For review only :aot for release
Committee on Surface Water
FLORIDA WATER RESOURCES STUDY COMMISSION
A. O. Patterson, Chairman
B. F. Buie-
W. J. Eichelberger
T. C. Skinner
R. L. Taylor
H. R. Wilber, M.D.
U. S. Geological Survey,
Surface Water Branch
Florida State University
Game & Fresh Water Fish Comm.
Florida Section, American
Society of Agricultural Engrs.
Florida Section, American
Society of Agricultural Engrs.
Corps of Engineers
Central & South Florida Flood
Florida Wildlife Federation
I __ _
Surface water is water in that phase of the hydrologic cycle where it ap-
pears in liquid form on the surface of the earth. It includes water occurring in
streams, lakes, ponds, canals, bays, and oceans. Water that seeps out of the
ground and issues from springs becomes surface water as soon as it appears at the
surface. Water moving from one surface body to another through pipes or man-made
conduits, even though underground, is considered to be surface water.
The importance of having adequate water supplies is well known. Not so
well known are the benefits to be derived by having, as Florida has, much of the
water supplies in the form of surface water. Surface water bodies can do much to
temper the climate of a region. They allow navigation and power generation.
Boating, fishing, and allied recreational activities are possible only in areas so
The economic gain to an area where surface water is plentiful can be tre-
mendous. The establishment and growth of communities and even large cities can
be traced directly to the existence of surface water features nearby.
The value of a water feature depends upon the purpose or purposes for
which it is used and how much use is made of it. Any use at all presupposes some
knowledge of the feature. As the use of a water body increases, more and more
knowledge of it is accumulated. As more and more prospective users learn of the
water body and of its characteristics it is used more and its value increases.
Knowing the flow characteristics of streams may prevent unnecessary ex-
penditures in the design of roads and bridges. Lake and stream stage data save
inillions of dollars annually by preventing the construction and subsequent loss of
homes and other structures in areas of infrequent but recurrent flooding.
ORIGIN OF SURFACE WATER IN FLORIDA
The water in Florida comes from four sources: rainfall over the state;
streams flowing in from other states; underground flow from other states; and wa-
ter flowing inland from the ocean. On the average Florida receives 150 billion
gallons of water per day from rainfall and another 25 billion gallons per day
from other states via surface streams. Neglecting any water that comes into Flor-
ida through underground formations or moves in from the ocean, this makes a total
of around 175 billions of gallons per day, on the average.
OCCURRENCE AND MOVEMENT OF SURFACE WATER IN FLORIDA
Florida's surface water, in its efforts to reach the sea, has established
itself into 12 large river basins and innumerable smaller ones. It is stored --
we might say temporarily, since it is continually being depleted and replenished
-- in upwards of 30,000 lakes throughout the state as well as in the stream chan-
nels. Reference to Figure 1 will give one an idea of the distribution of the
larger streams and lakes. In addition to the fresh water bodies of the interior,
many bays and lagoons lie along the coast of Florida and add to the usable pro-
tected surface waters of the state.
The majority of the lakes in Florida lie within the peninsular section.
Lake Okeechobee is the largest lake in the state and the second largest fresh
water lake in the United States. At a normal stage this lake covers some 700
square miles. Other large lakes include Lake George, Lake Apopka, Lake Kissimmee,
and Lake Istokpoga. The usefulness of many of Florida's lakes is enhanced by
their being connected by natural channels. Lakes in the St. Johns River system
are examples. In some instances, where natural channels were absent, lakes have
been connected by canals. Such canalization is usually done as a water control
. -------- -- -- _^_ .- ^_ -- .- -- ^- ^ ^
measure but it permits the passage of boats and increases the recreational use of
the lakes. One example is the chain of lakes in the Winter Haven area that have
been thus utilized.
There are large fluctuations in the rate of flow and in the amount of wa-
ter that is stored in the lakes and streams. The variation in storage and runoff
assumes a pattern very similar to the rainfall pattern with, of course, some lag.
On the average in peninsular Florida, the lowest water levels occur in May. Flow
and levels increase under the influence of the summer rains, which usually begin
in June, and the levels continue to increase to a maximum in September or October,
after which there is a steady decline until the following May. The pattern is
significantly different in the northwestern part of Florida. Here the lowest flows
usually occur in November and the highest flows occur in March. These conditions
are illustrated graphically in Figure 2 and Figure 3, which show by months the
normal discharge of the Kissinmee River near Okeechobee and the Shoal River near
i Crestview. Figure 4, which shows the maximum, minimum and average monthend ele-
vations for selected lakes, indicates the variation in lake levels that have been
experienced. The variation of the actual discharge from the normal discharge of
the Kissimmee River near Okeechobee since 1931 is shown in Figure 5.
The relatively low relief of the land surface of peninsular Florida is con-
ducive to the formation of slow moving, meandering streams connected to or passing
through numerous lakes. The stream gradients are usually slight with surface
slopes as low as 0.07 foot per mile. The many lakes in the river systems act as
reservoirs reducing the severity of flooding in wet seasons as well as sustaining
the flow in dry seasons.
In the northern and northwestern parts of the state the land surface shows
more relief and stream gradients are somewhat steeper than in the peninsula. The
Shoal River, for example, has a fall of about 3 feet per mile. Lakes are not as
numerous and short-term variations in the flow of the streams are more pronounced.
The flow map showing average flows(Figure 6) gives a general idea of the
movement of surface water in Florida. This map shows the estimated average flow of
various streams in the state. Although average values are often misleading, it is
of interest to note the small flows in the peninsular section of the state. This
is largely a result of the excessive losses from evaporation and transpiration.
Figures 7 and 8 show the flow maps for the months of March, 1944 and October,
1953 to illustrate the variations of surface flow that are experienced. The esti-
mates were based on records collected by the U. S. Geological Survey at gaging
sites throughout the state.
The flow of water from a spring represents a loss to the ground water res-
ervoir and a gain to the surface water component of the hydrologic cycle. Flor-
ida's springs have long been considered important to the tourist industry and the
recreational interests, but spring flows serve other useful functions as well. For
example, springs furnish many surface streams with their only substantial supplies
of water during dry periods and make surface water available for municipal, indus-
trial, navigational, or agricultural use.
The amount of water issuing from springs of all sizes in the state has been
estimated to average 3,700 million gallons per day. Like other phases of the water
cycle, though, this rate of water movement is not uniform. During the periods
when rainfall is inadequate and the ground water reservoir is not being recharged
at a sufficient rate, the quantity of water available for spring flow decreases.
While the fluctuations of spring flow are not as explosive as the rate of flow in
most surface streams, the changes are significant. Depletion of ground storage as
a partial result of low rainfalls is illustrated by the flow data of Table 1. Most
of the spring flows listed show significantly reduced rates during the summer of
1956. The gross reduction from the average of past flows from the 9 springs of
Table 1 is 77 per cent.
TABLE 1 Comparison of Past and Present Flows from Selected Springs in Florida.
All Values are in Millions of Gallons Daily.
Scoring Past Flow* 1956 FlowE
Ichatucknee Springs 216 162
Weekiwachee Springs 102 84
Sulphur Springs 34 22
Rainbow Springs 452 363
Silver Springs 500 349
Crystal Springs 42 32
Kissengen Springs 14 0
Blue Springs 104 107
Wakulla Springs 183 146
* Average of 49 or more individual flow measurements prior to 1947. Sources
Fla. Geological Survey Bulletin No. 31.
** Individual flow measurement made during April or May of 1956. Sources U.S.
i -- -- -
Large areas in Florida are subject to seasonal flooding since the natural
stream channels are inadequate and cannot remove the excess rainfall during the
wet seasons. The topography, particularly in central and southern Florida, is
very flat and rainfall often remains on the land for long periods unless it is re-
moved by drainage works. The largest floods of record have resulted from intense
rainfall during and immediately following tropical storms, or from prolonged per-
iods of rainfall. Florida is in the path of tropical hurricanes that originate in
the equatorial doldrums and move in from the Atlantic and Caribbean on curving
paths at speeds of 10 to 40 miles an hour. The destructive forces of these storms
are the winds whirling counter-clockwise about the storm center at velocities
reaching over 100 miles an hour. The majority of these storms strike the state
from an easterly or southeasterly direction, although hurricanes of lesser inten-
sity approach through the Yucatan Channel and cross the Gulf of Mexico to strike
Florida from the southwest or west. The most dangerous season includes August,
September and October, although tropical storms have been experienced as late as
November. The hurricane that struck Miami and the Lake Okeechobee area in 1926
caused severe property damage and large loss of life at Moore Haven, when waters
of Lake Okeechobee were driven over that town. In 1928, a similar but more de-
structive storm struck from Palm Beach to the Lake Okeechobee area, where wind
driven lake waters overflowed the southern lake shores and drowned 2,300 people,
producing one of the greatest disasters in the history of the country. The two
hurricanes of 1947, which struck the Everglades and Lake Okeechobee areas after a
long period of heavy rainfall, caused large property damage.
The accompanying map (Figure 9) shows the approximate areas in Florida
which are or have been periodically flooded. Of the total land area in the state
of Florida, it is estimated that about 20 per cent or over 7,000,000 acres is subject
-- 6 -
to damaging flooding. In the report to the legislature dated 29 March 1949, the
Water Survey and Research Division of the State Board of Conservation estimated
that frequently recurring droughts and floods have caused damages to average at
least $25,000,000 annually in Florida. The unprecedented floods of 1947, alone,
caused about $59,700,000 damages in central and southern Florida. During that
flood which lasted for over four months in many areas, about 3,500,000 acres of
usable lands were inundated. With the increased development in the central and
southern Florida area, the annual flood damages would exceed $10,000, 'i The
Central and Southern Florida Flood Control Project is expected, when completed, to
eliminate 80 per cent of the recurring damages in the central and southern Florida
The Suwannee River with its principal tributaries, the Sante Fe, Alapaha
and Withlacoochee Rivers drains an area of over 9,500 square miles. The basin ex-
perienced great floods in 1912, 1928 and 1948 with the flood of 1948 being the
most severe. In that flood, damages were distributed over a large area extending
from southern Georgia to the mouth of the river near Cedar Key, Florida. All
highway and rail traffic between west Florida and east and south Florida was de-
toured through Georgia for about three weeks. Total damages were estimated at
Adequate water supplies are vital to the development and growth of Florida.
Much of the state of Florida is subject to lengthy periods of little or no rain-
fall. Droughts occur practically every year in many parts of the state. In gen-
eral, a drought may be defined as a period in which rainfall has been so deficient
that vegetation and water supplies have been adversely affected. Although it is
recognized that droughts are frequent in Florida, very little data are available
as to the severity of droughts in terms of actual losses to agriculture or other
Deficiency in precipitation is the prime cause of drought. Although
droughts may be more effectively measured by the degree of existing soil moisture
or by stream flow and ground water levels, such records are relatively short in
comparison with the available records of rainfall. It may be presumed that the
intensity of a drought would be proportional to the amount and duration of rain-
fall deficiency. Reference to the section on occurrence and movement of water in
Florida discloses the periods of severe rainfall deficiency. In that section it is
shown that drought periods and severity vary in different locations. Large defici-
ency in rainfall at one area does not necessarily indicate a widespread drought
area in view of erratic rainfall distribution, particularly during the dry season.
Droughts need not necessarily be concurrent with periods of rainfall deficiency.
If rainfall during the following wet season is normal or below normal, water lev-
els in the succeeding dry season may even go lower than in the previous dry period.
The 1954-56 period is a prime example. Although rainfall deficiencies in any one
12-month period are not of record proportions, the prolonged nature of the defici-
ency coupled with less than normal rains during the intervening wet season is re-
suiting in one of the severest droughts of record. In many sections of the state,
particularly in central and northwest Florida, water levels are the lowest of re-
In an analysis for one of the major agricultural areas in Highlands and
Glades Counties, Florida, it was found that drought conditions occurred practically
every year. The 1942-43 drought which was quite severe was estimated to have a 1
year in 5 frequency based on rainfall records. If the average potential develop-
ment had been realized on the 195,000 acres of agricultural land considered, the
5-year drought would have caused over $1,000,000 damage. It was estimated that
1 j ______ _._ -.. -- "
the annual drought damages would amount to about $500,000 on that agricultural
land if no supplemental water supply was available.
Much of the data and discussion on the above were obtained from U. S. Geo-
logical Survey Water Supply Paper No. 1255, entitled Water Resources of Southeast-
HOW THE SURFACE WATER LEAVES FLORIDA
In the long run, the amount of water that leaves Florida equals that whIL-
enters. We have seen that the movement of surface water through the state aver-
ages some 175 billions of gallons per day. This tremendous amount of water exits
in several ways. The majority of the water that leaves is evaporated or trans-
pired into the atmosphere. Some water goes to the dea by seepage and underground
flow. Additional amounts are turned into steam in industrial plants and some is
discharged directly into the ocean by pulp mills and municipal sewerage systems.
From a legal point of view surface waters may be classified under two or
more categories. For the purposes of this study, two very broad categories will
suffices (1) diffused surface water-or that portion of surface water spread in a
diffused state before it reaches natural watercourses with well defined banks and
beds, and (2) surface water which has reached and become part of natural water-
courses with well defined banks and beds.
Generally speaking, when rain falls the greater amount of the resulting
water is evaporated or transpired into the atmosphere, and some passes through the
soil and underground strata and becomes either a part of streamflow or ground
water supplies. A small portion, probably less than 25%, moves across the land
in the form of diffused surface water.
Although this type of runoff is only a fraction of total rainfall, it
nevertheless forms a considerable and very valuable natural resource.
Very little is known at present about the relative volume of this supply;
and, therefore, too little is known about its present or potential value for
beneficial purposes. And in this regard, not enough is known about its behavior.
It is known that much diffused surface water is caught in artificial or
natural storage areas and is used for recreation, livestock water, irrigation,
and other purposes. In the last few years in Florida, many farmers and other
landowners have built ponds for livestock water and for fish production and other
forms of recreation. Some manage natural storage areas for these purposes.
Others have constructed irrigation reservoirs. Many of these water areas catch
and hold diffused surface water for the beneficial uses intended. Some, however,
are built on streams and store surface waters of the second category mentioned
above. In the case of some irrigation reservoirs, underground resources are
On the other hand, diffused surface waters may do much harm, also. For
example, they may move to and stand upon lower areas, and in so doing they may
cause damage to crops, pastures, buildings, highways, and other installations.
A considerable part of the drainage work done thus far in Florida has been to
provide relief in such situations, and much remains to be done in this regard.
Diffused surface waters moving uncontrolled across the land often can be
the cause of serious erosion problems. And resulting silt and other debris can
in turn cause damage to lower lying lands, stream channels, or drainage canals.
Some indication of the extent to which diffused surface waters are being
put to beneficial use is given by Figure 10. This map shows the number of farm
ponds and irrigation reservoirs which have been constructed with help from the
S. .4 k .. ...-
Soil Conservation Service. As of 1956 the number in Florida totaled 2591. These
structures have the capacity to store for use some $700 million gallons.
About 23 per cent of the surface water moves to the ocean via surface
channels. In its transit it forms many rivers and lakes in Florida and keeps them
in existence. Such waters may be said to fall into the second category mentioned
above -- that of surface waters in natural water courses with well defined banks
and beds. This water, averaging some 40 billions of gallons per day, is of utmost
importance to the state. The course it takes in reaching the sea, how rapidly
it gets there, the bodies where it is temporarily stored, and its fitness for
various uses, determine its value to the state as a natural resource.
The geographical distribution of surface flows in natural watercourses is
extremely poor regardless of the large quantities involved. Of the estimated 40
billion of gallons per day, more than 88 per cent of the flow is found in only 5
rivers the Apalachicola, the Choctamhatchee, the Escaabia, the Suwannee, and the
St. Johns Rivers.
The flow maps show the relative amounts leaving the state via its rivers
HOW WE LEARN ABOUT THE BEHAVIOR OF SURFACE WATER IN FLORIDA
The behavior of water can be separated into that which has happened in the
past and that which we believe will happen in the future. A later section will
deal with the methods used in predicting the future behavior of the water; this
section deals with the past behavior.
Prerequisites to a fund of knowledge of what has occurred up to the pre-
sent is that the events were recorded as they occurred and that the records of the
events have been preserved and are available for perusal. Information on how the
- 11 -
water was behaving has been collected through the years by various groups, includ-
ing federal and state agencies, private companies, and individuals. Some records
have been well preserved; others have been lost or destroyed. Much of the inform-
ation has been disseminated in published form; much of it is retained in the files
of the collecting groups. Federal agencies that collect surface water information
at the present time include the U. S. Geological Survey, the Corps of Engineers,
the U. S. Weather Bureau, and the U. S. Agricultural Research Service. The U. S.
Coast and Geodetic Survey collects information on the coastal waters of the state.
The primary function of the Surface Water Branch of the U. S. Geological
Survey is to collect and publish information on the surface waters of the 48
states, Alaska and Hawaii. Funds furnished by the state are matched dollar for
dollar from federal funds to carry on the work of this agency in Florida. As of
June 30, 1956, the U. S. Geological Survey was operating 129 streamflow stations
and nearly 200 water-level stations in the state.
Surface water information is collected in an effort to provide a continu-
ous inventory of the water. The job is to answer the questions, "Where is the
water?"; "Where is it going?"; and "How fast is it getting there?". The first two
questions are answered geographically by maps and charts showing the lakes, streams,
canals, and the like. Volumetrically, these questions are answered by information
gathered at water-level and streamflow stations.
Ordinarily a water-level station consists of a float-operated instrument,
installed near the bank of a lake or stream, which continuously records on a chart
the height of the water surface. Often, where fluctuations are not rapid, the
station consists of a so-called staff gage mounted in the water in such a manner
that an observer may read and record the height of the surface at intervals.
To obtain a record of stream flow is somewhat more complicated. The most
useful one gives the discharge or rate of flow past the station each day. To
- 12 -
obtain this type of record, a water-level gage is installed in the stream and a
daily record of the lavel obtained. The rate of flow, usually reported in cubic
feet per second (cfs) is measured periodically with a current meter. The relation
between the height of the water level and the rate of flow is determined and the
daily discharge is then computed.
The collection of surface water records in Florida by the U. S. Geological
Survey began about the turn of the century; however, it was not until 1930, when an
office of the Survey was established in Florida, that the amount of information
collected was significant. Since 1930 the scope of the work has increased greatly
in keeping with the ever-increasing importance of surface water to the state. Fig-
ure 11 shows the location of stations at which daily discharge records are being
collected and the major stream basins of Florida. In addition there are records
of 44 stations at which periodic or occasional discharge measurements are made in
Table 1 gives maximum, minimum, and average values of flows recorded in
selected rivers of Florida. It is of interest to note the extremes displayed by
the maxima and minima.
- 13 -
TABLE 1 Flow of Selected Rivers of Florida.
Pine Barren Creek
Santa Fe River
St. Marys River
N. Fork Black Creek
St. Johns River
near DeFuniak Springs
near Ft. White
near Sulphur Springs
- 14 -
in cu. ft./sec.)
PREDICTING THE FUTURE BEHAVIOR OF THE SURFACE WATERS OF THE STATE
In nearly every case where man becomes concerned with surface water he
must make a prediction as to how it will act in the future. In the design of
bridges, for example, the designer wants as estimate of the maximum flow and high-
est stage that will occur; in the design of an intake structure, he wishes to
know the lowest stage that is expected. If a stream is to be used to supply a wa-
ter plant, he wishes to know what the stream is likely to do so that he may pro-
vide the proper reservoir capacity.
Predictions, if they are to be reliable, must be based on past records
and, in general, the longer and more complete the past record, the more reliable
the prediction. Unfortunately, many predictions must be basedjon very short re-
cords because the need was not recognized at the time the record should have begun.
A simple method of predicting is to assume that the worst condition that
has happened in the period of record will happen again in the future. If a more
accurate and more detailed prediction is required, statistical methods are gener-
ally used. These methods have the further advantage of being able to indicate the
probable accuracy of their predictions.
A simple but useful device is the duration curve. In Figure 12 the stage
record of Lake Hatchineha near Haines City has been rearranged to show the per cent
of time (in the period 1942-1955) that the water was at or above various eleva-
tions. For example, 39 per cent of the time it was at or above 52 feet; 95 per cent
of the time it was at or above 49 feet. A valid assumption is that this curve re-
flects what probably will happen in the future, barring drastic changes in the
channels that lead into or out of this lake.
- 15 -
Topographic maps have broad fields of application and are of considerable
value to anyone making use of the land. Although such maps do not constitute an
integral portion of the water resources of Florida, they are neededni',combittson
with problems of irrigation, drainage, run-off, water diversions, deliniation of
ground water recharge areas and other such studies. In addition they fulfill a
need recognized by agricultural, industrial, municipal and recreational interests
wherever any planning for water use is involved. The U. S. Geological Survey map-
ping program, which was started in Florida over 60 years ago, is the basic mapping
program of the state, although other agencies (e.g., the State Road Department)
often conduct less comprehensive mapping projects.
Topographic maps are essential for national defense. In this respect,
Florida is fortunate since the military establishments in the state have necessi-
tated that much mapping be done by the Survey. There is a total of about 54,000
square miles in the state of Florida, of which about 59 per cent (32,000 square
miles) is covered by maps of the U. S. Geological Survey. The extent of this cov-
erage is indicated in Figure 13. Some of the maps in this area, however, were sur-
veyed as early as 1890 and, as a consequence, a significant portion of this work is
badly out of date, and remapping is required in order to provide maps for present-
At present mapping is in progress on an additional 14,000 square miles, or
26 per cent of the state area. The status of the map in this area ranges from
completion of the aerial photography to the publication of the completed maps. The
coverage is indicated in Figure 13. According to information received from the
Survey, only a modest amount of work is scheduled to be started during the next two
years and will cover about 1,700 square miles, leaving about 7,000 square miles
upon which no work has been done. The Survey's long-range mapping program
_____________________ ______________________ -
contemplates coverage of the state in about 20 years, but there are areas within
the state upon which topographical information is needed now to complete water
resources studies currently underway. There is a great need for maps covering
about 5,000 square miles in order to provide information on drainage areas to aid
in the analysis of stream flow records. Wherever the need for topographical maps
is pressing and cannot be fulfilled under the existing or planned federal program,
cooperative mapping projects may be initiated to expedite the work. The arrange-
ment requires sharing the cost of the work on a 50-50 basis with the federal gov-
ernment. At present, Florida is the only state that has not entered into a coop-
erative agreement with the U. S. Geological Survey in its topographical mapping
program. There are, however, some areas in the state in which a cost-sharing pro-
gram of this nature is desirable to furnish information for needed water resources
- 17 -