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Salt intrusion can be controlled ( FGS: Leaflet 7 )
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 Material Information
Title: Salt intrusion can be controlled ( FGS: Leaflet 7 )
Series Title: ( FGS: Leaflet 7 )
Physical Description: Book
Creator: Klein, Howard
Publisher: Florida Geological Survey
Publication Date: 1965
 Subjects
Subjects / Keywords: Saltwater encroachment -- Florida
 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: notis - AAA0582
notis - AJW7430
System ID: UF00001175:00001

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Table of Contents
    Title Page
        Page i
        Page ii
    Salt intrusion can be controlled, by Howard Klein
        Page iii
        Page iv
        Page v
        Page vi
        Page vii
        Page viii
        Copyright
            Copyright
Full Text






STATE OF FLORIDA
STATE BOARD OF CONSERVATION
DIVISION OF GEOLOGY


FLORIDA GEOLOGICAL SURVEY
Robert O. Vernon, Director











LEAFLET NO. 7


SALT INTRUSION
CAN BE CONTROLLED



By
Howard Klein













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


TALLAHASSEE
1965












































































Completed manuscript received
September 2, 1965
Printed by the Florida Geological Survey
Tallahassee

110







SALT INTRUSION CAN BE CONTROLLED

By
Howard Klein

Salt-water intrusion is the chief threat to the
resh-water supplies of Dade County. Intensive
investigations of the geology and hydrology of Dade
countyy by the U. S. Geological Survey in coopera-
;ion with the county show that uncontrolled drainage
,anals have been the primary cause of salt-water
intrusion in the Biscayne aquifer, the highly per-
neable limestone reservoir rock that yields all of
)ur drinking water. Intrusion occurs by two pro-
:esses:
(1) Uncontrolled canals drain fresh ground
vater stored in the aquifer, waste it to the ocean,
ind cause water levels to decline excessively;
-his permits salty ground water at depth to move
inland;
(2) Uncontrolled canals carry salt water seve-
:al miles inland from Biscayne Bay, and during dry
periods the salt water infiltrates outward from the
canals and contaminates adjacent parts of the
aquifer.
The maps in figure 1 show the areas progress-
ively affected by salt-water intrusion. The major
advance of salt water took place before 1946 when
there were no control dams in the major canals to
prevent the waste of fresh water from the aquifer.
The situation was critical along the Miami Canal
during the dry season of 1946. Several supply walls
in the Miami well field were contaminated by salt
water from the canal. Because the pattern of salt-
water intrusion closely followed the individual
canal channels, there was no doubt that the con-
tamination was a direct result of canal construction
and drainage.
Late in 1946 control dams were erected in all
major canals connected to Biscayne Bay. As -a
result, the salt water retreated seaward along most
,of the canal systems (compare 1946 and 1950 maps)
and the Miami well field was maintained secure.
The improvement in the fresh-water picture demon-
strated that salt intrusion could be controlled by









BISCAYNE CANAL


LITTLE RIER



36 ST
WEL. FLD
G

Ci
IiS

J -. 4

1943 l lL


I----- CANAL & CONTROL DAM


Figure 1. Maps of eastern Dade County showing areas
progressively affected by salt-water intrusion.


relatively simple methods -- chiefly through water
conservation and maintenance of water levels at
proper elevations.
A comparison of the 1950 map with the 1963
map shows a continued inland intrusion of salt
water along the Tamiami Canal toward Miami's
municipal well field, and east of the Biscayne
Canal near North Miami's municipal well field.
These later movements were due to the fact that
the control dams in those two canals were located
too far inland to give continuous protection to the


^5-7.5 s4


ho.7


-2. 5`7



'{I ^s- --




MIA M MIAMI




ES I MILES
1961*i








well fields. In 1960 the con trol dam in the Biscayne
Canal was moved from its original location, oppo-
site the North Miami well field to a site two miles
downstream. However, the move was too late and
the field was contaminated by a massive slug of
salt water. Recent samplings of water in that area
indicate a slow freshening as a result of relocating
the barrier. A boat lock and control dam have been
proposed in the Miami Canal at 27th Avenue. This
would furnish effective control for both the Miami
and Tamiami Canals and give good protection to
Miami's well field.
A perennial problem in the urban and agricul-
tural expansion in Dade County is that of flood
prevention during rainy seasons. Flood control
has been and is being provided by a network of
levees and drainage canals. However, the area
must not be drained excessively; to do so would
endanger the water supplies during prolonged
drought. Many troublesome areas result where pro-
perty of low elevations is developed without place-
ment of sufficient fill to proper flood-control eleva-
tions. These areas must be protected against flood-
ing. One such area is in North Miami Beach along
the Oleta River.
Provision for adequate drainage in the North
Miami Beach area necessitates deepening and wi-
dening the downstream reach of the Oleta River
channel. The existing unimproved drainage condi-
tion approximates condition A in figure 2. The
diagram, figure 2, shows the relative changes in
the position of the salt front in an aquifer within an
area where a drainage system is being developed.
Improvement of the Oleta River channel without a
control dam would result in effective surficial
drainage of the surrounding area, but also in a
general lowering of ground-water levels, and an
inland movement of salt water along the stream
channel and in the Biscayne aquifer beneath and
adjacent to the river. This condition would be
comparable to position B in figure 2.
Prevention of excessive drainage and of coin-
cident salt intrusion necessitates that a control
dam be provided. Proper operation of the control










Position-B: River is deepened, channel
improved; drainage is facilitated and un--
controlled, causing low water levels;
.. .. .. salt water m oves upstream .
Position-C: Improved channel is w
controlled, water .levels regulated; \\,\
salt water, blocked by control, moves \ \
seaward.
seward. CONTROL DAM





A _ALT FRONT
I liftI
Position-A: River isshallow, channel is C
unimproved; poor drainage and high water
levels; salt water near coast.

Figure 2. Sketch showing relative change in salt-front
pattern in an aquifer where a drainage system is being
developed.

dam would insure not only protection against flood-
ing but also protection to the water resources. This
condition is shown by position C, figure 2, where
the salt front has stabilized between its original
position, before improvement, and its probable
position if no control dam were installed. Position
C represents a medium condition that provides the
maximum possible combined protection from both.
flooding and salt-walr intsp n q
The map of No l Beach and vicinity,
figure 3, shows the location of the Oleta River with
respect to the Snake Creek Canal. The Snake Creek
Canal is a primary canal of the regional water-
control system. It extends westward for several
miles and serves as the main drainage for all of
northern Dade County. During the dry seasons the
control dam, near the coast, (shown in figure 3)
is closed in order to maintain the upstream water
level at as high an elevation as possible.
Improvement of drainage along the Oleta River
could reduce the ability of the control in the Snake
Creek Canal to maintain high water levels. If the
Oleta River should be improved but not controlled,~
eastward outseepage will occur from the Snake








































Figure 3. Map of North Miami Beach showing location
of Oleta River with respect to Snake Creek Canal.

Creek Canal system to the Oleta River under a
high gradient. However, if the Ole.ta River should
be improved and controlled, the outseepage from
Snake Creek Canal would occur under a lower gra-
dient, thereby decreasing the waste of fresh water.
The control salt intrusion in north Dade County
depends entirely upon maintaining a high water
level in the Snake Creek Canal system. If water
losses from the Snake Creek Canal should become
great enough to lower water levels excessively,
the salt front would begin to move inland and would







pose a threat to the municipal well field for Nort
Miami Beach (figure 3).
lade County is one of the fastest growing
areas in the country. If growth is to continue
constant consideration must be given to the prc
tection of the water resources of the area. Thi
means in part that the amount of water wasted b
canal discharge each year must be decreased an
salt-water intrusion controlled. In 1963 Dade Coun
ty's water needs were about 200 million gallons
day. It has been predicted that in 25 years Dad,
County will be using nearly 1 billion gallons i
day. That quantity will not be available unles
wastage to the ocean is controlled and the wate
resources are carefully conserved and properly:
managed.
Several reports have been prepared which]
describe in more detail the problem of salt intrt
sion in Dade County. They are available to in
terested persons at the office of the County Engi
neer, the Florida Geological Survey, and of th4
U. S. Geological Survey as well as at most loca
libraries. Information contained in the reports in
clude: 0, V!.
(1) Explanation of principles governing salt
water intrusion.
(2) Description of the mechanics of salt-watel
intrusion.
(3) Results of research on salt-water intru-
sion.
(4) Methods of combating salt-water intrusion.
(5) Description of areas affected by salt-watei
intrusion.
(6) Local problems of salt-water intrusion.
(7) Evaluation of water resources of Dade
County.










FLRD GEOLOSk ( IC SUfRiW


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