2
Each submarine groundwater discharge technique has individual strengths and weaknesses. Seepage meters provide a direct measurement of localized flow. They can also easily provide 'clean' seep water samples. However, seep meters may be susceptible to possible artifacts caused by interaction of tides and waves, although such limitations have not been thoroughly tested. The radioisotopes are less difficult to sample in the field than using seepage meters, but their measurement requires sophisticated laboratory equipment that is not widely available. One important characteristic of the radioisotope techniques is that they provide an integrated value of seepage rates across the entire lagoon. They are thus complementary to the seepage meter technique. Chloride concentrations indicate that only a minor component (1 - 5%) of seep water originates from meteoric ground water. This implies that 95 - 99% of the interstitial water has to be recycled lagoon seawater. The isotopic concentration of strontium ( 87 Sr/86 Sr) was nearly identical in the seep water and lagoon water, yet was measurably lower than that in modern seawater. The 87 Sr/86Sr ratios were also systematically lower during the rainy season, reflecting the greater influx of seep water into lagoon water and short groundwater residence times. Nutrient concentrations were 3-5 times elevated in the seep water over the lagoon water, and suggest that sediment/water interface exchange processes, such as submarine groundwater discharge, are critical components of coastal nutrient budgets (Johannes, 1980; Krest et al., 2000). References Cable, J.E., Bugna, G.C., Burnett, W.C., Chanton, J.P., 1996. Application of 222 Rn and CH4 for assessment of ground water discharge to the coastal ocean. Limnol. Oceanogr. 41,1347-1353. Johannes, R.E., 1980. The ecological significance of the submarine discharge of ground water. Mar. Ecol. Prog. Ser. 3,365-373. Krest J.M., Moore W.S., Gardner L.R., Morris J.T., 2000. Marsh nutrient export supplied by ground water discharge: Evidence from radium measurements, Global Biogeochemical Cycles 14,167-176. Leve, G.W., 1970. The Floridan aquifer in Northeast Florida. Ground Water 6,19-29. Martin J.B., Cable, J.E., Swarzenski, P.W., 2000. Quantification of ground water discharge and nutrient loading to the Indian River Lagoon. St. Johns River Water Management District Report pp. 154. Moore, W.S., 1999. The subterranean estuary: A reaction zone of ground water and seawater. Mar. Chem. 65,111-125. St. John's River Water Management District, August 2000 Hydrologic Conditions Report, pp.71. Spechler, R.M., 1994. Saltwater intrusion and the quality of water in the Floridan Aquifer system, northeastern Florida. U.S. Geol. Surv. Water Resources Invest. Report 92-4174, p. 76. Swarzenski, P.W., Reich, C.D., Spechler, R.M., Kindinger, J.L and Moore, W.S. Using multiple geochemical tracers to characterize the hydrogeology of the submarine spring off Crescent Beach, Florida. Chemical Geology, (in press). For further information, plaase contact: Peter W. Swarzenski 1 Jonathan B.Martin 2 Jaye E. Cable, and 3 Mary K. Lindenberg 2 Betsy Boynton 1 Rita Bowker 1 and Gilbert C. Sigua 4 1 U.S. Geological Survey Center for Coastal Geology 600 4th Street South St. Petersburg, FL 33701, USA Telephone: 727-803-8747 Fax:727-803-2032 Email: [email protected] 2 Department of Geological Sciences University of Florida Gainesville, FL 32611, USA Telephone: 352-392-6219 Fax: 352-392-9294 Email: [email protected] 3 Department of Oceanography Louisiana State University Baton Rouge, LA 70803, USA Telephone: 225-334-2390 Fax: 225-388-6326 Email: [email protected] 4 Environmental Sciences Saint John's River Water Management District P.O. Box 1429 Palatka, FL 32178 904-329-4821 Email: gcs®sjrwmd,state.fl.us Partial funding for this project has been provided by SJRWMD, as part of contract No: 99G245 This report is preliminary and has not been reviewed for conformity with U.S. Geological Survey editorial standards or with the North American Stratigraphic Code. Reference therein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. USGS science fora changing world ~T Quantifying Submarine Groundwater Discharge To Indian River Lagoon, Florida Figure 1. Sampling for submarine groundwater discharge in Indian River Lagoon. Introduction The Indian River Lagoon system (Fig. 1) extends over 250 km along the east-central coast of Florida and consists of three inter-connected lagoonal basins: Mosquito, Banana River, and Indian River lagoons. Exchange of lagoon water with the Atlantic Ocean is limited to four tidal inlets (Sebastian, Ft. Pierce, St. Lucie and Jupiter) that occur in the southern reaches of Indian River Upper Indian River Lagoon Station locations May, August 1999 wator Mkjmn BUM Figure 3. Site location map for upper Indian River Lagoon, Florida. The discharge of submarine ground water has recently been shown to be an important process in many environmentally fragile coastal ecosystems. However, groundwater discharge into coastal bottom water is still an often- overlooked component of many hydrologic and oceanic models. The exchange of interstitial water across the sediment/water interface may introduce anthro- pogenic pollutants, maybe an important part of coastal nutrient cycles, and may cause excess nutrient loading, thereby potentially degrading the coastal water quality. Here we report on Year-1 results from a co-operative (USGS-UF-LSU) project that is investigating the role of submarine groundwater discharge into Indian River Lagoon, Florida. lagoon. The following processes control the salinity of lagoon water: precipitation, the exchange of water through these inlets, wind, tidal forcing, evaporation, surface runoff and potential submarine groundwater discharge. In this system, the intensity and duration of wind have the most pronounced affect on lagoon water levels. The overall objective of this project was to determine the rate and potential ecological significance of submarine groundwater discharge to Indian River Lagoon (Fig. 2). The study area during the first year of the project included the northern most 10 km of the Indian River Lagoon (-48 km2 ). Of the 28 sampling stations, 22 were arranged in shore-perpendicular transects; the remaining six stations were distributed within the lagoon center (Fig. 3). At each station, lagoon and interstitial water samples were collected, and groundwater seepage rates were measured using conventional seepage meters. Interstitial water samples were obtained from four stations using custom-built multi-samplers. Six groundwater samples were collected from wells surrounding the lagoon. Two additional samples Submarine Groundwater Discharge e May occur where ever an aquifer is hydreulically connected to the sea through permeable bottom sediments; e Decreases with distance from shore (Ghyben-Herzberg Principle); e Directly affected by groundwater withdrawals; ( e Potential point source for contam inants. Figure 2. Parameters of submarine groundwater discharge. were collected from tributaries to the lagoon including Turnbull Creek and Haulover Canal. Sampling of the seepage stations, groundwater wells, and tributaries occurred in May 1999, to coincide with the end of the normal dry season, and in August 1999, during the normal rainy season. A third trip in December 1999 was used only to sample interstitial water. Hydrogeology The hydrogeology along the northeastern coast of Florida can be broadly divided into two aquifer systems - the Surficial and the Floridan aquifer system (Fig. 4). Sand, silt and clays of the U.S. Department of the Interior U.S. Geological Survey USGS Open File Report 00-492 October 2000

Groundwater Submarine Lagoon, Quantifying River … River Lagoon. St. Johns River Water Management District Report pp. 154. Moore, W.S., 1999. The subterranean estuary: A reaction

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Each

sub

mar

ine

grou

ndw

ater

di

scha

rge

tech

niqu

e ha

s in

divi

dual

st

reng

ths

and

wea

knes

ses.

Seep

age

met

ers

prov

ide

a di

rect

mea

sure

men

t of

loca

lized

flow

. Th

ey c

an a

lso

easi

ly p

rovi

de 'c

lean

' see

p w

ater

sa

mpl

es.

How

ever

, see

p m

eter

s m

ay

be s

usce

ptib

le to

pos

sibl

e ar

tifac

ts

caus

ed b

y in

tera

ctio

n of

tide

s an

d w

aves

, alth

ough

suc

h lim

itatio

ns h

ave

not b

een

thor

ough

ly te

sted

. Th

e ra

dioi

soto

pes

are

less

diff

icul

t to

sam

ple

in th

e fie

ld th

an u

sing

se

epag

e m

eter

s, bu

t the

ir m

easu

rem

ent

requ

ires

soph

istic

ated

labo

rato

ry

equi

pmen

t tha

t is

not w

idel

y av

aila

ble.

O

ne im

porta

nt c

hara

cter

istic

of t

he

radi

oiso

tope

tech

niqu

es is

that

they

pr

ovid

e an

inte

grat

ed v

alue

of s

eepa

ge

rate

s ac

ross

the

entir

e la

goon

. Th

ey

are

thus

com

plem

enta

ry to

the

seep

age

met

er te

chni

que.

Chl

orid

e co

ncen

tratio

ns in

dica

te

that

onl

y a

min

or c

ompo

nent

(1 -

5%

) of

see

p w

ater

orig

inat

es f

rom

met

eoric

gr

ound

wat

er.

This

impl

ies

that

95

- 9

9% o

f the

inte

rstit

ial w

ater

has

to

be

recy

cled

lago

on s

eaw

ater

. Th

e is

otop

ic c

once

ntra

tion

of s

tront

ium

(8

7Sr/8

6Sr)

was

nea

rly id

entic

al in

the

seep

wat

er a

nd la

goon

wat

er, y

et w

as

mea

sura

bly

low

er th

an th

at in

mod

ern

seaw

ater

. Th

e 87

Sr/86

Sr ra

tios

wer

e al

so s

yste

mat

ical

ly lo

wer

dur

ing

the

rain

y se

ason

, ref

lect

ing

the

grea

ter

influ

x of

see

p w

ater

into

lago

on

wat

er a

nd s

hort

grou

ndw

ater

resi

denc

e tim

es.

Nut

rient

con

cent

ratio

ns w

ere

3-5

tim

es e

leva

ted

in th

e se

ep

wat

er o

ver t

he la

goon

wat

er, a

nd

sugg

est t

hat s

edim

ent/w

ater

inte

rfac

e ex

chan

ge p

roce

sses

, suc

h as

su

bmar

ine

grou

ndw

ater

dis

char

ge, a

re

criti

cal c

ompo

nent

s of

coa

stal

nut

rient

bu

dget

s (J

ohan

nes,

1980

; Kre

st e

t al.,

20

00).

Refe

renc

es

Cabl

e, J

.E.,

Bugn

a, G

.C.,

Burn

ett,

W.C

., Ch

anto

n, J

.P.,

1996

. Ap

plic

atio

n of

222

Rn

and

CH4

for a

sses

smen

t of g

roun

d w

ater

dis

char

ge to

the

coas

tal o

cean

. Li

mno

l. O

cean

ogr.

41,1

347-

1353

.

Joha

nnes

, R.E

., 19

80.

The

ecol

ogic

al s

igni

fican

ce o

f the

sub

mar

ine

disc

harg

e of

gro

und

wate

r. M

ar. E

col.

Prog

. Ser

. 3,3

65-3

73.

Kres

t J.M

., M

oore

W.S

., G

ardn

er L

.R.,

Mor

ris J

.T.,

2000

. Mar

sh n

utrie

nt e

xpor

t su

pplie

d by

gro

und

wat

er d

isch

arge

: Evid

ence

from

radi

um m

easu

rem

ents

, G

loba

l Bio

geoc

hem

ical

Cyc

les

14,1

67-1

76.

Leve

, G.W

., 19

70.

The

Flor

idan

aqu

ifer i

n N

orth

east

Flo

rida.

Gro

und

Wat

er 6

,19-

29.

Mar

tin J

.B.,

Cabl

e, J

.E.,

Swar

zens

ki, P

.W.,

2000

. Qua

ntifi

catio

n of

gro

und

wat

er

disc

harg

e an

d nu

trien

t loa

ding

to th

e In

dian

Rive

r Lag

oon.

St

. Joh

ns R

iver W

ater

Man

agem

ent D

istri

ct R

epor

t pp.

154

.

Moo

re, W

.S.,

1999

. Th

e su

bter

rane

an e

stua

ry: A

reac

tion

zone

of g

roun

d w

ater

and

se

awat

er.

Mar

. Che

m. 6

5,11

1-12

5.

St. J

ohn'

s Ri

ver W

ater

Man

agem

ent D

istri

ct, A

ugus

t 200

0 Hy

drol

ogic

Cond

itions

Rep

ort,

pp.7

1.

Spec

hler

, R.M

., 19

94. S

altw

ater

intru

sion

and

the

qual

ity o

f wat

er in

the

Flor

idan

Aq

uife

r sys

tem

, nor

thea

ster

n Fl

orid

a. U

.S. G

eol.

Surv

. Wat

er R

esou

rces

Inv

est.

Repo

rt 92

-417

4, p

. 76.

Swar

zens

ki, P

.W.,

Reich

, C.D

., Sp

echl

er, R

.M.,

Kind

inge

r, J.

L an

d M

oore

, W.S

. Usin

g m

ultip

le g

eoch

emic

al tr

acer

s to

cha

ract

eriz

e th

e hy

drog

eolo

gy o

f the

sub

mar

ine

sprin

g of

f Cre

scen

t Bea

ch, F

lorid

a. C

hem

ical G

eolo

gy, (

in pr

ess)

.

For f

urth

er in

form

atio

n, p

laas

e co

ntac

t:

Pete

r W. S

warz

ensk

i 1

Jona

than

B.M

artin

2

Jaye

E. C

able

, and

3

Mar

y K.

Lin

denb

erg

2Be

tsy

Boyn

ton

1Ri

ta Bo

wke

r 1

and

Gilb

ert C

. Sigu

a 4

1 U.

S. G

eolo

gica

l Sur

vey

Cent

er fo

r Coa

stal

Geo

logy

60

0 4t

h St

reet

Sou

th

St. P

eter

sbur

g, F

L 33

701,

USA

Tele

phon

e: 7

27-8

03-8

747

Fax:7

27-8

03-2

032

Email

: psw

arze

n@us

gs.g

ov

2 De

partm

ent o

f Geo

logi

cal S

cienc

es

Unive

rsity

of F

lorida

G

aine

sville

, FL 3

2611

, USA

Te

leph

one:

352

-392

-621

9 Fa

x: 35

2-39

2-92

94

Email

: jm

artin

@ge

olog

y.uf

l.edu

3 De

partm

ent o

f Oce

anog

raph

y Lo

uisia

na S

tate

Uni

vers

ity

Bato

n Ro

uge,

LA

7080

3, US

A Te

leph

one:

225

-334

-239

0 Fa

x: 22

5-38

8-63

26

Email

: jca

ble@

lsu.e

du

4 En

viron

men

tal S

cienc

esSa

int J

ohn'

s Ri

ver W

ater

Man

agem

ent D

istri

ctP.O

. Box

142

9Pa

latk

a, F

L 32

178

904-

329-

4821

Email

: gcs

®sjr

wmd,

stat

e.fl.

us

Parti

al fu

ndin

g fo

r thi

s pro

ject

has

been

pro

vide

d by

SJR

WM

D, a

s par

t of c

ontra

ct N

o: 9

9G24

5

This

repo

rt is

prel

imin

ary

and

has

not b

een

revi

ewed

for

conf

orm

ity w

ith U

.S. G

eolo

gica

l Sur

vey

edito

rial s

tand

ards

or w

ith th

e N

orth

Am

eric

an S

tratig

raph

ic C

ode.

Ref

eren

ce t

here

in to

any

spe

cific

com

mer

cial

pro

duct

, pr

oces

s, o

r se

rvic

e by

trad

e na

me,

trad

emar

k,

man

ufac

ture

r, or

oth

erw

ise

does

not

nec

essa

rily

cons

titut

e or

im

ply

its e

ndor

sem

ent,

reco

mm

enda

tion,

or

favo

ring

by t

he U

nite

d St

ates

Gov

ernm

ent o

r any

age

ncy

ther

eof.

USGS

scie

nce

fora

cha

ngin

g w

orld

~T

Qua

ntify

ing

Subm

arin

e G

roun

dwat

er D

isch

arge

To

Indi

an R

iver

Lag

oon,

Flo

rida

Figu

re

1. Sa

mpl

ing

for

subm

arin

e gr

ound

wat

er

disc

harg

e in

Indi

an R

iver L

agoo

n.

Intro

duct

ion

The

Indi

an R

iver

Lag

oon

syst

em

(Fig

. 1)

ext

ends

ove

r 250

km

alo

ng

the

east

-cen

tral c

oast

of F

lorid

a an

d co

nsis

ts o

f thr

ee in

ter-

conn

ecte

d la

goon

al b

asin

s: M

osqu

ito, B

anan

a Ri

ver,

and

Indi

an R

iver

lago

ons.

Exch

ange

of l

agoo

n w

ater

with

the

Atla

ntic

Oce

an is

lim

ited

to fo

ur

tidal

inle

ts (

Seba

stia

n, F

t. Pi

erce

, St

. Luc

ie a

nd J

upite

r) th

at o

ccur

in

the

sout

hern

reac

hes

of In

dian

Riv

er

Uppe

r Ind

ian

Rive

r La

goon

Stat

ion

loca

tions

M

ay, A

ugus

t 199

9

wa

tor M

kjm

n BU

M

Figu

re 3

. Si

te lo

catio

n m

ap fo

r upp

er In

dian

Ri

ver L

agoo

n, F

lorid

a.

The

disc

harg

e of

sub

mar

ine

grou

nd w

ater

has

rec

ently

bee

n sh

own

to b

e an

impo

rtant

pro

cess

in m

any

envi

ronm

enta

lly fr

agile

coa

stal

eco

syst

ems.

H

owev

er, g

roun

dwat

er d

isch

arge

into

coa

stal

bot

tom

wat

er is

stil

l an

ofte

n-

over

look

ed c

ompo

nent

of m

any

hydr

olog

ic a

nd o

cean

ic m

odel

s.

The

exch

ange

of

inte

rstit

ial w

ater

acr

oss

the

sedi

men

t/wat

er in

terfa

ce m

ay in

trodu

ce a

nthr

poge

nic

pollu

tant

s, m

aybe

an

impo

rtant

par

t of c

oast

al n

utrie

nt c

ycle

s, a

nd m

ay

caus

e ex

cess

nut

rient

load

ing,

the

reby

pot

entia

lly d

egra

ding

the

coas

tal w

ater

qu

ality

. H

ere

we r

epor

t on

Year

-1 r

esul

ts fr

om a

co-

oper

ativ

e (U

SGS-

UF-L

SU)

proj

ect t

hat i

s in

vest

igat

ing

the

role

of s

ubm

arin

e gr

ound

wat

er d

isch

arge

into

In

dian

Riv

er L

agoo

n, F

lorid

a.

lago

on.

The

follo

win

g pr

oces

ses

cont

rol t

he s

alin

ity o

f lag

oon

wat

er:

prec

ipita

tion,

the

exch

ange

of w

ater

th

roug

h th

ese

inle

ts, w

ind,

tida

l fo

rcin

g, e

vapo

ratio

n, s

urfa

ce r

unof

f an

d po

tent

ial s

ubm

arin

e gr

ound

wat

er

disc

harg

e.

In th

is s

yste

m, t

he

inte

nsity

and

dur

atio

n of

win

d ha

ve

the

mos

t pro

noun

ced

affe

ct o

n la

goon

w

ater

leve

ls.

The

over

all o

bjec

tive

of

this

pro

ject

was

to d

eter

min

e th

e ra

te

and

pote

ntia

l eco

logi

cal s

igni

fican

ce

of s

ubm

arin

e gr

ound

wat

er d

isch

arge

to

Ind

ian

Riv

er L

agoo

n (F

ig. 2

).

The

stud

y ar

ea d

urin

g th

e fir

st

year

of t

he p

roje

ct in

clud

ed th

e no

rther

n m

ost

10 k

m o

f the

Ind

ian

Riv

er L

agoo

n (-

48 k

m2)

. O

f the

28

sam

plin

g st

atio

ns, 2

2 w

ere

arra

nged

in

sho

re-p

erpe

ndic

ular

tran

sect

s; th

e re

mai

ning

six

sta

tions

wer

e di

strib

uted

w

ithin

the

lago

on c

ente

r (F

ig. 3

). A

t ea

ch s

tatio

n, la

goon

and

inte

rstit

ial

wat

er s

ampl

es w

ere

colle

cted

, and

gr

ound

wat

er s

eepa

ge ra

tes

wer

e m

easu

red

usin

g co

nven

tiona

l see

page

m

eter

s. In

ters

titia

l wat

er s

ampl

es

wer

e ob

tain

ed fr

om fo

ur s

tatio

ns

usin

g cu

stom

-bui

lt m

ulti-

sam

pler

s. Si

x gr

ound

wat

er s

ampl

es w

ere

colle

cted

from

wel

ls s

urro

undi

ng th

e la

goon

. Tw

o ad

ditio

nal s

ampl

es

Subm

arin

e G

roun

dwat

er D

isch

arge

e M

ay o

ccur

whe

re e

ver a

n aq

uife

r is

hydr

eulic

ally

con

nect

ed to

the

sea

thro

ugh

perm

eabl

e bo

ttom

sed

imen

ts;

e De

crea

ses

with

dis

tanc

e fro

m s

hore

(G

hybe

n-He

rzbe

rg P

rinci

ple)

;

e Di

rect

ly a

ffect

ed b

y gr

ound

wat

er

with

draw

als;

(

e Po

tent

ial p

oint

sou

rce

for c

onta

m in

ants

.

Figu

re 2

. Pa

ram

eter

s of

sub

mar

ine

grou

ndw

ater

di

scha

rge.

wer

e co

llect

ed fr

om tr

ibut

arie

s to

the

lago

on in

clud

ing

Turn

bull

Cre

ek a

nd

Hau

love

r Can

al.

Sam

plin

g of

the

seep

age

stat

ions

, gro

undw

ater

wel

ls,

and

tribu

tarie

s oc

curr

ed in

May

199

9,

to c

oinc

ide

with

the

end

of th

e no

rmal

dr

y se

ason

, and

in A

ugus

t 19

99,

durin

g th

e no

rmal

rain

y se

ason

. A

th

ird tr

ip in

Dec

embe

r 19

99 w

as u

sed

only

to s

ampl

e in

ters

titia

l wat

er.

Hydr

ogeo

logy

The

hydr

ogeo

logy

alo

ng th

e no

rthea

ster

n co

ast o

f Flo

rida

can

be b

road

ly d

ivid

ed in

to tw

o aq

uife

r sy

stem

s -

the

Surf

icia

l and

the

Flor

idan

aqu

ifer

syst

em (

Fig.

4).

Sand

, silt

and

cla

ys o

f the

U.S.

Dep

artm

ent o

f the

Int

erio

r U.

S. G

eolo

gica

l Sur

vey

USGS

Ope

n Fil

e Re

port

00-4

92

Oct

ober

200

0

Syst

em

Qlu

rte

r-

nuy

Tcr

tiuy

Serie

t

Hol

ocen

e to

Upp

er

Mio

cene

Mio

cene

Eoce

ne

Fale

ocen

e

Str

atig

rapU

c U

nit

Und

iffe

rent

bttd

lu

rfic

ial d

epos

its

Haw

thom

1 ' 1

Oca

la

Avo

n Pa

rk

Old

smar

Ced

ar K

eys

Form

atio

n

Hyd

ro ge

olog

ic

Uni

t

Surfi

cial

aqu

ifer s

yste

m

Inte

rmed

iate

*

* co

nfin

ing

unit

Upp

er F

lorid

an

aqui

fer

&

Mid

dle

sem

i- jj

co

nfin

ing

unit

f" |

Upp

er

3 §

zo

ne

^

.2

unit

i Fe

rnan

dina

J5

pe

rmea

ble

zone

Sub-

Flor

idan

con

finin

gun

it

thic

knew

(m

)

6-

36 30.

150

30.

100

210.

33

5

90.

150

abou

t 15

0

Lit

holo

gy

Dis

cont

inuo

us s

ands

, da

ys, s

hell,

and

lim

esto

ne

Inte

rbed

ded

phos

phat

ic

sand

s, da

ys, l

imes

tone

an

d do

lom

ite

Mas

sive

foss

ilife

rous

ch

alky

to g

ranu

lar

mar

ine

limes

tone

Alte

rnat

ing

beds

of

gran

ular

and

chal

ky

Lim

esto

ne d

ense

do

lom

ites

Upp

erm

ost a

ppea

ranc

e of

ev

apor

itet,

dens

e lim

esto

nes

Hyd

rolo

gk p

rope

rties

Sand

s, sh

ell,

limes

tone

and

co

quin

a de

posi

ts p

rovi

de

loca

l gro

undw

ater

sou

rce

Lim

ited-

perm

eabi

lity

days

Prin

cipa

l so

urce

of g

roun

d-

wat

er

Low

-per

mea

bilit

y lim

esto

ne

Prin

cipa

l sou

rce

of g

roun

d-

wat

er

Low

-per

mea

bilit

y lim

esto

ne

and

dolo

mite

Hig

h pe

rmea

bilit

y, s

alin

ity

incr

ease

s w

ith d

epth

Con

tain

s hi

gh s

alin

ity w

ater

, lo

w p

erm

eabi

lity

Figu

re 4

. H

ydro

stra

tigra

phy

of n

orth

east

ern

Flor

ida

(ada

pted

from

Spe

chle

r, 19

94).

corr

espo

nds

to th

e O

cala

Lim

esto

ne

and

in s

ome

parts

, the

Avo

n Pa

rk

Form

atio

n (F

ig. 4

). Th

e O

cala

L

imes

tone

is c

hara

cter

ized

by

high

pe

rmea

bilit

ies

that

can

be

enha

nced

al

ong

bedd

ing

plan

es, f

ract

ures

and

co

ndui

ts.

Sign

ifica

nt v

aria

tions

in g

roun

d-

wat

er le

vels

occ

ur s

easo

nally

(Fi

g.

5).

Supe

rimpo

sed

on s

uch

seas

onal

va

riatio

ns is

a lo

ng-te

rm d

ecre

ase

in th

e po

tent

iom

etric

sur

face

that

is

larg

ely

attri

bute

d to

incr

ease

d gr

ound

wat

er w

ithdr

awal

s (F

ig. 6

). N

onet

hele

ss, r

ecen

t pot

entio

met

ric

surf

ace

map

s of

the

Upp

er F

lori

dan

aqui

fer

indi

cate

ele

vatio

ns th

at a

re

abov

e se

a le

vel f

or th

e en

tire

leng

thIn

term

edia

te c

onfin

ing

unit,

whi

ch

cons

titut

es m

ost o

f the

Haw

thor

n Fo

rmat

ion,

sep

arat

es th

ese

two

aqui

fer

syst

ems

(Lev

e, 1

970;

Spe

chle

r, 19

94).

The

Surf

icia

l aqu

ifer

syst

em c

onsi

sts

of M

ioce

ne to

Hol

ocen

e in

terb

edde

d sa

nd, s

hell,

silt

, cla

y an

d do

lom

itic

limes

tone

stra

ta.

The

Surf

icia

l aqu

ifer

syst

em is

mos

tly u

ncon

firm

ed, a

lthou

gh

the

hydr

ogeo

logy

can

be

very

he

tero

gene

ous.

Fo

ur c

last

ic, h

ighl

y re

gion

al s

urfic

ial a

quife

rs b

orde

r th

e In

dian

Riv

er L

agoo

n in

clud

ing

Terr

ace,

Atla

ntic

Coa

stal

Rid

ge,

Ten-

mile

Rid

ge, a

nd I

nter

-rid

ge

aqui

fers

. Te

rrac

e aq

uife

r oc

curs

on

the

barr

ier

isla

nds

sepa

ratin

g In

dian

R

iver

Lag

oon

from

the

Atla

ntic

O

cean

. Th

e A

tlant

ic C

oast

al R

idge

aq

uife

r oc

curs

in t

he n

orth

wes

tern

re

gion

of I

ndia

n R

iver

Lag

oon.

Thi

s aq

uife

r is

com

pose

d of

the

Plei

stoc

ene

Ana

stas

ia F

orm

atio

n, a

nd

prov

ides

m

ost o

f the

wat

er s

uppl

y fo

r to

wns

on

the

wes

tern

edg

e of

the

north

ern

Indi

an R

iver

Lag

oon

(Mim

s an

d Ti

tusv

ille)

.

The

Flor

idan

aqu

ifer

syst

em c

an

be f

urth

er d

ivid

ed in

to tw

o w

ater

­ be

arin

g aq

uife

rs (

Upp

er a

nd L

ower

Fl

orid

an),

sepa

rate

d by

less

per

mea

ble

sem

i-con

finin

g un

its.

The

Upp

er

Flor

idan

aqu

ifer

in th

e st

udy

area

Titu

svill

e W

ell I

n Br

evar

d Co

unty

22 20 18

I

g

16 14 12 10

Mon

thly

Sta

tistic

s Co

mpu

ttd F

rom

19

76-1

999

Wat

wL

wfl

t

Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

No

v De

c Ja

n22 20 18 16

S UJ

14 12 10

1

19

80

Mon

th E

nd W

ater

Lev

els

Augu

st W

ater

Lev

els

1985

1990

1995

2000

2005

Figu

re 5

. H

ydro

grap

h of

a T

itusv

ille w

ell (

adap

ted

from

St.

John

's R

iver W

ater

Man

agem

ent D

istri

ct, 2

000)

.

of In

dian

Riv

er L

agoo

n.

Such

po

tent

iom

etric

sur

face

ele

vatio

ns

incr

ease

fro

m n

orth

to s

outh

, whe

re

the

Haw

thor

n Fo

rmat

ion

incr

ease

s in

thic

knes

s. T

he e

leva

ted

pote

ntio

met

ric s

urfa

ce o

f the

Upp

er

Flor

idan

, com

bine

d w

ith th

e ge

nera

l la

ck o

f a c

onfin

ing

unit

in th

e vi

cini

ty o

f the

stu

dy a

rea

mak

es

muc

h of

upp

er In

dian

Riv

er L

agoo

n a

pote

ntia

l zon

e of

sub

mar

ine

grou

ndw

ater

dis

char

ge.

Geo

chem

istry

To d

eriv

e es

timat

es o

f gro

und-

w

ater

see

page

into

Ind

ian

Riv

er

lago

on, t

he f

ollo

win

g su

ite o

f tra

cers

, ch

emic

al c

onst

ituen

ts a

nd s

ampl

ing

devi

ces

wer

e m

easu

red

or u

tiliz

ed:

nutri

ents

, Cl~

, con

duct

ivity

, pH

, te

mpe

ratu

re, d

isso

lved

oxy

gen,

87S

r/86

Sr,

818

0,

223,

224,

226R

a) 2

22^

seep

met

ers,

mul

ti-sa

mpl

ers,

and

be

nthi

c flu

x ch

ambe

rs (

Mar

tin e

t al.,

20

00).

Seep

age

rate

s w

ere

spat

ially

an

d te

mpo

rally

het

erog

eneo

us, y

et

sim

ilar

to r

ates

pre

viou

sly

mea

sure

d in

Ind

ian

Riv

er L

agoo

n us

ing

iden

tical

te

chni

ques

. Th

e se

epag

e ra

tes

rang

ed

from

3 -

100

ml n

r2 m

ur1 d

urin

g M

ay

(dry

sea

son)

to 2

2 -

144

ml n

r2 m

ur1

durin

g A

ugus

t (ra

iny

seas

on).

The

aver

age

valu

e fo

r al

l met

ers

incr

ease

d fr

om 4

0 to

63

ml n

v2 m

in'1

from

the

dry

to t

he r

ainy

sea

son,

impl

ying

that

th

ere

may

be

a co

nnec

tion

betw

een

rain

fall

and

incr

ease

d se

epag

e ra

tes.

Th

e he

tero

gene

ous

natu

re o

f the

se

rate

s is

lik

ely

caus

ed b

y flu

ctua

tions

in

sed

imen

t per

mea

bilit

ies

and

othe

r ge

olog

ic c

hara

cter

istic

s.

Rad

on-2

22 a

nd R

a is

otop

es h

ave

prev

ious

ly p

rovi

ded

regi

onal

ly

inte

grat

ed e

stim

ates

of

seep

age

flux

in v

arie

d co

asta

l env

ironm

ents

(C

able

et

al.,

199

6; M

oore

, 19

99;

Swar

zens

ki

et a

l., i

n pr

ess)

. B

enth

ic f

luxe

s of

R

a to

the

Indi

an R

iver

Lag

oon

wer

e ca

lcul

ated

usi

ng th

ree

inde

pend

ent

met

hods

that

rely

on

the

activ

ities

of

sho

rt-liv

ed R

a is

otop

es:

1) la

goon

Cha

nges

in th

e Po

tent

iom

etric

Sur

face

of th

e Fl

orid

an A

quife

r A

ugus

t 19

98 -

Aug

ust 2

000

-7.5

Fe

et-5

.5 F

eet

-1.5

Fe

et+1

.0

Feet

/V

Cou

nty

Bou

ndar

ies

Indi

an R

iver

Lag

oon

Stud

y Si

te w T

E

0_4

Scal

e1:2

0610

37

Figu

re 6

. Po

tent

iom

etric

cha

nge

map

(ada

pted

from

St

John

's R

iver W

ater

Man

agem

ent D

istri

ct 2

000)

.

budg

et, 2

) be

nthi

c flu

x ch

ambe

rs a

nd

3) p

ore-

wat

er m

odel

ing.

Th

e fir

st tw

o m

etho

ds y

ield

dire

ct m

easu

rem

ents

of

flux

acr

oss

the

sedi

men

t/wat

er

inte

rfac

e, w

here

as th

e th

ird te

chni

que

gene

rate

s an

indi

rect

flu

x es

timat

e on

th

e ba

sis

of p

ore-

wat

er R

a pr

ofile

s.

Cal

cula

tions

of t

he b

enth

ic f

lux

of R

a ra

nge

up to

alm

ost 5

00 d

pm n

r2 d

ay1.

Usi

ng 2

26R

a po

re-w

ater

act

iviti

es,

a m

axim

um u

pwar

d su

bsur

face

wat

er

flow

of a

bout

5 -

17

cm d

ay1

is r

equi

red

to s

usta

in th

ese

fluxe

s.

Thes

e va

lues

are

sim

ilar t

o th

e va

lues

m

easu

red

dire

ctly

with

the

seep

age

met

ers.

By

usin

g 22

2Rn

and

226R

a as

mas

s ba

lanc

e tra

cers

of

seep

age

flux

to th

e no

rthe

rn I

ndia

n R

iver

Lag

oon,

it is

po

ssib

le to

obt

ain

mea

sure

men

ts o

f se

epag

e th

at a

re in

depe

nden

t of t

he

shor

t-liv

ed R

a is

otop

es.

Ass

umpt

ions

re

quire

d fo

r th

is m

ass

bala

nce

appr

oach

are

that

neg

ligib

le e

ffec

ts

wer

e ob

serv

ed fr

om s

urfa

ce w

ater

ex

chan

ge to

the

lago

on, t

ides

, and

di

ffus

ion

from

the

sedi

men

ts.

Ana

logo

us to

the

shor

t-liv

ed R

a is

otop

es,

seep

age

fluxe

s m

easu

red

on

the

basi

s of

exc

ess

226R

a ac

tiviti

es

are

sim

ilar i

n m

agni

tude

to th

ose

estim

ated

usi

ng s

eepa

ge m

eter

s.