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\begin{document}

\title{Complimentary use of dating and hydrochemical tools to assess mixing
processes involving centenarian groundwater in a geologically complex
alpine karst aquifer}



\author[1]{J.M. Gil-Marquez}%
\author[1]{Beatriz De la Torre}%
\author[1]{Matías Mudarra}%
\author[2]{Jürgen Sültenfuß}%
\author[1]{Bartolomé Andreo Navarro}%
\affil[1]{Universidad de Málaga}%
\affil[2]{University of Bremen}%


\vspace{-1em}



  
  \date{April 26, 2024}


\begingroup
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\selectlanguage{english}
\begin{abstract}
Environmental dating tracers (\textsuperscript{3}H,
\textsuperscript{3}He, \textsuperscript{4}He, CFC-12, CFC-11,
SF\textsubscript{6}) and the natural response of spring (hydrochemistry,
water temperature, and hydrodynamics) were jointly used to asses mixing
processes and to characterize groundwater flow in a relatively small
carbonate aquifer with complex geology in South Spain. Results evidence
a marked karst behavior of some temporary outlets, while some perennial
springs show buffer and delayed responses to recharge events. There is
also a general geochemical evolution pattern, from higher to lower
altitudes, in which mineralization and the relation Mg/Ca rises,
evidencing longer water-rock interaction. The large SF6 concentrations
in groundwater suggest terrigenic production, while CFC-11 values are
affected by sorption or degradation. The groundwater age in the
perennial springs deduced from CFC-12 and
\textsuperscript{3}H/\textsuperscript{3}He point out to mean residence
times of several decades, although the difference between both methods
and the large amount of radiogenic 4He in the samples indicates a
contribution of old groundwater (free of \textsuperscript{3}H and
CFC-12). Lumped Parameter Models and Shape-Free Models were created
based on \textsuperscript{3}H, tritiogenic \textsuperscript{3}He,
CFC-12, and radiogenic \textsuperscript{4}He data in order to interpret
the age distribution of the samples. The resulting groundwater-age
distributions evidence the existence of two mixing components, with an
old fraction ranging between 160 and 220 years. Some dating parameters
derived from the mixing models and their correlation to physicochemical
parameters permits to explain the hydrogeochemical processes occurring
within the system. All these results prove that large time residence
times are possible in small alpine systems with a clear karst behavior
when the geological setting is complex, and they highlight the
importance of applying different approaches, including groundwater
dating techniques, to completely understand the groundwater flow regime
within this type of media.%
\end{abstract}%



\sloppy


\textbf{}

\textbf{INTRODUCTION}

Environmental tracers are natural or anthropogenic compounds that are
widely distributed in the near-surface of the Earth (Cook \& Herczeg,
2000; Elliot, 2014). The determination of their concentrations in
groundwater allows to estimate its apparent age, which helps on the
characterization of the recharge regime of aquifers (M\selectlanguage{ngerman}üller et al.,
2016; Wilske et al., 2019; Yager et al., 2010), the resolution of mixing
process problems (Akesson et al., 2015; Corcho Alvarado et al., 2007),
the assessment of groundwater vulnerability to pollution (Jasechko et
al., 2017; Musgrove, Solder, Opsahl, \& Wilson, 2019), and the
development of optimized hydrogeological conceptual models (Gardner \&
Heilweil, 2014; Sültenfuss, Purtschert, \& Führböter, 2011).

Groundwater dating based on environmental tracers, such as radioactive
isotopes (\textsuperscript{3}H,
\textsuperscript{14}C,\textsuperscript{36}Cl, \textsuperscript{85}Kr),
noble gases isotopes (\textsuperscript{3}He, \textsuperscript{4}He,
\textsuperscript{40}Ar), and fluorinated synthetic gases (CFCs,
SF\textsubscript{6}), has been worldwide used since the last third of
the 20\textsuperscript{th}century, particularly in detrital formations
(Beyerle et al., 1999; Corcho Alvarado et al., 2007; Mayer et al., 2014;
Xu, Gong, \& Yang, 2018) and fractured bedrock aquifers (Cook, Solomon,
Sanford, Busenberg, \& Plummer, 1996; Jaunat et al., 2012; Koh et al.,
2018). However, groundwater dating studies based on environmental gas
tracers are uncommon in karst hydrogeology, compared to other specific
approaches (Goldscheider \& Drew, 2007). That is because the
interpretation of groundwater ages in karst media is challenging due to
the high heterogeneity commonly found in these aquifers. While
groundwater flows rapidly through conduits and fractures, the flow
velocity in the matrix or small fissures is very slow (Han, Hacker, \&
Gröning, 2007; Worthington \& Gunn, 2009). Such characteristics would
require the joint application of several environmental tracers that help
to constrain the age distribution of groundwater (Wilske et al., 2019),
particularly if a comprehensive understanding of groundwater flow
behavior is not achieved based on other experimental methodologies
(hydrodynamic, hydrothermal, hydrochemical, and stable isotopes).

During the last couple of decades, several studies have demonstrated the
applicability of environmental tracers for groundwater dating in karst
systems, which allow to better understand flow dynamics. In general
terms, they found a mixing between recently infiltrated water and older
groundwater components. The old fraction in the mix may have a few
decades (Delbart et al., 2014; Jiang, Guo, \& Tang, 2019) or, more
commonly, was infiltrated before the middle of the
20\textsuperscript{th} Century, previously to the anthropogenic release
of \textsuperscript{3}H and CFCs (Han et al., 2007; Long \& Putnam,
2009; Toth \& Katz, 2006; Yager et al., 2010; Zang, Zheng, Qin, \& Jia,
2015). In regional carbonate aquifers, some of which are partially
confined, the dating of the old groundwater components often indicates
ages of hundreds or even thousands of years (Land \& Huff, 2010; Müller
et al., 2016; Musgrove et al., 2019; Plummer, Busby, Lee, \& Hanshaw,
1990; Xanke et al., 2015). However, karst aquifers in alpine mountains
are generally characterized by recently infiltrated young groundwater,
with maximum mean recharge dates of a few years, although sometimes
mixed with a low percentage of older components (Althaus et al., 2009;
Rank, Volkl, Maloszewski, \& Stichler, 1992; Shah, Jeelani, \& Jacob,
2017).

Alpine karst occupies areas of high altitude and is characterized by
pronounced relief, commonly intense tectonic deformation deriving in a
strong hydrogeological complexity, and sparse or absent vegetal and soil
covers (Field, 1999; Palmer, 1984). The large height variations existing
in alpine karst generally imply a thick unsaturated zone and high
hydraulic gradients, resulting in rapid flow velocities and short
residence times within the conduit network (Werner, 1979). All these
characteristics are enhanced in small aquifers. Though alpine karst
formations are named after the Alps (Central Europe), this type of karst
is worldwide extended, particularly in Europe (Ballesteros,
Jiménez-Sánchez, Giralt, García-Sansegundo, \& Meléndez-Asensio, 2015;
Lauber \& Goldscheider, 2014; Mudarra \& Andreo, 2011; Turk et al.,
2015), Asia (Ebrahimi, Pasandi, \& Ahmadipour, 2007; Shah et al., 2017;
Wu et al., 2019), and North America (Ford, 1983; Smart, 1988; Spangler,
2001).

The main goal of this work is to highlight the complementarity of
conventional hydrogeological tools and groundwater dating techniques as
an effective approach to evaluate mixing processes involving components
of different ages in geologically complex karst areas located in alpine
mountains. To do so, environmental dating tracer data
(\textsuperscript{3}H,
\textsuperscript{3}He\textsubscript{trit},\textsuperscript{4}He\textsubscript{rad},
CFC-12, CFC-11, and SF\textsubscript{6}) and the hydrodynamic,
hydrochemical, and groundwater temperature data series from several
springs draining a relatively small and complex alpine karst aquifer
(Jarastepar) in South Spain are jointly considered. Based on the
concentration of environmental dating tracers in the samples, Lumped
Parameter Models, and Shape-Free Models were created to assess the
groundwater age distribution in diverse water conditions. The
simultaneous application of different methodologies provides a
significant and quantitative advance in the hydrogeological knowledge of
the karst system, from which an improved conceptual model of the aquifer
functioning can be established (basis for numerical model), more solid
than if convetional hydrogeological tools or dating techniques would
have been individually applied. This joint approach is uncommon in
alpine karst hydrogeology, but it can be useful in particular cases in
which conventional hydrogeological methods do not explain the whole
complexity of the aquifer.

\textbf{SETTING}

The pilot site is located in the central part of the Ronda Mountains, in
southern Spain (Fig. 1). The catchment area covers a rugged land surface
of 56 km\textsuperscript{2} (38 km\textsuperscript{2} of carbonate
rocks) with altitudes ranging from 400 to 1400 m a.s.l. and an average
slope of 20 \%. The climate is Mediterranean type. The mean
precipitaiton in the area is 1,050 mm/yr, and rainfall generally occurs
between autumn and springtime. The averages values of precipitation and
temperature recorded at the Jarastepar meteorological station (1,317 m
a.s.l.; Fig. 1) during the research period (October 2014 to December
2016) are 770 mm/yr and 12.2 ºC, respectively. However, during the
recharge times, an average temperature of 8 ºC was recorded.

From a geological standpoint, the research area presents a complex
structure that involves rocks from three main tectonic domains of the
Betic Cordillera (Figs. 1 \& 2): a) the External Zone (EZ) occupying the
lowest tectonic position and lithostratigraphically formed, from the
bottom to the top, by Upper Triassic clays and evaporites, Jurassic
dolostones and limestones (\textgreater{}500 m thick), and
Cretaceous-Tertiary marly-limestones and marls (Martín-Algarra, 1987);
b) the Internal Zone (IZ), overlapping the External Zone from the
southwest, composed of up 400 m of Paleozoic metamorphic rocks (mainly
schists) and more than 1,000 m of carbonate formations (mainly
dolostones); c) Flysch Complex (FC), formed by Tertiary clays and
sandstones and discontinuously imbricated between the two previous
domains (defining the tectonic suture). The geological structure of the
EZ is characterized by a NE-SW anticlinorium fold, which overthrusts
with vergence toward the NW over the Triassic clays of the anticline
core. Likewise, the internal structure of carbonate formations from the
IZ corresponds to the normal limb of a large ENE-WSW-trending
north-verging synform developed eastward of the study area
(Martín-Algarra, 1987). The set of geological units were affected by
more recent strike-slip faults (NW-SE) and normal fractures (NE-SW and
N-S) (Fig. 1).

In hydrogeological terms, the Jarastepar aquifer is comprised of
fractured and karstified Triassic (IZ) and Jurassic (EZ) carbonate rocks
that are bounded by low permeability formations, mainly Triassic clays
and Cretaceous-Paleogene marls of the EZ (Fig 1). However, the southern
border coincides with a major tectonic contact between the materials of
the EZ and the IZ, involving rocks with very different permeabilities
(Fig. 2). Recharge occurs by rainfall infiltration over the carbonate
outcrops (predominantly diffuse but locally concentrated through swallow
holes), while discharge takes place through springs located in the
southern border of the aquifer. There are three perennial outlets
(Huertos -560 m a.s.l.-, Charco -589 m a.s.l.- and La Zúa -603 m
a.s.l.-) that are located in the tectonic contact between the Triassic
dolostones and the metamorphic rocks of the IZ. There is also a
temporary discharge area (overflow springs -643 - 664 m a.s.l.-) at the
southern edge of the EZ, just North of the major tectonic contact (where
low permeable Flysch clays are imbricated) between the IZ and the EZ. In
low water conditions, the water table is accessible through a shaft with
a vertical development of 40~m in the overflow point.

\textbf{METHODS}

From October 2014 to December 2016 water temperature and electrical
conductivity (EC) were hourly recorded in La Zúa
(WTW\textsuperscript{TM} Cond 315i), Charco, and Huertos springs
(HOBO\textsuperscript{TM} Onset U24-001), as well as in the shaft of the
overflow springs (OTT\selectlanguage{english} EcoLog-800). The water level variations were
registered in La Zua (Odyssey\textsuperscript{TM} Capacitance Water
Level) and the shaft (OTT\selectlanguage{english} EcoLog-800) and later transformed to
flow-rate data series. Additionally, single flow measurements were made
in all the outlets and samples for hydrochemical analysis were
collected, with a weekly to daily periodicity (depending on the
hydroclimatic conditions).

Samples for major ion chemistry analysis were taken in 125 ml amber
glass bottles, while 1L PET bottles were used for \textsuperscript{3}H
analysis. For noble gas determination, spring water was conducted
through a transparent tube and collected into duplicate clamped-off
copper cylinders, using a 12v submersible pump, following the procedure
described by Sultenfuss \emph{et al.} (2011). For CFC and
SF\textsubscript{6} analysis, samples were collected in 500 ml
double-opening steel bottles, as explained by Jaunat \emph{et
al.}(2012). To avoid modern-air contamination, a Viton hose was used to
bring the water from the spring to the bottles. Suction was created
using a peristaltic pump with a transparent tubing-outlet, which
permitted the detection of bubbles that would indicate induced
degassing. The steel bottles were shaken after sealing, so the lack of
noise permitted to discard the involuntary formation of a headspace.
Samples for groundwater dating were collected on five different dates,
coinciding with diverse hydrodynamic situations: low, intermediate and
high water conditions (LW, IW, and HW in Fig. 3).

Major chemical components were determined in the Laboratory of the
Centre of Hydrogeology of the University of Malaga (CEHIUMA). Alkalinity
was analyzed by volumetric titration with 0.02N
H\textsubscript{2}SO\textsubscript{4} to pH 4.45. Major ions
(Ca\textsuperscript{2+}, Mg\textsuperscript{2+}, Na\textsuperscript{+},
K\textsuperscript{+}, Cl\textsuperscript{-},
SO\textsubscript{4}\textsuperscript{2-}) were determined by ionic
chromatography (METROHM Compact 930 IC flex for cations and Compact 881
IC Pro for anions). Determination of \textsuperscript{3}H, He isotopes,
Ne, CFC, and SF\textsubscript{6} was carried out in the Department of
Oceanography of the Institute of Environmental Physics, University of
Bremen. He isotopes, Ne, and \textsuperscript{3}H were determined in the
mass spectrometric facility described by Sultenfuss, Roether, and Rhein
(2009). The \textsuperscript{3}H analysis followed
the\textsuperscript{3}He--ingrowth method (Clarke, Jenkins, \& Top,
1976), so water samples of 0.5 kg were degassed and stored in gas-free
glass bulbs for production and accumulation of \textsuperscript{3}He,
the decay product of \textsuperscript{3}H. After 4-6 months of storing,
the produced \textsuperscript{3}He was determined with the mass
spectrometric system. On the other hand, CFC and
SF\textsubscript{6}concentrations were determined using a micro electron
capture detector (micro-ECD) mounted on a gas chromatograph (Agilent
GC6890N) with a capillary column, as explained by Bulsiewicz, Rose,
Klatt, Putzka, and Roether (1998). The CFC data were calibrated
according to the SIO scale 2005 (Bullister \& Tanhua, 2010).

Noble gas concentrations are expressed in ccSTP/kg of
H\textsubscript{2}O and the specific radioactive activity
of\textsuperscript{3}H is referred to Tritium Units (TU = 0.119 Bq/kg of
H\textsubscript{2}O). The CFC and SF\textsubscript{6} concentrations
(pmol/kg of H\textsubscript{2}O) were converted to atmospheric mixing
ratio (pptv) according to the recharge conditions: average recharge
altitude of 1,150 m a.s.l., mean temperature of 8 oC during rainy months
(October to May), and no salinity. The potential contribution of excess
air was quantified as proposed by Aeschbach-Hertig, Peeters, Beyerle,
and Kipfer (1999), based on the mean \selectlanguage{greek}Δ\selectlanguage{english}Ne values of each sample point.
\selectlanguage{greek}Δ\selectlanguage{english}Ne is the difference between the concentrations of Ne in the sample and
its theoretical content at recharge conditions minus 1, expressed in
percentage.

Groundwater age of the sample fraction containing \textsuperscript{3}H
(recharged after 1953), was calculated by
the\textsuperscript{3}H/\textsuperscript{3}He method (Torgersen, Clarke,
\& Jenkins, 1978). The apparent piston
flow\textsuperscript{3}H/\textsuperscript{3}He age (\selectlanguage{greek}\emph{τ} \selectlanguage{english}) is given
by:

\(\tau=\frac{1}{\lambda}ln\left(1+\frac{{}^{3}\text{He}_{\text{trit}}}{{}^{3}\text{He}}\right)\)(Equation 1)

where \selectlanguage{greek}\emph{λ} \selectlanguage{english}is the \textsuperscript{3}H decay constant, of 0.05626
yr\textsuperscript{-1} (ln(2)/12.32 yr; Lucas and Unterweger, 2000),
and\textsuperscript{3}He\textsubscript{trit}
(tritiogenic\textsuperscript{3}He) is the concentration of that isotope
in the sample derived from \textsuperscript{3}H decay. Its separation
from other \textsuperscript{3}He sources in groundwater (equilibrium,
excess-air, radiogenic) is possible using \textsuperscript{4}He and Ne
data (e.g. Cook \& Herczeg, 2000; S\selectlanguage{ngerman}ültenfuss et al., 2011). The CFC and
SF\textsubscript{6} ages were determined by comparing their
concentration in the sample and their mixing ratio in the Northern
Hemisphere atmosphere (USGS, 2018). The \textsuperscript{3}H input
function used in modeling tasks was generated from the correlation of
the \textsuperscript{3}H in precipitation recorded by the GNIP (Global
Network of Isotopes in Precipitation) station closest to the pilot site
(Morón, 55km northwards) and the data series of the GNIP Vienna station
(IAEA/WMO, 2018). The resulting function was scaled to 2016; that is, it
was converted to current concentration using the radioactive decay law
and the \textsuperscript{3}H decay constant. The difference from the
original and the decayed \textsuperscript{3}H input functions give rise
to a \textsuperscript{3}He\textsubscript{trit} input function.

To interpret the groundwater age distributions of each sample, different
models were created based on the concentration of
\textsuperscript{3}H,\textsuperscript{3}He\textsubscript{trit},\textsuperscript{4}He\textsubscript{rad}
(radiogenic\textsuperscript{4}He) and CFC-12 in samples taken during the
same hydrodynamic conditions: high water or intermediates water (Tab.
2). The software TracerLPM (Jurgens, Böhlke, Eberts, \& Survey, 2012)
was used for developing Lumped Parameter Models -LPMs- (Maloszewski \&
Zuber, 1982). This kind of model uses a convolution integral to sum up
all the tracer concentrations (\emph{C\textsubscript{i}} ) at each
possible time (\emph{t} '). It incorporates a weight function
\emph{g(t-t')}determining the importance of each age in the total
groundwater age at the sampling time (\emph{t} ) and a decay term for
radioactive tracers based on the decay constant (\selectlanguage{greek}\emph{λ} \selectlanguage{english}):

\(C_{s}\left(t\right)=\int_{-\infty}^{t}{C_{i}(}t^{\prime})g(t-t^{\prime})e^{-\lambda\left(t-t^{{}^{\prime}}\right)}dt^{\prime}\)(Equation 2)

Additionally, Shape-Free models were created (Visser, Broers,
Purtschert, S\selectlanguage{ngerman}ültenfuß, \& de Jonge, 2013). This approach is a
simplification of equation 2, but instead of using a weight function, it
describes the groundwater age distribution of the sample as a histogram
of \emph{n} bins, each of which has a uniform age. The number of bins is
constrained by the number of tracers considered (\emph{n - 1} ). The
measured tracer concentration in the sample (\emph{C\textsubscript{s}} )
is the result of summing the products of the mean tracer concentration
in each bin (\emph{C\textsubscript{i}} ) and the fraction they represent
in the whole groundwater sample (\emph{F\textsubscript{i}} ):

\(C_{s}(t)={\sum_{i=1}^{n}{F_{i}C_{i}(t^{{}^{\prime}})}}\) (Equation 3)

Two Shape-Free Models (SFMs) were used to describe the groundwater age
distribution of each sample: 5-bin models were created based on the four
more reliable tracers (CFC-12,
\textsuperscript{3}H,\textsuperscript{3}He\textsubscript{trit},
and\textsuperscript{4}He\textsubscript{rad}) and 4-bin models were
derived from the three young groundwater tracers. The latter model does
not include \textsuperscript{4}He data because its accumulation rate is
uncertain. In both cases, all the bins are equidistant except for the
oldest one, which represents a sample fraction without recent age
tracers (i.e.,
\textsuperscript{3}H,\textsuperscript{3}He\textsubscript{trit}, and
CFC). The characteristics of each bin are shown in table 3. The SFMs
were developed using SOLVER Add-In in Excel. Each bin fraction was
calculated adopting as constrains the piston-flow concentrations of the
selected tracers in the sample.

\textbf{RESULTS}

\textbf{Hydrodynamics and hydrochemistry}

During the research period, the mean flow rates of the perennial outlets
(IZ) varied from 23.4 l/s (Charco spring) to 208 l/s (La Zúa spring),
with coefficients of variation comprised between 15.1\% and 16.1\%,
respectively (Tab. 1). These springs show buffered and delayed
hydrodynamic responses to recharge events, reaching the flow peaks in
several weeks or even months (Fig. 3). On the contrary, the discharge
rate in the overflow area during activity periods has an average value
of 2.3 m³/s, though it can reach 21.4 m³/s. The water level variations
in the shaft of the overflow area denote a marked karst behavior, with
quick rises as a response to rainfall, as well as rapid falls (Fig. 3).

The mean contents of Ca\textsuperscript{2+}, Mg\textsuperscript{2+}, and
SO\textsubscript{4}\textsuperscript{2-} in the overflow springs are
respectively 65.4 mg/l, 5.1 mg/l, and 8.3 mg/l, while alkalinity is
203.5 mg/l (Tab. 1). The mineralization of groundwater greatly increases
towards lower altitudes in the IZ (Fig. 3), particularly
Ca\textsuperscript{2+}, Mg\textsuperscript{2+}, and
SO\textsubscript{4}\textsuperscript{2-}, which respectively reach
average values up to 437.3 mg/l, 87 mg/l, and 1201.1 mg/l in Huertos
spring (Tab. 1). These changes in the hydrochemistry of groundwater
cause the rise of EC toward lower altitudes (Fig. 3), from mean values
of 352~\selectlanguage{greek}µ\selectlanguage{english}S/cm in the overflow outlets, to averages comprised between 1565
\selectlanguage{greek}µ\selectlanguage{english}S/cm and 1875~\selectlanguage{greek}µ\selectlanguage{english}S/cm in the IZ (Tab. 1). Likewise, the mean temperature
value of the groundwater drained through the overflow area is 14.9 \selectlanguage{ngerman}ºC,
while it is comprised between 15.7 ºC and 16.7 ºC in the IZ springs.

The variability of the physicochemical parameters monitored in the
overflow springs is much higher than in the outlets of the IZ, as it is
shown by their coefficients of variation (Tab. 1). While the water
temperature and the EC values registered in the overflow area change
greatly and rapidly, the variations of these two parameters are smoother
and delayed in the perennial springs of the IZ. It is also observed that
the concentration of Mg\textsuperscript{2+} is more stable than the
contents of Ca\textsuperscript{2+} and
SO\textsubscript{4}\textsuperscript{2-} (Fig. 3). However,
Mg\textsuperscript{2+} and SO\textsubscript{4}\textsuperscript{2-} are
more stable in the overflow area than in the perennial outlets (Fig. 3).
Hence, the temporal hydrochemical evolution of the springs reflects two
clear distinct patterns depending on the geological location of the
springs in the aquifer (Fig. 3).

\textbf{Environmental tracers}

The \selectlanguage{greek}Δ\selectlanguage{english}Ne values of the samples are comprised between 27.0\% and 39.4\%,
showing certain air excess in the samples (Tab. 2). The \selectlanguage{greek}Δ\selectlanguage{english}Ne of the
duplicate differs 5\% at most, so the excess is not due to an inadequate
sampling process, but rather to the dissolution of air bubbles that are
trapped in the soil zone or the aquifer during recharge
(Aeschbach-Hertig et al., 1999; Mayer et al., 2014). The \selectlanguage{greek}Δ\selectlanguage{english}Ne values
permit to estimate the fraction of gases in the sample coming from
excess air, including \textsuperscript{4}He isotopes (Aeschbach-Hertig
et al., 1999). Non-atmospheric \textsuperscript{4}He is of underground
radiogenic origin (\textsuperscript{4}He\textsubscript{rad}) and
produced by alpha decay of the U and Th decay series. The
rest\textsuperscript{4}He comes from the atmosphere (solubility
equilibrium). Assuming that the liberation rate of
the\textsuperscript{4}He\textsubscript{rad} to groundwater is constant
and homogeneous, its concentration would be proportional to groundwater
travel time (Solomon, 2000). The concentrations
of\textsuperscript{4}He\textsubscript{rad} in the samples range from
1.3\selectlanguage{ngerman}·10\textsuperscript{-5} to 2.6·10\textsuperscript{-5} ccSTP/kg (Tab.
2). A rise in the content of \textsuperscript{4}He\textsubscript{rad} is
observed from La Zúa to Huertos spring, from higher to lower altitudes
(Fig. 4), which would indicate also an increase of the mean residence
time. The \textsuperscript{4}He\textsubscript{rad} accumulation rates
reported in the literature vary two order of magnitude, from
2.0·10\textsuperscript{-8}STPcc·kg\textsuperscript{-1}·yr\textsuperscript{-1}
(Lehmann et al., 2003) to
1.9·10\textsuperscript{-6}STPcc·kg\textsuperscript{-1}·yr\textsuperscript{-1}
(Beyerle et al., 1999), so it is not possible to estimate a
reliable\textsuperscript{4}He\textsubscript{rad} age using these values.
Nevertheless, assuming the fastest accumulation rate, of
1.9·10\textsuperscript{-6}STPcc·kg\textsuperscript{-1}·yr\textsuperscript{-1},
the observed data would require at least transit time of nearly a
decade, although slowest accumulation rates would lead to transit times
up to two orders of magnitude higher.

All the samples contain \textsuperscript{3}H, between 1.65 and 2.46 TU
(Tab. 2). The \textsuperscript{3}H activity in precipitation registered
in SW Spain by the GNIP from 1980 (IAEA/WMO, 2018) scaled to 2016 is in
the same range (De la Torre, 2020). Therefore, the concentrations
observed in the samples could correspond to piston flow ages within that
period; in other words, an unmixed groundwater sample with
that\textsuperscript{3}H content would have been recharged within that
interval. The \textsuperscript{3}H/\textsuperscript{3}He dating results
show infiltration ages between 33 and 40 years (Tab.~2), which could be
fairly consistent with the mentioned period. However, small rises in
the\textsuperscript{3}H/\textsuperscript{3}He ages (\selectlanguage{english}~2 years) would be
related to \textsuperscript{3}H activities that duplicate the observed
data. Therefore, mixing with a tritium-free component cannot be
completely discarded.

The measured CFC-12 values vary from 0.98 and 1.58 pmol/kg, which
correspond to atmospheric mixing ratios of 184 and 295 pptv (Tab. 2) at
the infiltration conditions of temperature and pressure. Note that the
effect of using different \selectlanguage{greek}Δ\selectlanguage{english}Ne within the observed range in each spring
would affect the CFC-12 mixing ratios in less than 5 pptv, which do not
have a practical effect on dating estimations. The results would
indicate piston flow ages from 36 to 43 years, which are slightly older
than the \textsuperscript{3}H/\textsuperscript{3}He ages (Tab. 2). Such
differences could be related to the dilution of the CFC-12 concentration
due to the presence of an old component with a lower tracer content or
free of it. That dilution would produce a bias towards older CFC-12
ages, but it would not modify
the\textsuperscript{3}H/\textsuperscript{3}He. A CFC-12 diminishing
could be also produced by sorption or microbial degradation, although it
seems unlikely in this case since CFC-12 sorption is generally
negligible (Cook \& Solomon, 1997) and its degradation requires anoxic
conditions (IAEA, 2006), which is not the case in the springs of the IZ
(mean dissolve oxygen = 4.5 mg/l).

CFC-11 values are comprised between 1.27 and 2.28 pmol/kg, equivalent to
62 and 111 pptv, respectively (Tab. 2). Such values are much lower than
the expected from the CFC-12 data and are not explainable by applying
mixing models. As no contamination sources exist in the recharge area,
the CFC-11 concentrations in groundwater have to be diminished by
sorption or another physical or biochemical process (IAEA, 2006). On the
contrary, the contents of SF\textsubscript{6} in the sample (0.17 - 0.22
pmol/kg) are related to extremely high SF\textsubscript{6} mixing
ratios, over 450 pptv (Tab. 2). Such results are more than one order of
magnitude higher than the current atmospheric mixing ratios
(approximately 10 pptv) and without a near pollution source, they can be
explained only by a terrigenic production. The dominance of dolostone
formations in the aquifer may be the natural source of
SF\textsubscript{6} (Busenberg and Plummer, 2000). Neither the CFC-11
nor the SF\textsubscript{6} are reliable to be included in the mixing
models.

\textbf{Groundwater mixing and age distribution models}

To find a model that properly describes the groundwater age distribution
of the samples, each possible type of Lumped Parameter Models (LPMs) was
checked: Piston Flow Model --PFM-, Exponential Model --EM-, Partial
Exponential Model --PEM-, Exponential Piston Model --EPM- and Dispersion
Model --DM- (e.g. Jurgens et al., 2012; Suckow, 2014). In general terms,
none of them show a good fitting to the sample concentrations. However,
according to the PFM and the DM (dispersion parameter = 0.05), a binary
mixing process could explain the tracer concentrations. In Figure 5, the
spring samples are plotted in three tracer-tracer graphs together with
the evolution of the tracers. The samples plot in areas between two
theoretical mixing lines drawn from an old component (200 years) to two
different modern groundwater components, of 0 and 40 years (Fig. 5).
This suggests that the tracer concentration measured in the sample could
be explained by a Binary Mixing Model (BMM). Based on that, two BMMs
were created for each sample, one of them combines two PFM as a
simplified proxy, and the other one integer two DM, which is a type of
LPM that does not need previous assumptions about the flow conditions.
The dispersion parameter of the DM that describes the young fraction of
the DMM is 0.05, and its mean age range from 25 to 31 years, depending
on the sample. The dispersion parameter in the old DM is 0.2, and the
mean ages are 160 years for La Z\selectlanguage{ngerman}úa spring, 180 years for Charco spring,
and 220 years for Huertos spring.

Different accumulation rates of
\textsuperscript{4}He\textsubscript{rad}were checked to include it in
the LPMs. The best results were found using a value of
2·10\textsuperscript{-7}STPcc·kg\textsuperscript{-1}·yr\textsuperscript{-1}.
This rate permitted estimate an apparent
\textsuperscript{4}He\textsubscript{rad} age for each sample (Tab. 2)
that varies between 66 years (La Zúa) and 131 years (Charco). These
values are not the same as the ones used to define the old fraction of
the LPM, as the \textsuperscript{4}He\textsubscript{rad}content in the
sample would be diluted by the younger component.
The\textsuperscript{4}He\textsubscript{rad} accumulation rate has
permitted to include this tracer to create a SFM of 5 bins. As the
concentration of this tracer in each bin is estimated from another model
(BMM DM-DM), the 4-bin SFM has been also generated
without\textsuperscript{4}He\textsubscript{rad}.

In Table 4 there is a summary of the main information extracted from
each of the models. Both types of LPMs suggest that the percentage of
the old component (free of \textsuperscript{3}H and CFC-12) is greater
in Huertos spring, while its ratio is lower in La Zúa. This pattern is
also observed in the results obtained from the application of SFMs (Tab.
4). Therefore, the proportion of groundwater infiltrated before 1940
increases towards lower altitudes.

The mean age of the groundwater samples only could be estimated by those
models that include the \textsuperscript{4}He\textsubscript{rad} data
(BMM DM-DM and 5-bin SFM), as the other two models (BMM PFM-PFM and
4-bin SFM) were created based only on \textsuperscript{3}H and CFC-12
that do not provide information about the age of the old fraction of the
samples. The mean age results of each sample differ considerably
depending on the model (Tab. 4), from 15 years of difference in La Zúa
spring (54 and 69 years) to 35 years in Huertos spring (95 and 123
years). Nonetheless, in both cases, the mean age of the samples
increases from the highest altitude (La Zúa) to the lowest height
(Huertos). It is also noteworthy that all the mean ages indicate several
decades of average transit time. Ages older than 63 years would indicate
a mean infiltration date before the anthropogenic liberation
of\textsuperscript{3}H (1953), while values higher than 76 would also be
previous to the generation of CFC-12 (1940).

The groundwater age distribution of the samples was calculated by
applying the LPMs and the SFMs (Fig. 6). All the models show that La Zúa
spring accumulates sooner a higher proportion of young water, while the
groundwater age distributions of the samples from Charco and Huertos
springs are progressively biased towards older ages. The two samples of
Huertos and Charco springs show similar distribution, independently on
the hydrodynamic conditions in which they were collected, while the
samples of La Zúa springs show some differences (Fig. 6); the sample
taken in high water conditions (December 2016) accumulates less
proportion of young groundwater than the one collected in an
intermediate water state (October 2014).

The median of the Groundwater Age distribution (hereby GA50) can be
easily identified in groundwater distribution plots, in that bin (for
SFM) or age (for LPM) in which the cumulative fraction reaches or
exceeds the 50\% (Gil-Márquez, Sültenfuß, Andreo, \& Mudarra, 2020).
This parameter permits to rapidly assess whether the sample is mainly
formed by recent or older groundwater, contrary to the mean age, which
sometimes leads to misinterpretation of mixed groundwater age data. The
GA\textsubscript{50} could reach more than 80 years in all the spring
according to the 5-bin SFM (Tab. 4 and Fig. 6), while the lowest values
are obtained from the BMM DM-DM, with GA\textsubscript{50} of 30 years
in La Zúa spring, 44 years in Charco, and 60 years in Huertos. Thus, the
groundwater drained by the spring accumulates less modern fraction
towards lower altitudes.

\textbf{DISCUSSION}

\textbf{Coupling hydrochemistry and groundwater age distribution}

The variations of the dating environmental-tracer concentrations under
different hydrodynamic conditions (Tab. 2) permit obtaining information
about the functioning of the aquifer. Particularly, it is observed that
the \textsuperscript{4}He\textsubscript{rad} concentration rises from
high water (HW) to low water (LW) conditions. It would indicate that
during recession periods the mix of groundwater drained through the
spring is older than in discharge rises. That is in agreement with the
registered increment of mineralization in the dry periods (Fig. 3). The
only exception to the pattern is found in La Zúa spring, where the
highest \textsuperscript{4}He\textsubscript{rad} content was measured in
high water conditions (Tab. 2). That can be explained because during the
sampling the spring was showing a piston-flow effect (Fig. 3). This term
is used in karst hydrogeology to indicate a rise of mineralization and
water temperature in the spring as a response to recharge events, which
is often produced by mobilization of older groundwater from the
saturated zone (Mudarra \& Andreo, 2011). The decrease
of\textsuperscript{3}H concentration in low water conditions (Tab. 2)
could also be produced by a higher proportion of old groundwater
(tritium-free) being drained. However, the evolution of
the\textsuperscript{3}H input function and the seasonal fluctuation of
the activity of this isotope in the atmosphere make it difficult to
obtained further conclusions with only a few samples. Delbart et al.
(2014) proved that a more exhaustive sampling routine would help to
understand the evolution of young-groundwater tracer (not only
\textsuperscript{3}H but also CFC and SF\textsubscript{6}), particularly
during discharge rises. In that sense, the present work also
demonstrates the potentiality of an old-groundwater tracer
(\textsuperscript{4}He\textsubscript{rad}) to analyze the natural
response of karst springs.

In Figure 7, some physicochemical and chemical parameters are compared
to groundwater dating data derived from the LPMs and the SFMs. It is
observed that electrical conductivity (EC) is positively related to the
proportion of old groundwater (free of \textsuperscript{3}H and CFC-12)
and the mean and median age of the samples (Fig. 7A \& B). The ascent of
EC is also related to a decrease in the spring height (Fig. 3). That
combined indicates that the groundwater drained by the springs located
at lower altitudes would have longer residence time within the aquifer,
thus it would have dissolved a greater amount of solutes (i.e., higher
EC).

A similar relationship is established between the groundwater dating
parameters and the temperature values measured in the spring water (Fig.
7C \& D), which are slightly higher (1-2ºC) than the mean annual
temperature of the area (De la Torre, Mudarra, \& Andreo, 2020).
Besides, the variability of the water temperature of the springs located
in the IZ is low (\textless{}1\%), contrary to the variability of the
flow rate and most of the chemical parameters (Tab. 1), and also to the
groundwater temperature in the overflow area. All this information
suggests that groundwater may flow within deep areas of the system.
However, the lack of thermalism \emph{stricto sensu} would indicate a
slow ascent of groundwater flows toward the discharge points, reaching
progressively temperature values near the equilibrium with the
atmospheric ones.

The water mineralization of the springs placed in the IZ is mainly
related to dissolved SO\textsubscript{4}\selectlanguage{english}\textsuperscript{2-},
Ca\textsuperscript{2+}, and Mg\textsuperscript{2+} contents (Tab. 1).
The presence of SO\textsubscript{4}\selectlanguage{english}\textsuperscript{2-} and
Ca\textsuperscript{2+} in the groundwater of Jarastepar aquifer allows
the dedolomitization of the Triassic dolostone rocks belonging to the
EZ. This geochemical process involves multi-mineral phases and consists
in the transformation of dolomite crystals in calcite (Appelo \& Postma,
2005; Wigley, 1973), resulting in a greater amount of dissolved
Mg\textsuperscript{2+} in groundwater than that explained by dolomite
dissolution only. While the concentration of Mg\textsuperscript{2+} in
groundwater shows a marked increase towards lower altitudes, the rise of
Ca\textsuperscript{2+} is less steep (Fig. 3). Besides, the molar
relation between Mg\textsuperscript{2+} and
Ca\textsuperscript{2+}(rMg/Ca) presents a positive and well-defined
relationship with the percentage of old groundwater in the samples and
their mean and median ages (Fig. 7E \& F). Therefore, there is an
enrichment of Mg\textsuperscript{2+} respect to Ca\textsuperscript{2+}
as groundwater became older. That indicates that the groundwater drained
at lower altitudes is hidrogeochemically more evolved due to longer
water-rock interactions. This process has been also are described in
other carbonate systems worlwide (Carucci, Petitta, \& Aravena, 2012;
McMahon, Bohlke, \& Christenson, 2004; Moral, Cruz-Sanjulian, \& Olias,
2008; Plummer et al., 1990). Besides, the good correlation degree
between the dating parameters obtained from the models and the rMg/Ca
indicates that the groundwater of Jarastepar aquifer is mainly stored in
dolomite-bearing formations, which form the permeable layers in the IZ
and the deepest part of the aquifer in the EZ (Figs. 1 \& 2).

The dissolution of the evaporite rocks from the EZ is the main source of
SO\textsubscript{4}\selectlanguage{english}\textsuperscript{2-} and Ca\textsuperscript{2+} in
the groundwater of the aquifer, according to the high stoichiometric
relation of both ions and to the isotope signature of
\selectlanguage{greek}δ\selectlanguage{english}\textsuperscript{34}S\textsubscript{SO4} and
\selectlanguage{greek}δ\selectlanguage{english}\textsuperscript{18}O\textsubscript{SO4} (De la Torre et al., 2020).
The SO\textsubscript{4}\textsuperscript{2-} concentration in the samples
is positively related to the presence of old groundwater and the mean
and median ages (Fig. 7G \& H). However, the correlation degrees are
lower than those found for EC and rMg/Ca. That could indicate that
gypsum dissolution does not occur during all the groundwater transit
time, contrary to dedolomitization. Thus, groundwater would dissolve
gypsum within the EZ substratum, which would enhance the gaining of
Mg\textsuperscript{2+} through dedolomitization, although it cannot be
discarded that some of the Mg\textsuperscript{2+} present in the
groundwater would come from the dissolution of evaporite rocks (Hamill
\& Bell, 1986; Chenini, Farhat \& Ben Mammou, 2010.). After groundwater
enters the IZ, the dissolution of gypsum ends (since there are no
evaporites in the IZ), but the
SO\textsubscript{4}\textsuperscript{2-}concentration is still high,
allowing dedolomitization to last longer while groundwater flows within
the Triassic dolostone formation.

The low correlation degree between the groundwater age parameters and
SO\textsubscript{4}\textsuperscript{2-} is somewhat produced by the
large variations of the concentration of this ion in the spring waters,
particularly in La Z\selectlanguage{ngerman}úa (Fig. 7G \& H). The higher outflow rate in La Zúa
spring and its greater hydrodynamic response (Tab.~1, Fig. 3) denotes a
better hydrogeological connection with the External Zone. That would
explain the higher variability of
SO\textsubscript{4}\selectlanguage{english}\textsuperscript{2-}, but also the changes in the
groundwater age distribution that are observed in every model made from
the samples of the spring (Tab. 4; Fig. 7). Despite the groundwater age
distribution of Huertos and Charco springs do not evidence many
variations, it cannot be discarded that a higher number of analyses of
dating environmental tracers could show otherwise.

\textbf{Implications of the geological setting on the groundwater
residence time}

All the SFMs show significant accumulation of groundwater between the 20
and 60 first years, while the fraction does not change in the
immediately following bin (Fig. 6). Therefore, the remaining groundwater
fraction is attributable to the old bin (free of \textsuperscript{3}H
and CFC-12). The groundwater age distributions obtained from the SFMs,
which do not require any previous assumption of the hydrogeological
functioning of the system, agree with the binary mixing LPMs that were
proposed. Thus, they confirm that the drainage of Jarastepar aquifer is
explained by two main flow components. One is formed by groundwater age
infiltrated during the last few decades, while the other one has a
greater mean residence time of around 200 years. The groundwater age
distribution of the springs of the IZ contrast with the high flow
velocities determined in the EZ of the aquifer (overflow area in figure
1) using dye tracing tests, which reached 600 m/h (De la Torre, 2020).

The rocks of the EZ have a large development of the conduit network,
with a great drainage capacity that allows the fast arrival of recently
infiltrated water towards the overflow area. There, temporary outlets
drain the aquifer only when the water coming from recharge exceeds the
transfer capacity between the IZ and the EZ, due to the hydarulica
hetereogeneity of the media. The chemical signature of the groundwater
drained through the overflow area and the dye tracing experiences
evidence that the origin of the groundwater drained through this area is
mostly related to the recharge events that give rise to the activation
of the temporary outlets, and it has a mean residence time of 54-64
hours (De la Torre et al., 2020). This behavior is typical in karst
areas, where the mean residence time of groundwater is between tens of
hours to several months, inferred by using natural and artificial
responses of the springs (Barbera et al., 2018; Birk, Liedl, \& Sauter,
2004; Lauber \& Goldscheider, 2014; Perrin, Jeannin, \& Zwahlen, 2003;
Shah et al., 2017). However, those age estimation only reflect the
fastest flowpaths throughout the conducts but not the slower flows
through narrow fractures and the matrix, which must be estimated based
on environmental tracers (Worthington \& Gunn, 2009). Therefore, it is
necessary to understand the intrinsic characteristics of the media, as
they can affect the interpretation of groundwater dating data.

The geological complexity of the Jarastepar aquifer, and particularly
the existence of a major tectonic contact with imbrication of impervious
materials (Flysch), together with the great thickness of the
semi-confined Jurassic and Triassic calcareous formations, confer the
springs placed in the IZ of the aquifer lagged and buffer responses to
precipitation events (Fig. 3). That is the typical behavior showed by
springs draining carbonate aquifers with dominated fissured or diffuse
flow functioning (Jeannin, Groves, \& Hauselmann, 2007; Mudarra \&
Andreo, 2011; Perrin et al., 2003). However, the mean ages estimated in
this case nearly reach the century (Tab.~4) instead of a few years or
decades, as it normally occurs in other small alpine karst aquifers
(Althaus et al., 2009; Lauber \& Goldscheider, 2014). Besides, the
models suggest that an old flow component with mean residence times
around 200 years exists (Tab. 4). This kind of binary mixing, including
centennial groundwater, is normally observed in large carbonate aquifers
that often are partially confined (Jiang et al., 2019; Toth \& Katz,
2006; Yager et al., 2010; Zang et al., 2015). However, the Jarastepar
aquifer is far from that definition, as its outcropping surface is
56~km\textsuperscript{2} and most of it corresponds to the unconfined
EZ, which can be rapidly drained through the overflow springs. The
distance from the tectonic suture to the perennial outlets is short,
particularly in the southwest, where the overflow area is 600~m far from
Huertos spring (Fig. 1). Assuming a straight-forward flow connecting
both points, groundwater should have a velocity of 6 m/year, as the mean
residence time of the groundwater drained by Huertos spring is estimated
in nearly 100 years (Tab.~4), and the groundwater drained through the
overflow springs is infiltrated only a few hours before. Such flow
velocities do not seem reasonable in karst formations.

Based on geological observations and hydrogeological methods
(hydrochemistry, hydrodynamics, stable isotopes), De la Torre et al.
(2020) proposed a hydrogeological conceptual model of the aquifer that
helps to understand the presence of old groundwater. The existence of
imbricated layer (discontinuous because of tectonic reasons) between the
EZ and the IZ, formed by Flysch-type clays and sandstones and
Cretaceous-Tertiary marls and marly limestones, slow down the
transference of groundwater from the Jurassic carbonate formation (EZ)
to the Triassic dolomites (IZ). That groundwater comes from the
saturated zone and is older than that drained through the overflow
springs (Fig. 8). Additionally, the flow deceleration produced by the
los permeability formations would lead to a greater residence time of
groundwater within the media. All that combined would explain the
existence of young groundwater components in the permanent springs with
mean transit times of few decades (Tab. 4 and Fig. 6).

The presence of an old groundwater flow component can be attributable to
the combined thickness of the Jurassic and the Triassic carbonate
formations, which could reach 1000 m. Both units are partially confined
bellow the metamorphic formations of the IZ and their extension
southwards is unknown. Furthermore, the karstification degree and the
permeability of the dolostones of the IZ are lower than in the EZ. In
any case, groundwater only can leave the system through the perennial
springs. Thus, after groundwater traverses a long flowpath to deep areas
of the aquifer, the tectonic contact with the low permeable rocks forces
the ascent of the groundwater flow towards the outlets (Fig. 8).
According to the low values of water temperature (Tab. 1), the upwelling
through the Triassic dolomite formation must occur slowly, allowing a
greater transference of Mg\textsuperscript{2+} to groundwater and the
temperature re-equilibrium. That explains why the correlation of
groundwater age parameters with rMg/Ca is high while it is lower with
SO\textsubscript{4}\textsuperscript{2-} (Fig. 7).

These findings not only demonstrate the existence of centennial
groundwater in a realtively small alpine karst aquifer, but they also
show how the particularities of the geological framework can greatly
affect the flow dynamics and the residence time of groundwater. There is
little evidence of centennial groundwater in this type of system except
for some karst springs in the Austrian Alps that drain deep reservoirs
connected to major faults (Han et al., 2007; Hilberg \& Schneider,
2011). The fact that groundwater age in alpine karst can be this old has
great implications in the hydrogeological management, but also regarding
its intrinsic vulnerability to pollution. Therefore, contrary to what is
expected, the complementary use of environmental dating tracers and
hydrochemistry in complex carbonate formations can be useful for the
management of its groundwater resources, particularly if the structure
of the aquifer is complex.

\textbf{CONCLUSIONS}

In this research work, conventional hydrogeological methods used in
karst aquifer studies (hydrochemistry, hydrodynamics, and water
temperature) were jointly applied with groundwater dating tools
(\textsuperscript{3}H, \textsuperscript{3}He, \textsuperscript{4}He,
CFC-12, CFC-11, and SF\textsubscript{6}) to explain the functioning of a
complex and relatively small alpine karst aquifer. Based on the
environmental-tracer concentrations, Lumped Parameter Models and
Free-Shape Models were created to define the groundwater-age
distribution of the springs water under different hydrodynamic
conditions. All that permitted to identify the existence of two main
flow components in the mix drained through the springs and to assed
their groundwater age distribution. This kind of binary mixing is
coherent with karst systems in which conduit flow and diffuse flow
coexist. However, in these cases, the mean ages of the springs are
several decades old, and the old component could have approximately 200
years. Those transit times are large for a relatively small alpine karst
area but here can be explained by a complex geological setting,
including a major tectonic contact that involves low permeability
material imbricated and a thick semiconfined saturated zone.

The hydrochemical characteristics of the springs, and particularly the
rise of mineralization and the rMg/Ca values towards lower altitudes,
are compatible with large residence times. Besides, the natural
responses registered in the spring waters, including the variations in
contents of the radiogenic \textsuperscript{4}He, are coherent with the
described binary mixing. In that sense, despite the number of analyzed
samples was limited, the study of the evolution of environmental tracer
concentration in the water of karst spring may be a useful tool in
future works to help with their hydrogeological understanding.

The results here presented demonstrate the applicability of using
environmental dating tracers in karst areas located in alpine mountains,
and show their usefulness on the interpretation of hydrogeological
functioning when combined with hydrochemical data and natural response
analysis. Therefore, this methodological approach is potentially useful
in other alpine karst aquifers of complex geology. In that way, the age
distribution of the groundwater drained through karst spring can be
understood, which is crucial for the assessment of pollution
vulnerability and the definition of safeguard zones for groundwater
protection.

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Table 1. Statistical parameters of flow rate, electrical conductivity
(EC), water temperature (Temp), major ion concentration, and ratio Mg/Ca
(rMg/Ca) in the groundwater drained by the main springs of Jarastepar
aquifer.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllll@{}}
\toprule
Spring/ Altitude & & \textbf{Flow rate} & \textbf{EC} & \textbf{Temp.} &
\textbf{Alk} & \textbf{Ca\textsuperscript{2+}} &
\textbf{Mg\textsuperscript{2+}} &
\textbf{SO\textsubscript{4}\textsuperscript{2-}} &
\textbf{rMg/Ca}\tabularnewline
\midrule
\endhead
(m a.s.l.) & & (l/s) & (\selectlanguage{greek}µ\selectlanguage{english}S/cm) & (\selectlanguage{ngerman}°C) & (mg/l) & (mg/l) & (mg/l) &
(mg/l) &\tabularnewline
Huertos 560 & \emph{n} & 99 & 14735 & 16890 & 110 & 110 & 110 & 110 &
110\tabularnewline
& \emph{min.} & 17.6 & 1747 & 16.3 & 214.0 & 387.3 & 75.6 & 991.7 &
0.11\tabularnewline
& \emph{max.} & 32.9 & 1938 & 16.9 & 232.9 & 484.7 & 94.2 & 1309.2 &
0.13\tabularnewline
& mean & \textbf{25.5} & \textbf{1875} & \textbf{16.7} & \textbf{226.4}
& \textbf{437.3} & \textbf{87.0} & \textbf{1201.1} &
\textbf{0.12}\tabularnewline
& \emph{cv (\%)} & 15.1 & 2.4 & 0.7 & 1.5 & 5.0 & 3.9 & 4.8 &
4.4\tabularnewline
Charco 589 & \emph{n} & 108 & 15164 & 15708 & 126 & 126 & 126 & 126 &
126\tabularnewline
& \emph{min.} & 17.0 & 1550 & 15.6 & 203.7 & 343.5 & 58.7 & 892.3 &
0.09\tabularnewline
& \emph{max.} & 29.7 & 1707 & 16.0 & 222.8 & 429.2 & 72.6 & 1165.1 &
0.11\tabularnewline
& mean & \textbf{23.4} & \textbf{1673} & \textbf{15.8} & \textbf{211.2}
& \textbf{396.1} & \textbf{66.0} & \textbf{1052.2} &
\textbf{0.10}\tabularnewline
& \emph{cv (\%)} & 15.7 & 1.6 & 0.7 & 2.0 & 4.4 & 4.2 & 6.7 &
4.3\tabularnewline
La Z\selectlanguage{ngerman}úa 603 & \emph{n} & 19754 & 8442 & 12436 & 126 & 126 & 126 & 126 &
126\tabularnewline
& \emph{min.} & 149 & 1540 & 15.3 & 190.7 & 345.0 & 37.9 & 834.4 &
0.06\tabularnewline
& \emph{max.} & 298 & 1591 & 16.0 & 226.0 & 451.4 & 50.9 & 1110.5 &
0.08\tabularnewline
& mean & \textbf{208} & \textbf{1565} & \textbf{15.7} & \textbf{207.2} &
\textbf{393.2} & \textbf{44.1} & \textbf{967.2} &
\textbf{0.07}\tabularnewline
& \emph{cv (\%)} & 16.1 & 0.7 & 0.7 & 2.2 & 5.9 & 6.6 & 6.4 &
2.8\tabularnewline
Overflow area 643-664 & \emph{n} & 897+ & 19752 & 19752 & 198 & 198 &
198 & 198 & 198\tabularnewline
& \emph{min.} & 0.1 & 260 & 13.6 & 165.4 & 49.6 & 1.4 & 1.7 &
0.02\tabularnewline
& \emph{max.} & 21433 & 494 & 16.8 & 309.1 & 103.3 & 8.8 & 18.1 &
0.10\tabularnewline
& mean & \textbf{2298} & \textbf{352} & \textbf{14.9} & \textbf{203.5} &
\textbf{65.4} & \textbf{5.1} & \textbf{8.3} &
\textbf{0.05}\tabularnewline
& \emph{cv (\%)} & 140.0 & 14.5 & 4.0 & 15.7 & 17.9 & 29.7 & 47.3 &
32.2\tabularnewline
\bottomrule
\end{longtable}

+ The number of data of flow-rate in the overflow spring is lower than
those of EC and Temp because it can only be measured in high water
conditions.

Table 2. Environmental tracer data from the water samples collected at
Jarastepar aquifer and derived groundwater date estimations.\selectlanguage{english}
\begin{longtable}[]{@{}llllllllllllllll@{}}
\toprule
\begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{Spring}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{Date of sample}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{System state}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\selectlanguage{greek}\textbf{ΔNe (\%)}\selectlanguage{english}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{H (TU)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{He\textsubscript{trit} (TU)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textsuperscript{\textbf{4}}\textbf{He\textsubscript{rad}
(ccSTP/kg)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{CFC-12 (pmol/kg)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{CFC-11 (pmol/kg)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{SF\textsubscript{6}} \textbf{(pmol/kg)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{CFC-12 (pptv)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{CFC-11 (pptv)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{SF\textsubscript{6}} \textbf{(pptv)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{Tracer ages (years)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{Tracer ages (years)}\strut
\end{minipage} & \begin{minipage}[b]{0.06\columnwidth}\raggedright\strut
\textbf{Tracer ages (years)}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{H/\textsuperscript{3}He}\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\textsuperscript{\textbf{4}}\textbf{He\textsuperscript{+}}\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\textbf{CFC-12}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
La Z\selectlanguage{ngerman}úa\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/10/14\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
30.5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.23\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
11.7\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.3E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
33\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
66\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
La Z\selectlanguage{ngerman}úa\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
21/05/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.58\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.28\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
295\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
111\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
36\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
La Z\selectlanguage{ngerman}úa\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
29/08/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
LW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
39.4\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.94\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
12\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.5E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
35\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
75\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
La Z\selectlanguage{ngerman}úa\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/05/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.30\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
0.22\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
243\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
601\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
41\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
La Z\selectlanguage{ngerman}úa\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
09/12/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
34.9\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.74\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
11.9\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.6E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
36\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
78\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Charco\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/10/14\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
27.0\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.46\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
15.7\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.0E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
36\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
101\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Charco\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
21/05/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.04\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.53\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
195\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
75\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
42\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Charco\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
29/08/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
LW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
34.5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.06\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
16.8\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.2E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
40\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
110\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Charco\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/05/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.11\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
0.22\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
209\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
593\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
42\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Charco\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
09/12/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
26.9\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.9\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
13.2\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.8E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
37\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
92\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Huertos\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/10/14\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
28.4\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.1\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
11.6\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.6E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
33\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
131\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Huertos\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
21/05/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
IW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
0.98\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.27\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
184\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
62\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
42\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Huertos\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
29/08/15\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
LW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
30.7\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.74\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
12.6\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.3E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
38\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
115\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Huertos\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
25/05/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
0.99\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
0.17\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
184\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
453\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
43\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
Huertos\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
09/12/16\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
HW\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
27.7\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
1.65\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
10.4\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
2.6E-5\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
35\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
129\strut
\end{minipage} & \begin{minipage}[t]{0.04\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

LW, IW, and HW refer to low, intermediate and high water hydrodynamic
situations. \textsuperscript{+}Ages calculated assuming
a\textsuperscript{4}He\textsubscript{rad} dissolution rate of
2\selectlanguage{ngerman}·10\textsuperscript{-7}ccSTP·kg\selectlanguage{english}\textsuperscript{-1}*yr\textsuperscript{-1},
according to the results of the Lumped Parameter Models.

Table 3. Characteristics of the bins included in the Shape-Free Models
(years).\selectlanguage{english}
\begin{longtable}[]{@{}llllll@{}}
\toprule
\begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{5-bin model}\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 1}\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 2}\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 3}\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 4}\strut
\end{minipage} & \begin{minipage}[b]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 5 (old bin)}\strut
\end{minipage}\tabularnewline
\midrule
\endhead
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
\textbf{Age range}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
0-20\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
20-40\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
40-60\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
60-80\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
80-160 (78-200) \textsuperscript{+}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Mean age}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
10\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
30\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
50\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
70\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
120 (140) \textsuperscript{+}\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{H (TU)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.10\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.64\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
8.64\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0.18\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{He\textsubscript{trit} (TU)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.5\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
14.9\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
101.6\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
6.9\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{CFC-12 (pptv)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
537.2\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
415.0\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
98.9\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
5.7\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{\textbf{4}}\textbf{He\textsubscript{rad}
(ccSTP/kg)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.1E-6\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
6.1E-6\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.0E-5\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.4E-5\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
2.4E-5\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{4-bin model}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 1}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 2}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 3}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Bin 4 (old bin)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
\textbf{Bin range}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
0-26\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
26-52\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
52-78\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
78-160 (78-200) \textsuperscript{+}\strut
\end{minipage} & \begin{minipage}[t]{0.16\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Mean age}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
13\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
39\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
65\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
119 (136) \textsuperscript{+}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{H (TU)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
1.95\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
4.15\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
3.56\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textsuperscript{\textbf{3}}\textbf{He\textsubscript{trit} (TU)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
5.17\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
37.86\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
63.53\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{CFC-12 (pptv)}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
533.49\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
263.473\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
15.84\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
0\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\textbf{Mean age}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
13\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
39\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
65\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
119 (136) \textsuperscript{+}\strut
\end{minipage} & \begin{minipage}[t]{0.14\columnwidth}\raggedright\strut
\strut
\end{minipage}\tabularnewline
\bottomrule
\end{longtable}

\textsuperscript{+} Values in brackets are referred only to samples from
Huertos spring.

Table 4. Results from groundwater distribution age models. BMM, Binary
Mixing Model; PFM, Piston Flow Model; DM, Dispersion Model, SFM,
Shape-Free Model; RMSE, Root of the Mean Square Error.\selectlanguage{english}
\begin{longtable}[]{@{}lllllllllllllllllll@{}}
\toprule
\textbf{Spring} & \textbf{Date of sample} & \textbf{Sample} &
\textbf{Sample} & \textbf{Sample} & \textbf{Sample} & \textbf{BMM
(PFM-PFM)} & \textbf{BMM (PFM-PFM)} & \textbf{BMM (PFM-PFM)} &
\textbf{BMM (DM-DM)} & \textbf{BMM (DM-DM)} & \textbf{BMM (DM-DM)} &
\textbf{BMM (DM-DM)} & \textbf{BMM (DM-DM)} & \textbf{5-bin SFM} &
\textbf{5-bin SFM} & \textbf{5-bin SFM} & \textbf{4-bin SFM} &
\textbf{4-bin SFM}\tabularnewline
\midrule
\endhead
& & \selectlanguage{ngerman}\textbf{³H (TU)} &
\textsuperscript{\textbf{3}}\textbf{He\textsubscript{trit} (TU)} &
\textsuperscript{\textbf{4}}\textbf{He\textsubscript{rad} (ccSTP/kg)} &
\textbf{CFC-12 (pptv)} & \textbf{F\textsubscript{young} (\%)} &
\textbf{F\textsubscript{old}} & & & & & & & & & & &\tabularnewline
(\%) & \textbf{F\textsubscript{young} age} & \textbf{Mean age (years)} &
\textbf{F\textsubscript{young} (\%)} & \textbf{F\textsubscript{young}
age} & \textbf{F\textsubscript{old} age} & \textbf{GA\textsubscript{50}
(years)} & \textbf{Mean age (years)} & \textbf{GA\textsubscript{50}
(years)} & \textbf{Old Bin (\%)} & \textbf{GA\textsubscript{50} (years)}
& \textbf{Old Bin (\%)} & & & & & & &\tabularnewline
La Z\selectlanguage{ngerman}úa & 25/10/2014 & 2.23 & 11.67 & 1.3E-05 & 295 & 100 & 0 & 33 & 69 &
68 & 25 & 160 & 30 & 54 & 20 & 0 & 52 & 32\tabularnewline
La Z\selectlanguage{ngerman}úa & 09/12/2016 & 1.74 & 11.90 & 1.6E-05 & 243 & 87 & 13 & 36 & 85 &
57 & 27 & 160 & 38 & 65 & 60 & 26 & 52 & 41\tabularnewline
Charco & 25/10/2014 & 2.46 & 15.66 & 2.0E-05 & 195 & 70 & 30 & 38 & 93 &
52 & 31 & 160 & 47 & 77 & \textgreater{}80 & 52 & \textgreater{}72 &
44\tabularnewline
Charco & 09/12/2016 & 1.90 & 13.20 & 1.8E-05 & 209 & 69 & 31 & 37 & 93 &
51 & 29 & 160 & 46 & 75 & 80 & 0 & \textgreater{}72 & 45\tabularnewline
Huertos & 25/10/2014 & 2.10 & 11.66 & 2.6E-05 & 184 & 58 & 42 & 38 & 119
& 48 & 29 & 200 & 66 & 94 & \textgreater{}80 & 57 & \textgreater{}78 &
51\tabularnewline
Huertos & 09/12/2016 & 1.65 & 10.40 & 2.6E-05 & 184 & 56 & 44 & 37 & 123
& 45 & 29 & 200 & 77 & 95 & 80 & 0 & \textgreater{}78 &
53\tabularnewline
\bottomrule
\end{longtable}\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

Fig. 1. Geographic location and geological sketch of the Jarastepar
mountain range. The cross-sections of figure 2 are indicated.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

Fig.
2. Geological cross-sections of Jarastepar aquifer. See locations in
figure 1.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

Fig. 3. Temporal evolution and boxplots of Ca\textsuperscript{2+},
Mg\textsuperscript{2+}, SO\textsubscript{4}\textsuperscript{2-},
Electrical Conductivity (EC) and water temperature recorded in the
groundwater drained through the main outlets of Jarastepar aquifer, from
October 2014 to December 2016. The hydrographs of La Z\selectlanguage{ngerman}úa, Charco, and
Huertos springs are also represented, as well as the limnigraph of the
overflow area and the daily rainfall. The sampling campaings for the
determination of \textsuperscript{3}H-He, adn CFC-12, CFC-11, and
SF\textsubscript{6} are represented as dashed and dotted lines,
respectively. IW, Intermediate water, LW, Low water, HW, high water\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

Fig. 4. \textsuperscript{4}He\textsubscript{rad} (left) and CFC-12
(right) in the samples and spring heights.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

Fig. 5. Tracer-tracer plots comparing measured to modeled tracer
concentrations for Piston Flow Model (PFM) and Dispersion Model (DM).
Binary mixing lines (0-200 and 40-200 years) are represented, and the
age of groundwater is indicated over the model lines.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

Fig. 6. Cumulative age distribution of the samples described by binary
mixing models (BMM) and discrete Shape-Free Models (SFM) of 4 and 5
bins. PFM: Piston Flow Model; DM: Dispersion Model.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image7/image7}

\end{center}
\end{figure}

Fig. 7. Electrical Conductivity (EC), water temperature,
SO\textsubscript{4}\textsuperscript{2-}, and rMg/Ca compared to the
percentage of old groundwater component (free of \textsuperscript{3}H
and CFC-12) deduced from different models (left) and the mean age and
the median age (GA\textsubscript{50}) derived from the BMM DM-DM and the
mean age obtained from the 5-bin SFM (right).\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image8/image8}

\end{center}
\end{figure}

Fig. 8. Hydrogeological conceptual model of Jarastepar aquifer, showing
the evolution of EC, Mg\textsuperscript{2+}, and groundwater age, as
well as the main geochemical and mixing processes. Lithology explanation
in figure 2.\selectlanguage{english}
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\textbf{Hosted file}

\verb`Table_1.docx`  available at \url{https://authorea.com/users/305548/articles/436280-complimentary-use-of-dating-and-hydrochemical-tools-to-assess-mixing-processes-involving-centenarian-groundwater-in-a-geologically-complex-alpine-karst-aquifer}

\textbf{Hosted file}

\verb`Table_2.docx`  available at \url{https://authorea.com/users/305548/articles/436280-complimentary-use-of-dating-and-hydrochemical-tools-to-assess-mixing-processes-involving-centenarian-groundwater-in-a-geologically-complex-alpine-karst-aquifer}

\textbf{Hosted file}

\verb`Table_3.docx`  available at \url{https://authorea.com/users/305548/articles/436280-complimentary-use-of-dating-and-hydrochemical-tools-to-assess-mixing-processes-involving-centenarian-groundwater-in-a-geologically-complex-alpine-karst-aquifer}

\textbf{Hosted file}

\verb`Table_4.docx`  available at \url{https://authorea.com/users/305548/articles/436280-complimentary-use-of-dating-and-hydrochemical-tools-to-assess-mixing-processes-involving-centenarian-groundwater-in-a-geologically-complex-alpine-karst-aquifer}

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