UNITED STATES DEPARTMENT OF THE INTERIOR
MAP SERIES NO. 59 GEOLOGICAL SURVEY


FLORIDA DEPARTMENT OF NATURAL RESOURCES
published by BUREAU OF GEOLOGY


ENCROACHING SALT WATER
IN NORTHEAST PALM BEACH COUNTY, FLORIDA


By
Harry G. Rodis





Prepared by the
U. S. GEOLOGICAL SURVEY
in cooperation with
PALM BEACH COUNTY BOARD OF COMMISSIONERS,
CENTRAL AND SOUTHERN FLORIDA FLOOD CONTROL DISTRICT
and the
FLORIDA DEPARTMENT OF NATURAL RESOURCES
DIVISION OF INTERIOR RESOURCES
BUREAU OF GEOLOGY
and
DIVISION OF RECREATION AND PARKS


Tallahassee, Florida
1973


In the upper reaches of the Loxahatchee River, dying cypress trees, and barnacles growing on logs, indicate a change from a
fresh-water to a salt-water environment. Red mangrove trees (at right) thrive in a salt-water environment and are replacing the
fresh-water vegetation.


Salinity-control structure on Canal 18 keeps upstream canal levels high near Jupiter well field, which retards the inland
movement of salt water. Barnacles clinging to rocks on the downstream side of the structure indicate presence of salt water.


Drainage of inland areas for agriculture and urban development causes rainfall to run off quickly through canal systems to
the sea. Water is, thus, diverted from the shallow aquifer and the Loxahatchee. The agricultural area shown above is near the
Loxahatchee headwaters; most of the rain falling on this area drains into Canal 18 rather than the Loxahatchee.


Wells in Tequesta Well Field "1" shown above are 60 to 70 feet deep and yield approximately 500 gallons per
minute. Other wells nearby range in depth from 30 to 180 feet and may yield from 5 to 750 gallons per minute. The water
is generally of good chemical quality, low in hardness, and low in chloride except where contaminated by adjacent
salty-water bodies. Below 180 feet, water becomes scarce and generally is very salty.


THE PROBLEM

Sea water is encroaching inland in northeast Palm Beach County and
adjacent parts of Martin County. It threatens the fresh-water resources
of growing coastal communities and a river. This atlas describes the
causes and possible solutions to the problem.
Before the advent of settlers, this area had coastal springs, which
seeped from saturated rocks and sand (shallow aquifer) into the sea,
and streams carried fresh water seaward to Jupiter Inlet. The Everglades
and lakes stored much of the rain that fell, and flow into the
Loxahatchee River estuary was nearly constant during the wet season.
Some of the water from the Everglades, lakes, and local rainfall
percolated downward to replenish the shallow aquifer. In the early
1900's, man began to drain the Everglades to make additional land
available for farms and homes and began to connect lakes and streams
to the sea. The flow of fresh water to the estuary and into the shallow
aquifer, thus, gradually diminished, thereby changing the balance
between the fresh- and salt-water environments and causing salt water
to move inland. Today, salt-water tides reach the upper Loxahatchee
River (northwest fork), destroying fresh-water flora and fauna. Salt
water, no longer held back by high-water levels, is encroaching as a
wedge into the shallow aquifer and is threatening to contaminate
fresh-water wells.
Although the general position of the salt-water wedge in the shallow
aquifer has not changed markedly in the past several years, parts of the
salt front near heavily pumped municipal and irrigation wells have
advanced inland about half-a-mile. During a drought in 1970-71,
pumping was discontinued in several wells in the Tequesta and Juno
Beach well fields because of increasing salt content in the water. More
than 5 million gallons per day of fresh water is withdrawn from
municipal and golf-course wells near the salt-water front. Much of this
water is ultimately discharged to the sea through treatment plants, is
evaporated, or is transpired. Water levels have declined sharply. The
result is a net loss of fresh water in the aquifer, much of which is
replaced by salt water. In other words, with a sufficient water-level
decline, salt water moves inland.
The upper reach of the Loxahatchee River is one of the last
remaining natural rivers in south Florida. The river requires a sustained
flow of fresh water to nourish plant and animal communities and to
prevent salt water from moving farther upstream. Except for occasional
floods, the flow of fresh water has diminished at an accelerated rate, as
rainfall runs off quickly through an expanding system of drainage
canals. During the 1970-71 drought, the flow of the river was about
200 gallons per minute. A sustained flow many times greater than this
is necessary to maintain the fresh-water environment of the river, even
in part.

OUTLOOK

By the year 2000, fresh-water needs for coastal communities may
increase 8 to 10 fold. The present source of fresh water in the shallow
aquifer near the coast will not be ample to meet the demand. Water in
deeper aquifers is generally too highly mineralized for most uses.
Potential fresh-water resources are available, however, from the shallow
aquifer in areas west of the present well fields. Municipalities possibly
could explore the potentials in these areas. Use of the present water
source can be prolonged by wider spacing of wells, reduced pumping
rates, improved design for municipal wells, and reuse of water. For
example, treated sewage and storm runoff could be used to irrigate golf
courses or to maintain a head of fresh water at the fresh-salt water
interface.
Much of the remaining fresh-water environment of the Loxahatchee
River can be maintained by a sufficient flow of fresh water. This could
be provided by diverting enough fresh water from inland canals and
water-storage areas to the river to retard the advance of salt water.
Preventing upstream movement of salt-water tides by constructing a
salinity barrier, dam, or lock downstream also would aid in maintaining
the fresh-water environment.


TEQUESTA US GEOLOGICAL SURVEY
WELL FIELD OBSERVATION WELL
NORTH FORK FEEC INTRACOASTAL
LOXAHATCHEE RIVER RR WATERWAY ATLANTC OCEAN
GOLF COUL LURSE "
fl7


US GEOLOGICAL SURVEY
OBSERVATION WELL


NOT TO SCALE
Before the turn of the century (about 1880) fresh water flowed to the ocean through Jupiter
Inlet, and fresh-water springs seeped from the ocean floor. Streamflow and the water table were high
enough to hold sea water at the coast.


FRESH WATER

SSALT WATER

SSALTY GROUND-WATER

A wedge of salty ground water threatens Tequesta Well Field, and smaller wedges extending from the lower reaches of the Loxahatchee River and the Intracoastal
Waterway have contaminated numerous shallow domestic wells. U. S. Geological Survey observation wells, one of which is shown above, determine movement of the
salt-water wedge near municipal well fields. Heavy pumpage at the well field pulls water levels down below sea level.


Today (1972) sea water encroaches the coast. Wedges of salty ground water threaten municipal wells and other wells in Juno Beach, Tequesta and Jupiter, while
salt-water tides invade the Loxahatchee River. Declining ground-water levels and diminishing streamflow permit sea water to move inland beneath fresh ground water as well
as into the Loxahatchee. The shallow aquifer shown above is about 200 feet thick and underlies the eastern part of Palm Beach and Martin Counties.


BJUPITER

JUNO
BEACH


RATON


BROWARD COUNTY




LOCATION MAP


M A M J J A S 0 N D J F M A M

1970 1971

Deficiency in rainfall during the 1970-71 drought, shown as a linear
projection above, resulted in lowering the water table. U. S. Geological Survey
observation wells continuously monitor fluctuations of the water table in several
coastal and inland areas. Location of Well 565 is shown on map at right.


The position of the salty ground-water wedge advanced
inland during the 1970-71 drought and caused pumping to be
discontinued at several wells in Tequesta Well Field.


6000r


Data from wells monitoring sea-water encroachment show
that declining water levels in most wells coincide with an increase in
salinity (chloride) in the water-bearing zones tapped by the wells. The
sharp rise in the water level and corresponding decline in chloride of
water from well 596 at Juno Beach during April 1971 apparently
coincided with reduced pumpage of a nearby municipal well, which had
become contaminated by salty water.


Diminishing flow of the Loxahatchee River brought about by land drainage and drought has caused ocean tides to reach farther up
the river. Stations in the middle and upper reaches, shown above, are sampled regularly by the U. S. Geological Survey for salinity
determinations.


w 5000
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4000




3000

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2000
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FLORIDA GEOLOGIC SURVEY MAP SERIES


- FA -d


DEPARTMENT OF NATURAL RESOURCES
BUREAU OF GEOLOGY

This public document was promulgated at a total
cost of $390.00 or a per copy cost of $.26 for the
purpose of disseminating hydrologic data.


.Cyl



NO. 59
1972
.R6


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