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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY





FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director




REPORT OF INVESTIGATIONS NO. 15





SALT-WATER STUDY OF THE MIAMI RIVER
AND ITS TRIBUTARIES,
DADE COUNTY, FLORIDA

By
S. D. Leach and R. G. Grantham
U. S. Geological Survey








Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with
DADE COUNTY
and
THE FLORIDA GEOLOGICAL SURVEY


1966










FLORIDA STATE BOARD

OF.

CONSERVATION





HAYDON BURNS
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





LETTER OF TRANSMITTAL


W1



Jflorida Gjeological Survey

Tallaassi.ee

August 16, 1966

Governor Haydon Burns, Chairman
State Board of Conservation
Tallahassee, Florida
Dear Governor Burns:
Messrs. S. D. Leach and R. G. Grantham, of the Water Resources
Division of the U. S. Geological Survey, have completed a study
of the Miami River and its tributaries in Dade County, and the
relationships of these tributaries to salt-water intrusion in the
area. The report will be published as Report of- Investigations
No. 45. The study was done in cooperation with the Division of
Geology, of the State Board of Conservation, and Dade County,
and outlines the main trend of the water resources of the Miami
area.
The Biscayne aquifer, which is composed of highly permeable
limestone, is being intruded upon by salt water along any canal
or stream that connects the aquifer to salt water. It has been found
that this intrusion could be prevented and reversed by careful
management of the water resources of the area by the construction
of salinity control dams near the coast, and through the judicious
development of water.
Respectfully yours,
Robert O. Vernon
Director and State Geologist






















































Completed manuscript received
August 16, 1966
Published for the Florida Geological Survey
By Rose Printing Company
Tallahassee
1966






CONTENTS

Page
Abstract ---.-----------.-------. ----. ....-...-.....--......---.. 1
Introduction ..--.- ---..---.. --..--. ..-.--.- ---------------......--... ........-........ 2
Area of investigations .--..... ........---.... ---... .... ... ..---..... .....-. ...-.. .......-- ... 4
History of salinity-control dam operation in the Miami Canal --...---..... 6
Rainfall in the Miami River drainage basin ...-----... --------...............-------- 8
Long-term hydrology- ...................--------- -------..---------. 9
Discharge in the Miami Canal ---....-............ .------.-.........-..---..--...--- 9
Water levels in the area of investigation --..--..-..--.....-----..--.......--......--.. 10
Water-level comparison between Miami River and Biscayne Bay ....---.. 11
Salt-water movement in the Miami River ----------- --------- -------- 14
Short-term comparison of chloride with water levels and discharge .--.-- 19
High and low tide salt-water movement ..........-........---.-------- .-----. 23
Chloride concentration extremes --.......-------------..--------...---. 23
The 1945 drought -..- --_ .-- ......------___.....---.-------------. ------25
Chloride concentration in the aquifer .........---.------------------- 25
Discharge at selected locations .------...--. ....-----------.------- 28
The effects of wind on water movement -----...----.....-------------..---..--- 31
Summary -----.--- ............-------...----------------.--........... 33------------3
References .----........... -------------------- ------------- 35


ILLUSTRATIONS

Figure Page
1 Map of the Greater Miami area showing the major canals and the
area investigated ...--...----............----- .. -------------...............---- 4
2 Map of the Miami River and its tributaries showing data-collection
sites in the area investigated ................-........--------------............ 5
3 Photographs of successive salinity-control dams in the Miami Canal
at N.W. 36th Street ......--------.....----...................---..........- -------.----.. 7
4 Graph of monthly mean rainfall, monthly extremes, and the year
the extremes occurred based on the averages of Hialeah, Pennsuco,
and Pennsuco 5 N.W. (Broken Dam) rain gages for the period
1944 through 1963 .-..---.... .--.......-- ...----------- ..---- ..------ .. -- ---- 8
5 Graphs showing monthly and annual mean discharge in the Miami
Canal above N.W. 36th Street control dam and the total an-
nual and monthly rainfall for the three rain gages in the Miami
Canal drainage basin --........--- ...........................------ --------. ..-----...--- 9
6 Graphs of water levels at three selected Miami Canal stations and
one Biscayne Bay Station, from 1944 to 1963 ----_--- --------------- 11
7 Hydrographs of monthly high, low, and average water elevations in
the Miami Canal at N.W. 27th Avenue and at Biscayne Bay, based
on 18 years of record'1946 to 1963 ....-.....................-------------...... ---- 12
8 Graphs showing a mean water-level elevation, mean high and low
water from the N.W. 36th Street control dam to the mouth at Bis-
cayne Bay, based on 18 years of record 1946 to 1963 ....---.-......---- .. 13
9 Graph showing percentage of time water containing 1,000 ppm
chloride was at or above various locations in the Miami Canal for
the period May 1945 to March 1958 -......--..........-------............ ----- 15






ILLUSTRATIONS


Figure Page
10 Graphs showing position of the 1,000 ppm chloride content in the
Miami Canal for the period January 1940 to March 1958 .---........---. 16
11 Graph showing relation between monthly mean discharge in cfs and
the location of water containing 1,000 ppm chloride in the Miami
Canal ..............--.... ..... .... .............---------------------........ .......... .......................-- 17
12 Graphs showing chloride concentration in the Miami Canal during
a typical wet year (1948) and a typical dry year (1956) .............. 18
13 Graphs showing the effect of changes of the N.W. 36th Street con-
trol dam on discharge,water levels, and chloride content at selected
locations in the Miami Canal from July 12 to 19, 1964 ..--..-.........-- 20
14 Graphs showing the effect of changes of the N.W. 36th Street con-
trol dam on discharge, water levels, and chloride content at selected
locations in the Miami Canal during the period August 14 to 19,
1964 .......................-.... -......---------------........... --... .........- ....- --.....--- ......----- 21
15 Profile of chloride content in the Miami Canal on July 16, 1964 at
low and high tide when the N.W. 36th Street control dam was par-
tially open .--- --.....--........ -- --.. ....... ...--. ......--. .--.------ -------- 22
16 Graphs showing chloride extremes at high tide in the Miami River
and the Miami Canal at various sampling locations ........--------...... 24
17 Graphs showing an extreme chloride concentration in the Miami
Canal above the N.W. 36th Street control dam on May 31, 1945 ... 26
18 Map showing salt-water encroachment at the base of the Biscayne
aquifer 1904-62 (Parker and others, 1955, p. 589), (Kohout, 1961)
updated ..- .-......................... .....-.--........ ................-- -............-.......... ......-... 27
19 Graphs showing monthly mean discharge at selected locations in
the Miami and Tamiami Canals, October 1960 through September
1963 ..........................................-...-..--.... ..-................................................... 29
20 Graph showing monthly mean discharge from or into the aquifer
below the control dams in the Miami River and its tributaries,
April 1961 through September 1963 ...............-------------------........................---- 30
21 Graphs showing the effects of Hurricane Cleo's winds at selected
discharge and water-level stations in the Miami Canal and Bis-
cayne Bay, August 26-27, 1964 -........----.............------ ..--- ----- 32









SALT-WATER STUDY OF THE MIAMI RIVER
AND ITS TRIBUTARIES,
DADE COUNTY, FLORIDA

By
S. D. Leach and R. G. Grantham


ABSTRACT
The main threat to water resources in the Miami area is salt-
water intrusion into the highly permeable Biscayne aquifer.
Saltwater pollution of the aquifer may be held at its present loca-
tion or moved seaward by raising the fresh-water levels in the
ground by increasing fresh-water heads behind the control dams,
or by moving the controls farther downstream in the canals.
Analysis of available data indicates that water containing
1,000 parts per million or more of chloride in the Miami Canal
is immediately downstream from the salinity-control dam at
N.W. 36th Street approximately 23 percent of the time and at
N.W. 27th Avenue about 60 percent of the time. Also, an analysis
of flow data indicates that when the discharge of the Miami
Canal at N.W. 36th Street is approximately 280 cubic feet per
second or less, the salt-water wedge is located at the downstream
side of the control dam at N.W. 36th Street. With the present
location of the control dams a minimum discharge of 550 cubic
feet per second would be required to hold the salt-water wedge
downstream from N.W. 27th Avenue.
The fresh-water discharge from 60 percent of the aquifer in
the Miami River and its tributaries below the control dams would
be salvaged by moving the controls downstream from the con-
fluence of the Tamiami Canal.
With reference to proposed downstream locations of controls,
it was determined that during dry years, as experienced in
1961-62, there would be a discharge of about 55 cubic feet per
second available for boat lockages in the Miami Canal at N.W.
27th Avenue and about 30 cubic feet per second in the Tamiami
Canal at LeJeune Road.
When a severe hurricane is imminent for the lower southeast
coast of Florida, the salinity controls in the major canals in Dade
County are generally fully opened before the hurricane strikes to
1






FLORIDA GEOLOGICAL SURVEY


reduce the possibility of flooding. High storm tides as a result of
strong easterly winds push large quantities of salt water up-
stream. This invasion of salt water above the opened controls
may contaminate the aquifer as well as increase the threat of
flooding. If the salinity controls were redesigned so that they
could be closed when the flow starts to reverse during hurricanes,
they could more effectively protect the area from floods, salt-water
encroachment, and better conserve the fresh-water resources of
the area.
The chloride records indicate the present controls in the Miami
and Tamiami Canals have proven to be barely adequate in pro-
tecting the City of Miami's Hialeah-Miami Springs well field
from salt-water contamination during the dry years. If the ex-
treme conditions that were experienced in the early sixties were
to recur along with increased withdrawals from the fresh-water
supply for public use, the salt water might move inland to the
extent that it could cause some reduction in the capacity of the
Hialeah well field to supply the fresh-water needs of the area.


INTRODUCTION

The Miami River has the largest discharge of all rivers in
southeastern Florida, and serves as the outlet for the Miami and
the Tamiami Canals. The widening and deepening of the Miami
River and the construction of the Miami and Tamiami Canals
have been beneficial in flood control but have increased the threat
of salt-water encroachment. The primary purpose of the investi-
gation is to present a study of the salt-water movement in the
Miami River and Canal and its effect on the fresh-water supply
of the area.
The rapid growth of population and industry in Dade County
has placed an ever-increasing demand on the available fresh-
water supply. A major part of the water supplies come from the
City of Miami's Hialeah-Miami Springs well field, and it is es-
sential that contamination by salt water continues to be prevented.
Two possible ways to accomplish this are to (1) hold higher
heads of fresh water behind the controls; or, (2) relocate the con-
trols downstream. However, holding higher heads of water behind
the controls may not be practical because much valuable low
land would be flooded. Relocating the control dams farther down-
stream would furnish additional protection against salt-water






REPORT OF INVESTIGATION No. 45


encroachment in the Biscayne aquifer and provide a widening of
the fresh-water safety zone between the salt water and the
Hialeah-Miami Springs well field. As the metropolitan area places
an ever-increasing demand on the available fresh-water supply,
there is a need to conserve as much fresh water as possible. In
connection with this conservation the study of the movement of
the salt-water wedge in the Miami River and its tributaries will
provide one additional tool to better understand and manage
the water resources of the area.
Salt-water intrusion historically has been the chief threat to
the water resources of the Miami area. This report, prepared in
cooperation with Dade County, gives detailed attention to the
movement of salt water in the Miami River and its tributaries.
The major hydrologic features in greater Miami and the area
investigated are shown in figures 1 and 2. Salt water in the
canal moves in response to the operation of salinity-control dams
located in the Miami and the Tamiami Canals (fig. 1). Other
factors that affect movement of the salt water in the Miami
River and its tributaries are as follows: Fresh-water discharge
through the controls; seaward movement of water in the aquifer
downstream from the controls; rainfall and evaporation; tidal
cycles, and seasonal changes in the tidal oscillations in Biscayne
Bay. Of the above factors, only the fresh-water discharge can be
easily controlled by man. Even in the operation of the control
dams he is limited by the available supply of fresh water. In this
endeavor hydrologic knowledge is a prerequisite to conserving as
much of the available fresh water as is safely possible without
inland flooding.
The investigation was made in cooperation with Dade County
and was under the general supervision of A. O. Patterson and
K. A. MacKichan, Ocala District Engineers of the Surface Water
and Quality of Water Branches, and subsequently, R. W. Pride,
acting District Engineer, Surface Water Branch, and C. S. Con-
over, District Chief, Water Resources Division of the U.S. Geo-
logical Survey.
Thanks are extended to F. D. R. Park and M. C. Brooks,
Water Control Engineeers of the Water Control Department,
Public Works Department of Dade County, for furnishing the
operation log of the Miami Canal salinity-control dam and the
chloride concentrations during 1961-62. C. F. Wertz, Director,
Department of Water and Sewers, City of Miami, furnished
photos of the salinity dams in the Miami Canal.






FLORIDA GEOLOGICAL SURVEY


Figure 1. The Greater Miami area showing the major canals and the area
investigated.

AREA OF INVESTIGATION
The area investigated in this report is the Miami River which
extends from Biscayne Bay to N.W. 27th Avenue, the Miami
Canal from N.W. 27th Avenue west to Levee 30, and the lower
reach of the Tamiami Canal (See figs. 1 and 2).
Samples of the fresh water taken between 1946 and 1958 in the














AIO CA z N. W 20h 0
A4 A so1 L1
Ni 1\ 2 |




MN.W. 7 th STh ST
BLUE "GOON L NKE

WEST FLAGLR ST.
EXPLANATION
--- CHLORIDE SAMPLING SITE TAMIAMI TRAIL
CONDUCTIVITY RECORDING GAGE
--- WATER LEVEL RECORDING GAGE
DISCHARGE
O3- WATER LEVEL RECORDING GAGE ILES
==*-- CONTROL DAM
0.5 0 0.5 I


Figure 2. Miami River and its tributaries showing data-collection sites in the area investigated.






FLORIDA GEOLOGICAL SURVEY


Miami Canal west of the salinity-control dam indicate that chlo-
ride concentration generally ranges between 10 and 15 ppm
(parts per million). This small amount of salt contamination
comes from the fresh-water contact with the rock aquifer and the
soil materials in the Everglades. The chloride concentration of
the fresh water varies slightly with seasonal changes in rainfall
and runoff from the area, and averages about 12 ppm for the
Miami Canal west of the salinity-control dam.
The main area covered in this report is the diluted zone
between the average chloride concentrations of 12 ppm in the
fresh water to the west of the salinity-control structures and
the average chloride concentrations of about 19,000 ppm in Bis-
cayne Bay. The area between these ranges is undergoing an ever-
continuing battle between the fresh water and its higher heads
and sea water and its density current. The greatest degree of
variability in salt-water content occurs in this reach. Therefore,
the main emphasis of the report is on this section.


HISTORY OF SALINITY CONTROL-DAM OPERATION
IN THE MIAMI CANAL
In 1945 salinity-control dams were installed in most of the
canals in the Miami area as barriers against further encroach-
ment of salt water in the Biscayne aquifer. The dams were con-
structed across the canals by driving sheet-steel piles into the
limestone aquifer.
On the Miami Canal four salinity control dams in the vicinity
of N.W. 36th Street have been in operation during various periods.
Their purpose was to furnish protection to a Miami municipal
well field located upstream. The first control dam of sheet-piling
was in operation from December 1939 to June 1942, when it
was replaced by a pneumatic dam. The pneumatic dam remained
in operation until it failed in March 1945. The high rise in
chloride concentration at that time may be noted in the figure on
page 16. Ten days later a temporary sheet-piling dam was in-
stalled and remained in operation until 1946 when the present
sheet-piling control dam was constructed. The present control dam
in the Miami Canal is operated by removing alternate steel piles
(called needles) during the wet periods and replacing them during
the dry periods. Photographs of various salinity-control dams in
the Miami Canal at N.W. 36th Street are shown in figure 3.























Original sheet-piling dam (1939-42)


5.. I.. .,

K u B, S| ^ ..... ^t, ^ -OK---


Pneumatic dam (1942-45)


Temporary sheet-piling dam (1945-46)

Figure 3. Successive salinity-control dams in the Miami Canal at N.W.
36th Street.





FLORIDA GEOLOGICAL SURVEY


RAINFALL IN THE MIAMI RIVER DRAINAGE BASIN
The area depends chiefly on rainfall for its available fresh-
water supply. The rainfall in the Miami River drainage basin
averages 57 inches per year. Extremes range from 74 inches in
1959 to 38 inches in 1951. The average and extremes are based
on 20 years of record (1944 through 1963) from three rain gages.
The rain records used in this report (fig. 1) are Hialeah, Penn-
suco 5 N.W. (Broken Dam), and Pennsuco. The monthly mean
rainfall for the above period is shown in figure 4. Rainfall for
the wet period, May through October, averages .44 inches or 71
percent of the average annual rainfall; rainfall for the dry
season, November through April, averages 13 inches per year.
Also shown in figure 4 are the monthly extremes and the year
in which they occurred.

1958 1957 1959 1957 1958 1962 1946 1956 1948 1952 1959 1957
2z 0 '.i ...i:- -


1 6 il iiIiii iiiiii iiiiii l




z 10

M8AN
.2 !ii~iiii.iiiiiiiiiii fjii g < - ^ --ai- \-' ii ili









1951 1944 1956 1946 1945 1952 1963 1954 1961 1962 1952 1961
Jan Feb Mar Apr May June July Aug Sept Oct Nov Dec
Figure 4. Monthly mean rainfall, monthly extremes, and the year the ex-
tremes occurred based on the averages of Hialeah, Pennsuco, and Pennsuco 5
N.W. (Broken Dam) rain gages for the period 1944 through 1963.







REPORT OF INVESTIGATION NO. 45 9


LONG-TERM HYDROLOGY


DISCHARGE IN THE MIAMI CANAL


The discharge of the Miami Canal depends on rainfall and the
operation of the salinity-control dam at N.W. 36th Street; The
monthly mean discharges of the Miami Canal at the salinity-
control dam, shown in figure 5, were determined from the gaging
stations located in the Miami Canal opposite the City of Miami's
water plant, and at N.W. 36th Street (figs. 1 and 2). The station
at the water plant was operated prior to February 1959, and the
N.W. 36th Street station was operated thereafter. A comparison
of overlapping records from the two stations indicates that the
discharge measured at the water plant exceeds that at N.W. 36th


roo
2 300
z





wo
, 31200
S2800-

R 2(00



2 1A00 *



800:


*45391T4.71 2 W5_7.35 0 P7Q 6 C


4i

h -; n


TOTE
*L" 7
_.-.:~iS

j-


L ANNUAL RAI
6i 2.58


IFAL, ININCHES ----
"1955 519 1957 16698 73164 3 11252 5311








195591956 15198 195196 961962 1963


Figure 5. Monthly and annual mean discharge in the Miami Canal above
N.W. 36th Street control dam and the total annual and monthly rainfall for
the three rain gages in the Miami Canal drainage basin.


944 1945 19461 1


91I 51 1195 1954i Bf


119441145119461 7 BOA


I





FLORIDA GEOLOGICAL SURVEY


Street by about 5 percent. As the difference in discharge between
the two stations was small, the records were considered com-
parable without adjustments and were used consecutively in figure
5. The total monthly rainfall in figure 5 is the average of three
rain gages in the drainage basin. The total annual rainfall, the
annual mean discharge, and the operation of the salinity-control
dam are also shown. The annual discharge (runoff) from the
drainage basin does not correlate with the annual rainfall during
wet periods because the excessive runoff lasts several months
into the next year. On the other hand, the discharge shown in
figure 5 does compare with the movement of salt water (see figure
on page 16) in the Miami Canal. During times of peak discharge
the 1,000 ppm chloride front is downstream in the canal, and in
periods of low flow the 1,000 ppm chloride front moves upstream to
the salinity-control dam. Further comparison of figures 5 and 10
indicates that there is very little lag in the salt-water movement
in relation to fresh-water discharge.


WATER LEVELS IN THE AREA OF INVESTIGATION
Long-term monthly mean water-level fluctuations in three
selected Miami Canal recording stations are shown in figure 6.
The Miami Canal at Broken Dam and Miami Canal at N.W. 36th
Street recording stations are located above the salinity-control
dam as shown in figures 1 and 2. The slope in the Miami Canal
may be determined from figure 6 by comparing the water levels
at Broken Dam gage (located to the west and 2 miles downstream
from Levee 30) and with those at the N.W. 36th Street gage
(just upstream from the salinity-control dam). An examination
of the records of the past 20 years (figs. 5 and 6) shows that
wet and dry cycles have lasted for several years.
When the discharge is high, the slope in the upper reaches of
the Miami Canal above the salinity-control dam is greatest, as
shown during the wet years 1947-49, 1953-54, and 1958-60.
During the dry years, when the mean annual discharge is less
than 600 cfs (cubic feet per second) at the N.W. 36th Street
salinity control, the difference in water level between Broken
Dam and N.W. 36th Street gages is less-indicating a decrease
in the slope of the canal during these years. A comparison of
the monthly mean water level in the Miami Canal at N.W. 27th
Avenue and at Biscayne Bay (fig. 6) shows they closely follow






REPORT OF INVESTIGATION NO. 45


J-- 77





S ,MI I C ANAL AT 3T 3 SREET ABOVE DAM)










I 9 4 ,94 1 94" 94 9 19 194 94 1 952 195 I 195, Jj I 1955 1956i 19.'57 1958 19s9 9019 1,I 19 63

Figure 6. Water levels at three selected Miami Canal stations and one Bis-
cayne Bay station, from 1944 to 1963.

each other except during the extremely wet years when the runoff
was high.


WATER LEVEL COMPARISON BETWEEN MIAMI RIVER
AND BISCAYNE BAY

Graphs of the mean monthly high, low, and average water
elevations of the Miami Canal at N.W. 27th Avenue and of Bis-
cayne Bay are based on 18 years of record from 1946 through 1963

as shown in figure 7. The seasonal changes in the average elevations
of Miami Canal at N.W. 27th Avenue and of Biscayne Bay (fig. 7)
are generally low around the beginning of the year, rise gradu-
ally until October, and then decline rapidly until the end of the

year.
Comparison of the monthly mean elevations of the record
shows that the Miami River always has a seaward gradient. This

indicates that even when the flow at the control in the Miami






FLORIDA GEOLOGICAL SURVEY


MIAMI CANAL AT N.W. 27th AVE.


BISCAYNE BAY


Figure 7. Monthly high, low, and average elevations in the Miami Canal
at N.W. 27th Avenue and at Biscayne Bay based on 18 years of record from
1946 through 1963.



and Tamiami Canals is nil, there is generally a discharge from the
aquifer to the Miami and Tamiami Canals in the reaches below
the present controls, except during extremely dry periods. The
fresh-water discharge from 60 percent of the aquifer could be
saved by moving the control downstream in the Miami Canal
below the confluence with the Tamiami Canal. The total monthly
mean flow from or into the Biscayne aquifer downstream of the







REPORT OF INVESTIGATION NO. 45


control dams from April 1961 to September 1963 is shown in
the figure on page 30.
If past conditions are repeated in the future, the mean high,
mean low, and average water levels shown in the Miami Canal
at N.W. 27th Avenue (fig. 7) would be experienced below any
control constructed at that location.
The annual mean high water, mean low water, and average
water-level elevations are shown in figure 8. By the use of
figure 8, the mean high water, mean low water, and the mean
water-level elevations may be determined throughout the lower
reaches in the Miami Canal below the N.W. 36th Street control


W
W-J
iij i
W f f "
02 0 U LU L
U_-I 2 F >
2-Ir .I I
>.L LU .c -T .
-J -
ID r- c^ r*-


_ -
I- ac




o 0
01 Kz
I- (TJ z Opf

J) Z) Iz


DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 8. Mean water-level elevation, mean high and low. water from the
N.W. 37th Street control dam to the mouth of Biscayne Bay, based on 18
years of record, 1946 to 1963.






FLORIDA GEOLOGICAL SURVEY


dam. The average annual gradient from the N.W. 36th Street con-
trol dam to Biscayne Bay is about 0.6 foot in 5.5 miles. The mean
annual water-level elevation of Biscayne Bay is 0.48 foot above
msl (mean sea level) datum of 1929, based on 18 years of
record (1946-63).


SALT-WATER MOVEMENT IN THE MIAMI RIVER
The Geological Survey has collected chloride data in the
Miami River and Canal from 1940 to June 1958 and from 1962
to 1964. The chloride samples were collected bi-weekly or monthly
from the bottom of the canal at or near high tide when the
upstream advance of salt water was at its greatest penetration.
The location of the sampling sites were in most cases bridges
from which the sampler could be lowered by a line to the deepest
section of the canal. The accessibility of these bridges by car
enabled the field men to move rapidly from station to station
in order that all samples might be taken as near high tide as
possible.
Prior to this study the objective was to determine the location
of the 1,000 ppm chloride concentration by collecting salinity
samples in the canals. Frequently, it was possible to determine
the location of the 1,000 ppm chloride concentration by taking a
relatively few samples. Thus all sampling stations were not
visited each sampling period.
The locations of periodic salinity sampling stations and their
distance, in miles, from the mouth of the Miami River at Bis-
cayne Bay are shown in the following tabulation:


Locations
Miami River at Brickell Avenue
Miami River at Miami Avenue
Miami River at West Flagler Street
Miami River at N.W. 7th Avenue
Miami River at N.W. 12th Avenue
Miami River at N.W. 17th Avenue
Miami Canal at N.W. 27th Avenue
Miami Canal at Seaboard
Airline Railway Bridge
Miami Canal below
N.W. 36th Street control dam


Miles from Biscayne Bay
0.10
0.40
1.10
1.57
2.11
2.65
3.83

5.32


5.45






REPORT OF INVESTIGATION No. 45


Locations (Continued) Miles from Biscayne Bay (Con't)
Miami Canal above
N.W. 36th Street control dam 5.48
Miami Canal at N.W. 36th Street 5.56
Miami Canal at N.W. 54th Street, (Hialeah) 7.06

In addition, two continuous conductivity recorders were
placed in the Miami Canal at N.W. 27th Avenue and below the
N.W. 36th Street control dam. These recorders were used to indi-
cate the continuous movement of the salt-water wedge during
tidal oscillations of the Miami Canal. Also, hydrologic data were
collected from eleven water-level recorders, six discharge stations,
and three rain gages at the locations shown in figures 1 and 2.
Beginning in January 1940 and continuing for a period of
18 years, chloride samples were taken bi-weekly at selected points
on the Miami River. The data were arranged to show the per-
centage of time that the chloride content was 1,000 ppm at selec-
ted points in the Miami River. Figure 9 shows that water con-
taining 1,000 ppm or more of chloride was at N.W. 27th Avenue


0 1 2 3 4 5 6
DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 9. Percentage of time water containing 1,000 ppm chloride was at
or above various locations in the Miami Canal for the period 1945 to March
1958.







16 FLORIDA GEOLOGICAL SURVEY

60 percent of the time, and extended as far upstream as the
control dam at N.W. 36th Street 23 percent of the time. The loca-
tion of the 1,000 ppm isochlor is shown in figure 10. During

SHEET PILE DAM PEM -- IAM




-0.T- rEMPo ---- DAM PRmTESENT EET PILE DAM-
*0 :- -- i-rI+p-T=-[- rL --.|r[-~WArTTTER; -PLA-FNT__p, ......Jt i_,.;
S' l T PLANT
-T NW. 2T AVE.






A-- L -,-e I SLP &
-----tdTEMP0 RA Y PRESENT SH EET PILE DAM


'0 7r -7 r -- r 7 r T 1 I rL I I r T-' r 1 -! I i I I I- I i I I


*: .:'-;t:4: : r t i.f^ + ^^ g4T^ I g 1 ,i :' WATER PLANT



J Mull:A. 'JJAS ND FuiAA'MlM J A s[o AOj D J U A llilujJ _S ND FiAAl S T N D


1955 1956 I19 1948 194




Figure 10. Position of the 1,000 ppm chloride content in the Miami Canal
1 rE.-ENT SHEET PILE DAM












for the period January 1940 to March 1958.


drought periods, 1943-45 and 1950-52, the 1,000 ppm chloride
front was at the N.W. 36th Street control dam a much greater






percent of the time. Since March 1946, when the present dam was
installed, the 1,000 ppm chloride front has rarely gone above the
p _,,.--;- +--'----' n: rr;+r- ++ t+ + + ,+[ +- "' VE"- + ,w.,-.'
,F-1- E- I! :+ 1. i I N 2VAVE
+ + I WI 1 r ?i L --.1 + E-;71: I I ~ 5-rl::il.):'| : I ?-AVE


















control dam. On May 18, 1951 the chloride was 1,550 ppm just
F0igur0 sto o e 1,0 pp Te o t n h 1














the salinity-control dam in the Miami Canal and caused salt water
to move upstream. During the 18 years of record the 1,000 ppm





chloride front reached the dam at least once during most years;
relatively high all y the 1,000 ppm chloride 1 e ne a e hie






front remained below 27th Avenue. Records show that prior to
building the present 36th Street dam it was normal for the 1,000
fron re000maine blow 27th Dveue Reords show that Jpro -A









ppm chloride front to extend into and even beyond the Hialeah
area during dry years.






REPORT OF INVESTIGATION NO. 45


When fluids of different density meet, they remain relatively
unmixed. The difference in density between fresh and salt water
affects the movement of water in the tide-affected reach of a river.
When the tide is rising in the Miami Canal the denser salt water
moves upstream as a wedge beneath the seaward-moving fresh
water. The salt-water wedge continues to move upstream until the
tidal force is equalized by the force of the discharging fresh
water or until the tide reverses. During dry periods, when there
is little or no discharge, salt water may move far enough up-
stream to contaminate the fresh ground-water supply.
The salt-water wedge advances farthest inland along the
bottom of a tidal canal at or near high tide. At high tide the
salt-water wedge is relatively blunt, and the distance it moves
inland along the bottom of the canal is comparable to the 1,000
ppm chloride shown in the figure on page 22. Therefore, the
movement of the 1,000 ppm chloride was used as an index to de-
termine the movement of the salt-water wedge (fig. 10). The
distance in miles above the mouth of the Miami River at Biscayne
Bay that the monthly average of 1,000 ppm chloride remained (fig.
10), was compared with the monthly mean discharge (fig. 5) to de-
termine the distance downstream from the salinity-control dam
that various discharges move the salt-water wedge. This relation
shown in figure 11 was developed from data collected from January


S I I I N.W. 36 CONTROL DAM
5 ------_
0 -0o 0
o 00 MIAMI CANAL
0 O ---N.W. 271h AVENUE--

-9 -o-0


0 oo1
I o

0 MONTHLY MEAN POSITION OF THE 1000 PPM CHLORIDE
nL I I I I I I I I I I I ,
0 200 400 600 800 1,000. 1,00 1,400 1600 1,00 2000 2,200 2.400
DISCHARGE, IN CUBIC FEET PER SECOND

Figure 11. Relation between monthly mean discharge in cfs and the loca-
tion of water containing 1,000 ppm chloride in the Miami Canal.




FLORIDA GEOLOGICAL SURVEY


1940 through February 1958, and suggests that a minimum dis-
charge of 280 cfs is required to move the salt-water wedge away
from the base of the salinity-control dam at N.W. 36th Street.
Also the graph indicates that approximately 550 cfs is required
to hold the salt-water wedge as far downstream as N.W. 27th
Avenue. Discharge from the Tamiami Canal and flow from the
aquifer to the canal downstream from the controls .also contributes
to holding the salt-water wedge downstream. During the period



5 5 NW 36st DAM
SEABOARD R.R.
^ "*^ i i ----------


4.5


-I 4.0- -
NW 27 AVE
1948!
3 5- .- -


3.0
] .NW 17 AVE
NW 12 AVE



NW 36st. DAM

L 1956 1

3: 4 1 w M
0
0 4.5


4.0-
NW 27 AVE


2.5 NW 12 AVE

JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 12. Chloride concentration in the Miami Canal during a typical wet
year (1948) and a typical dry year (1956).




REPORT OF INVESTIGATION NO. 45


1940 to 1958, when the salinity samples were taken in the canal,
the Tamiami Canal discharge was measured only from January
1940 through June 1943. Therefore, discharge of the Miami Canal
was taken as an index of the hydrologic conditions and was
used to determine the position of the inland extent of the salt
water wedge in the canal.
Chloride concentration during a typical wet and dry year is
shown in figure 12. The wet year 1948 was selected as it was the
only year in which discharge remained above 400 cfs throughout
the year and was above 1,900 cfs at the beginning and end of
the year. The dry year 1956 was used because, except for January
and February, the discharge remained generally below 400 cfs all
year. During the wet year 1948 the 1,000 ppm chloride remained
downstream from the N.W. 36th Street control but, during the
1956 dry year water containing 1,000 ppm or more of chloride
was at the bottom of the canal at the dam from March through
August, with 5,000 ppm on the downstream side of the control
in April, June, and August, and 10,000 ppm chloride in May. A
comparison of figures 5 and 12 shows a close relation between
discharge at the N.W. 36th Street control and the movement of
chloride in the Miami Canal.


SHORT-TERM COMPARISON OF CHLORIDE
WITH WATER LEVELS AND DISCHARGE
A comparison of water levels, discharge, and chloride content
at selected stations is shown in figures 13 and 14. At noon on
July 14 (fig. 13) the Miami Canal at N.W. 36th Street control
was reduced from 4 full needles and 4 one-half needles open to
4 one-half needles open; the mean daily discharge dropped from
about 300 cfs to 100 cfs. The stage above the control rose from
about 1.0 foot above msl on July 13 to about 1.75 feet on the 14th.
During that period the chloride content at N.W. 27th Avenue
increased from less than 1,000 ppm to 3,000 ppm. On July 15
at 2:30 p.m. the control opening was increased by 4 full needles
and the discharge increased to more than 200 cfs. Water levels
above the control declined to about 1.25 feet above msl and the
chloride dropped below 1,000 ppm. It is noted that when the dis-
charge through the control ranged from about 400 cfs at low
tide to about 200 cfs at high tide, the chloride of the water at
27th Avenue remained generally below 1,000 ppm. However, when








FLORIDA GEOLOGICAL SURVEY


JULY. 464
12 13 14 Is It
"r=Tr---'-


rI \ I\/\ I -- CANAL AT NW 36" STREET
I\ n It '


I? Is I9


400
I---


300
W- .-.2-'.0
.> TAMANI CANAL. AT 8 AVEd E
W 0 too0
to
o0


I

a.

n


Figure 13. The effect of changes of the N.W. 36th
discharge, water levels, and chloride content at selected
Canal from July 12 to 19, 1964.


Street control dam on
locations in the Miami


the discharge ranged from 300 cfs to 275 cfs at low tide to be-
tween 130 cfs and 100 cfs at high tide, the chloride content
generally rose above 1,000 ppm during each high tide. The hy-
drographs also show that small changes in the control at N.W.
36th Street have a negligible effect on water levels at N.W. 27th
Avenue.
A representative period of relatively low discharge, August
14-19, 1964 (fig. 14) has been selected to demonstrate the relation
between the discharge, water levels, and chloride concentration
in the Miami Canal. During August 14-16 when the discharge
generally declined, the chloride content below the salinity control
at N.W. 36th Street increased. When the control opening was
increased from 2 half needles to 1 full needle and 4 half needles


i.-






REPORT OF INVESTIGATION NO. 45


Figure 14. The effect of changes of the N.W. 36th Street control dam on
discharge, water levels, and chloride content at selected locations in the Miami
Canal during the period August 14 to 19, 1964.


at 10:30 a.m. on August 17, the salt-water front was forced down-
stream, as shown by the decline in chloride below the control and
at N.W. 27th Avenue (fig. 14.) Even when the control structure
was changed to 4 half needles open at 2:00 p.m. on August 18,
the chloride remained downstream at N.W. 36th Street through
August 19. On the other hand the chloride content at N.W. 27th
Avenue again began to increase on August 19. The maximum
chloride advances occurred about high tide on each cycle as shown
in the N.W. 27th Avenue salinity and stage hydrographs. At low
tide when the gradient in the Miami Canal is at its greatest, the
discharge increases and the salt water again moves in a seaward
direction. The anomaly in water levels at N.W. 27th Avenue
at mid-rising tide is caused when the upstream movement of the
salt-water wedge started passing this location (fig. 14). It was
most pronounced on the afternoon of August 19.














,------- --
. . .


t.
W!
A 9 A "


hS0 F---. MIAMP CANAL PROFILE..~4 ,370 O7.!. -
S- .-...-- -1-.;- -.--. .-'~ -.- CHLORIDE IN PPM
LOW TIDE


14 Io lvvoo
7o" lS F i id


4 -" -J .5 I 2 I" "
DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 15. Profile of chloride content in the Miami Canal on July 16, 1964 at low and high tide when the N.W.
86th Street control dam was partially open.


_~______ ___ ____~___ __~_ ____~~________1_






REPORT OF INVESTIGATION NO. 45


HIGH AND LOW TIDE SALT-WATER MOVEMENT

On July 16, 1964, two chloride profiles were made along the
Miami Canal. The first was made near low tide between 8:00
and 9:00 a.m. Canal water was sampled for chloride content at
2-foot intervals from the bottom to the water surface at each
of the stations named in figure 15. Another profile was made at
high tide, between 2:30 and 3:30 p.m. using the same procedure.
The lower profile of figure 15 shows the most inland advance
of the salt-water wedge. It may be noted that the seaward dis-
charge in the Miami and Tamiami Canals at high tide was 52 cfs
and 180 cfs, but at the same time the peak inland flow at Brickell
Avenue was 480 cfs. This combined flow of 712 cfs at that time
was going into storage in the Miami Canal, the Tamiami Canal,
several man-made lakes, and into the aquifer. The salt-water
wedge moved upstream in the Miami Canal during this period
because Biscayne Bay with its high chloride concentration was
supplying about 70 percent of the water going into storage
at that time. The low-tide profile (fig. 15) shows the isochlor
positions moved seaward. The discharge through the controls in
the Miami and Tamiami Canals was 90 cfs and 225 cfs down-
stream and 2,370 cfs seaward in the Miami Canal at Brickell
Avenue. The peak discharge affecting the downstream movement
of the salt-water wedge indicated that 2.055 cfs was coming out
of storage below the controls just prior to low tide. A comparison
of the two profiles shows the change in location of the salt-water
wedge in the Miami Canal between high and low tide. The above
discharges represent only the extremes of the high and low-tide
cycle; they do not determine the runoff for the tide cycle. Data
indicate these would be typical high and low tide profiles for
any period of average discharge and normal tides.


CHLORIDE CONCENTRATION EXTREMES

The chloride concentration extremes in the Miami River and
Canal are shown in figure 16 for the period of record 1942 to
1964. The water samples were taken at the bottom of the canal at
or near high tide when the salt-water wedge was at its most
inland advance. The chloride concentration reached 13,200 ppm
just above the temporary control dam located at N.W. 36th Street
and extended inland past the Hialeah water plant, and was meas-







FLORIDA GEOLOGICAL SURVEY


- A
to j
< ,I
. S,
-:1

olz ,2
w4U
Q- z
I .


Figure 16. Chloride extremes at high tide
Miami Canal at various sampling locations.


in the Miami River and the


ured at 2,800 ppm in the Miami Canal as far as Red Road during
the period 1942 to 1945.
The present sheet-steel piling control dam constructed in 1946
has proven adequate during all but the very dry periods. These
dry periods coupled with withdrawals of fresh water from the
Miami Canal by the adjacent Hialeah well field in the 1960's
and the drought experienced in the latter part of 1961 through
May 1962, there was not enough fresh water available in the
drainage basin to provide high enough heads in the canal up-
stream from the control dam to prevent the salt-water seepage
around the closed control dam. This salt water then moved
upstream in the Miami Canal for more than eight-tenths of a mile.
At the end of May 1962 the chloride concentration was measured
at 7,200 ppm just above the control and 790 ppm at a point
eight-tenths of a mile upstream. This water of high chloride
content was very near the influence of the Hialeah well field's






REPORT OF INVESTIGATION NO. 45


cone of depression. This condition was improved in June 1962
when above normal rainfall, 14.54 inches, fell in the Miami Canal
drainage basin. This rainfall provided enough fresh water to
permit the opening of the control dam and to flush the salt water
seaward.

THE 1945 DROUGHT
Control structures in the Miami Canal area will effectively
hold back the intrusion of salt water, provided that the fresh
water behind the dams is maintained at a high enough level.
However, the problem of maintaining high fresh-water levels is
complicated by the highly permeable limestone through which
the canals were constructed. During times when the water table
approaches msl, the denser salt water will move around the
closed control structures through the aquifer and contaminate
the fresh-water supply upstream.
On March 17, 1945, the pneumatic dam in the Miami Canal
failed, and the salt water moved upstream to a point more than
half-a-mile above the Hialeah water plant. Ten days later a
temporary sheet-steel piling dam was constructed. Additional salt
water moved around this closed temporary dam through the aqui-
fer because the water levels above this dam were lower than
the downstream mean tidal levels. Figure 17 shows the inland
extent of this salt-water penetration along the bottom of the
Miami Canal on May 31, 1945. Since the only samples taken at
that time were from the bottom of the canal, the isochlor lines
in ppm were estimated from these bottom samples and from an
isochlor profile made on May 15, 1945. The upstream advance of
the salt-water wedge was relieved when the rain gages in the
basin average 3.85 inches and 6.77 inches during June and July,
respectively. The rain was sufficient to move the salt water down-
stream from the N.W. 36th Street control structure during July.

CHLORIDE CONCENTRATION IN THE AQUIFER
The history of the City of Miami's fresh-water supply has
been a problem of moving westward when their well fields were
contaminated by the high chloride concentration from Biscayne
Bay and the Miami River. In later years when several uncon-
'rolled canals were constructed through the coastal ridge to de-
velop the low-lying lands in the Everglades for urban and agri-

















,- STANCE UPSTRtAM FROM iSCAYCE BAY, IN MILES .---- --B r-- -.. -.
9 7 6
.j 4 -- .- -
MEAN DAILY
........- -- -- WATER LEVEL
0 14f1 0.23 ft.
0O -- --- -
/ '" MIAMI CANAL PROFILE .


Z 0 ---- 0 0 ., 000 MAY 1I, 1945 2 ,- .
Se- ,,.t -..--e-----.. T-.- ---- .------- a

,' 'o ,,^b..l i ,.-,. ,- .








S3 o

Figure 17. Extreme chloride concentration in the Miami- Canal above the N.W. 36th Street control dam on May 31, 1945.






REPORT OF INVESTIGATION No. 45 27

cultural use, the canals provided flood protection for the lowlands
except during extremely wet periods when the drainage system
was overburdened. The uncontrolled canals caused overdrainage
during dry periods which resulted in lowering the water table
and permitted salt water to move upstream in the canals and
into the highly permeable Biscayne aquifer, the fresh-water bear-
ing formation from which Miami obtains its water supply.
Hydrologic data collected to date shows the salt front at
depth in the Biscayne aquifer has tended to move slowly, but
progressively, inland from the Tamiami Canal toward the Miami
well field, thereby flanking the control structure on the Miami
Canal at N.W. 36th Street. The proximity of the salt-water in-
trusion to the Hialeah-Miami Springs well field's cone of depres-
sion is indicated by the map for 1962 in figure 18. The inland ex-









MIAMI .MIAMI I. MIAMI




190 1918 194 194 r






191







Figure 18. Salt-water encroachment at the base of the Biscayne aquifer
1904-62 (Parker and others, 1955, p. 589), (Kohout, 1961) updated.






FLORIDA GEOLOGICAL SURVEY


tent of the 1,000 ppm chloride located at depth in the Biscayn:
aquifer is about 1 mile from the southeast edge of the cone oj'
depression. During extreme dry periods the canals act as inland
extensions of the sea, carrying salt water several miles upstream
and allowing it to leak out and contaminate the aquifer all along
its course. During these periods the low water table enables the
salt water to move inland toward the Miami well field. During
wet periods discharge in the canals rapidly moves the salt water
in the canals downstream and the overall higher water levels
tend to move the salt front in the aquifer seaward and toward
the Bay. Examination of the past records of the position of the
salt-water front in the ground has shown a very slow but a
steady movement toward the Miami well fields as the increasing
population places an ever-increasing demand on the available
water supply.

DISCHARGE AT SELECTED LOCATIONS
The past threats of salt intrusion and the expected increase in
withdrawals from the Hialeah well field show that the threat
of intrusion toward the well field will become progressively more
imminent with the present locations of the controls in the Miami
and Tamiami Canals. A control structure in the Miami Canal below
the confluence of the Tamiami Canal would reduce the threat of
salt-water encroachment to the well field from both canal systems.
A structure at such a location would move the salt water in the
canal more than 1 mile downstream in the Miami Canal, and
eliminate recurrence of the intrusion such as that of 1962. The
resulting rise in fresh-water levels attendant with the downstream
relocation would blunt the lobe of salt water in the aquifer and
cause it to move seaward and thereby create a larger buffer
zone of fresh water between the well field and the salt-water
front. In addition, the deep rockpits within the area, which pres-
ently contain water of high chloride concentration at depth,
probably would become progressively fresher, thus adding to the
area of fresh-water storage.
A lock and dam site in the Tamiami Canal at LeJeune Road
coupled with the present control structure in the Miami Canal
would be less effective than a single control structure downstream
in the Miami Canal below the confluence of the Tamiami Canal.
The mean monthly discharge, shown in figure 19, shows the water
that would be available for boat lockages at Tamiami Canal at Le-






REPORT OF INVESTIGATION NO. 45


500 '
400-- I _
300\ --
\ / \
200 ----- I --\
100

SON JFMAM J J A SON J
1960 D 1961 D
1_. I__~


" A M J J ASON JFMAMJJAS
1962 D 1963


Figure 19. Monthly mean discharge at selected locations in the Miami and
Tamiami Canals, October 1960 through September 1963.

Jeune Road, Miami Canal at N.W. 36th Street, and Miami Canal at
N.W. 27th Avenue. The discharge shown for Miami Canal at N.W.
36th Street was taken directly from published records. Because the
Geological Survey at present has no discharge stations at the
other two locations, the discharge was computed as follows: The
discharge for Tamiami Canal at LeJeune Road is the summation
of the three discharge stations (Tamiami Canal near Coral Gables,
North Line Canal near Coral Gables, and Coral Gables Canal
near Coral Gables) plus 30 percent of the flow difference between
the total of the above stations plus the discharge at Miami
Canal at N.W. 36th Street from the total flow of the Miami
River at Brickell Avenue. The computed discharge for Miami
Canal at N.W. 27th Avenue is the flow of Tamiami Canal at
LeJeune Road plus the discharge of the Miami Canal at N.W.
36th Street plus 30 percent of the flow difference between Tamiami
Canal at LeJeune Road plus Miami Canal at N.W. 36th Street
from the total discharge of the Miami River at Brickell Avenue.






FLORIDA GEOLOGICAL SURVEY


Locations of the above discharge stations are shown on the map
in figures 1 and 2. The mean monthly discharge for Miami
Canal at N.W. 36th Street indicates that during extreme dry
periods there would not be water available for lockages at this
location. On the other hand, the Tamiami Canal at LeJeune Road
would have a minimum flow during a dry period, such as that
experienced early in 1962, of about 30 cfs, and the Miami Canal
at N.W. 27th Avenue would have a minimum flow of about 55 cfs


1961 1962 1963
Figure 20. Monthly mean discharge from or into the aquifer below the
control dams in the Miami River and its tributaries, April 1961 through
September 1963.

available for boat lockages. This minimum flow also takes into
account the additional storage of fresh water that could be used
for boat lockages that would become available in the aquifer
and several lakes with the relocation of the controls downstream
from their present location.
The discharge from or into the Biscayne aquifer from the
Miami River and its tributaries below the control dams during the
dry period April 1961 through September 1963 is shown in figure
20. Even during this dry period the aquifer was discharging to
the Miami River at all times except for March 1962 when ab-






REPORT OF INVESTIGATION NO. 45


normally high tides occurred, and again in April and May 1963.
The most important factors that will control the ultimate
effectiveness of the proposed lock and dam structure are: (1) the
precautions taken to prevent the movement of salt water beyond
the structure during locking operations; and (2) the amount of
fresh water used for locking boats during prolonged drought.
If, in the future, the amount of fresh water used in locking plus
that required to maintain safe water levels at the control were
to exceed the quantity available in the canal system, the effective-
ness of the control of salt intrusion would be negated and a re-
advance of the salt front would occur.

THE EFFECTS OF WIND ON WATER MOVEMENT
The effects of wind on water levels and canal discharge are
shown in figure 21. When Hurricane Cleo passed through the
Miami area on August 26-27, 1964, the hydrologic effect was
recorded on all gages in the study area and the tidal gages in
Biscayne Bay. Discharge illustrated in the upper graph shows
the flow through the salinity control in the Miami Canal at N.W.
36th Street. Early in the morning on August 26 the discharge at
the control was averaging 170 cfs with 4 half needles open. In
anticipation of the impending hurricane and possible flooding,
the control was opened to 22 full and 6 half needles at 11:00
a.m. The flow then increased to 580 cfs at 3:00 p.m. on August 26,
but fell off rapidly to a negative (upstream) flow of 62 cfs at
11:00 p.m. when the strongest easterly winds hit the area and
pushed the water in the Miami River at Brickell Avenue to a
higher level than that above the open control dam as shown in
the center hydrographs from 10:00 p.m. to 11:30 p.m. on August
26. After the eye of Hurricane Cleo passed, the strong westerly
winds increased in intensity until a westward gradient of more
than 3.5 feet existed across Biscayne Bay. That effect is markedly
shown in the lower hydrograph when the Biscayne Bay at Coconut
Grove tide gage recorded a minimum of -1.4 feet (referred to
msl) at 3:00 a.m. on August 27, while the Biscayne Bay tide
gage located in the Key Biscayne Marina recorded a high of 2.55
feet at 3:20 a.m. on August 27. Hurricane Cleo was a relatively
dry storm. The average rainfall recorded at the three rain gages
in the basin was 0.77 inch on August 26, and 4.61 inches on
August 27.
When a severe hurricane is imminent for the lower southeast
coast of Florida, the present type of salinity controls in the major






32 FLORIDA GEOLOGICAL SURVEY



600
7 Ioo- 1 I --- 1---

s 00---- Ts-d

lu400--- -- ----- -- / -l \





I i STERLY WIND WESTERLY I
I/ I i
MIAMI CANAL o N. W 36 S .ABOVE
S200--------\--

g 10-t------- [-----L-I------ --\/----I----



o -ll ----


i I / ,



IMIAMI RlVER ot BRICKE

0 1 1I
BISCAYNEIAMI COCONUAL t N. W. 36 STGROVEABOVE
z i i __K



,- i--- k,.i- "-- .
0-C
P-0- ---- | ------f ------ 4 -\- -

us .j f


LL AVENUE

I I
_^-- ,_L_


AUGUST 26, 1964 AUGUST 27, 1964
Figure 21. Effects of Hurricane Cleo's winds at selected discharge and wa-
ter-level stations in the Miami Canal and Biscayne Bay, August 26-27, 1964.


1_1___-_ --4-\
L at N. W. 36 ST:






REPORT OF INVESTIGATION NO. 45


canals in Dade County are generally fully opened before the
hurricane strikes to reduce the possibility of flooding. High
storm tides as a result of strong easterly winds push large quanti-
ties of salt water upstream. This invasion of salt water above
the opened controls may contaminate the aquifer as well as in-
crease the threat of flooding. If the salinity controls were rede-
signed and operated so that they could be closed when the flow
starts to reverse during the hurricane, much better protection of
the fresh-water supply and from flooding would be assured. During
the period August 26-27, 1964, the control in the Miami Canal
at N.W. 36th Street was open in anticipation of Hurricane Cleo.
Following the passage of Hurricane Cleo which brought very
little rainfall to Dade County, it was necessary to discharge valu-
able fresh water from the reserve supply in order to push the salt
water downstream from the salinity controls. An example of the
magnitude of reverse flow caused by storm tides was that of
September 10, 1960, during Hurricane Donna, when a peak flow
of 1,220 cfs moved upstream through the open salinity control
in Snapper Creek Canal. These typical examples demonstrate the
need for salinity controls that can be operated during hurricanes
to more effectively protect the area from floods, salt-water en-
croachment and to conserve the fresh-water supply.

SUMMARY
Salt-water intrusion historically has been the chief threat to
the water resources of the Miami area. The early history of the
City of Miami's fresh-water supply has been that of moving west-
ward when the well fields were contaminated by the high-chloride
concentration from Biscayne Bay and the Miami River. In later
years several uncontrolled canals were constructed through the
coastal ridge to develop the lowlying lands in the Everglades for
urban and agricultural use. The canals provided flood protection
for the lowlands except during extremely wet periods when the
drainage system was overburdened. These canals were the chief
factor in salt-water contamination of the aquifer in two ways.
First, during dry periods the uncontrolled canals were avenues
for salt water to travel inland for several miles to contaminate
the aquifer. Second, the overdrainage lowered water levels in the
ground and permitted denser salt water to move inland through
the aquifer. The chloride contamination in the aquifer can be
halted or pushed back by holding higher water levels behind con-






FLORIDA GEOLOGICAL SURVEY


trol dams in the canals, or by moving the control dams further
downstream.
The average chloride content of water in the Miami Canal
ranges from about 12 ppm above the controls to about 19,000
ppm in Biscayne Bay. The data show that the salt-water wedge
in the Miami Canal was located at N.W. 27th Avenue about 60
percent of the time and at the downstream side of the present
control dam 23 percent of the time. It was determined that a
discharge of at least 550 cfs from the area is required to hold
the salt-water wedge downstream as far as N.W. 27th Avenue
and at least 280 cfs in the canal system would be required to
move the salt-water wedge away from the base of the N.W. 36th
Street control dam. During wet years the salt water will remain
downstream from the salinity-control dam all year, but during
dry years water containing 1,000 ppm chloride or more will
remain just below the control dam for several months. The fresh-
water discharge from 60 percent of the aquifer below the controls
in the Miami River and its tributaries would be saved by moving
the present controls below the confluence of the Miami and Tami-
ami Canals.
If a lock and dam were located in the Miami Canal in the
vicinity of N.W. 27th Avenue there would be about 55 cfs avail-
able for boat lockage during dry periods, such as early in 1962.
Records indicate that at times there would be no discharge avail-
able in the Miami Canal at N.W. 36th Street and about 30 cfs
at Tamiami Canal at LeJeune Road. Isochlor profiles indicate that
the salt-water wedge is very sensitive to tidal cycles and changes
in discharge. It moves upstream during rising and high tide when
the seaward flow in the canal is at a minimum and moves seaward
during falling and low tide when the flow in the canal is at a
maximum.
When a severe hurricane is imminent, the controls in major
canals in Dade County are generally left full open before the
hurricane strikes to reduce the possibility of flooding. During
the hurricane high storm tides as a result of strong easterly
winds may push large quantities of salt water upstream. Hurri-
cane Cleo brought very little rain to Dade County, so it was neces-
sary to discharge fresh water from storage in order to again
push the salt water below the salinity controls. If the salinity
controls were redesigned so that they could be closed when the
flow starts to reverse during the hurricane, much better protection






REPORT OF INVESTIGATION No. 45


of the fresh-water resources and flooding of the area would be
assured.
The present control in the Miami Canal has protected the
water supply of a City of Miami well field but if the extreme
conditions such as experienced in the early 1960's were to recur,
accompanied by increased withdrawals from the well field, the
salt-water wedge in the aquifer could move into the cone of de-
pression and contaminate the fresh-water supply. Considerable
reduction in the well field's pumping rate would be required to
control the salt-water intrusion.
The continuing changes in water control and the increasing
withdrawals for water supply will alter the flow system and
greatly increase the quantity of water required to maintain the
desired levels in the Miami Canal to hold back the salt-water
front in the aquifer. This study was limited in scope to data
collected since 1940 and to hydrologic conditions existing at this
time. However, the data presented will provide a basis for the
analyses of the effects of any major changes in the flow system
in the future.

REFERENCES
Chambers, A. C. (see Dole, R. B.)
Cooper, H. H., Jr.
1964 (and Kohout, F. A.; Henry, H. R.; and Glover, R. E.) Sea water
in coastal aquifers: U. S. Geol. Survey Water-Supply Paper
1613-C.
Dole, R. B.
1918 (and Chambers, A. C.) Salinity of ocean water at. Fowey Rocks,
Florida: Carnegie Inst. Washington Pub., v. 9, rept. 213.
Glover, R. E. (see Cooper, H. H., Jr.)
Henry, H. R. (see Cooper, H. H., Jr.)
Klein, Howard (also see Sherwood, C. B.)
1957 Interim report on salt-water encroachment in Dade County, Flor-
ida: Florida Geol. Survey Inf. Circ. 9.
Kohout, F. A. (also see Cooper, H. H., Jr.)
1960 Flow pattern of fresh water and salt water in the Biscayne
aquifer of the Miami area, Florida: Internat. Assoc. Sci. Hydro.,
no. 52.
1961 A case history of salt-water encroachment caused by a storm
sewer in the Miami area, Florida: Am. Water Works Assoc.
Jour., v. 53, no. 11.
1964 (and Leach, S. D.) Salt-water movement caused by control-dam
operation in the Snake Creek Canal, Miami, Florida: Florida
Geol. Survey Rept. of Inv. 24, pt. 4.






36 FLORIDA GEOLOGICAL SURVEY

Leach, S. D. (also see Kohout, F. A.)
1963 (and Sherwood, C. B.) Hydrologic studies in the Snake Creek
Canal area, Dade County, Florida: Florida Geol. Survey Rept. of
Inv. 24, pt. 3.
Parker, G. G.
1955 (and others) Water resources of southeastern Florida; with
special reference to the geology and ground water of the Miami
area: U.S. Geol. Survey Water-Supply Paper 1255.
Sherwood, C. B.
1962 (and Leach, S. D.) Hydrologic studies in the Snapper Creek Ca-
nal area, Dade County, Florida: Florida Geol. Survey Rept. of
Inv. 24, pt. 2.
1963 (and Klein, Howard) Surface and ground-water relation in a
highly permeable environment: Internat. Assoc. Sci. Hydro.,
no. 63.




Salt-water study of the Miami River and its tributaries, Dade County, Florida ( FGS: Report of investigations 45 )
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 Material Information
Title: Salt-water study of the Miami River and its tributaries, Dade County, Florida ( FGS: Report of investigations 45 )
Series Title: ( FGS: Report of investigations 45 )
Physical Description: 36 p. : illus. ;
Language: English
Creator: Leach, Stanley D
Grantham, Rodney G
Geological Survey (U. S.)
Geological Survey (U. S.) -- Water Resources Division
Publisher: Florida Geological Survey
Place of Publication: Tallahassee
Publication Date: 1966
 Subjects
Subjects / Keywords: Saline waters -- Florida -- Miami River   ( lcsh )
Geology -- Florida -- Miami-Dade County   ( lcsh )
Water-supply -- Florida -- Miami-Dade County   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by S. D. Leach and R. G. Grantham. Prepared by the United States Geological Survey in cooperation with Dade County and the Florida Geological Survey.
Bibliography: Bibliography.
 Record Information
Source Institution: University of Florida
Rights Management:
The author dedicated the work to the public domain by waiving all of his or her rights to the work worldwide under copyright law and all related or neighboring legal rights he or she had in the work, to the extent allowable by law.
Resource Identifier: aleph - 000957327
oclc - 01722582
notis - AES0063
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STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY





FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director




REPORT OF INVESTIGATIONS NO. 15





SALT-WATER STUDY OF THE MIAMI RIVER
AND ITS TRIBUTARIES,
DADE COUNTY, FLORIDA

By
S. D. Leach and R. G. Grantham
U. S. Geological Survey








Prepared by the
UNITED STATES GEOLOGICAL SURVEY
in cooperation with
DADE COUNTY
and
THE FLORIDA GEOLOGICAL SURVEY


1966









FLORIDA STATE BOARD

OF.

CONSERVATION





HAYDON BURNS
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





LETTER OF TRANSMITTAL


Wa



Jflorida Gjeological Survey

Tatakai.ssee

August 16, 1966

Governor Haydon Burns, Chairman
State Board of Conservation
Tallahassee, Florida
Dear Governor Burns:
Messrs. S. D. Leach and R. G. Grantham, of the Water Resources
Division of the U. S. Geological Survey, have completed a study
of the Miami River and its tributaries in Dade County, and the
relationships of these tributaries to salt-water intrusion in the
area. The report will be published as Report of- Investigations
No. 45. The study was done in cooperation with the Division of
Geology, of the State Board of Conservation, and Dade County,
and outlines the main trend of the water resources of the Miami
area.
The Biscayne aquifer, which is composed of highly permeable
limestone, is being intruded upon by salt water along any canal
or stream that connects the aquifer to salt water. It has been found
that this intrusion could be prevented and reversed by careful
management of the water resources of the area by the construction
of salinity control dams near the coast, and through the judicious
development of water.
Respectfully yours,
Robert O. Vernon
Director and State Geologist






















































Completed manuscript received
August 16, 1966
Published for the Florida Geological Survey
By Rose Printing Company
Tallahassee
1966






CONTENTS

Page
Abstract ---.-----------.-------. ----. ....-...-.....--......---.. 1
Introduction -----. -.----- ------------...... .. ..-...............---------................ 2
Area of investigations .--..... ........---.... ---... .... ... ..---..... .....-. ...-.. .......-- ... 4
History of salinity-control dam operation in the Miami Canal --...---..... 6
Rainfall in the Miami River drainage basin ...-----... --------...............-------- 8
Long-term hydrology- ................... -------.------------..----. 9
Discharge in the Miami Canal ---....--...--------.....--.........-- ..-----..---...-- 9
Water levels in the area of investigation --..--..-..--.....-----..--.......--......--.. 10
Water-level comparison between Miami River and Biscayne Bay ...---... 11
Salt-water movement in the Miami River ----------------------------- 14
Short-term comparison of chloride with water levels and discharge .--.-- 19
High and low tide salt-water movement ..........-........---.-------- .-----. 23
Chloride concentration extremes --.........---------------..---------. 23
The 1945 drought -..---. ----...--_--___. -.- ------- -----...._- .. ...----.---- 25
Chloride concentration in the aquifer .........---.------------------- 25
Discharge at selected locations .------...--. ....-----------.------- 28
The effects of wind on water movement -----...----.....-------------..---..--- 31
Summary -----.--- ............-------..------------- -----............. 33------------3
References .----........... -------------------- ------------- 35


ILLUSTRATIONS

Figure Page
1 Map of the Greater Miami area showing the major canals and the
area investigated ..----........---...--..-------..... ........ .-------------..---- 4
2 Map of the Miami River and its tributaries showing data-collection
sites in the area investigated ................-........--------------............ 5
3 Photographs of successive salinity-control dams in the Miami Canal
at N.W. 36th Street ........--------.....-..---.--.......... ---.-----.. ----------------. 7
4 Graph of monthly mean rainfall, monthly extremes, and the year
the extremes occurred based on the averages of Hialeah, Pennsuco,
and Pennsuco 5 N.W. (Broken Dam) rain gages for the period
1944 through 1963 .-..---.... .--.......-- ...----------- ..---- ..------ .. -- ---- 8
5 Graphs showing monthly and annual mean discharge in the Miami
Canal above N.W. 36th Street control dam and the total an-
nual and monthly rainfall for the three rain gages in the Miami
Canal drainage basin --........---...........................------ --------. ..-----...--- 9
6 Graphs of water levels at three selected Miami Canal stations and
one Biscayne Bay Station, from 1944 to 1963 ---__------ -----.------ 11
7 Hydrographs of monthly high, low, and average water elevations in
the Miami Canal at N.W. 27th Avenue and at Biscayne Bay, based
on 18 years of record'1946 to 1963 ....................-------------............ ----- 12
8 Graphs showing a mean water-level elevation, mean high and low
water from the N.W. 36th Street control dam to the mouth at Bis-
cayne Bay, based on 18 years of record 1946 to 1963 ....---.-......---- .. 13
9 Graph showing percentage of time water containing 1,000 ppm
chloride was at or above various locations in the Miami Canal for
the period May 1945 to March 1958 ---........................------.--- ------ 15






ILLUSTRATIONS


Figure Page
10 Graphs showing position of the 1,000 ppm chloride content in the
Miami Canal for the period January 1940 to March 1958 -..--....--..--. 16
11 Graph showing relation between monthly mean discharge in cfs and
the location of water containing 1,000 ppm chloride in the Miami
Canal ....----..............-..- ..........-.............----------------................-..--- .. 17
12 Graphs showing chloride concentration in the Miami Canal during
a typical wet year (1948) and a typical dry year (1956) .............. 18
13 Graphs showing the effect of changes of the N.W. 36th Street con-
trol dam on discharge,water levels, and chloride content at selected
locations in the Miami Canal from July 12 to 19, 1964 ..--..-.........-- 20
14 Graphs showing the effect of changes of the N.W. 36th Street con-
trol dam on discharge, water levels, and chloride content at selected
locations in the Miami Canal during the period August 14 to 19,
1964 .......................-.... -.......---------------............... ......... -....-...-...---- .....----- 21
15 Profile of chloride content in the Miami Canal on July 16, 1964 at
low and high tide when the N.W. 36th Street control dam was par-
tially open .--- --.....--........ -- --.. ....... ...--. ......--. .--.------ -------- 22
16 Graphs showing chloride extremes at high tide in the Miami River
and the Miami Canal at various sampling locations ......--------......... 24
17 Graphs showing an extreme chloride concentration in the Miami
Canal above the N.W. 36th Street control dam on May 31, 1945 ... 26
18 Map showing salt-water encroachment at the base of the Biscayne
aquifer 1904-62 (Parker and others, 1955, p. 589), (Kohout, 1961)
updated ...--.........-..-.. --...-....... ...-..... -..............--- .-...........------ ......... .....-...--- 27
19 Graphs showing monthly mean discharge at selected locations in
the Miami and Tamiami Canals, October 1960 through September
1963 -- ---.............---....... .....-- ..-----......---. ..--..------ .........-.....- .. .. ..........-- 29
20 Graph showing monthly mean discharge from or into the aquifer
below the control dams in the Miami River and its tributaries,
April 1961 through September 1963 ---..................----..........-...------- 30
21 Graphs showing the effects of Hurricane Cleo's winds at selected
discharge and water-level stations in the Miami Canal and Bis-
cayne Bay, August 26-27, 1964 --...-..-..-.........--------....-- -----. 32









SALT-WATER STUDY OF THE MIAMI RIVER
AND ITS TRIBUTARIES,
DADE COUNTY, FLORIDA

By
S. D. Leach and R. G. Grantham


ABSTRACT
The main threat to water resources in the Miami area is salt-
water intrusion into the highly permeable Biscayne aquifer.
Saltwater pollution of the aquifer may be held at its present loca-
tion or moved seaward by raising the fresh-water levels in the
ground by increasing fresh-water heads behind the control dams,
or by moving the controls farther downstream in the canals.
Analysis of available data indicates that water containing
1,000 parts per million or more of chloride in the Miami Canal
is immediately downstream from the salinity-control dam at
N.W. 36th Street approximately 23 percent of the time and at
N.W. 27th Avenue about 60 percent of the time. Also, an analysis
of flow data indicates that when the discharge of the Miami
Canal at N.W. 36th Street is approximately 280 cubic feet per
second or less, the salt-water wedge is located at the downstream
side of the control dam at N.W. 36th Street. With the present
location of the control dams a minimum discharge of 550 cubic
feet per second would be required to hold the salt-water wedge
downstream from N.W. 27th Avenue.
The fresh-water discharge from 60 percent of the aquifer in
the Miami River and its tributaries below the control dams would
be salvaged by moving the controls downstream from the con-
fluence of the Tamiami Canal.
With reference to proposed downstream locations of controls,
it was determined that during dry years, as experienced in
1961-62, there would be a discharge of about 55 cubic feet per
second available for boat lockages in the Miami Canal at N.W.
27th Avenue and about 30 cubic feet per second in the Tamiami
Canal at LeJeune Road.
When a severe hurricane is imminent for the lower southeast
coast of Florida, the salinity controls in the major canals in Dade
County are generally fully opened before the hurricane strikes to
1





FLORIDA GEOLOGICAL SURVEY


reduce the possibility of flooding. High storm tides as a result of
strong easterly winds push large quantities of salt water up-
stream. This invasion of salt water above the opened controls
may contaminate the aquifer as well as increase the threat of
flooding. If the salinity controls were redesigned so that they
could be closed when the flow starts to reverse during hurricanes,
they could more effectively protect the area from floods, salt-water
encroachment, and better conserve the fresh-water resources of
the area.
The chloride records indicate the present controls in the Miami
and Tamiami Canals have proven to be barely adequate in pro-
tecting the City of Miami's Hialeah-Miami Springs well field
from salt-water contamination during the dry years. If the ex-
treme conditions that were experienced in the early sixties were
to recur along with increased withdrawals from the fresh-water
supply for public use, the salt water might move inland to the
extent that it could cause some reduction in the capacity of the
Hialeah well field to supply the fresh-water needs of the area.


INTRODUCTION

The Miami River has the largest discharge of all rivers in
southeastern Florida, and serves as the outlet for the Miami and
the Tamiami Canals. The widening and deepening of the Miami
River and the construction of the Miami and Tamiami Canals
have been beneficial in flood control but have increased the threat
of salt-water encroachment. The primary purpose of the investi-
gation is to present a study of the salt-water movement in the
Miami River and Canal and its effect on the fresh-water supply
of the area.
The rapid growth of population and industry in Dade County
has placed an ever-increasing demand on the available fresh-
water supply. A major part of the water supplies come from the
City of Miami's Hialeah-Miami Springs well field, and it is es-
sential that contamination by salt water continues to be prevented.
Two possible ways to accomplish this are to (1) hold higher
heads of fresh water behind the controls; or, (2) relocate the con-
trols downstream. However, holding higher heads of water behind
the controls may not be practical because much valuable low
land would be flooded. Relocating the control dams farther down-
stream would furnish additional protection against salt-water






REPORT OF INVESTIGATION No. 45


encroachment in the Biscayne aquifer and provide a widening of
the fresh-water safety zone between the salt water and the
Hialeah-Miami Springs well field. As the metropolitan area places
an ever-increasing demand on the available fresh-water supply,
there is a need to conserve as much fresh water as possible. In
connection with this conservation the study of the movement of
the salt-water wedge in the Miami River and its tributaries will
provide one additional tool to better understand and manage
the water resources of the area.
Salt-water intrusion historically has been the chief threat to
the water resources of the Miami area. This report, prepared in
cooperation with Dade County, gives detailed attention to the
movement of salt water in the Miami River and its tributaries.
The major hydrologic features in greater Miami and the area
investigated are shown in figures 1 and 2. Salt water in the
canal moves in response to the operation of salinity-control dams
located in the Miami and the Tamiami Canals (fig. 1). Other
factors that affect movement of the salt water in the Miami
River and its tributaries are as follows: Fresh-water discharge
through the controls; seaward movement of water in the aquifer
downstream from the controls; rainfall and evaporation; tidal
cycles, and seasonal changes in the tidal oscillations in Biscayne
Bay. Of the above factors, only the fresh-water discharge can be
easily controlled by man. Even in the operation of the control
dams he is limited by the available supply of fresh water. In this
endeavor hydrologic knowledge is a prerequisite to conserving as
much of the available fresh water as is safely possible without
inland flooding.
The investigation was made in cooperation with Dade County
and was under the general supervision of A. O. Patterson and
K. A. MacKichan, Ocala District Engineers of the Surface Water
and Quality of Water Branches, and subsequently, R. W. Pride,
acting District Engineer, Surface Water Branch, and C. S. Con-
over, District Chief, Water Resources Division of the U.S. Geo-
logical Survey.
Thanks are extended to F. D. R. Park and M. C. Brooks,
Water Control Engineeers of the Water Control Department,
Public Works Department of Dade County, for furnishing the
operation log of the Miami Canal salinity-control dam and the
chloride concentrations during 1961-62. C. F. Wertz, Director,
Department of Water and Sewers, City of Miami, furnished
photos of the salinity dams in the Miami Canal.





FLORIDA GEOLOGICAL SURVEY


Figure 1. The Greater Miami area showing the major canals and the area
investigated.

AREA OF INVESTIGATION
The area investigated in this report is the Miami River which
extends from Biscayne Bay to N.W. 27th Avenue, the Miami
Canal from N.W. 27th Avenue west to Levee 30, and the lower
reach of the Tamiami Canal (See figs. 1 and 2).
Samples of the fresh water taken between 1946 and 1958 in the

















Sa A


N. W. 7th ST. 1
BLUE "GOON LAKE

-- WEST FLAGLER ST.
EXPLANATION
0- CHLORIDE SAMPLING SITE TAMIAMI TRAIL
CONDUCTIVITY RECORDING GAGE
--- WATER LEVEL RECORDING GAGE 8
DISCHARGE
O--- WATER LEVEL RECORDING GAGE
=4C-- CONTROL DAM IS
0.5 0 0.5 I


Figure 2. Miami River and its tributaries showing data-collection sites in the area investigated.




FLORIDA GEOLOGICAL SURVEY


Miami Canal west of the salinity-control dam indicate that chlo-
ride concentration generally ranges between 10 and 15 ppm
(parts per million). This small amount of salt contamination
comes from the fresh-water contact with the rock aquifer and the
soil materials in the Everglades. The chloride concentration of
the fresh water varies slightly with seasonal changes in rainfall
and runoff from the area, and averages about 12 ppm for the
Miami Canal west of the salinity-control dam.
The main area covered in this report is the diluted zone
between the average chloride concentrations of 12 ppm in the
fresh water to the west of the salinity-control structures and
the average chloride concentrations of about 19,000 ppm in Bis-
cayne Bay. The area between these ranges is undergoing an ever-
continuing battle between the fresh water and its higher heads
and sea water and its density current. The greatest degree of
variability in salt-water content occurs in this reach. Therefore,
the main emphasis of the report is on this section.


HISTORY OF SALINITY CONTROL-DAM OPERATION
IN THE MIAMI CANAL
In 1945 salinity-control dams were installed in most of the
canals in the Miami area as barriers against further encroach-
ment of salt water in the Biscayne aquifer. The dams were con-
structed across the canals by driving sheet-steel piles into the
limestone aquifer.
On the Miami Canal four salinity control dams in the vicinity
of N.W. 36th Street have been in operation during various periods.
Their purpose was to furnish protection to a Miami municipal
well field located upstream. The first control dam of sheet-piling
was in operation from December 1939 to June 1942, when it
was replaced by a pneumatic dam. The pneumatic dam remained
in operation until it failed in March 1945. The high rise in
chloride concentration at that time may be noted in the figure on
page 16. Ten days later a temporary sheet-piling dam was in-
stalled and remained in operation until 1946 when the present
sheet-piling control dam was constructed. The present control dam
in the Miami Canal is operated by removing alternate steel piles
(called needles) during the wet periods and replacing them during
the dry periods. Photographs of various salinity-control dams in
the Miami Canal at N.W. 36th Street are shown in figure 3.
































Original sheet-piling dam (1939-42)


was,
413 -
tl~~ I3 b\


Pneumatic dam (1942-45)


Temporary sheet-piling dam (1945-46)

Figure 3. Successive salinity-control dams in the Miami Canal at N.W.
36th Street.


~J ..
~ji~, -.s
~f~ ;a- -. .*- ~
~"P?:`:~Y:-- 1~"4~2~
--~-
-;i -
;..., .
,e-~-;i :-- -HS.Pi,
$*ct=~-~
-i~'i~
'
~i.; 4-w.- r I-~.--





FLORIDA GEOLOGICAL SURVEY


RAINFALL IN THE MIAMI RIVER DRAINAGE BASIN
The area depends chiefly on rainfall for its available fresh-
water supply. The rainfall in the Miami River drainage basin
averages 57 inches per year. Extremes range from 74 inches in
1959 to 38 inches in 1951. The average and extremes are based
on 20 years of record (1944 through 1963) from three rain gages.
The rain records used in this report (fig. 1) are Hialeah, Penn-
suco 5 N.W. (Broken Dam), and Pennsuco. The monthly mean
rainfall for the above period is shown in figure 4. Rainfall for
the wet period, May through October, averages 44 inches or 71
percent of the average annual rainfall; rainfall for the dry
season, November through April, averages 13 inches per year.
Also shown in figure 4 are the monthly extremes and the year
in which they occurred.

1958 1957 1959 1957 1958 1962 1946 1956 1948 1952 1959 1957
20





z 10 .i.i'.l'.'iiiii'iiiiiiiiii:iiiiii *il:''.'!!'/.'.ri~ii; i ----- i!iii- ---- ----- ----- ----- ---- --- '.i;i i: !i;
18






1 .----- -- ..." .
14













2 Z/001 7.


1951 1944 1956 1946 1945 1952 1963 1954 1961 1962 1952 1961
Jon Feb Mar Apr May June July Aug Sept Oct Nov Dec
Figure 4. Monthly mean rainfall, monthly extremes, and the year the ex-
tremes occurred based on the averages of Hialeah, Pennsuco, and Pennsuco 5
N.W. (Broken Dam) rain gages for the period 1944 through 1963.






REPORT OF INVESTIGATION No. 45 9


LONG-TERM HYDROLOGY

DISCHARGE IN THE MIAMI CANAL

The discharge of the Miami Canal depends on rainfall and the
operation of the salinity-control dam at N.W. 36th Street; The
monthly mean discharges of the Miami Canal at the salinity-
control dam, shown in figure 5, were determined from the gaging
stations located in the Miami Canal opposite the City of Miami's
water plant, and at N.W. 36th Street (figs. 1 and 2). The station
at the water plant was operated prior to February 1959, and the
N.W. 36th Street station was operated thereafter. A comparison
of overlapping records from the two stations indicates that the
discharge measured at the water plant exceeds that at N.W. 36th


z
S.oo,

a. 2o800-


I 200

m aloo.*
2 1200


a 800


.453914.7 -52 7.35o0 7o.r6fPT54.49






1944 9454
9441945 1946 947 194 8 1949J90


TOT
3.87154I




-,l:^d


L ANNUAL RACI
6. 658


951 1952 531954


IFAL, IN NCHES-----



1955561957 1916673 73641638



1955 &1.1;A119571 1959 196 1962


Figure 5. Monthly and annual mean discharge in the Miami Canal above
N.W. 36th Street control dam and the total annual and monthly rainfall for
the three rain gages in the Miami Canal drainage basin.


ff-I





FLORIDA GEOLOGICAL SURVEY


Street by about 5 percent. As the difference in discharge between
the two stations was small, the records were considered com-
parable without adjustments and were used consecutively in figure
5. The total monthly rainfall in figure 5 is the average of three
rain gages in the drainage basin. The total annual rainfall, the
annual mean discharge, and the operation of the salinity-control
dam are also shown. The annual discharge (runoff) from the
drainage basin does not correlate with the annual rainfall during
wet periods because the excessive runoff lasts several months
into the next year. On the other hand, the discharge shown in
figure 5 does compare with the movement of salt water (see figure
on page 16) in the Miami Canal. During times of peak discharge
the 1,000 ppm chloride front is downstream in the canal, and in
periods of low flow the 1,000 ppm chloride front moves upstream to
the salinity-control dam. Further comparison of figures 5 and 10
indicates that there is very little lag in the salt-water movement
in relation to fresh-water discharge.


WATER LEVELS IN THE AREA OF INVESTIGATION
Long-term monthly mean water-level fluctuations in three
selected Miami Canal recording stations are shown in figure 6.
The Miami Canal at Broken Dam and Miami Canal at N.W. 36th
Street recording stations are located above the salinity-control
dam as shown in figures 1 and 2. The slope in the Miami Canal
may be determined from figure 6 by comparing the water levels
at Broken Dam gage (located to the west and 2 miles downstream
from Levee 30) and with those at the N.W. 36th Street gage
(just upstream from the salinity-control dam). An examination
of the records of the past 20 years (figs. 5 and 6) shows that
wet and dry cycles have lasted for several years.
When the discharge is high, the slope in the upper reaches of
the Miami Canal above the salinity-control dam is greatest, as
shown during the wet years 1947-49, 1953-54, and 1958-60.
During the dry years, when the mean annual discharge is less
than 600 cfs (cubic feet per second) at the N.W. 36th Street
salinity control, the difference in water level between Broken
Dam and N.W. 36th Street gages is less-indicating a decrease
in the slope of the canal during these years. A comparison of
the monthly mean water level in the Miami Canal at N.W. 27th
Avenue and at Biscayne Bay (fig. 6) shows they closely follow






REPORT OF INVESTIGATION NO. 45


-I I i I r^- A 6





o AM I ;ANAL AT 31 STREET (ABOVE DAM)






S I s I 19 I I 9 I 1 1 I 9 I 196 I 957 1958 1 959 91 1961 1962 1963











WATER LEVEL COMPARISON BETWEEN MIAMI RIVER

AND BISCAYNE BAY


Graphs of the mean monthly high, low, and average water
elevations of the Miami Canal at N.W. 27th Avenue and of Bis-
cayne Bay are based on 18 years of record from 1946 through 1963
as shown in figure 7. The seasonal changes in the average elevations
of Miami Canal at N.W. 27th Avenue and of Biscayne Bay (fig. 7)
are generally low around the beginning of the year, rise gradu-
ally until October, and then decline rapidly until the end of the
year.
Comparison of the monthly mean elevations of the record
shows that the Miami River always has a seaward gradient. This
indicates that even when the flow at the control in the Miami
<
0 A- A 0




























indicates that even when, the flow at -the control in the Miami





FLORIDA GEOLOGICAL SURVEY


MIAMI CANAL AT N.W 27th AVE.


HIGH WATER
3 -t ---- "- --l-I. -- / --^









I






",, i ..
U. r - -
cc AVERAGE ELEVATION





U I



LOW WATER



0 44 t-' V Z


BISCAYNE BAY


Figure 7. Monthly high, low, and average elevations in the Miami Canal
at N.W. 27th Avenue and at Biscayne Bay based on 18 years of record from
1946 through 1963.



and Tamiami Canals is nil, there is generally a discharge from the
aquifer to the Miami and Tamiami Canals in the reaches below
the present controls, except during extremely dry periods. The
fresh-water discharge from 60 percent of the aquifer could be
saved by moving the control downstream in the Miami Canal
below the confluence with the Tamiami Canal. The total monthly
mean flow from or into the Biscayne aquifer downstream of the







REPORT OF INVESTIGATION No. 45


control dams from April 1961 to September 1963 is shown in
the figure on page 30.
If past conditions are repeated in the future, the mean high,
mean low, and average water levels shown in the Miami Canal
at N.W. 27th Avenue (fig. 7) would be experienced below any
control constructed at that location.
The annual mean high water, mean low water, and average
water-level elevations are shown in figure 8. By the use of
figure 8, the mean high water, mean low water, and the mean
water-level elevations may be determined throughout the lower
reaches in the Miami Canal below the N.W. 36th Street control


s r z
__j



22-c

Z Zei Z


w


C,)
0



pf)
c0


Ld
U)
V)Z


DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 8. Mean water-level elevation, mean high and low. water from the
N.W. 37th Street control dam to the mouth of Biscayne Bay, based on 18
years of record, 1946 to 1963.





FLORIDA GEOLOGICAL SURVEY


dam. The average annual gradient from the N.W. 36th Street con-
trol dam to Biscayne Bay is about 0.6 foot in 5.5 miles. The mean
annual water-level elevation of Biscayne Bay is 0.48 foot above
msl (mean sea level) datum of 1929, based on 18 years of
record (1946-63).


SALT-WATER MOVEMENT IN THE MIAMI RIVER
The Geological Survey has collected chloride data in the
Miami River and Canal from 1940 to June 1958 and from 1962
to 1964. The chloride samples were collected bi-weekly or monthly
from the bottom of the canal at or near high tide when the
upstream advance of salt water was at its greatest penetration.
The location of the sampling sites were in most cases bridges
from which the sampler could be lowered by a line to the deepest
section of the canal. The accessibility of these bridges by car
enabled the field men to move rapidly from station to station
in order that all samples might be taken as near high tide as
possible.
Prior to this study the objective was to determine the location
of the 1,000 ppm chloride concentration by collecting salinity
samples in the canals. Frequently, it was possible to determine
the location of the 1,000 ppm chloride concentration by taking a
relatively few samples. Thus all sampling stations were not
visited each sampling period.
The locations of periodic salinity sampling stations and their
distance, in miles, from the mouth of the Miami River at Bis-
cayne Bay are shown in the following tabulation:


Locations
Miami River at Brickell Avenue
Miami River at Miami Avenue
Miami River at West Flagler Street
Miami River at N.W. 7th Avenue
Miami River at N.W. 12th Avenue
Miami River at N.W. 17th Avenue
Miami Canal at N.W. 27th Avenue
Miami Canal at Seaboard
Airline Railway Bridge
Miami Canal below
N.W. 36th Street control dam


Miles from Biscayne Bay
0.10
0.40
1.10
1.57
2.11
2.65
3.83

5.32


5.45






REPORT OF INVESTIGATION No. 45


Locations (Continued) Miles from Biscayne Bay (Con't)
Miami Canal above
N.W. 36th Street control dam 5.48
Miami Canal at N.W. 36th Street 5.56
Miami Canal at N.W. 54th Street, (Hialeah) 7.06

In addition, two continuous conductivity recorders were
placed in the Miami Canal at N.W. 27th Avenue and below the
N.W. 36th Street control dam. These recorders were used to indi-
cate the continuous movement of the salt-water wedge during
tidal oscillations of the Miami Canal. Also, hydrologic data were
collected from eleven water-level recorders, six discharge stations,
and three rain gages at the locations shown in figures 1 and 2.
Beginning in January 1940 and continuing for a period of
18 years, chloride samples were taken bi-weekly at selected points
on the Miami River. The data were arranged to show the per-
centage of time that the chloride content was 1,000 ppm at selec-
ted points in the Miami River. Figure 9 shows that water con-
taining 1,000 ppm or more of chloride was at N.W. 27th Avenue

100- I
NW12 AVE

NW17AVE o



L. NW 27 AVE

- 50
z
W

W NW36 ST
nQ DAM





0 1 2 3 4 5 6
DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 9. Percentage of time water containing 1,000 ppm chloride was at
or above various locations in the Miami Canal for the period 1945 to March
1958.






16 FLORIDA GEOLOGICAL SURVEY

60 percent of the time, and extended as far upstream as the
control dam at N.W. 36th Street 23 percent of the time. The loca-
tion of the 1,000 ppm isochlor is shown in figure 10. During


ST T TTT7"T-- I t I
W---SATEIR PLANT

1w I 12 AVE.
A A.. S J [ I i 'A a I iF A' jJ sE JT DAM r N !JJn i
1 '940 9 1919 1942 943 1944 J
- -------EMPO-RARY PRESENT SHEET PILE DAM

' 0 A: J A7 S NA Ji A' J ]A Aio!1 I MD F A Jil !1[ lJ_ 7iI D N r F AI- I I



















drought periods, 1943-45 and 1950-52, the 1,000 ppm chloride
front was at the N.W. 36th Street control dam a much greater
I I.I'. WTTER PLANT





tl d On My 1, 11 te DAw
I AR k2IN27 AVE. 1A
IL I I r. I i i I t I1 I | i | I I It IW 12AVE,






9a e te dm, d 1y My 25 1941 e e h


















to 4,000 ppm. Also in March 1962 abnormally high tides topped
the salinity-control dam in the Miami Canal and caused salt water
SPWESENT SWEET PILE DA







to move upstream. During the 18 years of r the 1,000 ppmr cl
S il IL F V-1 I N 21'_ E













chloride front reached the dam at least once d uring most years;
the except w in 4 whe n the anal disare remain





relatively high all year. Most of 1954 the 1,000 ppm chloride
onr t rda OnMay 189PRESENT t lEET PLE Dws













fro nt remained below 27th Avenue. Records show that prior to
building the p n 36th Street dam it was nAormal fr the 1,000
preltie high alle yne Mo 1954 tVE Nthe: 1,00 pm chord
IF.rnt rem aine:S d el:Dw iF27th Avu Records so that pro to
















ppm chloride front 1,000 ppm extend ino deen beyond the Hialeah

area during d ary years. Ma 195
drought periods, 1943-45 and 1950-52, the 1,000 ppm chloride
front was at the N.W. 36th Street control dam a much greater
percent of the time. Since March 1946, when the present dam was
installed, the 1,000 ppm chloride front has rarely gone above the
control dam. On May 18, 1951 the chloride was 1,550 ppm just
above the dam, and by May 25, 1951 the chloride had increased
to 4,000 ppm. Also in March 1962 abnormally high tides topped








building the present 36th Street dam it was normal for the 1,000
ppm chloride front to extend into and even beyond the Hialeah
area during dry years.






REPORT OF INVESTIGATION NO. 45


When fluids of different density meet, they remain relatively
unmixed. The difference in density between fresh and salt water
affects the movement of water in the tide-affected reach of a river.
When the tide is rising in the Miami Canal the denser salt water
moves upstream as a wedge beneath the seaward-moving fresh
water. The salt-water wedge continues to move upstream until the
tidal force is equalized by the force of the discharging fresh
water or until the tide reverses. During dry periods, when there
is little or no discharge, salt water may move far enough up-
stream to contaminate the fresh ground-water supply.
The salt-water wedge advances farthest inland along the
bottom of a tidal canal at or near high tide. At high tide the
salt-water wedge is relatively blunt, and the distance it moves
inland along the bottom of the canal is comparable to the 1,000
ppm chloride shown in the figure on page 22. Therefore, the
movement of the 1,000 ppm chloride was used as an index to de-
termine the movement of the salt-water wedge (fig. 10). The
distance in miles above the mouth of the Miami River at Biscayne
Bay that the monthly average of 1,000 ppm chloride remained (fig.
10), was compared with the monthly mean discharge (fig. 5) to de-
termine the distance downstream from the salinity-control dam
that various discharges move the salt-water wedge. This relation
shown in figure 11 was developed from data collected from January


SO MONTH MEAN POSITION OF THE I00 PPM CHLORIDE I 1
0 200 400 600 800 1,000. 1,00 1,400 I600 1,800 2000 2,200 2.400
DISCHARGE, IN CUBIC FEET PER SECOND

Figure 11. Relation between monthly mean discharge in cfs and the loca-
tion of water containing 1,000 ppm chloride in the Miami Canal.






18 FLORIDA GEOLOGICAL SURVEY

1940 through February 1958, and suggests that a minimum dis-
charge of 280 cfs is required to move the salt-water wedge away
from the base of the salinity-control dam at N.W. 36th Street.
Also the graph indicates that approximately 550 cfs is required
to hold the salt-water wedge as far downstream as N.W. 27th
Avenue. Discharge from the Tamiami Canal and flow from the
aquifer to the canal downstream from the controls .also contributes
to holding the salt-water wedge downstream. During the period


-_ NW 36st DAM
55 -d
I-6 .SEABOARD R.R.
19561




2.0
year (1948) and4.typical dry year (1956).
2 NW 27 AVE

3.5

3.0
.,NW 17 AVE
25NW 12 AVE

2.0
JAN FE1 MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC

Figure 12. Chloride concentration in the Miami Canal during a typical wet
year (1948) and a typical dry year (1956).






REPORT OF INVESTIGATION NO. 45


1940 to 1958, when the salinity samples were taken in the canal,
the Tamiami Canal discharge was measured only from January
1940 through June 1943. Therefore, discharge of the Miami Canal
was taken as an index of the hydrologic conditions and was
used to determine the position of the inland extent of the salt
water wedge in the canal.
Chloride concentration during a typical wet and dry year is
shown in figure 12. The wet year 1948 was selected as it was the
only year in which discharge remained above 400 cfs throughout
the year and was above 1,900 cfs at the beginning and end of
the year. The dry year 1956 was used because, except for January
and February, the discharge remained generally below 400 cfs all
year. During the wet year 1948 the 1,000 ppm chloride remained
downstream from the N.W. 36th Street control but, during the
1956 dry year water containing 1,000 ppm or more of chloride
was at the bottom of the canal at the dam from March through
August, with 5,000 ppm on the downstream side of the control
in April, June, and August, and 10,000 ppm chloride in May. A
comparison of figures 5 and 12 shows a close relation between
discharge at the N.W. 36th Street control and the movement of
chloride in the Miami Canal.


SHORT-TERM COMPARISON OF CHLORIDE
WITH WATER LEVELS AND DISCHARGE
A comparison of water levels, discharge, and chloride content
at selected stations is shown in figures 13 and 14. At noon on
July 14 (fig. 13) the Miami Canal at N.W. 36th Street control
was reduced from 4 full needles and 4 one-half needles open to
4 one-half needles open; the mean daily discharge dropped from
about 300 cfs to 100 cfs. The stage above the control rose from
about 1.0 foot above msl on July 13 to about 1.75 feet on the 14th.
During that period the chloride content at N.W. 27th Avenue
increased from less than 1,000 ppm to 3,000 ppm. On July 15
at 2:30 p.m. the control opening was increased by 4 full needles
and the discharge increased to more than 200 cfs. Water levels
above the control declined to about 1.25 feet above msl and the
chloride dropped below 1,000 ppm. It is noted that when the dis-
charge through the control ranged from about 400 cfs at low
tide to about 200 cfs at high tide, the chloride of the water at
27th Avenue remained generally below 1,000 ppm. However, when







FLORIDA GEOLOGICAL SURVEY


JILY. 964
12 13 S 14 I I IT Is 19
4 -00---- --- 400
ST NW 36 STREET




\ Th \ I __ CON tROL. 6




t-w0 1 1 h g 1he c 0ot n
0 20D
TAMAM CANAL AT 82 AVEMJE -6*0 CANAL AT Nw xl STREET
V 0




SIAMI C~ AL AT NW 27 AVENUE
-AO ------ .s











discharge, water levels, and chloride content at selected locations in the Miami
Canal from July 12 to 19, 1964.



the discharge ranged from 300 cfs to 275 cfs at low tide to be-
3000 -3000







generally rose above 1,000 ppm during each high tide. The hy-
Figure 13. The effect of changes of the N.W. 36th Street control dam on







between the discharge, water levels, and chloride consent at selected locations in the Miami
Canal from July 12 to 19, 1964.







in the Miami Cangal. During Augus t 14-16 when the discharge
teen 130erally declined 100 fs at high tide, the chloride content below the salinity control
generally rose above 1,000 ppm during each high tide. The hy-
drographs also show that small changes in the control at N.W.




at N.W. 36th Street have a negligible effect on water levels at N.W. 27th
increased from 2 half needles to 1 full needle and4 half needles
A representative period of relatively low discharge, August
14-19, 1964 (fig. 14) has been selected to demonstrate the relation
between the discharge, water levels, and chloride concentration
in the Miami Canal. During August 14-16 when the discharge
generally declined, the chloride content below the salinity control
at N.W. 36th Street increased. When the control opening was
increased from 2 half needles to 1 full needle and 4 half needles







REPORT OF INVESTIGATION No. 45


' t I
kioo i O I
3 MIAMI CANAL at 36 ST. (BELOW CONTROL)
0 ----- ------ --
A I

zMIAM CA NL MIAMI CANAL at N.W 27 AVE.


S AUGUST 14. 1964 1 I IT 18 AUGUST 19. 1964

Figure 14. The effect of changes of the N.W. 36th Street control dam on
discharge, water levels, and chloride content at selected locations in the Miami
Canal during the period August 14 to 19, 1964.


at 10:30 a.m. on August 17, the salt-water front was forced down-
stream, as shown by the decline in chloride below the control and
at N.W. 27th Avenue (fig. 14.) Even when the control structure
was changed to 4 half needles open at 2:00 p.m. on August 18,
the chloride remained downstream at N.W. 36th Street through
August 19. On the other hand the chloride content at N.W. 27th
Avenue again began to increase on August 19. The maximum
chloride advances occurred about high tide on each cycle as shown
in the N.W. 27th Avenue salinity and stage hydrographs. At low
tide when the gradient in the Miami Canal is at its greatest, the
discharge increases and the salt water again moves in a seaward
direction. The anomaly in water levels at N.W. 27th Avenue
at mid-rising tide is caused when the upstream movement of the
salt-water wedge started passing this location (fig. 14). It was
most pronounced on the afternoon of August 19.











at: J r
II Ir
.7.1k


W .
A 9H


A-.. .. -- ---.-- -----t.. ..-


_0 I MIAM 'CANAL PROFILE ..4 _- ,70 O..F /
S --- o/ ..... CHLORIDE IN PPM
," .. LOW TIDE

18. ....... ......-*- 000
I ~ .~.~ 1' 510,0


..............-,........... ..-... -.. .-- -.-
a 4"" "5' "
DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES
Figure 15. Profile of chloride content in the Miami Canal on July 16, 1964 at low and high tide when the N.W.
86th Street control dam was partially open.


_______~ __ I __ __ ~ ~___~_ ___ ~___ _1_


Ir






REPORT OF INVESTIGATION NO. 45


HIGH AND LOW TIDE SALT-WATER MOVEMENT

On July 16, 1964, two chloride profiles were made along the
Miami Canal. The first was made near low tide between 8:00
and 9:00 a.m. Canal water was sampled for chloride content at
2-foot intervals from the bottom to the water surface at each
of the stations named in figure 15. Another profile was made at
high tide, between 2:30 and 3:30 p.m. using the same procedure.
The lower profile of figure 15 shows the most inland advance
of the salt-water wedge. It may be noted that the seaward dis-
charge in the Miami and Tamiami Canals at high tide was 52 cfs
and 180 cfs, but at the same time the peak inland flow at Brickell
Avenue was 480 cfs. This combined flow of 712 cfs at that time
was going into storage in the Miami Canal, the Tamiami Canal,
several man-made lakes, and into the aquifer. The salt-water
wedge moved upstream in the Miami Canal during this period
because Biscayne Bay with its high chloride concentration was
supplying about 70 percent of the water going into storage
at that time. The low-tide profile (fig. 15) shows the isochlor
positions moved seaward. The discharge through the controls in
the Miami and Tamiami Canals was 90 cfs and 225 cfs down-
stream and 2,370 cfs seaward in the Miami Canal at Brickell
Avenue. The peak discharge affecting the downstream movement
of the salt-water wedge indicated that 2.055 cfs was coming out
of storage below the controls just prior to low tide. A comparison
of the two profiles shows the change in location of the salt-water
wedge in the Miami Canal between high and low tide. The above
discharges represent only the extremes of the high and low-tide
cycle; they do not determine the runoff for the tide cycle. Data
indicate these would be typical high and low tide profiles for
any period of average discharge and normal tides.


CHLORIDE CONCENTRATION EXTREMES

The chloride concentration extremes in the Miami River and
Canal are shown in figure 16 for the period of record 1942 to
1964. The water samples were taken at the bottom of the canal at
or near high tide when the salt-water wedge was at its most
inland advance. The chloride concentration reached 13,200 ppm
just above the temporary control dam located at N.W. 36th Street
and extended inland past the Hialeah water plant, and was meas-






FLORIDA GEOLOGICAL SURVEY

DISTANCE UPSTREAM FROM BISCAYNE BAY, IN MILES


-to
.Z m
zL)n


Figure 16. Chloride extremes at high tide
Miami Canal at various sampling locations.


in the Miami River and the


ured at 2,800 ppm in the Miami Canal as far as Red Road during
the period 1942 to 1945.
The present sheet-steel piling control dam constructed in 1946
has proven adequate during all but the very dry periods. These
dry periods coupled with withdrawals of fresh water from the
Miami Canal by the adjacent Hialeah well field in the 1960's
and the drought experienced in the latter part of 1961 through
May 1962, there was not enough fresh water available in the
drainage basin to provide high enough heads in the canal up-
stream from the control dam to prevent the salt-water seepage
around the closed control dam. This salt water then moved
upstream in the Miami Canal for more than eight-tenths of a mile.
At the end of May 1962 the chloride concentration was measured
at 7,200 ppm just above the control and 790 ppm at a point
eight-tenths of a mile upstream. This water of high chloride
content was very near the influence of the Hialeah well field's


w _
w: ,t 5.
Sn 2 |Z -






REPORT OF INVESTIGATION NO. 45


cone of depression. This condition was improved in June 1962
when above normal rainfall, 14.54 inches, fell in the Miami Canal
drainage basin. This rainfall provided enough fresh water to
permit the opening of the control dam and to flush the salt water
seaward.

THE 1945 DROUGHT
Control structures in the Miami Canal area will effectively
hold back the intrusion of salt water, provided that the fresh
water behind the dams is maintained at a high enough level.
However, the problem of maintaining high fresh-water levels is
complicated by the highly permeable limestone through which
the canals were constructed. During times when the water table
approaches msl, the denser salt water will move around the
closed control structures through the aquifer and contaminate
the fresh-water supply upstream.
On March 17, 1945, the pneumatic dam in the Miami Canal
failed, and the salt water moved upstream to a point more than
half-a-mile above the Hialeah water plant. Ten days later a
temporary sheet-steel piling dam was constructed. Additional salt
water moved around this closed temporary dam through the aqui-
fer because the water levels above this dam were lower than
the downstream mean tidal levels. Figure 17 shows the inland
extent of this salt-water penetration along the bottom of the
Miami Canal on May 31, 1945. Since the only samples taken at
that time were from the bottom of the canal, the isochlor lines
in ppm were estimated from these bottom samples and from an
isochlor profile made on May 15, 1945. The upstream advance of
the salt-water wedge was relieved when the rain gages in the
basin average 3.85 inches and 6.77 inches during June and July,
respectively. The rain was sufficient to move the salt water down-
stream from the N.W. 36th Street control structure during July.

CHLORIDE CONCENTRATION IN THE AQUIFER
The history of the City of Miami's fresh-water supply has
been a problem of moving westward when their well fields were
contaminated by the high chloride concentration from Biscayne
Bay and the Miami River. In later years when several uncon-
'rolled canals were constructed through the coastal ridge to de-
velop the low-lying lands in the Everglades for urban and agri-















i .....- STANCE UPSTREAM FROM BiSCAYCE BAY, IN MILES ------ r-- --..


9


'-' MIAMI CANAL PROFILE "
!- O0 "*"" MAY 31, 1945 ,
'^ ^ ---- -- --- oo ---- -- -
,-- ,- --- o soo
'0-- 9

~: ~t ~i.:I


Si .;
2 36 f 3
4 M l eg 4

Figure 17. Extreme chloride concentration in the Miami- Canal above the N.W. 36th Street control dam on Mat 31, 1945.


r
.1 4



8 I


Es
w'


ll,





REPORT OF INVESTIGATION No. 45


cultural use, the canals provided flood protection for the lowlands
except during extremely wet periods when the drainage system
was overburdened. The uncontrolled canals caused overdrainage
during dry periods which resulted in lowering the water table
and permitted salt water to move upstream in the canals and
into the highly permeable Biscayne aquifer, the fresh-water bear-
ing formation from which Miami obtains its water supply.
Hydrologic data collected to date shows the salt front at
depth in the Biscayne aquifer has tended to move slowly, but
progressively, inland from the Tamiami Canal toward the Miami
well field, thereby flanking the control structure on the Miami
Canal at N.W. 36th Street. The proximity of the salt-water in-
trusion to the Hialeah-Miami Springs well field's cone of depres-
sion is indicated by the map for 1962 in figure 18. The inland ex-


SMIAMI
.90{ ,, ......^1


190


N :







19...1


Figure 18. Salt-water encroachment at the base of the Biscayne aquifer
1904-62 (Parker and others, 1955, p. 589), (Kohout, 1961) updated.





FLORIDA GEOLOGICAL SURVEY


tent of the 1,000 ppm chloride located at depth in the Biscayn:
aquifer is about 1 mile from the southeast edge of the cone oj'
depression. During extreme dry periods the canals act as inland
extensions of the sea, carrying salt water several miles upstream
and allowing it to leak out and contaminate the aquifer all along
its course. During these periods the low water table enables the
salt water to move inland toward the Miami well field. During
wet periods discharge in the canals rapidly moves the salt water
in the canals downstream and the overall higher water levels
tend to move the salt front in the aquifer seaward and toward
the Bay. Examination of the past records of the position of the
salt-water front in the ground has shown a very slow but a
steady movement toward the Miami well fields as the increasing
population places an ever-increasing demand on the available
water supply.

DISCHARGE AT SELECTED LOCATIONS
The past threats of salt intrusion and the expected increase in
withdrawals from the Hialeah well field show that the threat
of intrusion toward the well field will become progressively more
imminent with the present locations of the controls in the Miami
and Tamiami Canals. A control structure in the Miami Canal below
the confluence of the Tamiami Canal would reduce the threat of
salt-water encroachment to the well field from both canal systems.
A structure at such a location would move the salt water in the
canal more than 1 mile downstream in the Miami Canal, and
eliminate recurrence of the intrusion such as that of 1962. The
resulting rise in fresh-water levels attendant with the downstream
relocation would blunt the lobe of salt water in the aquifer and
cause it to move seaward and thereby create a larger buffer
zone of fresh water between the well field and the salt-water
front. In addition, the deep rockpits within the area, which pres-
ently contain water of high chloride concentration at depth,
probably would become progressively fresher, thus adding to the
area of fresh-water storage.
A lock and dam site in the Tamiami Canal at LeJeune Road
coupled with the present control structure in the Miami Canal
would be less effective than a single control structure downstream
in the Miami Canal below the confluence of the Tamiami Canal.
The mean monthly discharge, shown in figure 19, shows the water
that would be available for boat lockages at Tamiami Canal at Le-






REPORT OF INVESTIGATION NO. 45 29

too -TF T I I I I I I I I I I I I 1 1 I II I I I I IIF TTlF
1,400
1,300- ----M MIAMI CANAL at N.W 27 AVE.
-------MIAMI CANAL at N.W. 36 ST.

, \ \
1,,,oo-TAMIAMI CANAL at LeJUNE RD.

o i
Ioo00 ---- \ .... -____________ i_______

S900 I -- i
oo- -- \ --- V- --- ---- -- i I'-
o I I Ii i
L 700 ---- --- -----
u 600 i-*! '\




sM O I A 1FM AM J AS i
196500 1961 D 1962 D 1963 ___
z I
a 400- II. I





Figure 19. Monthly mean discharge at selected locations in the Miami and


Tamiami Canals, October 1960 through September 1963.

Jeune Road, Miami Canal at N.W. 36th Street, and Miami Canal at
N.W. 27th Avenue. The discharge shown for Miami Canal at N.W.
36th Street was taken directly from published records. Because the
Geological Survey at present has no discharge stations at the
other two locations, the discharge was computed as follows: The
discharge for Tamiami Canal at LeJeune Road is the summation
of the three discharge stations (Tamiami Canal near Coral Gables,
North Line Canal near Coral Gables, and Coral Gables Canal
near Coral Gables) plus 30 percent of the flow difference between
the total of the above stations plus the discharge at Miami
Canal at N.W. 36th Street from the total flow of the Miami
River at Brickell Avenue. The computed discharge for Miami
Canal at N.W. 27th Avenue is the flow of Tamiami Canal at
LeJeune Road plus the discharge of the Miami Canal at N.W.
36th Street plus 30 percent of the flow difference between Tamiami
Canal at LeJeune Road plus Miami Canal at N.W. 36th Street
from the total discharge of the Miami River at Brickell Avenue.
from the total discharge of the Miami River at Brickell Avenue.





FLORIDA GEOLOGICAL SURVEY


Locations of the above discharge stations are shown on the map
in figures 1 and 2. The mean monthly discharge for Miami
Canal at N.W. 36th Street indicates that during extreme dry
periods there would not be water available for lockages at this
location. On the other hand, the Tamiami Canal at LeJeune Road
would have a minimum flow during a dry period, such as that
experienced early in 1962, of about 30 cfs, and the Miami Canal
at N.W. 27th Avenue would have a minimum flow of about 55 cfs


1961 1962 1963
Figure 20. Monthly mean discharge from or into the aquifer below the
control dams in the Miami River and its tributaries, April 1961 through
September 1963.

available for boat lockages. This minimum flow also takes into
account the additional storage of fresh water that could be used
for boat lockages that would become available in the aquifer
and several lakes with the relocation of the controls downstream
from their present location.
The discharge from or into the Biscayne aquifer from the
Miami River and its tributaries below the control dams during the
dry period April 1961 through September 1963 is shown in figure
20. Even during this dry period the aquifer was discharging to
the Miami River at all times except for March 1962 when ab-






REPORT OF INVESTIGATION NO. 45


normally high tides occurred, and again in April and May 1963.
The most important factors that will control the ultimate
effectiveness of the proposed lock and dam structure are: (1) the
precautions taken to prevent the movement of salt water beyond
the structure during locking operations; and (2) the amount of
fresh water used for locking boats during prolonged drought.
If, in the future, the amount of fresh water used in locking plus
that required to maintain safe water levels at the control were
to exceed the quantity available in the canal system, the effective-
ness of the control of salt intrusion would be negated and a re-
advance of the salt front would occur.

THE EFFECTS OF WIND ON WATER MOVEMENT
The effects of wind on water levels and canal discharge are
shown in figure 21. When Hurricane Cleo passed through the
Miami area on August 26-27, 1964, the hydrologic effect was
recorded on all gages in the study area and the tidal gages in
Biscayne Bay. Discharge illustrated in the upper graph shows
the flow through the salinity control in the Miami Canal at N.W.
36th Street. Early in the morning on August 26 the discharge at
the control was averaging 170 cfs with 4 half needles open. In
anticipation of the impending hurricane and possible flooding,
the control was opened to 22 full and 6 half needles at 11:00
a.m. The flow then increased to 580 cfs at 3:00 p.m. on August 26,
but fell off rapidly to a negative (upstream) flow of 62 cfs at
11:00 p.m. when the strongest easterly winds hit the area and
pushed the water in the Miami River at Brickell Avenue to a
higher level than that above the open control dam as shown in
the center hydrographs from 10:00 p.m. to 11:30 p.m. on August
26. After the eye of Hurricane Cleo passed, the strong westerly
winds increased in intensity until a westward gradient of more
than 3.5 feet existed across Biscayne Bay. That effect is markedly
shown in the lower hydrograph when the Biscayne Bay at Coconut
Grove tide gage recorded a minimum of -1.4 feet (referred to
msl) at 3:00 a.m. on August 27, while the Biscayne Bay tide
gage located in the Key Biscayne Marina recorded a high of 2.55
feet at 3:20 a.m. on August 27. Hurricane Cleo was a relatively
dry storm. The average rainfall recorded at the three rain gages
in the basin was 0.77 inch on August 26, and 4.61 inches on
August 27.
When a severe hurricane is imminent for the lower southeast
coast of Florida, the present type of salinity controls in the major





FLORIDA GEOLOGICAL SURVEY


-- I I ___
SMIAMI RIVER at BRICKELL AVENUE
i / I I I

YNE BAY oat COCONUT GROVE

\ ,,\ ..
J ".iVEJ.\
I-o; -


/


i
BISCAY
----
I


11


AUGUST 26, 1964 AUGUST 27, 1964
Figure 21. Effects of Hurricane Cleo's winds at selected discharge and wa-
ter-level stations in the Miami Canal and Biscayne Bay, August 26-27, 1964.






REPORT OF INVESTIGATION NO. 45


canals in Dade County are generally fully opened before the
hurricane strikes to reduce the possibility of flooding. High
storm tides as a result of strong easterly winds push large quanti-
ties of salt water upstream. This invasion of salt water above
the opened controls may contaminate the aquifer as well as in-
crease the threat of flooding. If the salinity controls were rede-
signed and operated so that they could be closed when the flow
starts to reverse during the hurricane, much better protection of
the fresh-water supply and from flooding would be assured. During
the period August 26-27, 1964, the control in the Miami Canal
at N.W. 36th Street was open in anticipation of Hurricane Cleo.
Following the passage of Hurricane Cleo which brought very
little rainfall to Dade County, it was necessary to discharge valu-
able fresh water from the reserve supply in order to push the salt
water downstream from the salinity controls. An example of the
magnitude of reverse flow caused by storm tides was that of
September 10, 1960, during Hurricane Donna, when a peak flow
of 1,220 cfs moved upstream through the open salinity control
in Snapper Creek Canal. These typical examples demonstrate the
need for salinity controls that can be operated during hurricanes
to more effectively protect the area from floods, salt-water en-
croachment and to conserve the fresh-water supply.

SUMMARY
Salt-water intrusion historically has been the chief threat to
the water resources of the Miami area. The early history of the
City of Miami's fresh-water supply has been that of moving west-
ward when the well fields were contaminated by the high-chloride
concentration from Biscayne Bay and the Miami River. In later
years several uncontrolled canals were constructed through the
coastal ridge to develop the lowlying lands in the Everglades for
urban and agricultural use. The canals provided flood protection
for the lowlands except during extremely wet periods when the
drainage system was overburdened. These canals were the chief
factor in salt-water contamination of the aquifer in two ways.
First, during dry periods the uncontrolled canals were avenues
for salt water to travel inland for several miles to contaminate
the aquifer. Second, the overdrainage lowered water levels in the
ground and permitted denser salt water to move inland through
the aquifer. The chloride contamination in the aquifer can be
halted or pushed back by holding higher water levels behind con-





FLORIDA GEOLOGICAL SURVEY


trol dams in the canals, or by moving the control dams further
downstream.
The average chloride content of water in the Miami Canal
ranges from about 12 ppm above the controls to about 19,000
ppm in Biscayne Bay. The data show that the salt-water wedge
in the Miami Canal was located at N.W. 27th Avenue about 60
percent of the time and at the downstream side of the present
control dam 23 percent of the time. It was determined that a
discharge of at least 550 cfs from the area is required to hold
the salt-water wedge downstream as far as N.W. 27th Avenue
and at least 280 cfs in the canal system would be required to
move the salt-water wedge away from the base of the N.W. 36th
Street control dam. During wet years the salt water will remain
downstream from the salinity-control dam all year, but during
dry years water containing 1,000 ppm chloride or more will
remain just below the control dam for several months. The fresh-
water discharge from 60 percent of the aquifer below the controls
in the Miami River and its tributaries would be saved by moving
the present controls below the confluence of the Miami and Tami-
ami Canals.
If a lock and dam were located in the Miami Canal in the
vicinity of N.W. 27th Avenue there would be about 55 cfs avail-
able for boat lockage during dry periods, such as early in 1962.
Records indicate that at times there would be no discharge avail-
able in the Miami Canal at N.W. 36th Street and about 30 cfs
at Tamiami Canal at LeJeune Road. Isochlor profiles indicate that
the salt-water wedge is very sensitive to tidal cycles and changes
in discharge. It moves upstream during rising and high tide when
the seaward flow in the canal is at a minimum and moves seaward
during falling and low tide when the flow in the canal is at a
maximum.
When a severe hurricane is imminent, the controls in major
canals in Dade County are generally left full open before the
hurricane strikes to reduce the possibility of flooding. During
the hurricane high storm tides as a result of strong easterly
winds may push large quantities of salt water upstream. Hurri-
cane Cleo brought very little rain to Dade County, so it was neces-
sary to discharge fresh water from storage in order to again
push the salt water below the salinity controls. If the salinity
controls were redesigned so that they could be closed when the
flow starts to reverse during the hurricane, much better protection







REPORT OF INVESTIGATION No. 45


of the fresh-water resources and flooding of the area would be
assured.
The present control in the Miami Canal has protected the
water supply of a City of Miami well field but if the extreme
conditions such as experienced in the early 1960's were to recur,
accompanied by increased withdrawals from the well field, the
salt-water wedge in the aquifer could move into the cone of de-
pression and contaminate the fresh-water supply. Considerable
reduction in the well field's pumping rate would be required to
control the salt-water intrusion.
The continuing changes in water control and the increasing
withdrawals for water supply will alter the flow system and
greatly increase the quantity of water required to maintain the
desired levels in the Miami Canal to hold back the salt-water
front in the aquifer. This study was limited in scope to data
collected since 1940 and to hydrologic conditions existing at this
time. However, the data presented will provide a basis for the
analyses of the effects of any major changes in the flow system
in the future.

REFERENCES
Chambers, A. C. (see Dole, R. B.)
Cooper, H. H., Jr.
1964 (and Kohout, F. A.; Henry, H. R.; and Glover, R. E.) Sea water
in coastal aquifers: U. S. Geol. Survey Water-Supply Paper
1613-C.
Dole, R. B.
1918 (and Chambers, A. C.) Salinity of ocean water at. Fowey Rocks,
Florida: Carnegie Inst. Washington Pub., v. 9, rept. 213.
Glover, R. E. (see Cooper, H. H., Jr.)
Henry, H. R. (see Cooper, H. H., Jr.)
Klein, Howard (also see Sherwood, C. B.)
1957 Interim report on salt-water encroachment in Dade County, Flor-
ida: Florida Geol. Survey Inf. Circ. 9.
Kohout, F. A. (also see Cooper, H. H., Jr.)
1960 Flow pattern of fresh water and salt water in the Biscayne
aquifer of the Miami area, Florida: Internat. Assoc. Sci. Hydro.,
no. 52.
1961 A case history of salt-water encroachment caused by a storm
sewer in the Miami area, Florida: Am. Water Works Assoc.
Jour., v. 53, no. 11.
1964 (and Leach, S. D.) Salt-water movement caused by control-dam
operation in the Snake Creek Canal, Miami, Florida: Florida
Geol. Survey Rept. of Inv. 24, pt. 4.






36 FLORIDA GEOLOGICAL SURVEY

Leach, S. D. (also see Kohout, F. A.)
1963 (and Sherwood, C. B.) Hydrologic studies in the Snake Creek
Canal area, Dade County, Florida: Florida Geol. Survey Rept. of
Inv. 24, pt. 3.
Parker, G. G.
1955 (and others) Water resources of southeastern Florida; with
special reference to the geology and ground water of the Miami
area: U.S. Geol. Survey Water-Supply Paper 1255.
Sherwood, C. B.
1962 (and Leach, S. D.) Hydrologic studies in the Snapper Creek Ca-
nal area, Dade County, Florida: Florida Geol. Survey Rept. of
Inv. 24, pt. 2.
1963 (and Klein, Howard) Surface and ground-water relation in a
highly permeable environment: Internat. Assoc. Sci. Hydro.,
no. 63.