UNITED STATES DEPARTMENT OF THE INTERIOR
MAP SERIES NO. 54 GEOLOGICAL SURVEY


FLORIDA DEPARTMENT OF NATURAL RESOURCES
puMished by BUREAU OF GEOLOGY


A HYDROLOGIC DESCRIPTION OF LAKE MINNEHAHA

AT CLERMONT, FLORIDA

By
Peter W. Bush

Prepared by
UNITED STATES GEOLOGICAL SURVEY
in cooperation with
SOUTHWEST FLORIDA WATER MANAGEMENT DISTRICT
and the
FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF INTERIOR RESOURCES
BUREAU OF GEOLOGY


More and more people are seeking lakeside property for its esthetic
appeal and for water-onented recreation. Inevitably, much of the land
near lakes that is undeveloped or used principally for agriculture will
become residential or urban. Land surrounding a lake can be developed
so that the esthetic qualities of the lake are enhanced, property values
are increased, and the quality of water in the lake is preserved if
planning precedes the development. However, without planning,
urbanized lakes deteriorate. Planning for development, including
management of the lake itself, requires a knowledge of the hydrology
of the lake.
A lake's hydrology is influenced by numerous factors, such as
geography, geology, chmate, topography, and land use. A study of
these factors and their' nterrelations for Lake Minlehaha and its
surrounding area was made by the U. S. Geological Survey, in
cooperation with the Southwest Florida Water Management District,
during October 1971 to lmne 1972. This map report was prepared to
acquaint both pubhc officials and private interests with the hydrology
of Lake Mmnehaha.,

GEOGRAPHIC SETTING

Lake Mmnehaha is n south-central Lake County, a predominantly
rural area m the heart of Florida's otrus belt. The 3.77 square-mile lake
(2,410 acres) is bounded on three sides by ctrus groves, with homes
scattered among the trees along the shoreline. The city of Clermont
borders the lake along its north shore.
Lake Minnehaha hes on the northwest edge of the Lake Wales Ridge,
the most prominent topographic feature of the Florida peninsula. A
highly undulating surface of broad sand ridges and hills dotted with
many lakes and closed depressions characterizes the Lake Wales Ridge
area. West of Lake Mmnehaha is a land-form of low to moderate relief
with many small lakes and marshes that interconnect during periods of
high water.
The approximately 130-square-mile drainage basin (fig. 2) coincides
with the head of the Oklawaha River basm. Drainage from as far south
as Lake Lowery near Haines City moves northward through wide
shallow swamps confined by parallel sand ridges. This area of wide
shallow swamps, known as the Green Swamp Run, drams mto Big
Creek near the Polk-Lake County line. Big and Little Creeks dram the
basum between the Green Swamp Run and Lake Louisa.
Lake Louisa is the farthest upstream and Lake Minnehaha is the next
major lake in a chain of takes that are connected by the Palatlakaha
River. The Palatlakaha flows north into the Oklawaha chain of lakes.
The Oklawaha flows from these lakes into the St. Johns River, which
empties into the ocean.
About 31 percent of the land m the Lake Mmnehaha basin is devoted
to citrus groves. Only about 2 percent of the land is urban and
residential. Swamps, wooded land, lakes, and pasture constitute the
remainmg 67 percent.

GEOMORPHOLOGY AND GEOLOGIC SETTING

The formation of Lake Minnehaha and other lakes in the area is
apparently due to localized differential solution of the underlying
limestone by percolating ground water, and corresponding subsidence
of the surface, thus creating depressions which evolved into lakes. The
evolutionary process that created Lake Minnehaha began a few million
years ago and ultimately produced the surface depression that
impounded the lake.
Figure 3 indicates the general ithology around Lake Mmnehaha.
Relatively permeable sands of the Citronelle Formation and
undifferentiated surficial deposits constitute the water table aquifer
nearest land surface. The water table aquifer becomes increasingly
clayey and therefore less permeable with depth.
Beneath the Citronelle is the Hawthorn Formation, the clay content
is greater and continues to increase with depth so that most of the
Hawthorn acts as a confining bed. Although the transition from
water-table aquifer to confining bed does not occur abruptly, its
generally coincident with the Citronelle-Hawthorn contact. Under the
Lake Wales Ridge on the east side of the lake, where the water-table
aquifer is thickest, the confining bed is thin or missing.
Beneath the confining bed is a sequence of highly permeable
hlimestones about 2,000 feet thick known as the Flondan Aquifer. The
Floridan Aquifer acts as a large underground reservoir, and is the
principal source of water in the area. The depth to the Flondan Aquifer
in the vicinity of the Lake is variable and not necessarily dependent on
the land-surface elevation, that is, the depth to the Flondan Aquifer
does not necessary increase as the land-surface elevation increases. The
depth to the Flondan Aquifer ranges from about 60 feet to more than
200 feet below land surface.
The bottom of Lake Mmnehaha is in the water-table aquifer, and the
bottom is hard and sandy except m very few of the deeper holes or
depressions where some muck has accumulated.

LAKE-LEVEL FLUCTUATIONS AND RELATED HYDROLOGY

Since May 1945, the stage of Lake Mminehaha (fig. 4) has fluctuated
between 99.0 feet above mean sea level, on April 5, 1960, and 92.7 feet
above mean wa level, on January 22, 1963. The stage of Lake
Mmnehaha (and also, the stages of Cherry Lake, Lake Mmneola, and
Lake Louisa, fig. 2) have been regulated to some degree since 1956 by a
discharge control structure at the outlet from Cherry Lake, about 8.6
miles downstream of the outlet from Lake Mminehaha.
Water enters the lake as surface inflow from the Palatlakaha River, as
direct runoff, as ground water seepage, and as rainfall. Water leaves the
lake as surface outflow through the Palatlakaha River, as grounid-water
seepage, and by evaporation. An insignificant amount is withdraw n for
origation. The lake stage fluctuates m response to changes min the
relativeuoslowes of those sorcets.
Figures 5 and 6 relate the monthly rainfall, evaporation, and lake
stage from 1960 through 1971.Average annual rainfall for the 12 years
at the National Oceanic and Atmospheric Admiinstration (NOAA)
station 6 miles south-southwest of Clermont was 51.4 inches, nearly the
same as the long-term average at that station, 51.2 inches. The influence
of ramfall on the lake level is evident-the level nses during the wetter
months and falls during the drier months.
For the same 12 years, discharge from Big Creek into Lake Louisa
averaged 33.9 cfs (cubic feet per second), and discharge from Cherry
Lake averaged 50.7 cfs. To convert cubic feet per second into millions
of gallons per day, multiply the value min cubic feet per second by 0.65,
thus 33.9 cfs = 22.0 million gallons per day. Big Creek drains the upper
half of the Lake Mmnehaha basn, an area of approximately 70 square
miles. Cherry Lake receives drainage from approximately 160 square
miles that includes the 130-square-mile Lake Mmnehaha basan. Thus,
the additional 90-square-mile area surrounding Lakes Louisa (including
Little Creek drainage), Mmnehaha, Mmneola, and Cherry Lake
contributes, on the average, only 16.8 cfs. Surface runoff east of these
lakes is low because rainfall readily infiltrates the permeable sand hills
in that area. The numerous small lakes and marshes west of Lakes
Louisa, Mmnehaha, Minneola, and Cherry Lake indicate low surface
runoff m that area. Most of the rainfall that is not retained as surface
storage either evaporates or soaks into the ground.
The direction and volume of ground-water flow into or out of Lake
Minnehaha depends on the permeability of the subsurface strata, and
the hydraulic gradient. The hydraulic gradient is the difference in head
per unit of distance in a given direction. The level to which water nses
above a datum (for example, mean sea level) in a well cased into an
aquifer is the measured head at that point in the aquifer. At points
along the bottom of a lake, the level of the lake is the head. Water flows
from points of high head to points of low head.
Therefore, if the surface of a lake is higher than the head in
surrounding aquifers, water will seep out of the lake, and vice versa,
provided the lake bottom is permeable. The potentiometnc surface of a
confined aquifer is an imaginary surface that coincides with the head min
the aquifer. Contours representing the elevation of the potentiometcn
surface of the Floridan Aquifer in figure I show that, in March 1972,
the surface was lower than the lake level and sloped generally from
southwest to northeast.
The confining bed of clay and sand limits the rate of downward
movement of water from above, thus helping to hold both the lake level
and the water table above the potentiometnc surface. An indication, in
addition to lithologic data from wells, that the confining bed is thin or
missing east of Lake Minnehaha is the fact that the elevations of small
lakes such as Jacks Lake and Wdma Lake (fig. 1) are about 10 to 15
feet lower than that of Lake Mmnehaha, and nearly the same as the
potentiometric surface. This also indicates that these smaller lakes are
sources of local recharge to the Flondan Aquifer dunng wet periods
and that ground-water discharges mto the lakes during dry periods.
A section along line A-A' (fig. 1), parallel to the direction of
ground-water flow in the Floridan Aquifer (flow is at right angles to the
contours on the potentiometnc surface) is shown in figure 7 to
illustrate generalized ground-water flow relative to the lake. Because the
vertical gradient between the lake and the Floridan Aquifer is
considerably greater than the horizontal gradient due to the slope of
the water table and potentiometnc surface, flow through the
water-table aquifer is to the Floridan Aquifer.
The vertical component of flow is relatively large also because the
average permeability of the lower layer (Floridan Aquifer) is probably
several hundred times greater than the average permeability of the
upper layer (water-table aquifer and confining bed taken as a unit). In a
layered system where an aquifer with essentially horizontal flow is
recharged from above, the dominant path of flow more nearly
approaches the vertical as the ratio of permeability in the lower layer to
permeabihty in the upper layer increases.
Figure 7 also shows that ground water seeps into Lake Minnehaha
from'the water-table aquifer around the edges. Slight mounding of the
water table is believed to occur beneath the sand hills surrounding the


lake, creating a lateral gradient toward the lake. The magnitude of the
gradient, and therefore the volume of ground-water inflow, is variable
depending on the amount and duration of rainfall over a period of time.
During relatively dry penods, the head in the water-table aquifer close
to the lake, within the interval 76 to 73 feet above mean sea level (34
to 37 feet below land surface, well 832.2, figs. 1 and 8) is lower than
the lake level. Mounding of the water table as probably extremely slight
during such penods, especially on the east side of the lake. Dunng wet
periods, inmereased mounding of the water table is likely. After 5.3
inches of ram March 30-31, 1972 the head was higher at the point
where well 832.2 is open to the aquifer than the lake level for several
days. Thus, the gradient relative to the lake at that point was reversed,
indicating a probable increase m ground-water flow toward the lake
from the upper elevations of the saturated zone around the lake.
The water level in Flondan Aquifer well 832.1, at the same site as
water-table aquifer well 832.2, rose nearly as much as the level in well
832.2 after the 5.3-inch rainfall of March 30-31, 1972. This does not
necessarily mean that similar quantities of water were taken into
storage m the two aquifers, confined aquifers generally take far less
water into storage per unit change in head than water-table aquifers.
On the basis of short-term (less than 5 years duration) water-level
records for wells in the general vicinity of Lake Minnehaha, the
potentiometric surface may rise above the lake level on the west side of
the lake during wet penods. But this condition is probably the
exception rather than the rule.
The net volume of ground-water seepage, to and from Lake
Mmnnehaha has little effect on changes in the level of the lake. During
1962, no water was released from Cherry Lake through the outlet
controL Inflow to Lake Louisa from Big Creek averaged only 4.2 cfs.
Thus, Lakes Louisa, Mmnehaha, Mmneola, and Cherry Lake were, for
practical purposes, a closed surface system. With virtually no surface
flow passing through Lake Minnehaha, stage changes were the direct
result of rainfall accretions and evaporation losses, and ground-water
seepage. For each month of 1962, the change in lake level was close to
the net difference between rainfall and evaporation. That is, average
monthly change in level of Lake Minnehaha during 1962 was -0.09
foot, while the average monthly evaporation exceeded average monthly
rainfall by 0.12 foot. Thus, the thickness and relative impermeability of
the confining layer beneath Lake Mmnehaha apparently limits the
volume of water seeping out of the lake to small amounts relative to
other sources of inflow and outflow.
The effect of discharge control at Cherry Lake from 1960 through
1971 on the stage of Lake Minoehaha (and also Lakes Louisa,
Mmneola, and Cherry Lake) can be seen from figures 5, 6, and 9. For
example, on the average im January, rainfall exceeded evaporation by
0.43 inch, but the level of Lake Minnehaha dropped, on the average,
1.27 inches m January. Apparently, the average discharge of 44 cfs ma
January was greater than inflow to the four lakes. On the average in
May, evaporation exceeded rainfall by 3.39 inches, but the lake level
fell, on the average, 5.96 inches. Thus, the average May discharge of
40.5 cfs exceeded average inflow to the four lakes. On the average in
August, the lake rose 4.77 inches, but rainfall exceeded evaporation by
only 2.84 inches. Cherry Lake's average discharge in August, 51.3 cfs,
was therefore less than average inflow.
The desirable range min stage for Lake Minnehaha established by
Southwest Florida Water Management District is 96.00 to 97.25 feet
above mean sea level, but the control structure is not operated by the
Southwest Florida Water Management District. Figure 10 shows that,
sonce the installation of the Cherry Lake discharge control structure in
1956, the stage of Lake Minehaha has been within that range 37
percent of the time. For the years of record when no control existed,
the stage was within that range 41 percent of the time. As shown mi
figure 10, the stage has been lower more of the time since discharge has
been controlled. Yet average annual ramfall at the Clermont station for
the period of record when discharge was controlled (53.3 inches)
averaged 4.5 .inches more than dunng the period when discharge was
uncontrolled (48.8 inches). Rainfall at the Clermont station is believed
to be as representative an estimate of rainfall on the basin as can be
obtained with available data. No evidence exists to indicate that
pumping from wells has lowered ground-water levels. Apparently the
discharge control, together with other channel improvements
downstream of the control, are less restnctive to flow than the natural
channel that existed before 1956.
The extreme high stages m 1960 of nearly 99 feet and the extreme
low stages in late 1962 and early 1963 of less than 93 feet probably are
relatively rare occurrences. Total rainfall at the Clermont station for
1959 and 1960, 134.36 inches, was by far the highest 2-year total sone
the record began in 1892. Total rainfall at the station for 1961 and
1962, 72.61 inches, was the lowest 2-year total on record. The location
of the 100-foot contour on the land surface around Lake Minrnehaha
shows that extreme high stages such as 99 feet in 1960 are not likely to
cause extensive flood damage. Also the lake is deep enough close to
shore so that extreme low stages do not expose much of the lake
bottom. Serious problems associated with lake-level fluctuations are not
anticipated.

WATER QUALITY

The quality of water in Lake Mmnehaha is good, and presently
appears to be stable. Comparisons of the chemical analysts of lake water
sampled nm March 1972 (Table 1) with previous analyses as far back as
1956 Indicates no significant changes in concentration of any
constituent for which analysesar are available. No chemical or physical
constituent determined exceeds the limits established by the U. S.
Public health Service for dnnkmig water. However, no bactenological
analyses were made. The disolved solids concentration min Lake
Mmnehaha is relatively low (48 milligrams per liter) m comparison with
the 700-mleigram-per-hter upper limit of dissolved solids in water
considered suitable for irrigation of most crops under most conditions.
Eutrophication is the natural aging process of a lake. A eutrophic
lake is chaacterized by high nutrient concentrations, and
corresponding high biologic productivity. Nuisance growths of algae
frequently occur in eutrophic akes. A nutrient is any substance
necessary for growth, repair of tissue, or reproduction. Nitrngen,
phosphorus, and carbon are considered key elements among the
nuotriens essential for the growth of water weeds, including algae.
Minimum requirements of these elements for the growth of algae vary,
but concentrations of mtrogen, phosphorus, and carbon m Lake
Minnehaha are relatively low. Algae has not been a problem in Lake
Minnehaha.
Dissolved oxygen, specific conductance, and temperature profiles at
a number of locations in the lake indicate that water in the lake is well
mixed. The mixing is evidently the result of wind action more than
surface-water flow through the lake.
Measurable amounts of the insecticides DDT, DDE, DDD, and
dieldrn were in a sediment sample from the bottom of the lake near
the center (table 2). Runoff from agricultural land may be the prime
source, although dust containing the substances likely s a significant
contributor. DDE, DDD, and dieldnn are insoluble m water, and DDT
is practically insoluble. These substances tend to adhere to suspended
sediment and settle to the bottom with the sediment; thus their
concentrations are likely to be higher n the bottom sediments than m
the water. The recommended limits of DDT and dieldrin m public
water supplies are 42 and 17 micrograms per hter, respectively, well
above the concentrations noted m Lake Minnehaha sediment. DDD and
DDE are similar in composition to DDT, but both are less toxic to
mammals than DDT.
Urban storm runoff to lakes and streams is a significant source of
pollutants. Stormwater from Clermont discharges directly into Lake
Mmnehaha at a number of points. The quality and volume of
stormwater from Clermont have n notnoticeably affected the quality of
water in the lake. However, land development and urbarnzation usually
result in an increase in the quantity and degradation of the quality of
storm runoff. The quality of lake water will be adversely affected m the
future if, as land around the lake is developed, its accompanying storm
runoff from streets, parking lots, and rooftops is allowed to drain to the
lake. Alternatives exist to discharging storm runoff into convenient
lakes. One possibility is to collect storm runoff m holding ponds. If
properly located, designed and maintained, the ponds will permit
stormwater to be disposed of by evaporation and infiltration.
In general, the good quahty of water min Lake Minnehaha can be
attributed to a largely undeveloped drainage bastm A previous study of
69 lakes in southwestern Orange County and two lakes m Lake County,
indicates that the variation in quahty among the lakes is due primarily
to land-use practices mo the lake basins. Lakes in predominantly
undeveloped basins are of better quality than lakes in basins where the
major land use is for citrus groves or housing. The fact that surface
runoff from grove land in the Lake Minnehaha basin is very low
minimizes the amount of nutnents, pesticides and other agricultural
chemicals reaching the lake.
The continued good quality of Lake Minnehaha will depend for the
most part on the future course of planned growth and development in
the drainage basin. Sedimentation and enrichment by nutrients are the
principal contnbutors to eutrophication of lakes. Much sedimentation
occurs during land development. Earth-moving, grading, road building,
installation of utilities and other construction activities leave the
ground bare and vulnerable to erosion during stormins. Erosion control,
or at least the containment of eroded material at construction sites can
decrease sedimentation. Some nutment enrichment of Lake Minnehaha
as inevitable. However, the rate of enrichment as the lake's drainage
basin is developed can be minimized if all reasonable care is exercised in
the location, design, and installation of septic tanks and sewage
treatment facilities. Septic tanks in areas where the water table is near
land surface, or in areas close to takes or streams where the direction of
ground-water flow is toward the lake or stream can cause accelerated
nurient enrichment of the lake. Control of nutrient and sediment
sources as the basin develops is one way to prevent the quality of water
in Lake Minnehaha from deteriorating.


Table 1.-Chemical analysis of water in Lake Minnehaha;
integrated sample collected March 22, 1972 at center of lake;
constituents in milligrams per liter except as noted; metals
wae total recoverable.

Silica (Si02) 0.7
Calcium (Ca) 3.2
Magnessium (Mg) 1.5
Strontium (Sr) .03
Sodium (Na) 6.4
Potassium (K) .4
Bicarbonate (HCO3) 3
Carbonate (C03) 0
Sulfate (SO4) 7.6
Chloride (Cl) 12
Fluonde (F) .1
Total organic nitrogen (N) .61
Nitrate (NO3) .0
Nitrite (NO2) .04
Ammonia (NH4) .05
Total phosphorus (P) .025
Ortho phosphate as P .013
Total organic carbon (TOC) 9
Dissolved solids 48
(residue at 180C
Alkalinity as CaCO3 2
Hardness (Ca-Mg) 14
Noncarbonate hardness 12
Iron (Fe) .13
Mercury (Hg) less than .0005
Manganese (Mn) .00
Zinc (Zn) .02
Cadmium (Cd) .000
Chromium (Cr) .00
Lead (Pb) .000
Copper (Cu) .00
Specific conductance 70
(micromhos at 250C)
Biochemical oxygen demand (BOD) .5
pH (field measurement) 6.5
Dissolved oxygen 8.5
(field measurement)
Temperature, F 68
(field measurement)
Color 50
Turbidity 4
(Jackson turbidity units)

Analysis by U. S. Geological Survey.




Table 2.-Insecticide analysist of lake-bottom sediment;
sample collected March 23, 1972 at center of lake;
constituents in micrograms per kilogram.

Aldrin 0.0
Chlordane .0
DDD 1.6
DDE 2.8
DDT .6
Dieldrin .1
Endrin .0
Heptachlor .0
Heptachlor e poxide .0
Lindane .0
Toxaphene .0
Diazmnon .0
Ethion .0
Malathion .0
Methyl parathion .0
Methyl tritlhon .0
Parathion .0
Trithion .0
PCB .0

Analysis by U. S. Geological Survey.


28 33'


Figure 2. Lake Minnehaha drainage basin.


s,<"


EXPLANATION

Z Citronelle Formation and undifferentiated surficial
0 0 deposits, sand, red to orange, tan near surface,
medium to fine grained, slightly clayey at depth.

SHawthorn Formation. sand and clay gray to green, '
S with phosphorite particles and some limestone
S fragments, more clayey at depth.
WELL
OTTOM Ocala Group: limestone, gray to tan, fossiliferous, soft
to hard.

Avon Park Limestone: limestone, gray to dark brown,
dolomitic, fossiliferous, soft to hard.

Figure 3. Lithology at 3 well sites near Lake Mimnchaha.


I10


199 1/- - -







994-- -- -------------- -- ----------------- ----














9 e 47 4849 50 I 52. 53 54 55 56157 5 59 60 I 62 63 64 66 66 67 66 6970 718172

Figure 4. Month-end level of Lake Minnehaha. May 1945-May 1972.


+7







+4

+3


WELL
BOTTOM
-203 FEET


28 31'


Figure 9. Average monthly discharge
from Cherry Lake, 1960-71.


Figure 6. Average monthly change in
stage of Lake Minnehaha, 1960-71.


Figure 5. Average monthly rainfall at
NOAA station 6 miles south-southwest
of Clermont, average monthly
evaporation from NOAA station at
Lisbon, adjusted for lakes (Kohler,
1954), and excess of one over the other,
1%0-71.


DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY

This public document was promulgated at a total
coa of 1919.00 or a per copy cos of S.61 for the
purpose of d iseundhag hydrologic data.


LAKE MNEHAlA

.'T h J I I- -













W 1


3723

Figure 8. Comparison of water level in Lake Minnehaha and
Sweater levels in well 832.2, open 34-37 feet below land surface








in the water-table aquifer, and in well 832.1, open 95-140

feet in the Floridan aquifer, and daily rainfall from U. S.
Geological Survey rain gage in Clennont.


EXPLANATION


- 10 Depth contours, April 1972. Contour interval 2 feet Datum
is lake stage of 94.7 feet above sea level


Known dredged areas number is maximum observed depth, in
30 feet.


150- Land elevation (topographic) contours. Contour interval 50
feet. Datum is mean sea leveL


- 82 Potentiometric surface contours, March 1972. Contour
interval 2 feet. Datum is mean sea level


oAILY AVERAGES, JANUARY 194t-DECEMER 1955
S( BEFORE OPENING OF CHERRY LAKE DISCHARGE CONTROL )
J -- / --


<- -- ------ 7 ^ ^


. I


A A' Line of geohydrologic section (see fig. 7).


0831 Well location and number.


SPRECIPITATst WrWITRATigo T FLOW L E
AT I UATiuRTE ZOrsNaoE i an m 1Eh

Figure 7. Generalized ground-water flow along section A-A' (fig. 1) for Lake Minnehaha.


OERTIs6o R


DAILY AERAGES JANUARY 1957-ECEIE R 1970
I AFTER OPENING OF rCreeRv LAnE CIaWHM CONT .0ll"I

---lU


28 33'











































32'












































280 31'


a -- -- o-- o-- o__ _oso t ;2 2974 ;
0 0 in 32 en 55 or s q x sin a
PEREENTAGE OF TIRE rINICATIED STtGE EQUALED OR EXCEkEO (f


Figure 10. Stage'durationcurves for Lake Minnehaha before and after opening of 3 3931
Cherry Lake discharge control in 1956. .I 1

q-_< M o r

LORTDA Gf-IOLOGIC SURVEY MAP SERIES .8