Geochemical identification of fresh water sources in brackish groundwater mixtures; the example of Lake Kinneret (Sea of Galilee), Israel Ofra Klein-BenDavid * , Haim Gvirtzman 1 , Amitai Katz 1 Institute of Earth Sciences, the Hebrew University of Jerusalem, Givat-Ram, Jerusalem 91904, Israel Received 14 January 2004; accepted 19 August 2004 Abstract Fresh waters that dilute brines are considered to have a negligible effect on the ion ratios of the resultant mixture. We show that the major element composition of the fresh end-member can be deduced from the chemical composition of the mixed waters. That composition, then, can be used to differentiate between different neighboring carbonate aquifers, which supply the water. This is demonstrated for the Fuliya and Tabgha saline springs, located on the northwestern shore of Lake Kinneret (Sea of Galilee), Israel. At these springs, shallow fresh groundwater mixes with brines from deep aquifers. Seven saline springs and wells located at the Fuliya and Tabgha blocks were sampled over a year, and 32 eastern Galilee fresh springs and wells were sampled as representatives of the fresh water end-member. All samples were analyzed for major and minor ions. The saline spring data were used to construct mixing lines, followed by their extrapolation to low concentrations in order to derive the ion/ chloride ratio characterizing the fresh component. We constructed ion/Cl vs. Cl curves; projection of the composition of fresh water on the calculated curve was used to identify a certain fresh water source as a possible end-member. Results indicate that the composition of the water feeding the Fuliya springs is different from that at Tabgha, reflecting interactions with different rocks in each basin. The major fresh water end-member diluting the Fuliya brines is characterized by high Mg/Cl and low Sr/Cl ratios, and is consistent with the composition of fresh groundwater in the dolomitic Cenomanian and Turonian aquifers widely exposed in the Fuliya drainage basin. The major fresh water end-member diluting the Tabgha brines, on the other hand, is characterized by low Mg/Cl and high Sr/Cl ratios, and is consistent with the composition of fresh groundwater in the chalky Eocene Timrat Fm. and Senonian outcrops. Although the chalky formations in the Tabgha drainage basin are exposed over only 20% of the area they contribute most of the solutes to the fresh water end-member. Rain flows over the chalky formations and then infiltrates into the Bar-Kokhba Eocene outcrops. D 2004 Elsevier B.V. All rights reserved. Keywords: Saline springs; Brine freshwater mixing; End-member; Fuliya; Tabgha 0009-2541/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.chemgeo.2004.08.025 * Corresponding author: Fax: +972 2 5662581. E-mail addresses: [email protected] (O. Klein-BenDavid)8 [email protected] (H. Gvirtzman)8 [email protected] (A. Katz). 1 Fax: +972 2 5662581. Chemical Geology 214 (2005) 45 – 59 www.elsevier.com/locate/chemgeo
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Chemical Geology 21
Geochemical identification of fresh water sources in brackish
groundwater mixtures; the example of Lake Kinneret
The last two groups are the focus of this article.
The Fuliya and Tabgha springs exhibit abrupt
seasonal salinity variations (Goldschmidt et al.,
1967; Rimmer et al., 1999). At Fuliya salinity is
maximal in March, following the last rains, and at
Tabgha, salinity is maximal in November, by the end
of the dry season (Fig. 2). Mazor and Mero (1969)
plotted the concentration of various ions vs. the Cl
concentration in the Fuliya and Tabgha springs. They
showed that the springs construct linear arrays on such
diagrams indicating a two-component mixing system;
one end-member is brine and the other end-member is
a fresh water component. Extrapolating these mixing
lines to high and low concentrations can give an
estimation of the ion ratios in the end-members.
Many authors have tried to infer the composition
of the saline end-member; it is generally accepted
that the brines are residual evaporated, ancient
seawater that invaded the DSR during the Neogene,
precipitated evaporitic minerals and interacted with
the aquifers (Klein-BenDavid et al., 2004; Starinsky,
1974; Stein et al., 1997, 2000; Zak, 1997).
Fig. 2. Seasonal variation in the Cl concentration in the En Sheva spring o
Gvirtzman et al. (1997) showed that circulating
fresh water from the Galilee aquifers flushes the
brine to the surface. However, The chemical charac-
teristics of the diluting fresh water in the different
spring groups were never established in detail.
Because the fresh end-member d18O and yD is
similar in the Fuliya and Tabgha recharge areas, the
chemical composition of the water may be the only
way to distinguish between them.
Recharge water in the eastern Galilee aquifers flows
over and through different rock formations and
interacts with them. The common rock types are
dolomite, limestone, chalk, marl and basalt. The
changes in Ca, Mg, Sr and Cl concentrations are
examined as indicative of the interaction with the
different rocks. Elevated Mg/Ca and low Sr/Cl ratios
are expected in the interaction with dolomite, whereas
high Sr/Cl and low Mg/Ca ratios will be representative
of chalk-related samples. Water that interacted with
limestone would give intermediate values and water
that flows through basalts would give both high Mg/Ca
and Sr/Cl ratios (Kafri et al., 2002).
The objective of this study is to define chemical
constraints to the composition of the fresh water
end-member feeding the Fuliya and Tabgha groups
of springs through the comparison of the ion ratios
in the calculated Fuliya and Tabgha fresh end-
member and the measured eastern Galilee sources
and to relate the observed groundwater compositions
to specific eastern Galilee aquifers.
f the Tabgha group and in the Fuliya 6/2 spring of the Fuliya group.
Fig. 3. The Tabgha, Fuliya and Tiberias hot springs drainage basin drawn on the eastern Galilee geological map.
O. Klein-BenDavid et al. / Chemical Geology 214 (2005) 45–5948
O. Klein-BenDavid et al. / Chemical Geology 214 (2005) 45–59 49
2. Hydrogeological setting
The DSR is a left-lateral transform, along which
several rhomb-shaped grabens were formed, including
the Dead Sea and Lake Kinneret (Freund et al., 1970;
Garfunkel, 1981; Ben-Avraham et al., 1996; Al-Zoubi
and Ten-Brink, 2001). This basin includes the deepest
terrestial location on Earth as well as Lake Kinneret—
the lowest fresh water lakes on Earth (Fig. 1). Lake
Kinneret drains groundwater from five surrounding
aquifers: (1) the 200-m-thick, Neogene Bashan Group
basalt (Shaliv, 1989); (2) the 350-m-thick, Eocene
Avdat Group limestone and chalk (Saltzman, 1967;
Michelson, 1975; Sneh, 1988); (3) the 600-m-thick,
Cenomanian–Turonian Judea Group of predominantly
carbonates (Bein, 1967; Kafri, 1972); (4) the 400-m-
thick, Lower Cretaceous Kurnub Group of mainly
sandstones (Eliezry, 1959; Michelson, 1975); and (5)
the 2500-m-thick, Jurassic Arad Group of mainly
carbonates (Dubertret, 1966). The recharge areas of the
first three aquifers are exposed over the eastern Galilee
Mountains (Fig. 3; Table 1), the fourth is exposed over
a small area, while the fifth is totally confined.
The subsiding rift valley is filled by a Miocene–
Quaternary sequence that is at least 4 km thick
(Marcus and Slager, 1985). On the western margin
of the graben, some faulted blocks expose the Judea
aquifer along the margins of Lake Kinneret, channel-
ing the main discharge of the system (Goldschmidt et
al., 1967; Gvirtzman et al., 1997). The faults and the
shear zone along the rift allow mixing of water from
Table 1
Recharge areas of the different formation at the Fuliya and Tabgha
drainage basins
Stratigraphy Age Fuliya Tabgha
km2 % km2 %
Fill units Miocene–Holocene 64 31 33 9
Cover Basalt Pliocene–Pleistocene 17 8 76 21
Bar Kokhba Fm. Middle Eocene 2 1 25 7
Timrat Fm. Lower–Middle Eocene 7 3 32 9
Mount Scopus Group Senonian–Paleocene 17 8 36 10
Bina Fm. Turonian 6 3 8 2
Sakhnin Fm. Cenomanian 20 10 56 15
Deir-Hanna Fm. Cenomanian 42 20 84 23
Kammon Fm. Albian–Cenomanian 19 9 17 5
Ein el Assad Fm. Lower Cretaceous 9 5 5 1
Sum 203 100 371 100
Numbers are rounded to zero decimals.
deep aquifers with shallow fresh groundwater, which
emerges as springs (Moise et al., 2000).
Groundwater drains from the eastern Galilee
Mountains toward Lake Kinneret within three subsur-
face drainage basins: Tiberias, Fuliya and Tabgha.
These basins are separated from each other by major
faults. The borders of these recharge basins are shown
in Fig. 3. The total discharge of groundwater at the
onshore springs at Tiberias, Fuliya and Tabgha is
approximately 1.2, 11 and 25 million m3/year (Bein,
1978). The total estimated discharge of the onshore
and offshore springs is 5, 20 and 40 million m3/year,
respectively (Gvirtzman, unpublished data).
3. Methods
3.1. Sampling
Three springs belonging to the Fuliya group and
four springs and one artesian well from the Tabgha
group were sampled for chemical analyses. Sampling
was performed every 2 weeks (or at shorter intervals)
between April 1997 and May 1998. In addition, 47
samples from 32 fresh water springs and wells spread
over the eastern Galilee (Table 2 and Fig. 1) were
sampled once or twice between August 1996 and May
1998. They were selected according to their geo-
graphic and stratigraphic locations to represent the
entire region’s fresh groundwater. In the Fuliya basin,
wells from the Cenomanian, Turonian and Neogene
(Yavne’el) aquifers were sampled. In Tabgha the water
was sampled from the Eocene aquifer and springs
form Neogene (Korazim), Cenomanian–Turonian,
Senonian and Eocene formations.
Samples were collected as close as possible to the
discharge point. The samples were stored in 330 mL
PET (polyethylene teraphtalate) gas-tight plastic bot-
tles. The water was refrigerated (4–5 8C) until analysis.
3.2. Chemical analysis
Water samples were filtered using Whatmank #40
filters in order to remove all insoluble particles and
were diluted with deionized water (18.3 MV/cm) to
achieve optimal analytical ranges. Each sample was
analyzed in triplicate. Na, K, Mg, Ca, Sr, Si, and S were
measured using ICP-OES by an automated Perkin-
Table 2
Calculated linear regression parameters for ion vs. Cl correlation in the Fuliya and Tabgha saline sources (full analysis in Klein-BenDavid et al.,
2004)
Water source Number
of samples
Temperature
range (C8)aMg
(mg/L)
Ca
(mg/L)
Sr
(mg/L)
Cl
(mg/L)
Fuliya Group
Fuliya 5 31 27.0–28.0 Average 65.3 156 1.45 755
S.D.b 2.95 8.07 0.14 69.6
Slopec 0.042 0.114 0.002
Interceptd 33.9 70.7 �0.066
R2e 0.963 0.960 0.965
Fuliya 6 30 18.3–27.0 Average 64.1 151 1.34 720
S.D. 2.21 7.74 0.12 54.8
Slope 0.037 0.119 0.002
Intercept 37.7 65.5 �0.138
R2 0.825 0.709 0.954
Fuliya 6/2 29 26.7–28.1 Average 73.0 178 1.78 939
S.D. 4.17 11.4 0.19 98.4
Slope 0.041 0.113 0.002
Intercept 34.3 72.1 �0.066
R2 0.942 0.954 0.986
Tabgha Group
En Sheva 35 24.8–28.0 Average 62.3 249 4.84 1112
S.D. 9.93 27.0 0.83 222
Slope 0.044 0.118 0.004
Intercept 13.3 117 0.75
R2 0.975 0.946 0.972
Druzi Springf 17 16.8–28.7 Average 69.9 249 5.00 1277
S.D. 6.98 18.2 0.53 159
Slope 0.043 0.110 0.003
Intercept 14.9 108 0.78
R2 0.958 0.926 0.966
Ma’ayan Matok 33 26.0–28.0 Average 84.8 316 7.12 1770
S.D. 7.32 19.7 0.61 166
Slope 0.044 0.115 0.004
Intercept 7.78 113 0.68
R2 0.976 0.935 0.979
Kinneret 7 33 23.9–28.0 Average 41.7 189 3.31 734
S.D. 10.2 28.3 0.87 206
Slope 0.049 0.137 0.004
Intercept 5.50 88.2 0.21
R2 0.995 0.987 0.997
a Temperatures were measured as close as possible to the spring.b Standard deviation.c a-Linear slope ( Y=aX+b).d b-Linear intercept ( Y=aX+b).e Correlation coefficient.f The Druzi spring was not sampled through the whole sampling period.
O. Klein-BenDavid et al. / Chemical Geology 214 (2005) 45–5950
Elmer Optima-3000 radial ICP system. Chloride, Br
and NO3 were analyzed using an automated Lachat
Instruments model QE flow injection analysis (FIA)
system with colorimetric detection (Eaton et al., 1995).
Instrumental drift was monitored by analyzing calibra-
tion standards every 10 samples and corrected for by an
in-house correction program (Katz, 1997). The ICP, Cl
and Br (FIA) precision is equal to or smaller than 1%.
The NO3 precision is F2%. Bicarbonate was titrated
using 0.02 NHCl with the BDHk #4480 indicator, at a
O. Klein-BenDavid et al. / Chemical Geology 214 (2005) 45–59 51
precision ofF0.5–1%. Further analytical details can be
found in Klein-BenDavid et al. (2004).
4. Results
Ions vs. Cl diagrams were plotted for seven Fuliya
and Tabgha saline sources. The Cl content of the
Fig. 4. Magnesium, Ca and Sr vs. Cl plots for the Fuliya (left column) and T
for the Fuliya charts: Fuliya 5 o; Fuliya 6 x; Fuliya 6/2 5. Legend for t
Kinneret 7 4.
selected saline sources ranges between 500 and 2000
mg/L. Fig. 4 displays the positive linear regression
between Ca,Mg and Sr and Cl. Such a behavior reflects
mixing between a fresh water component and brine.
We calculated the linear regression equation for
these lines. As the mixing occurs between brine and
fresh water, rather than distilled water, the lines do not
extrapolate through the origin and different points
abgha (right column) sources. Linear regressions are plotted. Legend
he Tabgha charts: En Sheva x; Ma’ayan matok 5; Druzi spring ;
O. Klein-BenDavid et al. / Chemical Geology 214 (2005) 45–5952
along the line display different ion/Cl ratios. Thus, in
order to estimate the ion/Cl ratios of the fresh water
end-member we extrapolated the line to low concen-
trations and calculated the ratios for a pre-determined
Cl concentration.
Through extrapolation, we tested Cl concentrations
between 10 and 100 mg/L. As fresh groundwater in the
recharge basin displays this concentration range we
assumed that it is representative of the fresh end-
member. Table 2 presents the regression equations for
the Ca, Mg, Sr and Cl relationships and the correlation
coefficient R2. Table 3 presents the calculated ion/Cl
ratios in the tested Cl concentration range. We
calculated the error in the equivalent ion/Cl ratio to
the extrapolation to low concentrations. The calcula-
tions were conducted according to the procedure of
Natrella (1963) sections 5-3 and 5-4.1.2.1, using a 1�afactor of 0.95. The error for the ratios calculated from
16 of the lines is smaller than F10% (mostly smaller
than F5%). Two lines yielded up to 17% error. Three
Table 3
The ion/Cl equivalent ratios calculated from the extrapolated linear re
concentrations ranging between 10 and 100 mg/La
Cl (mg/L) 10 20 30 40
Fuliya
Fuliya 5 Mg/Cl 10.01 5.07 3.42 2.5
Ca/Cl 12.70 6.45 4.37 3.3
Sr/Clb �0.0037 �0.0010 �0.0001 0.0
Fuliya 6 Mg/Cl 11.11 5.61 3.78 2.8
Ca/Cl 11.80 6.00 4.07 3.11
Sr/Clb �0.0095 �0.0039 �0.0021 �0.0
Fuliya 6/2 Mg/Cl 10.14 5.13 3.46 2.6
Ca/Cl 12.95 6.57 4.45 3.3
Sr/Clb �0.0038 �0.0011 �0.0002 0.0
Tabgha
En Sheva Mg/Cl 4.00 2.06 1.42 1.1
Ca/Cl 20.97 10.59 7.13 5.4
Sr/Cl 0.063 0.033 0.023 0.0
Druzi Spring Mg/Cl 4.48 2.30 1.58 1.2
Ca/Cl 19.36 9.78 6.58 4.9
Sr/Cl 0.066 0.034 0.024 0.0
Ma’ayan Matok Mg/Clc 2.40 1.26 0.88 0.6
Ca/Cl 20.25 10.23 6.89 5.2
Sr/Clc 0.058 0.030 0.021 0.0
Kinneret 7 Mg/Cl 1.75 0.95 0.68 0.5
Ca/Cl 15.84 8.04 5.44 4.1
Sr/Cl 0.02 0.012 0.009 0.0
a Errors are up to F10% (mostly smaller then 5%).b ~100% error (see text).c F17% error.
lines, calculated for Sr vs. Cl in the Fuliya springs, gave
errors within the range of 100%. The reason for this
large error is the fact that the regression line crosscuts
the axis very close to the origin and the value of the
ratio is in the order of 10�4. Any minor change in the
value will cause a very large relative error.
A comparison of the ion ratios in the eastern
Galilee fresh water sources to the calculated fresh end-
member may distinguish between different eastern
Galilee sources as possible fresh water feeders to the
Fuliya and Tabgha springs. Table 4 lists the chemical
composition of 32 springs and wells sampled in the
Fuliya and Tabgha drainage basins from eight differ-
ent aquifers and lithologies.
5. Discussion
In order to compare the calculated ion/Cl ratios
in the fresh end-member with the actual ion/Cl
gression equations for Fuliya and Tabgha saline sources for Cl
50 60 70 80 90 100
9 2.10 1.77 1.53 1.36 1.22 1.11
3 2.70 2.28 1.99 1.76 1.59 1.45
003 0.0006 0.0007 0.0009 0.0010 0.0010 0.0011
6 2.31 1.94 1.68 1.48 1.33 1.21
2.53 2.14 1.87 1.66 1.50 1.37
011 �0.0006 �0.0002 0.0001 0.0003 0.0004 0.0006
2 2.12 1.79 1.55 1.37 1.23 1.12
9 2.75 2.32 2.02 1.79 1.62 1.47
002 0.0005 0.0007 0.0008 0.0009 0.0010 0.0011
0 0.90 0.77 0.68 0.61 0.56 0.52
0 4.36 3.67 3.18 2.80 2.52 2.29
18 0.015 0.013 0.012 0.011 0.010 0.009
1 1.00 0.85 0.75 0.67 0.61 0.56
9 4.03 3.39 2.93 2.59 2.32 2.11
18 0.015 0.013 0.012 0.011 0.010 0.009
9 0.58 0.51 0.45 0.41 0.38 0.35
2 4.21 3.54 3.07 2.71 2.43 2.21
17 0.014 0.012 0.011 0.010 0.009 0.008
5 0.46 0.41 0.37 0.34 0.32 0.30
4 3.36 2.84 2.47 2.19 1.98 1.80
08 0.007 0.006 0.006 0.006 0.005 0.005
Table 4
Summary of chemical analyses of fresh water samples collected at springs and wells in the eastern Galileea