Constraining groundwater flow, residence times, inter-aquifer mixing, and aquifer properties using environmental isotopes in the southeast Murray Basin, Australia

Applied Geochemistry 27 (2012) 1698–1709

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Constraining groundwater flow, residence times, inter-aquifer mixing, and aquifer properties using environmental isotopes in the southeast Murray Basin, Australia Ian Cartwright a,b,⇑, Tamie R. Weaver c, Dioni I. Cendón d, L. Keith Fifield e, Sarah O. Tweed f, Ben Petrides g, Ian Swane h a

School of Geosciences, Monash University, Clayton, Vic. 3800, Australia National Centre for Groundwater Research and Training, Flinders University, Adelaide, SA 5001, Australia c URS Australia Pty Ltd., 6/1 Southbank Boulevard, Southbank, Vic. 3006, Australia d Australian Nuclear Science and Technology Organisation, Kirrawee DC, NSW 2232, Australia e Department of Nuclear Physics, Research School of Physical Sciences and Engineering, Australian National University, ACT 0200, Australia f School of Earth and Environmental Sciences, James Cook University, Cairns, Qld 4870, Australia g Coffey Environments Pty Ltd., Abbotsford, Vic. 3067, Australia h Terrenus Pty Ltd., 12 Granville Street, Wilston, QLD 4051, Australia b

a r t i c l e

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Article history: Available online 22 February 2012

a b s t r a c t Environmental isotopes (particularly d18O, d2H, and d13C values, 87Sr/86Sr ratios, and a14C) constrain geochemical processes, recharge distribution and rates, and inter-aquifer mixing in the Riverine Province of the southern Murray Basin. Due to methanogenesis and the variable d13C values of matrix calcite, d13C values are highly variable and it is difficult to correct 14C ages using d13C values alone. In catchments where d13C values, 87Sr/86Sr ratios, and major ion geochemistry yield similar a14C corrections, 15% of the C is derived from the aquifer matrix in the silicate-dominated aquifers, and this value may be used to correct ages in other catchments. Most groundwater has a14C above background (2 pMC) implying that residence times are <30 ka. Catchments containing saline groundwater generally record older 14C ages compared to catchments that contain lower salinity groundwater, which is consistent with evapotranspiration being the major hydrogeochemical process. However, some low salinity groundwater in the west of the Riverine Province has residence times of >30 ka probably resulting from episodic recharge during infrequent high rainfall episodes. Mixing between shallower and deeper groundwater results in 14 C ages being poorly correlated with distance from the basin margins in many catchments; however, groundwater flow in palaeovalleys where the deeper Calivil–Renmark Formation is coarser grained and has high hydraulic conductivities is considerably more simple with little inter-aquifer mixing. Despite the range of ages, d18O and d2H values of groundwater in the Riverine Province do not preserve a record of changing climate; this is probably due to the absence of extreme climatic variations, such as glaciations, and the fact that the area is not significantly impacted by monsoonal systems. Ó 2012 Elsevier Ltd. All rights reserved.

1. Introduction Environmental stable and radiogenic isotopes, especially d18O, d2H, d13C and d34S values, 87Sr/86Sr ratios, and 14C and 3H activities are invaluable tracers of regional-scale hydrogeological processes. Oxygen and hydrogen isotopes are the only true tracers of the water molecule and since all processes in the hydrological cycle fractionate 18O/16O and 2H/1H ratios, d18O and d2H values may be used to determine the extent of evaporation, recharge conditions ⇑ Corresponding author at: School of Geosciences, Monash University, Clayton, Vic. 3800, Australia. Tel.: +61 03 9905 4903; fax: +61 03 9905 4887. E-mail address: [email protected] (I. Cartwright). 0883-2927/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.apgeochem.2012.02.006

(e.g., temperature or altitude), or groundwater mixing (e.g., Gonfiantini, 1986; Herczeg et al., 1992; Weaver et al., 1995; Clark and Fritz, 1997; Edmunds, 2009; Currell et al., 2010). Because of its capacity to date groundwater that is up to 30 ka old, and due to the ubiquitous presence of dissolved inorganic C (DIC) in groundwater, 14C is the most widely used radiogenic dating technique in regional aquifers (e.g., Clark and Fritz, 1997; Kalin, 2000; Celle-Jeanton et al., 2009; Coetsiers and Walraevens, 2009; Edmunds, 2009) and is invaluable in constraining the timescales of groundwater flow and recharge. Stable C and S isotopes trace the sources of dissolved inorganic and organic C and SO4 in groundwater (e.g., Dogramaci et al., 2001; Dogramaci and Herczeg, 2002; Cendón et al., 2008) and constrain processes such as bacteriological

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reduction and methanogenesis (e.g., Dogramaci et al., 2001; Cartwright, 2010; Cartwright et al., 2010a). 87Sr is produced by the decay of 87Rb with a half-life of 48.8 Ga. As Rb substitutes for K and to a lesser extent Na in minerals, the 87Sr/86Sr ratio of a mineral is governed by its initial 87Sr/86Sr ratio, its Rb/Sr ratio, and its age (e.g., Bullen et al., 1996; Katz and Bullen, 1996; Négrel et al., 2001; Dogramaci and Herczeg, 2002; Negrel and Petelet-Giraud, 2005). Strontium derived from K-rich minerals such as biotite and K-feldspar has high 87Sr/86Sr ratios while Sr derived from Carich minerals such as calcite or gypsum has low 87Sr/86Sr ratios. Thus Sr isotopes are important tracers of water–rock interaction and mixing between groundwater from aquifers of contrasting mineralogy. Unlike C, O, H or S isotopes, mineral precipitation and dissolution does not fractionate 87Sr/86Sr ratios making Sr isotopes reasonably straightforward to interpret. When coupled with major ion geochemistry and physical hydrogeology, environmental isotopes constrain groundwater residence times, distribution and rates of groundwater recharge, water–rock interaction, and groundwater flow paths and are thus fundamental to understanding hydrogeological systems and managing groundwater resources. Constraining recharge rates is required to assess the sustainability of groundwater use while delineating recharge areas is required to determine potential threats to groundwater from near-surface contamination. Determining whether there is a climate control on recharge or if landuse changes have altered recharge rates is also important in understanding the long-term and future behaviour of aquifer systems. Aquifers in northern Europe, Canada, northern China and Africa contain groundwater with distinctive d18O and d2H values that were recharged under colder or wetter conditions than present (e.g., Rozanski, 1985; Rosenthal et al., 1990; Weaver et al., 1995; Darling et al., 1997; Tantawi et al., 1998; Edmunds et al., 2006; Galego Fernandes and Carreira, 2008; Gates et al., 2008; Ma et al., 2009; Currell et al., 2010), indicating that recharge rates have varied on timescales of thousands of years. In southern Australia, land clearing over the last 200 a following European settlement has increased recharge (Allison et al., 1990; Jankowski and Acworth, 1997; Cartwright et al., 2007c). Thus modern recharge rates measured from bore hydrograph fluctuations or lysimeters may not indicate the long-term behaviour. Documenting inter-aquifer flow is also important. If groundwater flow is largely parallel to stratigraphy, deeper groundwater may be protected from near surface contamination; likewise, shallow groundwater and connected surface water systems may be isolated from the impacts of pumping of deeper aquifers. By contrast, significant inter-aquifer flow may compromise both the quality and quantity of surface water and groundwater. Groundwater flow parallel to the main stratigraphic units is reasonably straightforward to constrain using hydraulic heads and hydraulic conductivities. However, because vertical hydraulic conductivities are less commonly measured groundwater flow between, and vertically within, formations is more difficult to determine using physical hydrogeology (e.g., Sayed et al., 1992) and relies on the application of geochemical tracers. This paper reviews the contribution of environmental isotopes to understanding the regional hydrogeology of the Riverine Province of the SE Murray Basin, Australia. In particular, it assesses: patterns and rates of recharge; whether the groundwater preserves a record of climate change; groundwater flow paths; and the degree of inter-aquifer mixing. There have been few attempts to integrate the environmental isotope data from the SE Murray Basin and previous studies (Calf et al., 1986; Arad and Evans, 1987; Macumber, 1991, 1992; Herczeg et al., 1992; Ivkovic et al., 1998; Swane et al., 2001; Cartwright and Weaver, 2005; Cartwright et al., 2006, 2007a,b,c, 2010a; Petrides et al., 2006; Macumber, 2007; Cartwright, 2010) have largely discussed processes in

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specific regions or concentrated on individual isotopic tracers. The application of geochemical tracers to the adjacent Mallee– Limestone Province (Fig. 1a) is discussed by Leaney and Allison (1986), Love et al. (1993, 1994), Leaney and Herczeg (1995, 1999), Herczeg et al. (1997, 2001), Dogramaci et al. (2001), and Leaney et al. (2003). A significant part of rural SE Australia depends on groundwater from the Murray Basin for agricultural, industrial, and, increasingly, domestic water supply. This demand will increase as population grows, and ongoing development of this region relies on the long-term sustainable use of groundwater. While this review concentrates on the long-term regional hydrogeology, it is also recognised that the salinisation of groundwater, soils, and rivers due to rising water tables following land clearing (e.g., Allison et al., 1990) is an important environmental issue. 1.1. Murray Basin hydrogeology The Murray Basin (Fig. 1a) occupies 300,000 km2 of SE Australia and contains late Palaeocene to Recent sediments that overlie Proterozoic to Mesozoic basement (Lawrence, 1988; Brown and Radke, 1989; Evans and Kellett, 1989; Macumber, 1991; Herczeg et al., 2001). The basin is up to 600 m deep and comprises three sub-basins or provinces (Riverine, Scotia, and Mallee–Limestone: Fig. 1a) that are separated by basement ridges. Except for a small region in the SW that discharges to the Southern Ocean, the Murray Basin is closed and groundwater discharges to salt lakes and rivers near the basin centre. The Murray–Darling river system is the only major surface water feature draining the basin. The Riverine Province underlies the Riverine Plain of Victoria and New South Wales (Figs. 1 and 2). There are three main stratigraphic units in the eastern Riverine Province (Brown, 1988: Fig. 1b). The lowermost Renmark Group consists of Palaeocene to late Miocene fluvial silts, sands, gravels, and clays that form a confined aquifer system. Overlying the Renmark Formation are the Pliocene sands of the Calivil Formation. In most of the Riverine Province, the Calivil Formation is in hydraulic continuity with the underlying Renmark Formation and these formations commonly form a single aquifer (Lawrence, 1988; Macumber, 1991). The Calivil–Renmark Formation is thickest in ancestral drainage channels (‘‘deep leads’’) of present day rivers (e.g., the Murray, Campaspe, Lodden, Avoca, Ovens, and Goulburn Rivers) that were incised after the Middle Miocene marine regression and subsequently filled with sediments (Macumber, 1991). Groundwater in these deep leads flows northwards and feeds into the Murray deep lead where groundwater flow is eastwards (Figs. 1 and 2). Lateral hydraulic conductivities of the Calivil–Renmark sediments within the deep leads based on pumping or slug tests are 40–200 m/day (e.g., Tickell and Humphries, 1986); hydraulic conductivities in the areas between the deep leads are lower (Tickell, 1978, 1991; Calf et al., 1986; Tickell and Humphries, 1986). The Calivil and Renmark Formations do not crop out and this aquifer is recharged by downward flow through the overlying units. The uppermost Shepparton Formation comprises fluvio-lacustrine clays, sands and silts that are laterally discontinuous resulting in a highly heterogeneous aquifer system. Tickell and Humphries (1986) estimated that lateral hydraulic conductivities are 30 m/ day for the coarser units of the Shepparton Formation and substantially less in the fine-grained units; vertical hydraulic conductivities are 105 to 101 m/day (Tickell, 1978, 1991; Tickell and Humphries, 1986; Evans and Kellett, 1988). The heterogeneous nature of the Shepparton Formation may inhibit lateral flow, promoting downward leakage into the underlying Calivil–Renmark Formation (Arad and Evans, 1987). In the western Riverine Province, the Loxton–Parilla Sands comprises a sequence of marine sands and silts that underlies the Shepparton Formation. Locally in this region, the Shepparton Formation is absent and the

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Fig. 1. (a) Map of the Murray Basin (after Evans and Kellett, 1989) showing depth to basement and groundwater flow paths. MLP = Mallee–Limestone Province, RP = Riverine Province, SP = Scotia Province. Catchments (west–east) are: W = Wimmera, Ty = Tyrrell, L = Loddon, PH = Pyramid Hill, C = Campaspe, G = Goulburn, B = Benalla, O = Ovens. (b) Stratigraphic cross-section across the Mallee–Limestone and Riverine Provinces at approximately X–X0 (after Evans and Kellett, 1989) showing major units in the Murray Basin.

Fig. 2. Variation in groundwater TDS in the shallowest aquifers of the Riverine Province of Victoria (data from Victorian State Government Groundwater Beneficial Use Maps: http://www.ourwater.vic.gov.au/environment/groundwater/beneficial-use/maps). The TDS distributions represent broad averages and many local variations exist. Catchments are as for Fig. 1. Dotted area denotes coarser-grained sediments in the deep leads (Macumber, 1991).

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Loxton–Parilla Sands is the surficial unit. In the far west of the Riverine Province, the Loxton–Parilla Sands is underlain by the Murray Group, which comprises up to 130 m of marine and marginal marine limestone with calcareous sands, marls and silts (Dogramaci and Herczeg, 2002). The Ettrick Formation, Geera Clay, Bookpurnong Beds, and Winnambool Formation envelope the Murray Group; these units are collectively referred to as Mid Tertiary Aquitard units (Brown and Radke, 1989), although hydraulic conductivities are locally sufficiently high to allow flow across these units (Dogramaci et al., 2001; Dogramaci and Herczeg, 2002; Leaney et al., 2003; Cartwright et al., 2010a). Only the Geera Clay, which comprises up to 75 m of massive clays with minor sand and silt layers (Fig. 1b), is an effective aquitard. The shallowest formations of the Riverine Province are unconfined and recharge of groundwater occurs across broad areas (Calf et al., 1986; Arad and Evans, 1987; Evans and Kellett, 1989; Macumber, 1991; Chiew et al., 1992). Aside from direct recharge, the Murray River and some of its tributaries recharge the shallow aquifer systems, especially at high river stages (Macumber, 1991; Lamontagne et al., 2005; Cartwright et al., 2010b). Additionally, except in the west of the province, there are few aquitards (Fig. 1b), potentially allowing widespread inter-aquifer flow to occur (Arad and Evans, 1987; Evans and Kellett, 1988; Dogramaci and Herczeg, 2002; Cartwright et al., 2007a, 2010a). The Riverine Province comprises several catchments (Figs. 1 and 2). The Ovens, Goulburn, Campaspe, and Loddon catchments are typical deep lead systems that contain lower salinity groundwater (total dissolved solids, TDS, typically 500–3500 mg/L: Fig. 2), while the Benalla, Lake Cooper, Pyramid Hill, and Wimmera regions outside the deep leads generally contain more saline groundwater (TDS locally up to 100,000 mg/L and commonly >20,000 mg/L). Annual rainfall in the area depicted in Fig. 2 varies from up to 2000 mm in the SE of the region to 400 mm in the NW; most of the region has 400–600 mm annual rainfall (Bureau of Meteorology, 2010). Rainfall occurs dominantly in the austral winter months (July–September) and for much of the year potential evapotranspiration rates exceed rainfall (Bureau of Meteorology, 2010). 1.2. Groundwater chemistry The processes controlling the major ion geochemistry are similar throughout the southern Murray Basin and are described in detail by Arad and Evans (1987), Love et al. (1993), Dogramaci et al. (2001), Herczeg et al. (2001), Dogramaci and Herczeg (2002), Cartwright et al. (2004, 2006, 2007a,b, 2008), Cartwright and Weaver (2005) and Petrides et al. (2006). The dominant hydrochemical process is evapotranspiration of rainfall during recharge with minor silicate weathering and minor precipitation and/or dissolution of carbonate, gypsum, and halite. Cation exchange (especially the sorption of Na onto clays and the release of Ca and Mg) modifies the composition of the most saline groundwater. Many of the silicate-dominated aquifers in the southern Murray Basin are relatively unreactive and water–rock interaction during groundwater flow is limited; indeed processes in the unsaturated zone probably control much of the groundwater geochemistry (Herczeg et al., 2001). Carbonate dissolution is locally important in controlling the geochemistry of groundwater in the Murray Group aquifer (Love et al., 1993; Dogramaci and Herczeg, 2002); however, it is only a minor process elsewhere. Given that evapotranspiration is the dominant process, there in a broad inverse correlation between the TDS concentration of groundwater and recharge rates (Calf et al., 1986; Arad and Evans, 1987; Macumber, 1991; Cartwright et al., 2006); catchments containing saline groundwater have lower recharge rates than catchments containing lower salinity groundwater.

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2. Sampling and analytical techniques Sampling and analytical techniques are discussed in detail in the original studies. In summary, groundwater was from monitoring bores that are maintained by the Department of Sustainability and Environment, Victoria (http://www.vicwaterdata.net/vicwaterdata/home.aspx), that have screen lengths of 1–25 m and which sample only one lithological unit. The pH, EC, alkalinity, dissolved CO2 and dissolved O2 were measured in the field using calibrated metres or titration. Cations were determined using ICP-AES on filtered and acidified samples. Anions were determined on filtered unacidified samples using ion chromatography. Stable isotope ratios were measured using gas source mass spectrometers. The 87Sr/86Sr ratios were determined by thermal ionisation mass spectrometry and 14C activities (a14C) were measured using AMS techniques.

3. Sr and C isotopes The 87Sr/86Sr ratios of groundwater in the SE Riverine Province of the Murray Basin, Australia are between 0.709 and 0.723 (Figs. 3 and 4), and are generally higher than the 87Sr/86Sr ratio of rainfall in southern Australia (0.713: Ullman and Collerson, 1994; de Caritat et al., 2005). As Sr/Cl ratios are also higher than those of the oceans (Dogramaci and Herczeg, 2002; Cartwright et al., 2007b), there must be additional sources of Sr apart from rainfall containing marine aerosols, such as silicate and carbonate weathering in the unsaturated zone and/or mineral reactions in the saturated zone of the aquifers. The bulk silicate fraction of the Renmark and Shepparton aquifers in the Riverine Province has 87Sr/86Sr ratios of 0.718–0.931 while calcite in these aquifers has 87Sr/86Sr ratios of 0.709–0.754 (Dogramaci and Herczeg, 2002; Cartwright et al., 2007b, 2010a; Cartwright, 2010: Fig. 4). The silicate fractions with the highest 87Sr/86Sr ratios are from the Ovens Valley and reflect the high degree of immature sediment derived from Palaeozoic metasediments and granites in this region. The relatively high 87 Sr/86Sr ratios of the calcite throughout the Riverine Province reflect that it is largely non-marine. The d13C values of calcite in most aquifers are very variable, ranging between 17‰ and +2‰ (Fig. 4), which also reflects the largely non-marine nature of the calcite. Only in the Wimmera region is the calcite dominantly marine. Calcite from the limestones of the Murray Group has d13C values of 2.4‰ to +2.2‰ while Renmark Formation and Loxton–Parilla Sands contain calcite with d13C values of 3.5‰ to 0.7‰ (Dogramaci and Herczeg, 2002; Cartwright et al., 2010a). Groundwater from the various catchments has different 87 Sr/86Sr ratios (Ovens: 0.716–0.723; Goulburn: 87Sr/86Sr = 0.716– 0.719; Campaspe: 0.714–0.719; Pyramid Hill: 0.714–0.716; Lake Cooper: 87Sr/86Sr = 0.715–0.719; Tyrrell = 0.711–0.716; Wimmera = 0.709–0.715: Figs. 3 and 4). Aside from the Wimmera region, the Riverine Province aquifers are dominated by silicate minerals, thus carbonate weathering and/or mixing between groundwater from carbonate and silicate aquifers are not likely to be a major processes. However, locally, carbonate cements and veins do exist. Given that carbonate minerals are generally more reactive than silicates, calcite dissolution may still control the 87Sr/86Sr ratios and d13C values of groundwater. For groundwater from most of the catchments the lack of correlation between 87Sr/86Sr ratios and d13C values (Fig. 4) suggests that there has not been significant carbonate dissolution. This conclusion is difficult to make from the isotope data alone as in some catchments the d13C values of calcite are variable. In addition, methanogenesis has locally increased d13C values of DIC in the Campaspe, Wimmera, Pyramid Hill, and Tyrrell catchments (Dogramaci et al., 2001; Cartwright, 2010; Cartwright et al., 2010a). However, the following observations imply that

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Fig. 3. Variation in 87Sr/86Sr ratios of Riverine Province groundwater with distance from the basin margins in the Ovens (a), Goulburn (b), Lake Cooper (c), Campaspe (d), Pyramid Hill (e), Tyrrell (f), and Wimmera (g) catchments (data from: Cartwright et al., 2007b, 2010a; Cartwright, 2010).

calcite dissolution is not a major process: (1) carbonate cements and veins are a minor component of the aquifers, especially in the east of the province; (2) trends in Sr/Cl or Sr/Na vs. 87Sr/86Sr are not consistent with carbonate dissolution in most of the catchments (Cartwright et al., 2007b); and (3) as noted earlier, the major ion geochemistry implies that carbonate dissolution is limited. The 87Sr/86Sr ratios in the Ovens, Goulburn, Lake Cooper and Tyrell catchments in both the Shepparton and Calivil Renmark Formations broadly decrease with distance from the basin margins. This spatial variation in 87Sr/86Sr ratios reflects variations in the distribution of minerals within the aquifers. Potassium-rich minerals, such as biotite and K-feldspar that generally have higher 87 Sr/86Sr ratios are more abundant in the proximal parts of the aquifers close to the basin margins, while more distal sediments contain higher relative abundances of plagioclase that has lower 87 Sr/86Sr ratios (Lawrence, 1988; Brown, 1989). The major ion chemistry (especially the low cation/Cl ratios) implies that progressive silicate weathering during groundwater flow is only a minor process (Arad and Evans, 1987). Cation exchange (especially the exchange of Na for Ca, Mg, and Sr) is well documented in Murray Basin groundwater and the 87Sr/86Sr ratios probably

change as a result of cation exchange on clays that are derived from weathering of (and which have the similar 87Sr/86Sr ratios to) the primary silicate minerals (Cartwright et al., 2007b). The variation of 87Sr/86Sr ratios and d13C values in the Wimmera groundwater (Figs. 4 and 5) reflects both inter-aquifer mixing and calcite dissolution. Calcite in the Renmark Formation and Loxton– Parilla Sands in the Wimmera region has 87Sr/86Sr ratios 0.709– 0.713 and d13C = 3.5‰ to 0.7‰ (Dogramaci and Herczeg, 2002; Cartwright et al., 2010a). The variation in 87Sr/86Sr ratios and d13C values in groundwater from the Loxton Parilla Sands and in the Renmark Formation where it is not overlain by the Murray Group results from the dissolution of calcite by groundwater that initially had high 87Sr/86Sr ratios and low d13C values. However, groundwater in the Renmark Formation where it underlies the Murray Group has lower 87Sr/86Sr ratios than those of calcite in the Renmark Formation (Fig. 5), implying that additional mixing of water from the Murray Group has occurred. Mass balance calculations based on the Sr and C isotopes and concentrations suggest that locally up to 40–70% of the groundwater in the Renmark Formation was derived from the overlying Murray Group (Cartwright et al., 2010a). In support of this assertion, groundwater from the Renmark

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Fig. 4. 87Sr/86Sr ratios vs. d13C values of Riverine Province groundwater in the Ovens (a), Goulburn (b), Lake Cooper (c), Campaspe (d), Pyramid Hill (e), Tyrrell (f), and Wimmera (g) catchments. (h) 87Sr/86Sr ratios of the aquifer matrix and predicted trends for carbonate dissolution (dashed lines) (data from Dogramaci and Herczeg, 2002; Cartwright and Weaver, 2005; Cartwright et al., 2007b, 2010a; Cartwright, 2010).

Formation where it underlies the Murray Group has Ca:HCO3 ratios that are similar to those of groundwater from the Murray Group but dissimilar to those of groundwater from the Renmark Formation elsewhere (Cartwright et al., 2010a). Similar calculations imply that locally 80–95% mixing from the Loxton–Parilla Formation is required to explain the Murray Group groundwater with high 87 Sr/86Sr ratios and low d13C values (Fig. 5: Cartwright et al., 2010a). Comparable estimates of upward leakage between the Renmark Formation and the Murray Group NW of the Wimmera region of 15–85% were made by Dogramaci and Herczeg (2002).

4. Distribution of

14

C ages

Figs. 6 and 7 summarise the distribution of 14C ages in the Riverine Province. While 14C is the most commonly used tracer to determine groundwater residence times in regional aquifers, its application is not without considerable problems. These include the anomalously high a14C activities in groundwater recharged since the 1950s due to the atmospheric nuclear tests. Additionally,

corrections are required for input of old 14C-free C from: (1) dissolution of carbonate minerals or organic material from the aquifer matrix; (2) deep-seated geogenic CO2 from volcanic activity; and (3) CH4 generated via the breakdown of organic material in the aquifer matrix. There are numerous schemes for correcting 14C ages based on d13C values of DIC (e.g., Fontes and Garnier, 1979; Aravena et al., 1995; Clark and Fritz, 1997; Kalin, 2000; Coetsiers and Walraevens, 2009). Most of these schemes assume that DIC in groundwater is derived largely from open-system dissolution of CO2 from the soil zone and that subsequent dissolution of (or exchange with) carbonates in the aquifer matrix is the main process that impacts d13C values and a14C in the aquifers. Despite most aquifers in the Riverine Province of the Murray Basin being dominated by silicate minerals and the input of geogenic CO2 not being likely, the correction of a14C in Murray Basin groundwater is not straightforward. In some catchments, such as the Campaspe, the d13C values of DIC range from 18‰ to +2‰ (Fig. 4). Using these d13C values to correct 14C ages assuming that dissolution of matrix calcite had occurred implies that locally >90% of the DIC is derived from calcite dissolution. However,

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Fig. 5. (a) Distribution of groundwater 87Sr/86Sr ratios and d13C values in the Wimmera region, dashed lines show extent and thickness (m) of Geera Clay. (b) Variation of 87 Sr/86Sr ratios from east to west across the Wimmera region. (c) Variation of d13C values from east to west across the Wimmera region. Dashed arrows indicate where the Geera Clay is thickest. From Cartwright et al. (2010a: Fig. 6).

Fig. 6. Variation in 14C ages of Riverine Province groundwater with distance from the basin margins in the Ovens (a), Benalla (b), Goulburn (c), Lake Cooper (d), Campaspe (e), Pyramid Hill (f), Loddon (g), Tyrrell (h), and Wimmera (i) catchments (data from Calf et al., 1986; Leaney and Herczeg, 1999; Cartwright and Weaver, 2005; Cartwright et al., 2007a,b, 2008, 2010a; Cartwright, 2010). 87

Sr/86Sr ratios and major ion geochemistry of groundwater imply that calcite dissolution is only a minor process. DIC with high d13C values is present in groundwater from other catchments (e.g., DIC from Wimmera groundwater has d13C values up to +14‰ while that from the Pyramid Hill and Tyrrell catchments has d13C values as high as +1‰). The variable and high d13C values are most probably due to methanogenesis that occurs in the locally anoxic conditions in these aquifers (Dogramaci and Herczeg, 2002; Cartwright, 2010; Cartwright et al., 2010a). The following observations support that methanogenesis is via the reduction of DIC in groundwater rather than the breakdown of organic material from the aquifer matrix via acetate fermentation. Firstly, DIC reduction

results in an increase in pH, and groundwater with d13C values >0‰ in both the Campaspe and Wimmera catchments have pH values >7.5 that are substantially higher than most of the other samples; by contrast, acetate fermentation does not increase pH. Secondly, acetate fermentation rarely produces DIC with d13C values >0‰ (Aravena et al., 1995), whereas DIC reduction can produce d13C values in the range of those observed in the Wimmera and Campaspe groundwater (Valentine et al., 2004; Leybourne et al., 2006). If methanogenesis has occurred, bacteriological reduction of other oxidised species such as NO3 and SO4 is also likely. In the Campaspe, Tyrrell, and Wimmera groundwater dissolved SO4 in the high d13C groundwater has d34S values of 25–50‰ (Fig. 8a).

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Fig. 7. Variation in 14C ages of Riverine Province groundwater with depth in the Ovens (a), Benalla (b), Goulburn (c), Lake Cooper (d), Campaspe (e), Pyramid Hill (f), Loddon (g), Tyrrell (h), and Wimmera (i) catchments (data from Calf et al., 1986; Leaney and Herczeg, 1999; Cartwright and Weaver, 2005; Cartwright et al., 2007a,b, 2008, 2010a; Cartwright, 2010).

Fig. 8. d34S values vs. d13C values (a) and S/Cl ratios (b) in groundwater from the Wimmera (Wim), Campaspe (Cam), and Tyrrell (Tyr) catchments. S concentrations are expressed as ratios to Cl to remove the effects of variable salinity in the groundwater. Data from (Petrides et al., 2006; Cartwright, 2010; Cartwright et al., 2010a).

These values are much higher than those of gypsum in the local regolith or playas (d34S = 15–24‰: Chivas et al., 1991) and/or atmospheric sources (d34S = 15–23‰: Dogramaci et al., 2001) and reflects bacteriological SO4 reduction (Dogramaci et al., 2001; Cartwright et al., 2010a). The high d13C groundwater also has lower SO4 and NO3 concentrations (Fig. 8b) that are also consistent with bacteriological reduction. Methanogenesis by this mechanism has only a minor impact on a14C. Saliege and Fontes (1984) estimated that the mass-dependant fractionation of 14C relative to 12C is 2.3 that of 13C; thus, an increase in d13C of 10‰ should result in an increase in a14C of only 2.3%. In addition to methanogenesis, the d13C of calcite in the aquifer matrix is not always well constrained and may be variable. This is especially the case in the eastern part of the Riverine Province where the sediments are largely non-marine. Given these uncertainties, a statistical correction which assumes that in silicate aquifers 15% of the C is derived from the aquifer matrix (Vogel, 1971) has been applied. In the Wimmera and Goulburn catchments where calcite in the silicate aquifers has a restricted range of d13C values this statistical correction produces ages that are similar to those calculated using the d13C values (Calf et al., 1986; Leaney

and Herczeg, 1999; Cartwright and Weaver, 2005). The ages in Figs. 6 and 7 were calculated using the statistical correction, with the exception of the Wimmera region where the corrected ages based on d13C values are shown. Calculating ages in groundwater with low a14C is difficult due to analytical uncertainties and the possibility of contamination from the atmosphere during sampling; groundwater that has a14C <2 pMC is considered to be indistinguishable from background and is assigned an age of >30 ka. Groundwater with calculated a0 values that are >100 pMC contains a component of water that was recharged during or following the atmospheric nuclear tests in the 1950s and 1960s (Clark and Fritz, 1997). While it is possible to use high 14C groundwater to constrain modern recharge processes (Le Gal La Salle et al., 2001), for the purposes of this regional study this groundwater is considered to be modern with an effective age of 0 a. 4.1. Contrasting age distributions between catchments There is a distinct difference between the patterns of groundwater ages in the different catchments. Ages of the deeper Calivil–Renmark Formation groundwater in the Goulburn, Loddon,

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and Campaspe catchments increase with distance from the basin margins (Fig. 6). Groundwater with residence times of 9–13.5 ka is recorded 70 km from the basin margin in the Campaspe catchment, groundwater with residence times of up to 16.5–18.5 ka is present at 85–110 km in the Goulburn catchment, and groundwater with ages of 21 ka is present at 125 km in the Loddon catchment. The age of groundwater from the Pyramid Hill Catchment also increases away from the basin margins (ages are up to 20 ka between 40 and 55 km); however, this trend is defined by relatively few samples. One groundwater sample from the distal part of the Goulburn catchment yields an anomalously young age (13 ka). This sample, which has higher NO3 concentrations and different d18O values to adjacent groundwater (Cartwright and Weaver, 2005), is from the vicinity of a groundwater mound and may be recording the mixing of recently recharged groundwater with deeper groundwater. Overall, the distribution of ages in these catchments implies a relatively simple pattern of lateral groundwater flow in the deeper Calivil–Renmark Formation with little mixing from the overlying Shepparton Formation. Elsewhere, groundwater ages do not increase with distance from the basin margins (Fig. 6). Indeed, in the Lake Cooper, Tyrell, and Wimmera catchments the oldest groundwater from the Renmark Formation is commonly close to the basin margins. In none of the regions do the ages of Shepparton or Loxton–Parilla groundwater increase with distance from the basin margins (Fig. 6); however in several of the catchments there is an irregular increase in age with depth.

5. Oxygen and hydrogen isotopes The d18O and d2H values of groundwater from all catchments are similar (Fig. 9a) and cluster around the global and Melbourne meteoric water lines at approximately the composition of modern precipitation for Melbourne (d18O = 5.0‰, d2H = 28‰). The occurrence of samples to the left of the Melbourne meteoric water line is probably due to climatic differences between Melbourne (which is coastal) and the Riverine Province (which is inland and more arid). Groundwater with similar d18O and d2H values occurs elsewhere in the Murray Basin (Ivkovic et al., 1998; Leaney and Herczeg, 1999). The groundwater as a whole defines an array with a slope of 5 that is probably due to evaporation in a semi-arid environment (Gonfiantini, 1986; Clark and Fritz, 1997). However, most samples show an increase in d18O of <3‰ and there is no correlation of d18O values with TDS. A 5‰ increase in d18O values is produced by 20% evaporation (Gonfiantini, 1986; Allison et al., 1987), which is far less than that required to produce the high TDS contents of the Murray Basin groundwater. Thus transpiration, which does not significantly affect d18O values, is probably the more important process in concentrating solutes in these waters. Prior to land clearing, the southern Murray Basin was dominated by native vegetation (particularly eucalypts) that was an efficient user of available rainfall leading to significant transpiration (Allison et al., 1990). Despite groundwater recharge occurring in both high rainfall areas (e.g. the Ovens catchment) and low rainfall inland areas (e.g. Tyrell and Wimmera catchments), there are no spatial variations of d18O and d2H (Fig. 9b). Most recharge in the Murray Basin occurs on the Riverine Plains that has limited topographical variation and there is no altitude affect in the d18O and d2H data. Even in the Ovens catchment, there are no major differences between the d18O and d2H values from groundwater in the more elevated upper catchment and that in the lower catchment. As discussed above, groundwater in many of the catchments (particularly those that are not deep leads) has undergone mixing that may have homogenised the d18O and d2H values. However, even in the Goulburn and Campaspe catchments where (as discussed below) mixing is more

Fig. 9. (a) d18O vs. d2H values of Riverine Province groundwater by aquifer. Data cluster around the global (GMWL) and Melbourne (MMWL) meteoric water lines at about the value of modern rainfall in Melbourne. The arrowed line is a linear best fit to the entire dataset and the inset shows changes in d18O vs. d2H resulting from various hydrological processes. (b) d18O vs. d2H values for Riverine Province groundwater from the different catchments. (c) d18O vs. 14C ages for Riverine Province groundwater (data from Calf et al., 1986; Arad and Evans, 1987; Macumber, 1991; Ivkovic et al., 1998; Leaney and Herczeg, 1999; Cartwright and Weaver, 2005; Cartwright et al., 2007a,b, 2008, 2010a; Cartwright, 2010).

limited there is no change in the d18O and d2H values of groundwater along the catchment, and in no catchment is there a correlation between 14C age and d18O or d2H values (Fig. 9c).

6. Discussion Environmental isotope geochemistry has allowed an understanding of hydrogeochemical processes and regional groundwater flow in the Riverine Province that was not possible from a consideration of physical parameters and major ion chemistry alone.

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6.1. Groundwater ages, salinity, and recharge rates Recharge in all catchments occurs across broad areas as the basin is unconfined. In most of the Riverine Province, catchments outside the deep leads contain higher salinity groundwater with older 14C ages while lower salinity groundwater from the deep leads is relatively young. This inverse correlation is expected in basins where the dominant hydrogeochemical process is evapotranspiration. The coarser-grained sediments of the deep leads result in lower degrees of evapotranspiration and higher recharge rates, and as a first approximation groundwater salinity (Fig. 2) is an indication of relative recharge rates. Recharge rates in the Shepparton Formation may be calculated using the 14C data. Although the trends of increasing age with depth are irregular in many of the catchments, groundwater with 14C ages of 15–25 ka commonly occurs at 40–60 m depth (Fig. 7). The general trends of age with depth imply infiltration rates of approximately 1–4 mm/a with higher rates in the deep leads than in the intermediate areas. For porosities of 0.2–0.3, these infiltration rates equate to recharge rates of 0.3–1.2 mm/a (1% of modern rainfall). These are similar to recharge rates estimated in the Murray Basin by Cl mass balance (0.03–2 mm/a: Allison et al., 1990; Cartwright et al., 2006). For an average vertical hydraulic gradient of 0.05 and porosities of 0.2– 0.3, vertical hydraulic conductivities calculated using Darcy’s Law are approximately 105 to 104. These are within the range of vertical hydraulic conductivities for the Shepparton Formation of 105 to 101 m/day reported by Tickell (1978, 1991) and Tickell and Humphries (1986). Groundwater from the Renmark Formation and Murray Group in the west of the Riverine Province and in the adjacent Mallee Limestone Province commonly has residence times of >30 ka (Leaney and Herczeg, 1999; Leaney et al., 2003: Figs. 6 and 7), implying that recharge rates in this region are also low. By contrast with groundwater elsewhere in the Riverine Province, this groundwater has low TDS contents implying that the low recharge rates are not the result of extreme degrees of evapotranspiration. Rather, significant recharge may occur mainly during infrequent higher-precipitation periods in this low rainfall region. If this is the case, rapid recharge through the sandy soils that dominate this region may account for the low salinity of the groundwater (Leaney and Herczeg, 1999; Leaney et al., 2003). 6.2. Groundwater flow and inter-aquifer mixing The increase in 14C ages with distance (Fig. 6) implies that that groundwater flow in the Calivil–Renmark Formation in the deep leads is relatively simple with little leakage from overlying units. By contrast, the variation in 14C ages in the other regions implies that flow paths are complex and that there is considerable interaquifer mixing. This conclusion is supported by the distribution of TDS contents in groundwater. The highest salinity groundwater in the Lake Cooper, Wimmera and Tyrrell catchments commonly occurs close to the basin margins (Fig. 2) precluding simple lateral groundwater flow, whereas TDS contents of Calivil–Renmark groundwater in the deep leads are relatively constant or increase along the flow paths. The variation of 87Sr/86Sr ratios in the Campaspe catchment (Fig. 3) is also consistent with dominantly lateral groundwater flow in the Calivil–Renmark Formation with little vertical leakage. The 87Sr/86Sr ratios of the Calivil–Renmark groundwater within the Campaspe Valley are 0.7159–0.7165 while those of the Shepparton groundwater are 0.7141–0.7148 (Fig. 3). If inter-aquifer leakage were widespread, 87Sr/86Sr ratios in the Calivil–Renmark groundwater should decrease along the flow path, which is not observed. The higher 87Sr/86Sr ratios of the Shepparton groundwater at 75 km from the basin margin are probably primary as hydraulic gradients in this region are downwards preclud-

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ing upwards mixing from the Calivil–Renmark Formation. A similar difference between 87Sr/86Sr ratios of the Calivil–Renmark groundwater and most of the groundwater in the Shepparton Formation is observed in the Pyramid Hill region (Fig. 3), which also precludes significant inter-aquifer mixing in that area. In many of the other catchments, there is not sufficient distinction in the 87Sr/86Sr ratios to use these tracers to test whether mixing has occurred. As discussed above, the increase in 14C ages with depth in the Shepparton Formation and the Loxton–Parilla Sands indicates that flow in these aquifers has a strong downward component. Downward flow in the shallow aquifers probably results from the much higher hydraulic conductivities of the deeper Calivil–Renmark Formation compared with the near surface units that results in refraction of groundwater flow paths. That significant mixing of this groundwater with the deeper groundwater is not observed in all catchments is probably a result of the relative hydraulic conductivities. In the deep leads the high groundwater fluxes within the higher hydraulic conductivity Calivil–Renmark Formation effectively dilutes the relatively minor leakage from the overlying units. The distribution of ages (Fig. 6) allows estimation of hydraulic parameters in the Campaspe, Goulburn, and Loddon catchments. The increase in groundwater ages in the Calivil–Renmark Formation of 9–13.5 ka over 60 km in the Campaspe catchment implies flow velocities of 4.4–6.7 m/a, which for a porosity of 0.2-0.3 equates to a groundwater flux of 0.89–2.0 m3/m2/a. Lateral hydraulic gradients in the Murray Basin are typically 104 to 5  104 and Darcy’s Law yields lateral hydraulic conductivities of 4000– 8900 m/a (11–24 m/day). Similar calculations in the Loddon catchment assuming an increase in groundwater age of 21 ka over 120 km yields hydraulic conductivities of 9–31 m/day, while assuming that the age increase in the Goulburn catchment is 18.5 ka over 80 km yields hydraulic conductivities of 7–25 m/day. These estimates are slightly below those estimated from pumping tests in the deep leads (typically 40–200 m/day: Tickell, 1978, 1991; Tickell and Humphries, 1986). The difference may relate to errors in the assumed hydraulic gradients; due to the increase in recharge rates following the land clearing over the past 200 a, the present-day hydraulic gradients may be higher than those that were typical in the southern Murray Basin over the length of time that these flow systems have operated. Alternatively, as pump tests record hydraulic conductivities over a relatively small region, they may not be representative of the aquifer as a whole. Nevertheless, the broad agreement between the hydraulic conductivities calculated from the 14C ages and those measured using pump tests implies that the interpretation of groundwater ages and flow systems is robust. 6.3. Variations with climate Unlike large basins elsewhere (e.g., Rozanski, 1985; Rosenthal et al., 1990; Weaver et al., 1995; Darling et al., 1997; Tantawi et al., 1998; Edmunds et al., 2006; Galego Fernandes and Carreira, 2008; Gates et al., 2008; Ma et al., 2009; Currell et al., 2010) there is no correlation between 14C ages and d18O values in the Riverine Province, and deeper groundwater has similar d18O values to shallower groundwater and to modern surface water and rainfall. The lack of variation in d18O and d2H values is surprising given that groundwater present in the basin was recharged over at least 30 ka and that palaeoclimate studies show that between approximately 30–22 ka and 7–4 ka rainfall was higher than at present, while between 20 and 10 ka, conditions were considerably drier (Wasson and Donnelly, 1991). There is little evidence for these climatic changes in the stable isotope data in the Riverine Province groundwater, nor are there any obvious gaps in the 14C age spectrum that might result from extended periods of little recharge during periods of drier climate.

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Rainfall in SE Australia derives from a variety of sources (mainly the Southern, Indian and Pacific Oceans) rather than dominantly from a single weather system (Bureau of Meteorology, 2010). While there are differences between the d18O values of rainfall derived from these systems (notably heavy winter rains from the Southern Ocean have low d18O values) the variations in climate may have been too slight to produce major differences in the overall weather patterns (or at least in the resultant d18O values). This is in contrast to areas such as northern China that lie at the margins of the current monsoon systems where older groundwater has distinct d18O values due to variations in monsoon intensity (Edmunds et al., 2006; Ma et al., 2009; Currell et al., 2010). Likewise, there was not any dramatic change in hydrogeological conditions following glaciations, such as occurred in the higher latitudes of the northern hemisphere. Groundwater elsewhere in southern Victoria also does not preserve a record of changing climate (Petrides and Cartwright, 2006). By contrast, low salinity groundwater from the Mallee–Limestone Province of the Murray Basin was recharged dominantly at 20 ka (Leaney and Herczeg, 1999; Leaney et al., 2003), and Herczeg et al. (2001) related changes in salinity and d18O values along groundwater flow paths to climate variations. The recharge areas of the Mallee–Limestone Province are more arid than those of the Riverine Province (current annual rainfall in the Mallee–Limestone Province is 300 mm), and thus groundwater recharge may be more sensitive to climate variations. 6.4. Resource implications Groundwater in the Riverine Province (especially in the Goulburn and Campaspe catchments) is locally used for irrigation, stock watering, and increasingly for domestic supply. Population and economic activity in this region is increasing, as is the development of more intensive agriculture (e.g. orchards and vineyards). This increased activity and the realisation that surface water provides an unreliable supply in times of drought mean that groundwater will be used increasingly for water supply. However, the results of these studies indicate that, in general, recharge rates are low and the groundwater is several thousands of years old; this water, therefore, constitutes a finite resource. Additionally, given the broad recharge areas, groundwater in the Shepparton Formation and Loxton–Parilla Sands is susceptible to contamination from agricultural activities, urban discharge, and the numerous smallscale industries scattered throughout the region. Secondary salinisation (both dryland and irrigation) caused by rising water tables is affecting the shallow groundwater and the shallow saline water produced by salinisation represents another potential threat to the deeper groundwater. Where significant vertical groundwater flow into the Calivil–Renmark Formation occurs, the deeper groundwater too may be susceptible to contamination. Predicting exactly where these impacts are most likely, however, is difficult because the heterogeneous nature of the Shepparton Formation results in localised pathways of preferential flow. Vertical hydraulic gradients in the Riverine Province are increasing due to land clearing and irrigation that have locally raised water tables by several metres increasing the potential for vertical flow. Excessive groundwater extraction from the Calivil–Renmark Formation may also cause drawdown of saline or contaminated water through the preferential pathways in the Shepparton Formation. Acknowlegements We would like to thank the many colleagues that have assisted us over the years, including Marlen Yanni, Massimo Raveggi and Rachelle Pierson (Monash) for the stable isotope and anion analyses, Linda McMorrow (ANU) for the cation analyses, David Bruce (Adelaide) for the Sr isotope analyses, Fred Leaney (CSIRO, Ade-

laide), Geraldine Jacobsen (ANSTO), and Stuart Fallon (ANU) for the 14C determinations. Marcus Onken and Kaye Hannam helped collect the samples. Ongoing funding by the Australian Research Council, the National Centre for Groundwater Research and Training, and Monash University is gratefully acknowledged. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at doi:10.1016/j.apgeochem.2012.02.006. References Allison, G.B., Colin-Kaczala, C., Filly, A., Fontes, J.C., 1987. Measurement of isotopic equilibrium between water, water vapour and soil CO2 in arid zone soils. J. Hydrol. 95, 131–141. Allison, G.B., Cook, P.G., Barnett, S.R., Walker, G.R., Jolly, I.D., Hughes, M.W., 1990. Land clearance and river salinisation in the western Murray Basin, Australia. J. Hydrol. 119, 1–20. Arad, A., Evans, R., 1987. The hydrogeology, hydrochemistry and environmental isotopes of the Campaspe River aquifer system, North-Central Victoria, Australia. J. Hydrol. 95, 63–86. Aravena, R., Wassenaar, L.I., Plummer, L.N., 1995. Estimating 14C groundwater ages in a methanogenic aquifer. Water Resour. Res. 31, 2307–2317. Brown, C.M., 1988. Overview of the Geology of the Murray Basin. Record – Bureau of Mineral Resources, Geology and Geophysics, 23–30. Brown, C.M., 1989. Structural and stratigraphic framework of groundwater occurrence and surface discharge in the Murray Basin, southeastern Australia. BMR J. Aust. Geol. Geophys. 11, 127–146. Brown, C.M., Radke, B.M., 1989. Stratigraphy and sedimentology of mid-Tertiary permeability barriers in the subsurface of the Murray Basin, southeastern Australia. BMR J. Aust. Geol. Geophys. 11, 367–386. Bullen, T.D., Krabbenhoft, D.P., Kendall, C., 1996. Kinetic and mineralogic controls on the evolution of groundwater chemistry and 87Sr/86Sr in a sandy silicate aquifer, northern Wisconsin, USA. Geochim. Cosmochim. Acta 60, 1807–1821. Bureau of Meteorology, 2010. Commonwealth of Australia Bureau of Meteorology. . Calf, G.E., Ife, D., Tickell, S., Smith, L.W., 1986. Hydrogeology and isotope hydrology of upper Tertiary and Quaternary aquifers in northern Victoria. Aust. J. Earth Sci. 33, 19–26. Cartwright, I., 2010. Using groundwater geochemistry and environmental isotopes to assess the correction of 14C ages in a silicate-dominated aquifer system. J. Hydrol. 382, 174–187. Cartwright, I., Weaver, T., 2005. Hydrogeochemistry of the Goulburn Valley region of the Murray Basin, Australia: implications for flow paths and resource vulnerability. Hydrogeol. J. 13, 752–770. Cartwright, I., Weaver, T.R., Fulton, S., Nichol, C., Reid, M., Cheng, X., 2004. Hydrogeochemical and isotopic constraints on the origins of dryland salinity, Murray Basin, Victoria, Australia. Appl. Geochem. 19, 1233–1254. Cartwright, I., Weaver, T.R., Fifield, L.K., 2006. Cl/Br ratios and environmental isotopes as indicators of recharge variability and groundwater flow: an example from the southeast Murray Basin, Australia. Chem. Geol. 231, 38–56. Cartwright, I., Hannam, K., Weaver, T.R., 2007a. Constraining flow paths of saline groundwater at basin margins using hydrochemistry and environmental isotopes; Lake Cooper, Murray Basin, Australia. J. Earth Sci. 54, 1103–1122. Cartwright, I., Weaver, T., Petrides, B., 2007b. Controls on 87Sr/86Sr ratios of groundwater in silicate-dominated aquifers: SE Murray Basin, Australia. Chem. Geol. 246, 107–123. Cartwright, I., Weaver, T.R., Stone, D., Reid, M., 2007c. Constraining modern and historical recharge from bore hydrographs, 3H, 14C, and chloride concentrations: applications to dual-porosity aquifers in dryland salinity areas, Murray Basin, Australia. J. Hydrol. 332, 69–92. Cartwright, I., Weaver, T.R., Tweed, S.O., 2008. Integrating physical hydrogeology, hydrochemistry, and environmental isotopes to constrain regional groundwater flow: Southern Riverine Province, Murray Basin, Australia. In: Carrillo, R.J.J., Ortega, G.M.A. (Eds.), International Association of Hydrogeologists Special Publication 11: Groundwater Flow Understanding from Local to Regional Scale. Taylor and Francis, London, pp. 105–134. Cartwright, I., Weaver, T., Cendón, D.I., Swane, I., 2010a. Environmental isotopes as indicators of inter-aquifer mixing, Wimmera region, Murray Basin, Southeast Australia. Chem. Geol. 277, 214–226. Cartwright, I., Weaver, T.R., Simmons, C.T., Fifield, L.K., Lawrence, C.R., Chisari, R., Varley, S., 2010b. Physical hydrogeology and environmental isotopes to constrain the age, origins, and stability of a low-salinity groundwater lens formed by periodic river recharge: Murray Basin, Australia. J. Hydrol. 380, 203–221. Celle-Jeanton, H., Huneau, F., Travi, Y., Edmunds, W.M., 2009. Twenty years of groundwater evolution in the Triassic sandstone aquifer of Lorraine: impacts on baseline water quality. Appl. Geochem. 24, 1198–1213. Cendón, D.I., Ayora, C., Pueyo, J.J., Taberner, C., Blanc-Valleron, M.M., 2008. The chemical and hydrological evolution of the Mulhouse potash basin (France): are ‘‘marine’’ ancient evaporites always representative of synchronous seawater chemistry? Chem. Geol. 252, 109–124.

I. Cartwright et al. / Applied Geochemistry 27 (2012) 1698–1709 Chiew, F.H.S., McMahon, T.A., O’Neill, I.C., 1992. Estimating groundwater recharge using an integrated surface and groundwater modelling approach. J. Hydrol. 131, 151–186. Chivas, A.R., Andrews, A.S., Lyons, W.B., Bird, M.I., Donnelly, T.H., 1991. Isotopic constraints on the origin of salts in Australian playas. 1. Sulphur. Palaeogeog. Palaeoclimatol. Palaeoecol. 84, 309–332. Clark, I.D., Fritz, P., 1997. Environmental Isotopes in Hydrogeology. Lewis, New York, USA. Coetsiers, M., Walraevens, K., 2009. A new correction model for 14C ages in aquifers with complex geochemistry – application to the Neogene Aquifer, Belgium. Appl. Geochem. 24, 768–776. Currell, M.J., Cartwright, I., Bradley, D.C., Han, D., 2010. Recharge history and controls on groundwater quality in the Yuncheng Basin, north China. J. Hydrol. 385, 216–229. Darling, W.G., Edmunds, W.M., Smedley, P.L., 1997. Isotopic evidence for palaeowaters in the British Isles. Appl. Geochem. 12, 813–829. de Caritat, P., Kirste, D., Carr, G., McCulloch, M., 2005. Groundwater in the Broken Hill region, Australia: recognising interaction with bedrock and mineralisation using S, Sr and Pb isotopes. Appl. Geochem. 20, 767–787. Dogramaci, S.S., Herczeg, A.L., 2002. Strontium and carbon isotope constraints on carbonate–solution interactions and inter-aquifer mixing in groundwaters of the semi-arid Murray Basin, Australia. J. Hydrol. 262, 50–67. Dogramaci, S.S., Herczeg, A.L., Schiff, S.L., Bone, Y., 2001. Controls on d34S and d18O of dissolved sulfate in aquifers of the Murray Basin, Australia and their use as indicators of flow processes. Appl. Geochem. 16, 475–488. Edmunds, W.M., 2009. Geochemistry’s vital contribution to solving water resource problems. Appl. Geochem. 24, 1058–1073. Edmunds, W.M., Ma, J., Aeschbach-Hertig, W., Kipfer, R., Darbyshire, D.P.F., 2006. Groundwater recharge history and hydrogeochemical evolution in the Minqin Basin, North West China. Appl. Geochem. 21, 2148–2170. Evans, W.R., Kellett, J.R., 1988. Overview of the hydrogeology of the Murray Basin. Record – Bureau of Mineral Resources. Geol. Geophys., 65–69. Evans, W.R., Kellett, J.R., 1989. The hydrogeology of the Murray Basin, southeastern Australia. BMR J. Aust. Geol. Geophys. 11, 147–166. Fontes, J.C., Garnier, J.M., 1979. Determination of the initial 14C activity of the total dissolved carbon; a review of the existing models and a new approach. Water Resour. Res. 15, 399–413. Galego Fernandes, P., Carreira, P.M., 2008. Isotopic evidence of aquifer recharge during the last ice age in Portugal. J. Hydrol. 361, 291–308. Gates, J.B., Edmunds, W.M., Darling, W.G., Ma, J., Pang, Z., Young, A.A., 2008. Conceptual model of recharge to southeastern Badain Jaran Desert groundwater and lakes from environmental tracers. Appl. Geochem. 23, 3519–3534. Gonfiantini, R., 1986. Environmental Isotopes in Lake Studies. Elsevier, Amsterdam, Netherlands, pp. 113–168. Herczeg, A.L., Barnes, C.J., Macumber, P.G., Olley, J.M., 1992. A stable isotope investigation of groundwater–surface water interactions at Lake Tyrrell, Victoria, Australia. Chem. Geol. 96, 19–32. Herczeg, A.L., Leaney, F.W.J., Stadler, M.F., Allan, G.L., Fifield, L.K., 1997. Chemical and isotopic indicators of point-source recharge to a karst aquifer, South Australia. J. Hydrol. 192, 271–299. Herczeg, A.L., Dogramaci, S.S., Leaney, F.W., 2001. Origin of dissolved salts in a large, semi-arid groundwater system: Murray Basin, Australia. Marine and Freshwater Resources 52, 41–52. Ivkovic, K.M., Watkins, K.L., Cresswell, R.G., Bauld, J., 1998. A Groundwater Quality Assessment of the Upper Shepparton Formation Aquifers: Cobram Region, Victoria. Australian Geolical Survey Organisation, Record 1998/16. Jankowski, J., Acworth, R.I., 1997. Impact of debris-flow deposits on hydrogeochemical processes and the development of dryland salinity in the Yass River Catchment, New South Wales, Australia. Hydrogeol. J. 5, 71–88. Kalin, R.M., 2000. Radiocarbon dating of groundwater systems. In: Cook, P., Herczeg, P. (Eds.), Environmental Tracers in Subsurface Hydrology. Kluwer, New York, pp. 111–144. Katz, B.G., Bullen, T.D., 1996. The combined use of 87Sr/86Sr and carbon and water isotopes to study the hydrochemical interaction between groundwater and lakewater in mantled karst. Geochim. Cosmochim. Acta 60, 5075–5087. Lamontagne, S., Leaney, F.W., Herczeg, A.L., 2005. Groundwater–surface water interactions in a large semi-arid floodplain; implications for salinity management. Hydrol. Process. 19, 3063–3080. Lawrence, C.R., 1988. Murray Basin. In: Douglas, J.G., Ferguson, J.A. (Eds.), Geology of Victoria. Geological Society of Australia (Victoria Division), Melbourne, pp. 352– 363. Le Gal La Salle, C., Marlin, C., Leduc, C., Taupin, J.D., Massault, M., Favreau, G., 2001. Renewal rate estimation of groundwater based on radioactive tracers (3H, 14C) in an unconfined aquifer in a semi-arid area, Iullemeden Basin, Niger. J. Hydrol. 254, 145–156. Leaney, F.W., Allison, G.B., 1986. Carbon-14 and stable isotope data for an area in the Murray Basin: its use in estimating recharge. J. Hydrol. 88, 129–145.

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Leaney, F.W., Herczeg, A.L., 1995. Regional recharge to a karst aquifer estimated from chemical and isotopic composition of diffuse and localised recharge, South Australia. J. Hydrol. 164, 363–387. Leaney, F.W., Herczeg, A.L., 1999. The Origin of Fresh Ground Water in the Southwest Murray Basin and Its Potential for Salinisation. CSIRO Land and Water Technical Rep. 7/99. Leaney, F.W., Herczeg, A.L., Walker, G.R., 2003. Salinization of a fresh palaeo-ground water resource by enhanced recharge. Ground Water 41, 84–92. Leybourne, M.I., Clark, I.D., Goodfellow, W.D., 2006. Stable isotope geochemistry of ground and surface waters associated with undisturbed massive sulfide deposits; constraints on origin of waters and water–rock reactions. Chem. Geol. 231, 300–325. Love, A.J., Herczeg, A.L., Armstrong, D., Stadter, F., Mazor, E., 1993. Groundwater flow regime within the Gambier Embayment of the Otway Basin, Australia: evidence from hydraulics and hydrochemistry. J. Hydrol. 143, 297–338. Love, A.J., Herczeg, A.L., Leaney, F.W., Stadter, M.F., Dighton, J.C., Armstrong, D., 1994. Groundwater residence time and palaeohydrology in the Otway Basin, South Australia: 2H, 18O and 14C data. J. Hydrol. 153, 157–187. Ma, J., Ding, Z., Edmunds, W.M., Gates, J.B., Huang, T., 2009. Limits to recharge of groundwater from Tibetan plateau to the Gobi desert, implications for water management in the mountain front. J. Hydrol. 364, 128–141. Macumber, P., 1991. Interaction Between Groundwater and Surface Systems in Northern Victoria. Victoria Department of Conservation and Environment. Macumber, P.G., 1992. Hydrological processes in the Tyrrell Basin, southeastern Australia. Chem. Geol. 96, 1–18. Macumber, P.G., 2007. Aspects of the hydrogeology of the Mallee region. Proc. Roy. Soc. Victoria 118, 7–8. Negrel, P., Petelet-Giraud, E., 2005. Strontium isotopes as tracers of groundwaterinduced floods: the Somme case study (France). J. Hydrol. 305, 99–119. Négrel, P., Casanova, J., Aranyossy, J.-F., 2001. Strontium isotope systematics used to decipher the origin of groundwaters sampled from granitoids: the Vienne Case (France). Chem. Geol. 177, 287–308. Petrides, B., Cartwright, I., 2006. The hydrogeology and hydrogeochemistry of the Barwon Downs Graben aquifer, southwestern Victoria, Australia. Hydrogeol. J. 14, 809–826. Petrides, B., Cartwright, I., Weaver, T., 2006. The evolution of groundwater in the Tyrrell catchment, south-central Murray Basin, Victoria, Australia. Hydrogeol. J. 14, 1522–1543. Rosenthal, E., Adar, E., Issar, A.S., Batelaan, O., 1990. Definition of groundwater flow patterns by environmental tracers in the multiple aquifer system of southern Arava Valley, Israel. J. Hydrol. 117, 339–368. Rozanski, K., 1985. Deuterium and oxygen-18 in European groundwaters – links to atmospheric circulation in the past. Chem. Geol.: Isotope Geosci. 52, 349–363. Saliege, J.F., Fontes, J.C., 1984. Essai de determination experimentale du fractionnement des isotopes 13C et 14C du carbone au cours de processus naturels. Int. J. Appl. Radiat. Isotopes 35, 55–62. Sayed, S.A.S., Saeedy, H.S., Székely, F., 1992. Hydraulic parameters of a multilayered aquifer system in Kuwait City. J. Hydrol. 130, 49–70. Swane, I.P., Weaver, T.R., Lawrence, C.R., Cartwright, I., 2001. Hydrologic controls on groundwater salinisation, Murray Basin, Australia. In: Cidu, R. (Ed.), Proceedings of 10th International Symposium on Water–Rock Interaction. Balkema, Lisse, 589–592. Tantawi, M.A., El-Sayed, E., Awad, M.A., 1998. Hydrochemical and stable isotope study of groundwater in the Saint Catherine-Wadi Feiran area, south Sinai, Egypt. J. Afr. Earth Sci. 26, 277–284. Tickell, S.J., 1978. Geology and Hydrogeology of the Eastern Part of the Riverine Plain in Victoria, Melbourne. Geological Survey of Victoria Report 1977–8. Melbourne, Australia. Tickell, S.J., 1991. Shepparton Geological Report, Melbourne. Geological Survey of Victoria Report 88. Melbourne, Australia. Tickell, S.J., Humphries, J., 1986. Groundwater Resources and Associated Salinity Problems of the Victoria Part of the Riverine Plain. Department Industry and Technical Research Victoria, Melbourne, Australia. Ullman, W.J., Collerson, K.D., 1994. The Sr-isotope record of late Quaternary hydrologic change around Lake Frome, South Australia. Aust. J. Earth Sci. 41, 37– 45. Valentine, D.L., Chidthaisong, A., Rice, A., Reeburgh, W.S., Tyler, S.C., 2004. Carbon and hydrogen isotope fractionation by moderately thermophilic methanogens. Geochim. Cosmochim. Acta 68, 1571–1590. Vogel, J.C., 1971. Groningen radiocarbon dates IX. Radiocarbon 12, 444–771. Wasson, R.J., Donnelly, T.H., 1991. Palaeoclimatic Reconstructions for the Last 30,000 years in Australia. A Contribution to Prediction of Future Climate. CSIRO Division of Water Reources Techical, Report, 91/3. Weaver, T.R., Frape, S.K., Cherry, J.A., 1995. Recent cross-formational fluid flow and mixing in the shallow Michigan Basin. Geol. Soc. Am. Bull. 107, 697–707.