MAP SERIES NO. 31 UPDATED


6*7


UNITED STATES DEPARTMENT OF THE INTERIOR
GEOLOGICAL SURVEY


s85


FLORIDA DEPARTMENT OF NATURAL RESOURCES
published by BUREAU OF GEOLOGY


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30-o


28*


27"


26"*


SEASONAL VARIATION OF

STREAMFLOW IN FLORIDA


-by
W. E. Kenner

Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with the
BUREAU OF GEOLOGY
FLORIDA DEPARTMENT OF NATURAL RESOURCES
TALLAHASSEE, FLORIDA
1969
UPDATED 1975


Florida's pattern of streamflow variation is unusual in two
respects. First, the month-to-month variation in average
streamflow is relatively small; second, the seasonal variations of
streams in different sections of the state are different. A
convenient way to show seasonal variations of streamflow is to
graphically compare monthly average flow, in terms of the
percentage of average flow as shown on the map.
Several factors contribute to the variation of streamflow.
The small month-to-month variability in streamflow is the result
of (1) the relatively low variability of average monthly rainfall
(Figure 1); (2) the relatively high rate of evapotranspiration in
the summer (Figure 2); (3) the large volume of slowly released
natural storage in Florida's numerous lakes; and (4) the large
and relatively stable inflow of ground water to streams from
extensive limestone and alluvial aquifer systems. Two examples
illustrate the small variability of average monthly flow of streams
of different sizes that drain different geologic terrain.
The Santa Fe River near Fort White has an average
discharge of 1,670 cfs (cubic feet per second), drains about 1,100
square miles, and is fed largely by springs issuing from limestone
aquifers. The highest average monthly flow (September) is 10.8
percent, and the lowest average monthly flow (May) is 7.1
- percent, based on continuous streamflow records for 1933 to
1972. The Shoal River near Crestview has an average discharge
of 1,042 cfs, drains about 475 square miles, and is fed largely by
seepage from shallow alluvial aquifers and direct runoff. The
highest average monthly flow (March) is 11.0 percent and the
lowest average monthly flow (November) is 6.2 percent of the
average annual flow, based on continuous streamflow records for
1939 to 1972.
Although the average month-to-month variation in
streamflow is small, recognizable patterns of seasonal
streamflow exist statewide; the pattern in northwestern Florida
is distinctly different from the seasonal streamflow pattern of
southern Florida.
The graphs on the map show the monthly streamflow, in
terms of the percentage of average annual flow that occurred for
each of 10 representative streams or canals. Averages and
percentages representing the seasonal pattern of runoff were
computed on the basis of the periods of streamflow record
indicated on the graphs, the shortest being the 32-year record for
Tamiami Canal outlets. Where more than 32 years of record was
available, the longer record was used in the computations. In
general, during the spring, streamflow is highest in extreme
northwest Florida, moderate in central Florida, and lowest in
southern Florida. A gradual but progressive decrease in
springtime streamflow from north to south is evident. For
example, the combined average for the Escambia River for the
spring months of March, April, and May is 40 percent of the
annual average; for the Santa Fe River about 25 percent; for the
Peace River, about 13 percent; and for the Tamiami Canal
Outlets, about 8 percent.
Conversely, the autumn streamflow shows a progressive
increase from north to south. The combined average for the
autumn months of September, October, and November for the
Escambia River is only about 12 percent; for the Withlacoochee
River in west-central Florida autumn flow was about 37 percent;
for the St. Johns River was 38 percent; and for the Tamiami
Canal Outlets was about 48 percent.
The percentage of summer (June, July, August) flow in
relation to the annual flow averages about the same throughout
the state and is about equal to that during the winter months
(December. January, February), even though about three times
as much rainfall occurs during the summer as during the winter.
About 20 percent of the annual flow occurs in each of these
seasons. An exception is the Upper Peace River basin where a
considerably larger percentage of streamflow occurs in the
summer than in the winter.
Florida's unusual pattern of seasonal variation of streamflow
is due largely to its position in the transition zone between the
continental weather pattern of southeastern United States and
the tropical weather pattern of the Caribbean Sea. During the
winter and early spring the continental pattern, characterized by
high pressure air masses that move southeasterly from western
Canada across the Central Plains States, predominates in
northern Florida. Generally, these air masses flow eastward over
the Mississippi Valley, thence to the northeast over the Atlantic
Seaboard, and over the Atlantic Ocean. The leading edges of cold
air masses meet the warmer moist air masses of the Gulf region
and produce the "frontal" weather that results in severe storms
and copious rainfall. These weather fronts frequently move
across southern Alabama and Georgia and northern Florida but
rarely reach as far south as Lake Okeechobee.

DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY

This public document was promulgated at a total
cost of $242.00 or a per copy cost of $.097 for the
purpose of disseminating hydrologic data.


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S V A J j-J -s--e- .CALHOuNi E-M A MA3SS 0 JFFESO S ANN ra r~y
Average eet v ef owl 042cublYeet Avergef o 1,870c feet
persecond persec pers n BAKER
(Recordused: 1935-72) (Record used: 'f (Record sed: 1929-72) -- -
S I, LIBR TY \ AKULLA ,1, dOLiia /
'N0 1' \ \-, V ( Qo!"' l I| I' I I I I I I [ i SA1'A IVER
J F;M M J J A SO D N0NU .-' (nrarF hit)
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GULFF T. WHI UI
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x ILCR|nST ALA.HU. A ragelaw6A, u ic feet
DIXIE second
--R ord used: 7) \

S- -, F C*LER\
Florida's summer and fall climate is sub-tropical and is Y o ) -
aracterized by local thunderstorms and humid, low-pressure ______../-_ )
r masses (easterly waves) that usually form in the Caribbean
a and move westward or northwestward. As these masses of \
oist air pass over peninsular Florida, precipitating their 0i / '
moisture as rain, they gradually dissipate with correspondingly RION V.usI \
ss rainfall on northwestern Florida and southern Georgia and
abama. Occasionally an easterly wave becomes intensified and "DE L ANDOE'
rms into a tropical storm or hurricane. High winds and heavy _
infall accompany such storms which often add to the normal HOLDER -T A
te summer and fall rains in southern Florida. J F M A M J A S O N D ITHLACO EE d E T. JOHNS VER
n DEFUNIACE SPRINGS LJ I LACI ERIVE ST. JOHNS VER
The line of demarcation between areas dominated by the two Eru N N IA s G c T
weather types is not sharp. The continual north-south shifting of < n ear20cT r.E)
e tropical and continental air masses results in a seasonal 1 0 20 -
stribution of rainfall that has a predominantly continental s n SEMINOLE
pattern in northwestern Florida, is less continental and more 10
opical in central Florida, and is predominantly tropical in
uthern Florida. The pattern of seasonal rainfall caused by the n 0o a 1
terplay of the two weather systems, seasonal variations in ^ O A' N M M J S D






H- nOGARINESVLLE G < --

arat J F MoAaM J J A S 0A O N D I \ 1 PO \ 9
Qa-
Iound water are all reflected in Florida's pattern of seasonal LAKECITYA a (l 1 c.








i 0<" ....GAINESVILLE ; \ A -
.oation of stream ow.
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nInnn o _2_. z I- ^' .1 -', t.- t^ O C H I \\
J FM A M J J A S O N D '
AVON PARK SAiAso I ,-* ,. t- ,\ -'Y
S OKEECHOBKEECOEE
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nL LE E RGL
\ (near readia) I |\ ,ISSlMME RrrC

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1931-1960 at De Funiak Springs, Lake City, Gainesville, per sekorW.. LEE perses cond.
Avon Park, and Belle Glade. (Record hett 2-72) --- (Records sed: 1929-72)
S - L_ _1,r-J q j /

'r +.y I ", .H. I T

ID _8 --



J F MA M J J A S O N D CANAL OUTLET
WOODRUFF DAM ( mito Monroe) AMI

10

5 Z
0 EXPLANATION
^ ll lI II III n FM-A NJ J A S 0 N D /
J F M A M J J A S O N D 0- A ..rad IA 90 i cubic feet
'GAINESVLLE GAGING STATION person nd
A a959-l 7e (Recor used: 1941-72






J F M A M J J A S O N D J
HIALEAH .
(1943-67)


Figure 2. Monthly Average Pan Evaporation at Woodruff
Dam, Gainesville, and Hialeah. ca


O 10 20 0 o40 50 MILES


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FLORIDA GEOLOGIC SURVEY MAP SERIES


G 39;
.C1
No. 3:
1975
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