6.45 .20

18 Little Salt Spring (near NWl sec. 20, T. 39 S., R. 21 E., at head of unnamed ditch, 7 miles northwest of Murdock, Char- 4-24-56 1.22
Murdock) lotte County. 6- 5-62 .89

Coastal area between Myakka and Alafia Rivers

28 East Branch Coral Creek NW% sec. 32. T. 41 S., R. 21 E., at culvert on State Highway 771, 3 miles north of Placida, 4-11-62 0
(near Placida) Charlotte County. 5-13-63 0
5- 3-65 0

24 Oyster Creek (near Englewood) SW 4 sec. 3, T. 41 S., R. 20 E., Charlotte County, at culvert on State Highway 776, 8.5 miles 4-11-62 ** .17
southeast of Englewood, Sarasota County. 5-13-63 .02
5- 3-65 ** .04

25 Alligator Creek (near Venice) NW% sec. 27, T. 39 S., R. 19 E., at lateral canal 1.0 mile upstream from bridge on U. S. High- 5-14-68 .48
way 41, 4 miles southeast of Venice, Sarasota County. 6-11-64 .41

2997. Cow Pen Slough near Bee Ridge Lat. 27014'56". long. 82023'10", in E% sec. 22, T. 37 S., R. 19 E., near right bank on down- 5-16-63 16.64 .02
stream side of bridge on State Highway 72, 64A miles southeast of Bee Ridge, Sarasota 4- 5-65 17.41 .61
County, and 13 miles upstream from U. S. Highway 41. Drainage area:. 38 sq mi. approxi- 5- 5-65 16.99 0
mately. 6- 2-65 17.58 .81







2997.2



26



27



28



2997.5



29


80


* Base runoff
** Field estimate
a Flow reversed by tide


Cow Pen Slough near Laurel



Cow Pen Slough (near Laurel)



Fox Creek (near Laurel)



South Creek (near Osprey)



Phillippi Creek near Sarasota



Phillippi Creek (near Sarasota)


Main-B Canal (at Sarasota)



Phillippi Creek (at Sarasota)


Walker Creek (at Sarasota)


Sec. 15, T. 38 S., R. 19 E., at bridge on private road, 4/' miles northwest of Laurel, Sarasota
County. Drainage area: 56 sq mi., approximately.


Sec. 22, T. 38 S., R. 19 E., 800 feet above bridge on private road, 4 miles northeast of Laurel,
Sarasota County.


Sec. 20, T. 38 S., R. 19 E., 0.6 mile above bridge on private road, 21/ miles northeast of Laurel,
Sarasota County.


NW% sec. 13, T. 38 S., R. 18 E.. at Seaboard Airline R. R. bridge, 2'% miles southeast of
Osprey, Sarasota County.


Lat. 27'18'30", long 82*27'06" in E%/, sec. 36, T. 36 S., R. 18 E., near center of span on down-
stream side of bridge on State Highway 785, 0.2 mile downstream from Main-C Canal and 21/%
miles southeast of Sarasota city limits, Sarasota County. Drainage area: 24 sq. mi., approxi-
mately.
SWIi sec. 26, T. 36 S., R. 18 E., at bridge on Bahia Vista Street, 0.7 mile southeast of Sarasota
city limits, Sarasota County.

Sec. 22, T. 36 S., R. 18 E., at bridge on State Highway 780 (Fruitville Road), In Sarasota, Sara-
sota County.


SE', sec. 28, T. 36 S., R. 18 E., at bridge on Bahia Vista Street, Sarasota, Sarasota County, 1.5
miles east of U. S. Highway 41, and about 5 miles above mouth. Drainage area: 45 sq mi.,
approximately.
Sec. 6, T. 36 S., R. 18 E., at bridge on 38th Street in Saracota, Sarasota County.


5-14-63
4- 8-65
5- 4-65
6- 3-65
5-14-63
6-11-64
5- 4-65
6- 3-66
5-14-63
6-11-64
5- 4-65
6- 3-65
5-14-63
5-20-64
5- 4-65
6- 3-65
5-15-63
4- 9-65
5- 5-65
6- 2-65
4- 9-65
5- 5-65
6- 2-65
5-15-63
5-19-64
5- 4-65
6- 2-65
2-19-62
7-22-64

1-29-63
6-12-64
4- 8-65
5- 4-65
6- 2-65


6.80
6.79
7.03
7.11













7.06
7.82
7.70
7.78








0.63
2.31


* .11
.99
.15
.02
.94
1.15
.76
.39
.04
.02
**..01
0
.27
.29
** .30
** .22
3.30
3.74
1.90
2.25
4.30
*2.68
*2.83
*1.28
2.85
*1.44
*1.23
8.52
al0.6

1.44
.43
.57
.50
.24








REPORT OF INVESTIGATIONS NO. 53


colation and recharge to the Bone Valley and Hawthorn Formations
throughout much of this upland area, despite a generally favorable
hydraulic gradient.
Some of the direct runoff from showers in the headwaters of the
Myakka River is temporarily stored in a swamp just north of
Myakka City. Most of this stored water is believed to be lost by
evapotranspiration, because the piezometric head in the Hawthorn
Formation is too high to permit recharge and because little runoff
from sporadic showers is measured at the gaging station at Myakka
City. As a drought progresses and the water table falls, the upper
Myakka River will cease flowing, drying up altogether in its shal-
lower reaches.
Southwest of Myakka City, the Myakka River flows through the
southern part of the 4,300-acre Tatum Sawgrass before it enters
upper Myakka Lake. Much of the streamflow that results from
showers occurring during seasonal droughts is lost to evapotrans-
piration in this marsh, in Upper and Lower Myakka Lakes, and in
the marsh and swamp that separate the lakes. Thus, flow from the
lakes ceases nearly every year.
The fair to poor permeabilities of surficial materials in the flat
areas between the larger streams coupled with the lack of a well
developed drainage system retards the movement of water out of
the area. Thus the water table remains within a few feet of ground
surface unless artificial drainage is imposed.
Low water stages of the Myakka River in the reach between
Lower Myakka Lake and Rocky Ford (station No. 6, fig. 1) are less
than 8 feet above msl (mean sea level), and the flatlands bordering
the well-incised channel are about 15 feet above msl. Land immedi-
ately adjacent to the channel may be fairly well drained, while land
only a few hundred yards away may have a water table within 3
feet of ground surface. Downstream from Rocky Ford, the Myakka
River channel is deeply incised and the flow is reversed by the tide
during periods of very low flows. In general, the water table in the
flatlands slopes at low gradients toward the natural streams and
sloughs except when the water table is lower than these channels,
and the channels are completely dry.
The major sloughs in the study area have been deepened in the
past 40 years, mainly to drain agricultural lands. The deepened
drainage channels include Deer Prairie Creek, Big Slough, Alligator
Creek, Curry Creek (Blackburn Canal), Cow Pen Slough, and Phil-
lippi Creek. Channel deepening has probably increased low flows;
however no measurements were made under natural conditions,








Low STREAMFLOW-MYAKKA RIVER


prior to excavation. In Alligator Creek, as in other creeks draining
small coastal basins, the deepened channels permit inland intrusion
of sea water in the stream.
Streamflow and quality characteristics indicate that the artesian
ground-water contributions to the Myakka River, in the reach of
possible artesian flow between Myakka City and the outlet to Lower
Myakka Lake, is negligible. It is possible that the underlying arte-
sian aquifers contribute, by means of natural hydraulic connec-
tions with the stream channels, a small and relatively insignificant
amount of moderately mineralized ground waters to the low flows
of some streams-for example, the Myakka River and Big Slough.
Upper and Lower Myakka Lakes appear to be solution features and
thereby offer the possibility that ground water from artesian zones
may contribute to these lakes through debris-filled fractures or
sinks. However, the lakes and the Myakka River channel are shal-
lowly underlain by rather impermeable clays. A sinkhole, more than
125 feet deep near the river channel at the outlet of Lower Myakka
Lake, was estimated to be discharging 0.1 cfs on June 5, 1946; there
was no flow from the lake at that time. This flow of artesian water,
which is chemically similar to that obtained from wells which pene-
trate the deeper artesian zones of the Floridan aquifer that underlie
the Hawthorn Formation, probably ceases when the Myakka River
is high enough to flood out the hole.
Drainage from agricultural lands irrigated with ground water
pumped from the deeper aquifers is at times an appreciable part of
the low flow in sloughs. From quality and discharge data collected
on Big Slough (station No. 2996.5), it was estimated that for dis-
charges of about 0.1 cfs, pumped ground water contributes from
less than 10 to more than 60 percent of the discharge, depending on
the pumpage rate and climatic conditions.
Warm Mineral and Little Salt Springs (station Nos. 16 and 18,
fig 1.), which are sources of highly saline ground water, are located
a few miles downstream from the Big Slough station. Smaller
springs of this type, which are debris filled and, therefore, not
noticeable at the ground surface, may occur in the lower Big Slough
basin and contribute slightly to the somewhat saline character of
low flows in the channel.
It is believed that the hardpans and clays which overlie the
Hawthorn Formation in the Cow Pen Slough, Phillippi Creek, and
other coastal basins prohibit significant amounts of artesian water
from seeping upward to-the stream channels. Rainfall-runoff rela-
tionships are too indeterminate, and the contributions made by







REPORT OF INVESTIGATIONS No. 53


wells too inadequately known, to accurately determine the relation-
ships between ground water and streamflow in these coastal basins.
However, the concentrations of dissolved solids-about 400 to 500
ppm (parts per million)-at low flows in coastal streams whose
watersheds are relatively unpopulated, such as Fox and South
Creeks, are usually 4 to 10 times the concentrations of dissolved
solids (about 50 to 100 ppm) in those streams that drain upland
areas. Thus, the low flows of most coastal streams are not derived
solely from the drainage of surficial deposits. In the non-tidal
streams the water is of the bicarbonate type and is otherwise
similar to water from the upper part of the Floridan aquifer. Fur-
thermore, the concentration of fluoride in the non-tidal streams is
less than half the concentration of fluoride in water from the
Hawthorn Formation and is only slightly greater than the concen-
tration in most upland streams.
On the basis of the chemical analyses of low flows and knowl-
edge of the ground-water hydrology, it is concluded that much of
the low flows in these coastal streams is ultimately derived from
the large number of wells that tap the Floridan aquifer. Whatever
the sources of water in the non-tidal streams may be, the combined
runoff is usually insufficient to sustain streamflow during severe
droughts, excluding Phillippi Creek as previously mentioned.
LOW-FLOW CHARACTERISTICS
The flow characteristics and the physical and chemical traits of
a stream vary with time, location along the stream, and manmade
changes within the watershed. The low-flow characteristics of a
stream are often the factors which control its value and utilization
for water power, water supplies, recreation, navigation, and fish
production. Low-flow characteristics of particular significance in
the Myakka River basin are: the length of periods of low stream-
flow, the median minimum annual discharges for selected periods of
time, and the frequency at which a given discharge will recur as
the average minimum flow for a selected period of time.
For the purposes of this report, "low flow" refers to the average
minimum discharges for periods of selected lengths, in days, within
the climatic year, and "frequency" refers to the average recurrence
interval (R.I.), in years, of a low-flow discharge. "Base flow" refers
to sustained or fair weather streamflow.
FREQUENCY
The occurrences of annual periods of relatively small stream-
flows are primarily determined by climatic conditions. Base flow









Low STREAMFLOW-MYAKKA RIVER


conditions, when streamflow is composed chiefly of ground water,
usually occur twibe yearly in southern Florida-in May and June
and in November or December. Rainfall and streamflow records in-
dicate that there have been five droughts since 1938 during which
the non-tidal reaches of practically all streams in the area either
dried up or ceased flowing. These occurrences of extremely low
flows were in 1939, 1944, 1945, 1950, and 1956. Each of the corre-
sponding meteorological droughts was moderate to severe; and in
each instance, rainfall for the prior year was below normal.
Because of thh effects of the time distribution of rainfall upon
the net volume of drought discharges in the Myakka River area, the
relative severity of droughts is probably best determined by com-
paring rainfall deficiencies. For the period December through May
in both 1944-45 And 1949-50, rainfall at Myakka River State Park
was 60 to 65 percent below normal. Rainfall records for the Park
and other sites :indicate that these were the two most severe
droughts since lb39. For comparison, an areal rainfall deficiency
of 29 percent, in the period December 1964 to May 1965, produced a
relatively mild drought. Minimum discharges for the Myakka and
Manatee Rivers, such as the averages for this period, may be ex-
pected to recur about every 2.4 years, on the average.
Discharge records for Myakka River near Sarasota (station No.
2990) are the only available records, for a stream within the study
area, that are of sufficient length to adequately define magnitude
and frequency relationships for low-flow periods. These relation-
ships for this locality on the Myakka River are summarized for
periods of 90, 120, 150, 183, and 274 days in table 2.
Records of daily streamflow, collected from 1946 to 1951 at two

TABLE 2. MAGNITUDE AND FREQUENCY OF ANNUAL LOW FLOW
OF MYAKKA RIVER NEAR SARASOTA.

Lowest average flow, in cfs, for indicated
Period recurrence interval, in yoars
(C o n sec u tiv e_ -. .. -
days)
2 3 7 to 16 20 80

00 7.3 0.7 <0.1 0 0 0 0 0
120 12 8.2 .8 <.1 0 0 o 0
150 27 6.8 1.7 .9 .5 .25 .15 <.1
188 43 10 3.5 2.1 1.4 .9 .7 .5
10


--------- ---- --- --- ~ ~--~~-~ ~ ~-- --







REPORT OF INVESTIGATIONS No. 53


other stations on the Myakka River at the State Park (station Nos.
2985 and 2995), indicate that the low-flow characteristics for the
outlets of Upper and Lower Myakka Lakes are approximately equiv-
alent to those, as given above, for the long-term station.
The droughts which occur nearly every year during the spring
months produce conditions of low streamflow on all non-tidal
streams in the area. The average rainfall for each of the months of
February, March, April, and May is 2.9 to 3.2 inches, but monthly
rainfalls vary considerably from year to year. Table 3 gives the
mean, median, and minimum discharges for the months of March,
April, and May, for the respective periods of record, at continuous
record gaging stations (figs. 1 and 2). The median monthly dis-
charge is more reliable than the mean for estimation of the normal,
or expected, monthly discharge. Records for the short-term stations
are not of sufficient length to give reliable estimates of the expected
monthly discharges.
The decline in mean discharges for the period March through
May, as shown by the long-term stations in table 3, results from
drainage of the water-table aquifer and increasing evapotrans-
piration rates. Because of the combined effects of storage and
evapotranspiration in both the Myakka Lakes and surrounding
marshlands, no-flow conditions occur with slightly greater fre-
quency at the Park stations on the Myakka River than they do on
most of the other streams. The Myakka River temporarily ceases
flowing at station 2990 every 1.3 years, on the average. However,
the longest period of no flow that has been recorded at this station
was 133 days in 1950.
Although extended periods of no flow are common in the upper
Myakka River, the median of the annual minimum 7-day flow (the
average discharge for the 7-day period of lowest flow that may be
expected to recur every 2 years) for most other streams in the study
area may be used as an index of low-flow characteristics. Further-
more, for the few streams where discharges are partially sustained
by flowing wells, springs, and domestic sources of water, the 7-day
10-year annual low flow may be used as an index of low flow. These
low-flow characteristics were estimated for all stations, lying within
the study area (fig. 1), for which low flows are relatively unaffected
by tidal influences. These estimates are based upon regression
curves that relate measured and rated discharges at some of these
stations with contemporaneous flows at Manatee River near Braden-
ton (station No. 3000), the 7-day frequency curve of minimum flows
at Manatee River near Bradenton, correlations of base-flow meas-











TABLE 3. MONTHLY MEAN, MEDIAN, AND MINIMUM DISCHARGES FOR MARCH, APRIL, AND MAY AT
CONTINUOUS-RECORD STATIONS


Number March April May
Map of Drainage
No. Station name water area
(fig. 1) years (sq mi.) Discharge (cfs) Discharge (cfs) Discharge (cfs)
of
record
recorMean Median Minimums Mean Median Minimum Mean Median Mininium

*2980. Horse Creek near Arcadia 15 218 118 94.6 3.20 85.8 72.7 0.63 49.3 4.65 0.68
2982. Myakka River at Myakka City 2 125 85.9 .... 49.8 30.9 .... 2.43 4.88 .... .16
2985. Myakka River below Upper Myakka Lake near Sarasota 5 a 220 45.7 9.95 0 26.3 .13 0 4.08 0 0
2990. Myakka River near Sarasota 29 a 235 135 36.9 0 74.9 36.0 0 26.1 3.77 0
2995. Myakka River below Lower Myakka Lake near Sarasota 5 a 240 41.8 7.82 0 24.5 .83 0 4.86 0 0
2996.5 Big Slough near Murdock 2 87.5 81.8 .... 11.4 6.88 .... 1.66 1.52 .... .87
2997. Cow Pen Slough near Bee Ridge 2 a 88 18.5 .... 3.10 6.42 .... .54 .62 .... .04
2997.5 Phillippi Creek near Sarasota 2 a 24 15.7 .... 5.79 7.98 .... 3.05 5.53 .... 1.68
3000. Manatee River near Bradenton 26 a 80 75.3 83.9 4.19 31.1 16.9 2.81 16.4 7.56 1.87

Not shown in figure 1.
a Approximately.
I Mean monthly discharge-for a specified month, the total of the monthly average discharges divided by the number of years of record.
Median discharge-the average monthly discharge that is the mid-most value when all monthly averages are scaled from highest to lowest.
1 Minimum discharge-for a specified month, the lowest average monthly discharge for the period of record.






REPORT OF INVESTIGATIONS NO. 53


urements (especially those made in 1965), and comparisons of base-
flow yields per square mile with the yields at the continuous-record
stations. The calculated low-flow characteristics for the stations
whose records were amendable to these analyses are presented in
table 4.
The low-flow estimates shown for the short-term continuous-
record stations should be more reliable than the short-term records.
for estimating future low flows on these respective streams. How-
ever, watershed development projects currently in progress, changes
in man-made accretions to low flows, and additional streamflow
regulation may be expected to somewhat alter the low-flow char-
acteristics of nearly all of these streams within the next decade.

DURATION AND MAGNITUDE
The duration of a low-flow period is directly related to both an-
tecedent and prevailing climatic conditions. The magnitude of base-
flow discharges during these periods is primarily dependent on the
permeability and porosity of the surficial geologic units and the
level of the water table within these units.
Flow-duration data for the nine daily-record stations in the
Myakka River basin area are given in table 5. Two stations, Horse
Creek near Arcadia and Manatee River near Bradenton, are not
within the area of investigation, but data from these stations were
useful in adjusting the records for short-term stations to a standard
base period, 1940-64, for comparative purposes. The headwaters of
both Horse Creek and the Manatee River adjoin those of the
Myakka River. Adjustments of short-term records to the longer
period were made for those streams where channel conditions have
remained essentially unchanged throughout the base period, and
where the contribution of ground-water flow from wells is usually
an insignificant part of the total flow.
The flow-duration data given in table 5, when plotted on loga-
rithmic probability paper, provide a convenient method for com-
parison of flow characteristics. Duration curves for low flows at
four selected stations, for the 25-year base period, are shown in
figure 3 to illustrate the variability of low flows in adjacent basins
which lie in a homogeneous climatic region.
Duration curves for the streams in the study area commonly
have a steep slope, which indicates a high variability of low flows.
The low discharge ends of the duration curves for the three Myakka
stations shown in figure 3 have very similar steep slopes. The steep-
ness of these curves, which is slightly greater than that for most






TABLE 4. LOW-FLOW CHARACTERISTICS AT SHORT-TERM-CONTINUOUS, PARTIAL AND MISCELLANEOUS RECORD
STATIONS

Estimated 7-day annual low flow,
Map Drainage area cubic feet per second
No. Station name (sq. mi.)
(fig. 1) 2-year 10-year
1 Myakka River (near Myakka City) 0 0
2 Wingate Creek (near Myakka City) .5 .1
3 Ogleby Creek (near Myakka City) 0 0
2982. Myakka River at Myakka City 123 0 0
2985. Myakka River, below Upper Myakka Lake, near Sarasota a 220 0 0
2995. Myakka River, below Lower Myakka Lake. near Sarasota 240 0 0
6 Myakka River (at Rocky Ford near Venice) .8 .2
14 Deer Prairie Creek (near Venice) .3 <.1
S15 Deer Prairie Creek at dam (near Venice) .3 <.1
2996. Big Slough near Myakka City 36.5 <.1 0
17 Big Slough (near Murdock) .1 0
2996.5 Big Slough near Murdock 87.5 .35 b .15
20 Morningstar Waterway (at Port Charlotte) b<.1 b 0
25 & 22 Niagara and Fordham Waterways (at Port Charlotte) a 3.5 b .3 b <.
23 East Branch Coral Creek (near Placida) 0 0
24 Oyster Creek (near Englewood) <.1 0
2997. Cow Pen Slough near Bee Ridge ja 3. b 0 b 0
2997.2 Cow Pen Slough near Laurel a 56 b <. b 0
26 Cow Pen Slough (near Laurel) b .2 b <.1
27 Fox Creek (near Laurel) 0 0
28 South Creek (near Osprey) <.2 0
2997.5 Phillippi Creek near Sarasota a 24 b 1.1 b .6
30 Main-B Canal (at Sarasota) b .4 b .2
31 Walker Creek (at Saracota) b .2 b <.1

a Approximate.
b Subject to diversion and/or regulation.











TABLE 5. DURATION OF DAILY FLOW AT CONTINUOUS.RECORD STATIONS

.------- -


Aver-
Period flow
(cfes


Flow. in cubic feet per second, which


93.S 99' 9' 9i 5 90l, m0' 7ui 60 5


IN MYAKKA RIVER BASIN AREA


was equaled or exceeded for indicated percent of time


46 30 20


10 5


SI 0,5


Peace River basin

Horse Creek near Arcadia


Myakka River basin

Myakka River at Myakka City

Myakka River below Upper Myanka
Lake, near Sarasota
Myakka River near Sarasota


Myakka River below Lower Myakka
Lake, near Sarasota
Big Slough near Murdock

Coastal basins

Cow Pen Slough near Bee Ridge
Phillippi Creek near Sarasota
Manatee River near Bradenton


_______________________________________I


a Approximate
$ Data are adjusted on basis of relation to data at nearby gaging station.
*April 1963 to September 1965.
** April 1963 to March 1965.
SAverage flow-the total efs.days for the period of record shown divided by the number
to obtain the average flow.


of days. For adjusted record, duration curves were correlated


Station name


Drain-
age
area
(sq mi.)


218 1951-64
1 tl1940-644


-.3---,


2982.

2985.


2996.5



2997.
2997.5
3000.


125

a 220

a 235


a 240

87.5


59 I 975
600 1,000


2,420 3,310
2,400 3,300


0.2 0.41 1.5
.1 .2 $6


0 0 I
0 0 .1


0 0 0

0 0 0
0 0 0

0 0 i
0 0 0 i

.3 .4 .6
.2 .2 .4


.1 .1 .2
1.9 2.4 2.9
2.5 3.21 4.61


*
1t940.-44
1946-50
t1940-64
1937-64
1940-64
1944.50
1946-50
$1940-64

t1940-64






1940-4


5.0 T11


4.o
12
8.2
8.6
1.91

1.2
9.5
2.7
2.0



1.0
6.3
12


11 32


0 .62
10 41
10 31






1.8 3.5

8.2 11
17 i24


105 176
85 155


62 105
46 86

76 170
94 185
109 193
111 192
93 170
75 183
94 205
26 50
21 40


7.4 15

14 19
37 61


30-
S295


210
170
S390
360
355


453
430

95
86


32
27
114


1.710 ,
1.750:


1.160 i
1,290
2,450
1,780
2,060
1,950
2.580
2,600
1,950
700
850


196
166
905


432
403
870
690
760
715
1,020
1.020
830
221
220


73

48
264


680
740

1.530
1,100
1,280
1.190
1,600
1.700
1.260

445


123
81
485


1,540
1,790

3,100
2,380
2,740
2,680
3,400
3,300
2,550
1.030
1,270



248
270

1,330


1,810
2,380
3,750
3.080
3,550
3,510
4,380
4,060
3,280
1.300
1,840



302
413
1.890


------- -----------~---s'---""~--7-" ( ~-'I- -1 4-


-- -~-~-~-~~


I


I


rp









Low STREAMFLOW-MYAKKA RIVER


go












10


,- =-_ ... ...












E EXXPLANATION
( Myokka River at Myokka City adjustedd)
( Station 2982)
( Myokka River near Sarasotao
( Staton 2990)
S Myokko River below Lower Myakka Lake
near Sarasota (odjusted)
(Station 2995)
Manatee River near Brodenton
(Station 3000)


95 90 99 99 5 998 999


PERCENT OF TIME DISCHARGE EQUALLED OR EXCEEDED THAT SHOWN
Figure 3. Duration curves of daily low flow for selected streams, standard
period-1940-64.

other streams in the study area, results from the climatic condi-
tions, the hydraulic characteristics of the surficial deposits, and the
topography of the upper Myakka River basin. The hydrologic sig-
nificance of these factors was previously discussed under the section
"Factors Affecting Low Flows."
The relatively flat curve for Manatee River near Bradenton in-
dicates that this stream has a higher sustained low flow than do


2 CS I 2 8 10 20 30 4 o







REPORT OF INVESTIGATIONS NO. 53


the other streams. The low flow of the Manatee River near Braden-
ton is sustained by the slow drainage of ground water from the
moderately to poorly permeable beds of fine sand and clay into
which the river is fairly deeply entrenched. The deep entrenchment
of the river channel permits drainage to the stream of a greater
thickness of the surficial materials than would occur if the channel
were shallower.
Phillippi Creek near Sarasota (station No. 2997.5) is the only
nontidal reach of stream channel in the outlined area of investiga-
tion that may be expected to maintain a flow in excess of 0.2 cfs
throughout critical droughts, such as those of 1939, 1944, 1945, and
1950. However, low flows at this station are augmented by effluent
from sewerage plants and ground water from irrigation and domes-
tic wells. Most of the wells tap moderately mineralized waters in
artesian zones.
Some of the deeper drainage canals and waterways have some-
what greater low-flow yields per unit of drainage area than do many
natural, or slightly improved, channels. As an example, for the low-
est of 10 low-flow measurements made since April 1962 on the
Niagara and the Fordham Waterways in North Port Charlotte, the
combined discharge was 0.25 cfs (table 1). This discharge corre-
sponds to a yield of 0.057 cfs per sq. mi. (cubic feet per second per
square mile) for the 3.5 square-mile drainage area, after subtracting
0.05 cfs as the estimated contribution of a flowing well. This yield
is significantly greater than the minimum yields that have been
recorded since 1963 for some of the larger basins. The 125 square
miles of the upper Myakka River basin has yielded no flow for 14 to
27 days during each spring, for a total of 57 days of zero flow in 3
years. The minimum yield at Big Slough near Murdock (station No.
2996.5; drainage area, 87.5 sq mi.) has been 0.0023 cfs per sq mi.,
without adjustment for the contributions from wells.

LOW-FLOW QUALITY
In general, streams which derive their low flows from drainage
of surficial deposits, provided that these deposits are relatively un-
affected by natural artesian flow or waters from irrigation wells,
have low concentrations of total dissolved solids, sulfate, chloride,
and fluoride, as well as low concentrations for other dissolved ma-
terials. The Myakka River near Sarasota (station No. 2990) was
sampled daily from 1962 to 1966 for standard chemical analysis.
Although evaporation tends to concentrate the dissolved materials
in this water, the maximum concentrations determined for the fol-








Low STREAMFLOW-MYAKKA RIVER


lowing constituents were: total dissolved solids, 98 ppm (parts per
million); sulfate, 25 ppm; chloride, 30 ppm; and fluoride, 0.7 ppm.
The U.S. Public Health Service (PHS, 1962, p. 7, 8) recommends
that concentrations of these constituents in drinking water do not
exceed the following limits: total dissolved solids, 500 ppm, sulfate,
250 ppm; chloride, 250 ppm; and fluoride, 1.2 ppm in warm climates.
Above the outlet to Lower Myakka Lake, the water in the
Myakka River probably always has a carbonate hardness of less
than 60 ppm, which is moderately soft. Thus, the water in the
Myakka Lakes is of generally good quality. However, water tem-
peratures sometimes exceed 900F., and color (platinum-cobalt in-
dex) may exceed 220. Objectionable quality characteristics that
occasionally occur during periods of high runoff are dissolved iron
concentrations of about 0.3 ppm and suspended organic matter, in-
cluding some algae.
The dissolved solids content may be moderately high in streams
that contain water derived from irrigation, stock, and other wells
that yield moderately to highly mineralized water from the deep
aquifers. Furthermore, streams and canals which are affected by
sea and salty spring waters are usually very saline. Table 6 gives
selected chemical analyses of surface waters in the study area. Note
the high concentrations of chloride and dissolved solids for stations
2995.5, 8, 9, 16, 18, and 24. Salinity barriers in tidal reaches of
streams generally provide good protection from sea water intru-
sions. Occasionally, there is some leakage of sea water through
these barriers, as evidenced by the sample taken on the immediate
upstream side of the lower barrier on Morningstar Waterway (sta-
tion No. 20) on April 4, 1965.
The ranges in concentrations of some noteworthy constituents
in Phillippi Creek near Sarasota (station No. 2997.5) measured for
the water year October 1964 to September 1965, were: total dis-
solved solids, 160 to 1,030 ppm; sulfate, 52 to 430 ppm; chloride, 11
to 60 ppm; and fluoride, 0.3 to 1.3 ppm. The higher concentrations
occurred during periods of low flow, when most of the discharge
was derived from irrigation wells and domestic waste water. The
quality characteristics of Cow Pen Slough and Big Slough are simi-
larly, but to a lesser extent, influenced by inflow of ground water
from wells.

CURRENT USAGE OF SURFACE WATER
Big Slough is the only major stream in the study area currently
being directly utilized as a municipal water supply. In 1965, the








TABLE 6, CHEMICAL ANALYSIS OF SURFACE WATERS DURING LOWPLOW PERIODS

I I"
U. S Hardnessi
all Cacq3-


sttr Saonra t
i

1 I I a 3 21

SS, I ? IPartsl par million I f

1 Myakka River (near Myakka City) 1-18-6 1.76 4. .1 0 1.4 2.2 6.8 0.8 14 1.8 160.3 0.4 7 25 1 86 6.4 10 -8
5- 3-65 .002 1.7 .17 8.8 2.9 8.6 .8 21 5.8 14 .8 .0 53 84 17 120 6.7 100 78

2 W ate Crk (near r r Myakka City) 5- 365 .2 4.7 .02 8.8 2.4 4.2 .8 25 4.8 8 .1 46 2 12 100 6.8 20 66
2982. Myakka River at Myakka City 1-6 16.4 2.1 .09 7.6 2.7 7.1 1.8 19 3.6 16 .2 4 51 30 14 95 6.6 100 -
6- 3-65 .70 1.2 .10 12 1.0 6.0 .4 81 3.2 12 .1 .0 54 4 28 17095 7.0 60 72
4 Myakka River (above Upper Myakka Lake 5-16-068 <.2 2.4 .07 19 7.9 10 1.8 43 33 17 .6 2.5 115 80 45 260 6.8 70 0SO

2985. Myakka River below Upper Myakka Lake 5-16-68 0 .6 .11 10 1.7 8.2 1.1 21 8.4 16 .4 .7 58 82 15 110 6.2 100 83
near Sarasota at gage ste
2990 Mpakka River near Saraota 2-20-62 .4 8.8 .05 12 4.9 13 1.0 16 25 25 .3 .7 98 58 83 168 7.0 80 75
S Myac7-1063 d280' .7 .15 6.8 2.7 5.6 .6 15 10 9 .8 .1 47 28 16 76 6.6 220 d
e6- 5-65 0 1.2 .10 12 5.1 10 1.2 28 19 29 .4 .0 92 51 28 170 7.1 80 -

2995. Myakka River below Lower Myakka Lake 7-15-65 > 1,0001 5.1 .27 8.0 2.8 5.6 .6 28 8.4 10 .4 .1 53 32 12 85 6.7 200' 82
near Sarasota
5 Deep Hole (at Lower Myakka Lake Outlet) 5-16-63 2.1 .04 98 34 16 2.5 66 808 26 .9 .7 521 884 8o0 760 6.6 50 -
7-15-685 1 .14 115 41 15 1.8 71 384 80 .9 4.5 641 456 398 922 6.9 100 77

6 Myakka River (at Rocky Ford near Venice) 8- 1-62 .85 3.8 .02 128 29 24 2.0 188 260 87 .7 .2 578 489 285 860 7.6 85 80
4- 7-65 9.55 1.8 .06 19 3.5 11 1.1 89 20 21 .5 .4 98 62 80 180 7.0 100 78
5- 5-65 .97 3.9 .05 51 9.0 14 1.4 121 50 28 .4 .0 219 164 65 370 7.4 50 78

2995.6 Myakka River near Venice 5-15-63 f 2.5 .04 152 161 1,370 58 171 450 2,320 .7 .8 4,600 1.040 900 5,200 7.5 60 88
4- 7-65 2.1 .06 26 6.6 15 1.8 58 80 27 .5 .0 138 92 44 252 7.0 100 78
5- 4-65 f 4.5 .05 288 11 113 3.7 164 413 235, .6 1.1 1,100 639 504 1.620 7.6 50 77
7 Blackburn Dolomite Pit (near Venice) 2-22-62 8.1 .02 184 58 148 4.0 312 214 290 .6 .8 1.010 578 818 1.650 8.0 8 71





L.


Blackburn Canal (near Venice)

Myakka River Tributary (near Venice)

Myakka River Tributary No. 2 (near Venice)

Myakka River Tributary No. 8 (near Venice)
Myakka River Tributary No. 4 (near Venice)

Myakka River Tributary No. 5 (near Venice)

Deer Prairie Creek (near Venice)


Deer Prairie Creek at dam (near Venice)
Warm Mineral (Salt) Spring (near Murdock)
Big Slough Canal near Myakka City


Big Slough (near Murdock)

Big Slough near Murdock, Fla.


Little Salt Spring (near Murdock)
Bil Slough Canal at dam (at North Port
Charlotte)
Morningstar Waterway (at Port Charlotte)

Fordham Waterway (at Port Charlotte)


Niagara Waterway (at Port Charlotte)


Oyster Creek (near Englewood)


4- 7-65

4- 6-65
5- 5-65
4- 6-65
5- 5-65
4- 6-65
4- 6-65
6- 8-65
4- 6-65
6- 8-65
8- 1-62
4- 7-65
5- 8-65
5- 8-65
6-15-62
5-17-68
4- 5-65
5- 5-65
2-28-62
5- 3-65
2-28-62
4- 6-65
5- 8-65
2-22-62
1- 7-65

5-15-63
4- 5-65
4-11-62
5-15-68
4- 5-65
6-11-62
5-15-68
4- 5-65
4-11-62
5- 8-65


14


15
16
2996


17

2996.5


18
19

20

21


22


8.9 .02

1.8 .08
1.1 .04
9.9 .08
10 .08
8.8 .01
8.4 .00

7.8 .00

5.2 .02
6.1 .01
7.0 .02


206

140
161


.01
.08
f-.18
.02
f-.69
.14
.60
.56
.55


<.07
.43
.07
.70
.89
.96
1.53
1.11
1.25




"- (
.1
0
.54
.2
0
.19
.1
1.40
f0.17
f .04


5.8 1248


78

87
67
10
7.8
12
8.0

3.8

3.2
4.1
2.9


1.5
1.6
.2
.8
.8
.1

.2

.8
.4
.4


176
.7
.4
.3
1.2
.7
1.1
.6
.5
24


- '


800
256
896
410
240
802

280

184
187
199


158
161
228
164
161
157
149
207
208
168


704

426
524
88
42
50
60

72

6.8
6.4
7.2


1,600
172
28
94
160
112
228
84
62
467


16 36 1.5 215 66 70 .6

7.2 22 .4 252 16 84 .5
88 680 26 308 232 1.220 .6
14 75 1.0 170 37 188 .6
1.7 28 .4 186 9.6 46 .6
5.1 58 .0 226 88 112 .7
1.5 20 .0 87 4.4 36 .1
.4 22 .4 87 4.4 38 .4
4.9 24 .2 148 7.2 54 .2
282 1,880 49 156 608 8,800 1.2
835 2,480 54 168 488 5.080 1.4


17 .00 508
5.0 .02 69
.9 .03 54
.8 .01 51
1.8 .02 86
3.6 .01 68
1.8 .05 91
2.4 .02 78
2.7 .05 80
19 .01 206
2.4 .02 80

12 .01 78
6.4 .00 186
4.4 .08 71
10 .05 51
9.4 .02 91
6.3 .27 18
4.8 .09 19
5.6 .18 53
5.6 .04 410
11 .02 470


400

280
885
70
84
44
80

84

18
19
20


9,100
54
86
44
68
94
78
65
66
1,825


r.

.1
.4


.2


.2


.2
.8
.2


B 1.6 1,810 1,010 807 2,520 7.6 45

S 1.2 1,270 780 484 1,900 7.8 60
$ .0 ,1,470 910 700 2,250 7.6 50
1 .1 498 370 46 800 8.070
3 .1 458 374 38 900 7.9 60
.0 388 244 48 560 7.8 30
.4 818 252 4 522 7.8 20
1,910
.0 800 288 8 508 7.9 1
16,000
.8 196 160 9 858 7.7 15
S .1 200 164 11 340 7.8 20
S .1 215 179 16 370 7.7 10
378
S15 7.400 3,604 3,470 26,600 7.8 5
S .6 484 340 208 720 7.5 40
.0 274 222 40 478 7.7 50
.0 331 255 120 570 7.7 40
.0 465 342 210 810 7.8 80
.0 481 270 142 720 7.6 40
.0 552 892 270 975 7.5 80
.0 391 276 106 643 7.8 50
.2 869 250 84 680 7.7 20
8.0 2,947 1,000 862 5,000 7.6 10
.0 879 264 88 618 7.5 40

.5 295 224 18 510 7.9 80
5.5 2,550 700 448 4,240 7.6 20
.2 420 284 95 766 7.8 60
.6 215 134 22 380 7.2 80
.0 420 248 63 726 7.7 45
.0 105 51 20 242 6.8 100
.6 107 49 18 140 6.5 100
.0 222 152 80 389 7.6 75
.4 7,059 2.980 1,850 12.000 7.4 50
.8 8,950 2.550 2,410 15.000 7.8 50


12
12
12


5,880
41
22
28
36
50
42
37
84
700


.. m .. ... .. I .... -


m i m m m m ... .


79
79
76
78
79


81
82
81
89
75
78
75
78
86
77
86
82
s8
84
88
70
72
.81
65

77
88
86
81
.85
77
87
76
75










TABLE 6. (Continued)






SSta


SAlligator Creek (near Venice)

Cow Pen Slough near Bee Ridge


Cow Pen Slough near Laurel

Cow Pen Slough (near Laurel)


Fox Creek (near Laurel)


South Creek (near Osprey)

Phillippi Creek near Sarasota


Phillippi Creek (near Sarasota)

Maln-B Canal (at Saraota)


1-17-63
4- 8-65

2-20-62
5-16-63
4- 5-65

1.15-63
4- 8-65

2-21-62
1-15-63
4- 8-65

2-21-62
1-15-63
5- 4-65
1-17-63
5- 4-65

2-20-62
5-20-64
4- 9-65
5- 5-65

6. 2-65

2-19-62
4- 9-65
5- 4-65


,b
S2 I Hardneu
A as CaCOs


P e l o n I I
ion II I |


P a r eII I Iio
a ---------------
t a Parts per million


3.24
f

.05
.02
.61

3.87
.99

.7
5.30
2.22

.05
.62
.01

2.17
.30

3.16
8.6
3.74
1.90

2.83

1.50
2.20
1.44


2.4
8.1

4.9
6.7
4.1

9.8
6.0

7.3
10
7.0

9,9
8.2
10

5.1
10

10
9.5
6.0
9.9


11
9.4
10


.12 125
.04 214

.02 54
.02 119
.00 59

.15 109
.02 115

.03 148
.02 119
.01 144

.03 140
.04 111
.05 123

.05 97
.00 180

.02 138
.08 122
.01 130
.03 184


.03 42
.03 40
.03 39


20
8.3

14
41
11

17
9.5

15
15
12

4.0
5.6
2.2

12
29

53
48
47
15


12
8.0
11


6.8
2.6'
3.5


260 130
313 225

140 56
86 371
131 71

215 134
264 100

28 192
25 128
291 152

438 6.0
32 22
392 8.0

283 32
327 283

203 348
179 346
191 352
171 360


145 118
97 45
95 67


595 396 183
881 568 812

268 192 78
638 466 376
321 192 84

448 336 160
453 326 110

551 431 202
461 360 154
542 408 170

412 366 7
40T 300 34
397 316 0


396 292
791 570

730 562
680 502
703 516
757 520


418 154
217 133
292 142


60
302

396
355
360
380


36
.54
64
U1


'a
9l


830 8.0 85
1,400 7.9 50

452 7.4 15
7.0 20
534 7.6 20

610 8.0 50
728 7.8 45

854 7.9 55
630 7.9 50
790 7.9 50

715 7.8 25
605 8.0 80
650 8.0; 50

600 8.0 70
1,200 7.6 20

1.080 7.7 45
960 7.7 45
980 7.8, 45
1,200 7.4 80

961

655 7.5I 85
350 7.2 20
530 7.1 30


88

72
85
81
-
78

81
65
7 9
77
70
63

66
74 0'
ccO
71
79
71
84

83
73
75
85


. .. L


t I .. ...


I t I


I I / I i


, I [ I


' I


,;m i

















2998. Philippi Creek at Sarasota 2-19-62 8.52 71.0 .02 79 30 43 4.8 187 168 55 1.1 1.2 484 820 168 760 7.5 45 76
4-9-65 f I 5.3 .01 91 28 30 2.4 185 190 44 .9 .1 486 344 192 740 7.5 30 80
5- 5-65 0 6.7 .01 92 32 42 4.1 181 213 56 1.3 .2 539 360 212 840 7.4 30 80
81 Walker Creek (at Sarasota) 1-29-63 1.44 8.0 .01 o152 36 60 3.5 204 312 104 1.1 .0 779 528 359 1,000 7.8 50 72
4- 8-65 .57 8.5 .02 88 27 62 2.5 215 161 86 1.2 .3 544 330 154 880 7.7 50 80
3000. Manatee Rivar near Bradenton c5-10-65 d6.0 5.0 .02 13 4.3 5.5 1.0 50 7.6 9 4 .4 .0 72 50 9 119 7.2 20 -


I


a In solution when analyzed.
b Calculated from determined constituents.
c Ten-day composite sample.
d Ten-day mean.
e Five-day composite sample.
I Flow reversed by tide.
< Less than.
> Greater than.
SRelatively high flow. Chemical data shown for comparison of high and low flow quality of water.


8







REPORT OF INVESTIGATIONS NO. 53


City of North Port Charlotte withdrew about 200,000 gallons daily
from waters impounded behind a low-head dam. Fordham Water-
way at Port Charlotte is used as a surface-water collection pond for
municipal supply. This source is supplemented with water from
shallow wells. On the West Branch Coral Creek near Placida, a low
concrete dam maintains a high ground-water level in the well field
which supplies Cape Haze, a nearby housing development, with up
to 3 million gallons of water per month.
On the north side of the study area, the Braden River has served
as the major water supply for the city of Bradenton since October
1939. The reservoir, impounded by a dam, was pumped at the aver-
age rate of 2.64 mgd in 1965. A well is maintained as a reserve for
severe droughts. Damming of the Manatee River for the Manatee
County public supply system was completed in 1967.
The amount of irrigation water withdrawn annually from
streams and canals is relatively insignificant.
The flow characteristics of major streams in the study area are
indicated by tables 1-5 and the duration curves in figure 3. These
streams practically cease flowing for periods of 3 months or more
during critical springtime droughts, and storage must be provided
if a continuous draft is to be maintained.

DRAFT-STORAGE RELATIONS

Only for the upper Myakka River is the period of discharge
record long enough to permit derivation of reliable draft-storage
relationships. Upper and Lower Myakka Lakes are the largest and
probably the most practicable storage sites in the study area. Their
utilization as storage reservoirs is possible because of the consider-
able volume of water which they can store, their central location
with respect to the populated coastal area (fig. 1), and the relatively
large amount of water delivered to them annually by the Myakka
River (table 5).
Figure 4 shows the stage-volume relationships for Upper and
Lower Myakka Lakes below altitudes of 16.0 feet and 14.0 feet
above msl, respectively. The total storage, at these two altitudes, is
approximately 8,100 acre-feet, including about 40 acre-feet of chan-
nel storage at 14.0 feet above msl. The lakes begin to overflow onto
much of the surrounding terrain when their altitudes exceed the
maximum altitudes shown in figure 4, precluding the practicability
of obtaining more sLorage by maintaining higher lake altitudes. It
is noteworthy that, with the present natural and manmade features










Low STREAMFLOW-MYAKKA RIVER


0 1000 2000 3000 4000 5000 6000
VOLUME, ACRE-FEET

Figure 4. Stage versus volume, Upper and Lower Myakka Lakes.


which control the flow of flood waters through the State Park, these
altitudes will be exceeded about once a year on the average.
A draft-storage analysis was made using the discharge records
for Myakka River near Sarasota (station No. 2990). Flow at this
station, which is downstream from Upper Myakka Lake, is influ-
enced by both the evaporation from Upper Myakka Lake and the
upper channel, and seepage inflow in the 2.5 miles of channel be-


-J
W
W
-J
_J
w

z
4
w

W



I-
w
w
U.








-j
.
UJ

w
o
tL







REPORT OF INVESTIGATIONS NO. 53


tween Upper Myakka Lake outlet and the gage. Correlation of
monthly mean discharges for the three Myakka River stations near
the Park (Nos. 2985, 2990, 2995), for the period January 1946 to
June 1951, showed their flows to be nearly equivalent within rea-
sonable limits of error.
A mass curve of daily volumes of flow is shown in figure 5. On
the assumption of a full reservoir and beginning with October 1,
1943, volumes in cfs-days were accumulated, chronologically, to pre-
pare this curve. This analysis shows, for example, the storage re-
quired to sustain a constant draft rate of 10 cfs (6.46 mgd) from
the Myakka River at the Park, during the period of most deficient
streamflow since 1936. A line of constant slope equal to a draft rate
of 10 cfs was drawn from the point where the slope of the mass
curve became less than that of the draft rate to the point of inter-
section with the mass curve at a later time. The greatest vertical
distance between the draft rate line and the mass curve indicates
the minimum storage required to supply the hypothetical draft rate
which was applied. This study showed that 1,930 cfs-days (3,830
acre-feet) would have been required for a draft of 10 cfs during the
period November 1943 through June 1944. This period represented
a drought that may be expected to recur, on the average, once every
30 years. Other draft rates may be substituted in figure 5, as shown,
to determine the storage required.
A frequency-mass curve for a 30-year recurrence interval of
minimum flows, prepared from cumulative volumes, in cfs-days,
that were computed from the data in table 2, indicated that only
1,780 cfs-days would have been required to supply the indicated
draft rate throughout a drought with a 30-year recurrence interval.
It is noteworthy that a draft of 10 cfs (6.46 mgd) is 1.4 times
the average output of the city of Sarasota water system in May
1965, the month of peak pumpage that year. The average aggregate
output for 1965 of all public water utilities in Sarasota County was
about 6.9 mgd.
In the spring of 1941, the present concrete control at the main
outlet of Upper Myakka Lake was constructed to replace, at the
same site, a control at a lower altitude which had partially washed
out. The crest of the present dam is 13.65 feet above msl. The me-
dian level of Upper Myakka Lake, as determined from the flow-dura-
tion curve (adjusted to 1940-65) and the stage-discharge relations
for station No. 2985, is about 14.0 feet, under present conditions.
During the period January 1, 1946 to October 2, 1960, the level fluc-
tuated between about 12.0 and 20.3 feet. Lower Myakka Lake ex-









Low STREAMPLOW-MYAKKA RIVER


45









40
CO
0

cn
V)
tL)

U.
0
U)
o 35
z
C,
o
I-
w



-J
3
o 00


w

_-


u

25


SN DJ F M AM J J ASO N D J FMAM J


1945


1944
YEAR


1943


Figure 5. Mass curve of daily volumes, Myakka River near Sarasota, Florida.


Note: Net flows after evaporation from
Upper Myakka Lake and seepage
-- inflow between lake and gaging
station.



Storage required: -


-((3015 acre -ft.) --














:
- ---














S -- Storage required:
1930 cfs- days--
(3830 acre -ft.)


20


j I I I ) i


I


I )








REPORT OF INVESTIGATIONS NO. 53


perienced similar fluctuations in stage during this period and was
completely dry in the spring of 1945 and nearly dry in 1950, after
the earthen dam at its outlet had washed out.
If controls had been in place during the drought of 1943-44 to
provide 8,100 acre-feet of usable storage in the two lakes, a draft
rate of 6.46 mgd could have been obtained and the lake levels would
have been no lower than the minimum levels that were actually
recorded for that drought. Under such conditions the lower lake
would have been nearly dry while the upper lake would have had a
minimum altitude of 11.5 feet, with a considerably reduced area.
With the present control altitudes shown in figure 4, total dead
storage is about 4,300 acre-feet. However, if these controls were re-
moved during fair weather, the configuration of the lake bottoms
are such that, after drainage, Lower Myakka Lake would contain
about 100 acre-feet of water and Upper Myakka Lake would contain
about 650 acre-feet. The volume of stored water that could be
drained from the lakes (8,100 acre-feet full capacity) if the existing
controls were removed is estimated to be 7,350 acre-feet.
Streamflow records collected since 1936 indicate that the period
June through October 1944 was the summer of most deficient
streamflow in the past 30 years. However, the total discharge of
the Myakka River near Sarasota during the drought period was in
excess of 31,000 acre-feet. This volume is nearly four times that
required to fill the two lakes to the suggested practical storage of
8,100 acre-feet. Thus, the assumption of a full reservoir at the be-
ginning of a 30-year drought is reasonably safe.

CONCLUSIONS
Flow-duration data at sites on streams with daily discharge
records, and other low-flow measurements, indicate that all natural,
or uncontrolled, flow nearly ceases in the non-tidal reaches of those
streams included within the area of investigation during severe
droughts. The condition of no flow in all streams may be expected
to occur once about every 5 years on the average; however, most
small streams practically go dry during the period March through
May of most years.
The smaller streams, canals, and sloughs are not reliable sources
of water due to their intermittency and low annual yields. Fordham
Waterway in Port Charlotte; West Branch of Coral Creek near
Placida; and the Braden River are currently being utilized, directly
or indirectly, as municipal water supplies. The quality of the water








Low STREAMFLOW-MYAKKA RIVER 33

in the streams and canals is generally good except where affected
by tidal waters, salty springs, or ground-water flow from wells.
Upper and Lower Myakka Lakes, through which the Myakka River
flows, have a total practicable storage capacity of about 8,100 acre-
feet. Usable storage, without dredging of the lake bottoms, is about
7,350 acre-feet. Since 1936, river discharge during the summer
months has been more than three times the practicable storage
capacity. This supply of water, if adequately controlled by dams,
would amply provide for a draft rate of 6.5 mgd of water of good
chemical quality during a 30-year drought. This water would be
subject to the quality limitations that are characteristic of water in
shallow reservoirs located in sub-tropical regions: high tempera-
tures, high color, a dissolved iron content of about 0.3 ppm, and
occasionally suspended organic matter.









REPORT OF INVESTIGATIONS No. 53


REFERENCES

Anderson, W. (see Lichtler, William F., and Joyner, B. F.)
Baker, D. R. (see Kohler, M. A., and Nordenson, T. J.)
Caldwell, R. E.
1958 Soil Survey, Manatee County, Fla.: U.S. Dept. of Agriculture
Series 1947, No. 8.
Dubar, J. R.
1962 Neogene biostratigraphy of the Charlotte Harbor area in south-
western Florida: Florida Geological Survey Bull. 43.
Joyner, B. F. (see Lichtler, William F., and Anderson, W.)
Kohler, M. A.
1959 (and Nordenson, T. J., and Baker, D. R.) Evaporation maps for
the United States: U.S. Weather Bureau Tech. Paper 37.
Lichtler, William F.
1964 (and Anderson, W., and Joyner, B. F.) Interim report on the
water resources of Orange County, Florida: Florida Geological
Survey Inf. Circ. 41.
Nordenson, T. J. (see Kohler, M. A., and Baker, D. R.)
Powell. D. P. (see Wildermuth, R.)
Public Health Service
1962 Drinking water standards, 1962: U.S. Dept of Health, Education,
and Welfare, PHS Publ. 956.
Wildermuth, R.
1959 (and Powell, D. P.) Soil Survey, Sarasota County, Fla.: U.S.
Dept. of Agriculture Series 1954, No. 6.