Groundwater Submarine Lagoon, Quantifying River … River Lagoon. St. Johns River Water Management...
Transcript of Groundwater Submarine Lagoon, Quantifying River … River Lagoon. St. Johns River Water Management...
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
: 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
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9 Fa
x: 35
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2-92
94
: 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
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-239
0 Fa
x: 22
5-38
8-63
26
: 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
: 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
o
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.