UNITED STATES DEPARTMENTS OF THE INTERIOR
MAP SERIES NO. 55 GEOLOGICAL SURVEY


FLORIDA DEPARTMENT OF NATURAL RESOURCES
published by BUREAU OF GEOLOGY


3 Oklawaha River near Ocala


4 FM AS M S i A r O N 0
4 Silver Springs near Ocala


6 Orange Creek near Orange Springs


Oklaaha River at Riverside Landing near Orange
Springs


2 Withlacoochee River near Holder


-T~IF


5 Rainbow Springs near Dunnellon


J FM A M R i A S 0 N o
7 Withlacoochee River at Dunnellon


1 Orange Lake at Orange Lake


2 Lake Weir at Okla-Eha
2 Lake Weir at Oklamaha


QUANTITY AND QUALITY OF SURFACE WATER

IN MARION COUNTY, FLORIDA
By
Warren Anderson and Glen L. Faulkner


Surface water is abundant around much of the periphery of Marion
County and along the Oklawaha River, which flows from south to
north through the east central part of the county (see central map).
Surface water is sparse elsewhere in the county because, with a few
exceptions, rainfall infiltrates the sandy soils too rapidly to run off or
accumulate in depressions. Thus, only about 25 percent of Marion
County is subject to direct surface drainage and the remainder is
drained through the subsurface. Most of the water that infiltrates the
ground enters the principal aquifer, which in Marion County is the
Floridan aquifer. The Floridan aquifer stores the water while
transporting it to two major discharge points. Silver Springs and
Rainbow Springs, and several lesser discharge points within the county.
Nearly all the spring flow leaves Marion County by way of the
Oklawaha River. Blue Run, Juniper Creek, and Salt Springs Run.
The annual rainfall on Marion County averages 53.2 inches, an
average of about 4.1 bgd (billion gallons per day). About 240 mgd
(million gallons per day) enter the county from the south in the
Oklawaha River and a net input of about 440 mgd flows into the
county in the Floridan aquifer. Thus, Marion County receives an
average of 4.8 billion gallons of water per day. An average of about 3.1
bgd returns to the atmosphere by evaporation and transpiration leaving
an average of about 1.7 bgd to replenish the aquifers, lakes, and streams
in the county. The fact that the part of the rainfall that returns to the
atmosphere within the county is termed "water loss" does not preclude
its use during the period it remains on or beneath the land surface.
However, httle can be done to prevent its eventual loss.
In addition to this huge quantity of water, on the average, about 760
mgd passes along the southwestern county line in the Withlacoochee
River and about 2,300 mgd enters Lake George, which abuts the
eastern county line. Thus, the total quantity of water entering the
county or flowing along the county line is nearly 4.8 bgd on the
average, more than a tenth of the total surface water runoff from the
state of Florida.
Important functions of streams other than as sources of water are
removal of excess water and conveyance and dilution of wastes. In the
25 percent of the county subject to direct surface drainage, this
function is performed with varying degrees of efficiency. Flat swampy
areas drain more slowly than areas of greater relief. However, except for
the contribution from springs, flow from these areas becomes negligible
during dry periods. In the other 75 percent of the county, excess water
is removed from the surface with great efficiency by infiltration. Of
course, dissolved pollutants contained in the water also infiltrate the
ground.
Fortunately, much of the pollution is eliminated by the natural
purifying action of the sod. However, the capacity of the soil to purify
is limited, thus every effort should be made to manage urban, industrial
and agricultural development so as to avoid introduction of wastes of a
kind and volume that cannot be naturally degraded in areas internally
drained.
Lakes in or abutting Marion County range in size from water-filled
sink holes of less than an acre to Lake George which covers about
46,000 acres. Lake altitudes range from about I foot for Lake George
to more than 190 feet above mean sea level for several lakes in the
vicinity of Irvme. Many of the lakes along the Oklawaha River are at
altitudes of 50 to 60 feet whereas those near the eastern county line are
at 20 to 30 feet. The lakes m the vicinity of Irvine rest on a thick layer
of relatively impermeable deposits which overlie the more permeable
limestones of the Floridan aquifer. These lakes drain to smks which
bottom at altitudes about 100 feet lower than the lakes. These sinks are
points of relatively large amounts of recharge to the Floridan aquifer.
Among the more significant benefits of takes in Marion County is their
value for recreation, homesites, and scenic beauty.
Problems with surface water almost always result from its variability,
whether in amount or in quality. The alternate conditions of surplus
and deficiency in the surface-water supply of Marnon County results
from imbalance between the rate and chronological distribution of the
input (rainfall and inflow) and the output evapotranspirationn, runoff,
and infiltration). The accompanying illustrations show how this
hydrologic imbalance affects selected streams and lakes m and near
Marion County.
Variability of streamflow in Marion County is illustrated by the three
small maps beneath the large central map. Although the variation min
flow is shown to be large, the amount of variation in the flow of
streams in Marion County, except Orange Creek and the Oklawaha
River upstream from Silver River, is much less than that in the flow of
most other streams in Florida because of the high base flows supplied
by the large springs m the county. Maximum flows, which are usually
the result of a severe storm following an extended period of above
normal rainfall, are several times the average flows. Average flows are
generally less than three times the minimum flows.
The stage- and flow-duration curves show the percentage of time
during the periods of record that specific stages or discharges were
equaled or exceeded. For example, on 50 percent of the days of record,
the stage of Lake Weir (curve 2) was 57.2 feet or more above mean sea
level and the discharge of Orange Creek at Orange Springs (curve 6) was
100 cubic feet per second or more. The stage-duration curves show that
the range in stage of the gaged lakes in Marion County is generally
about 7 feet. However, the ranges of some other lakes in the county
may be appreciably greater or less than this amount.




62


61 -

601 (1963-68; RECORDS
ADJUSTED

59

58

57
LAKE WEIR AT OKLAWAE
56 -


i 55 -
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S54 -
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28


27 -

26 LAKE KERR NEAR El
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The hydrographs show the similarity in the pattern of the seasonal
variation in the average conditions of streams and takes. The seasonal
changes in streamflow and lake stages result from differences m the
seasonal amounts of rainfall and evaporation shown by the graphs of
average monthly rainfall and evapotranspiration. The effect of
unbalances between rainfall and evaporation on lake stages is illustrated
by the graphs that show a comparison of the differences between
average monthly rainfall and evaporation totals with the average
monthly change in the stage of Lake Weir. The hydrographs for Sdver
Springs and Rainbow Sprngs show that the seasonal variation in the
average monthly mean flows and the range in monthly mean flows is
very small. This is due to the very large storage capacity of the Floridan
aquifer from which the spnngflow emerges. The hydrographs for
Oklawaha River near Ocala, Withlacoochee River near Holder, and
Orange Creek at Orange Springs show the seasonal variation in the flow
of these streams to be greater than that of the spnngs and the extremes
in monthly mean flows to be considerably more. The variation in
average monthly mean flow of the Oklawaha River near Ocala is shown
to be less than that of the Withlacoochee River near Holder and that of
Orange Creek at Orange Springs. This is because the flow of the
Oklawaha is regulated at Moss Bluff to more evenly distribute the flow
throughout the year. The extremes in monthly mean flow of the
Oklawaha River at Ocala are, however, shown to vary more than those
of the Withlacoochee River near Holder and, except for the summer
months, to vary as much as those of Orange Creek at Orange Springs.
The seasonal variation in the average monthly mean flows of the
Oklawaha River at Riverside Landing is shown to be about the same as
that of the river near Ocala but the extremes min monthly mean flow are
shown to be far less. The more stable flow at Riverside Landing is
attributable to the inflow between the two points from Silver Springs.
The mineral (dissolved solids) content, color, and pH of water in
streams and lakes in Marion County are indicated by the graph under
the text. Rainwater usually contains a very small amount of dissolved
minerals when it reaches the land surface. The dissolved solids content
of a natural surface water is mostly a measure of the minerals dissolved
by the water as it moves over the land surface or through the soil or
rock to a stream or lake. Most water in streams in Marion County, and
to a lesser degree in lakes, is of the calcium and magnesium bicarbonate
type, meaning that the principal dissolved solids in the water come
from the limestone and dolomite present m many places near the land
surface and which make up the Floridan aquifer. Because calcium and
magnesium bicarbonate cause hardness in water, a high mineral content
in water in Marion County usually means that the water is hard. The
mineral content of streams in Marion County ranges from 20 mg/I
(milligrams per liter), soft, to more than 400 mg/1, very hard.
The mineral content of Orange Creek varies much less than that of
other streams in the county because nearly all its flow is derived from
Orange Lake, direct surface runoff, or seepage from the water-table
aquifer, which consists mostly of sand. The mineral content of water
from all these sources is low. The mineral content of the other streams
vanes more than that of Orange Creek because most of their base flow
comes from the Floridan aquifer when the weather is dry, whereas most
of their flood flow is from direct runoff or rainfall. Water from the
Flondan aquifer contains more dissolved minerals than water from the
other sources contains. The minimum imneral content of Oklawaha
River at Moss Bluff probably results from local runoff of rain water
between Moss Bluff and Lake Griffin. The higher content is typical of
that for water in Lake Griffin. The generally lower mineral content of
water in the Oklawaha River near Ocala than at Moss Bluff is probably
due to surface inflow and to seepage from the water-table aquifer
between these sites. The main reason for the much higher mineral
content of the Oklawaha River at Riverside Landing near Orange
Springs than at the upstream sites is inflow from Silver Springs and
saline ground water that enters the river downstream from Silver
Spnngs. The relatively high minimum mineral content at Riverside
Landing reflects the influence of discharge from Silver Spnngs and
other ground-water sources which make up a relatively large part of the
flow here even during floods. Spring flow is a relatively small part of
the flood flow of the Withlacoochee River near Holder but it is a
relatively large part of its base flow. Consequently, the mineral content
of the river is low at high discharge and high at low discharge. The
mineral content of Silver Springs is much more than that of Rainbow
Springs, indicating that either the water from Silver Spnngs remains in
contact with the limestone aquifer longer than that from Rainbow
Springs or the limestone of the aquifer feeding Silver Springs are more
soluble than those feeding Rainbow Springs. The mineral content of all
lakes in Manrion County is low.
Color in the streams is caused mostly by organic matter that reaches
the stream in direct runoff during rainy periods. Thus, color is low
during low flow and high during high flow. In general, the springs are
almost colorless but some lakes, for example Orange Lake, exhibit color
caused by large amounts of surface inflow during wet weather.
The pH of a water indicates whether the water is acidic or alkaline. If
its pH is 7.0 the water is neutral. If its pH is less than 7.0 it is acidic and
if greater than 7.0 it is alkaline. Most natural waters tend to be either
slightly acidic or slightly alkaline. For instance, rainwater usually has a
pH of about 5.5, whereas the pH of Silver Springs water usually ranges
between 7.5 and 8.0. The pH of lake water in Marion County is lower,
as a rule, than that of streams. The higher pH of the streams reflects the
larger proportion of the more alkaline flow derived from the limestone
of the Floridan aquifer.


20 30 40 50 60 70 80
PERCENT OF TIME ALTITUDE EQUALED OR EXCEEDED THAT SHOWN

Stage-duration curves for selected lakes in and.near Marion County.


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STREAM AND LAKE HYDROGRAPHS FOR SELECTED STATIONS IN MARION COUNTY AND VICINITY


Unshaded part of blue graphs shows maximum and minimum monthly mean discharge for the periods indicated.

Heavy black lines show the average monthly mean discharges for the periods indicated.

(See central map for location of station.)


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N
LOCATION
MAP


DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY

This public document was promulgated at a total
cost of $754.45 or a per copy cost of $.75 for the
purpose of disseminating hydrologic data.


M tr.io.r.,




Orange Ln.kO0
O Irvine


Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
and the
BOARD OF COUNTY COMMISSIONERS OF MARION COUNTY, FLORIDA


1973











82000'


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EXPLANATION

M3 STREAMFLOW STATION FOR WHICH DATA ARE SHOWN
2 LAKE STATION FOR WHICH DATA ARE SHOWN

A STREAMFLOW STATION FOR WHICH DATA ARE NOT SHOWN

A LAKE STATION FOR WHICH DATA ARE NOT SHOWN

(NUMBERS ARE FOR STATION IDENTIFICATION)






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Unshaded part of red graphs shows maximum and minimum month-end altitudes for the periods indicated.

Heavy black lines show the average month-end altitudes for the periods indicated.

(See central map for location of station.)


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FLOW SCALE
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Average flow

COMPARATIVE FLOW CONDITIONS FOR STREAMS IN MARION COUNTY


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J F M A M J J A S O N D J F M A M J J A S O N D
Average monthly rainfall in Marion Average monthly lake evaporation in
County Marion County.


05 1 2 5 10 20 30 40 50 60 70 80 90 95 98 99 995 998999
PERCENT OF TIME DISCHARGE EQUALED OR EXCEEDED THAT SHOWN
Flow-duration curves for selected streamflow sites in and near Marion County.


9999


OBSERVED RANGE IN pH
0 I 2 3 4 5 6 7 8 9 I




OKLAWAHA RIVER AT MOSS BLUFF





OKLAWAHA RIVER NEAR OCALA





SILVER SPRINGS NEAR OCALA





ORANGE CREEK AT ORANGE SPRINGS





OKLAWAHA RIVER AT RIVERSIDE LANDING NEAR ORANGE SPRINGS





WITHLACOOCHEE RIVER NEAR HOLDER





RAINBOW SPRINGS NEAR DUNNELLON





LAKE KERR NEAR EUREKA





LAKE WEIR AT OKLAWAHA





ORANGE LAKE AT ORANGE LAKE

o 200 300 400 5 C


'00


OBSERVED RANGE IN MINERAL CONTENT, MILLIGRAMS PER LITER AND COLOR, UNITS, 22 ,974
MINERAL CONTENT COLOR P pH, : 2 9
( SEE CENTRAL MAP FOR LOCATION OF STATION ) '
Quality of water from selected surface sources in and near Marion County '- 3


-. 1A


931


.C1
No.
197;


3 Lake Kerr near Eureka


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