Browsing by Author "Suckow, A"

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    Application of stable noble gases, 85Kr and 39Ar to investigate the freshwater lens on Rottnest Island, Western Australia
    (Goldschmidt, 2017-08-13) Kersting, A; Aeschbach, W; Deslandes, A; Meredith, KT; Peterson, MA; Purtschert, R; Suckow, A
    We report on a multi-tracer study of a freshwater lens on Rottnest Island west of Perth (Western Australia). The potable water supply of this carbonate island is entirely based on a shallow freshwater lens ‘floating’ on more saline water. Former studies (Bryan 2016) identified rain as the sole source of the fresh groundwater and that this very vulnerable system is threatened by anthropogenic usage and reduced rainfall due to climate change, causing salt water intrusion.Since the freshwater lens only has a thickness of approx. 20m, even the short screens of the observation wells (1-2m length) cause significant mixing of water of different ages. The combination of tritium (3H) and radiocarbon (14C) used earlier cannot resolve details of the age distribution because of the low values for tritium in precipitation on the southern hemisphere and because of mixing corrosion of the carbonate aquifer together with seawater intrusion changing the initial radiocarbon values. Therefore,this study focussed on the applicationof 85Kr(half-life 10,8yr) and 39Ar (half-life 269yr) as well as the stable noble gases. Here 85Kr complements 3H to resolve the component of very young waterin the age distribution,whereas39Ar fillsthe dating gap between 3H and 14C. The heavy noblegases (Ar, Kr, Xe) can give additional information on the infiltration of freshwater or seawater and 4He can identify admixtures of old water.
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    Hydrochemical and isotopic fingerprinting of the Walloon coal measures and adjacant aquifiers in the Clarence-Moreton and Eastern Basins in Southeast Queensland
    (Geological Society of Australia, 2014-07-07) Raiber, M; Cendón, DI; Feitz, A; Sundaram, B; Suckow, A
    The Clarence-Moreton Basin in New South Wales and Queensland is one of six nationwide priority regions where the potential impacts of future coal seam gas extractions and coal mining on water-dependent assets are being assessed through a national programme of Bioregional Assessments. The Clarence-Moreton Basin is an elongated intracratonic sag basin that contains sedimentary sequences of Middle and Late Triassic to Lower Cretaceous age with a combined thickness of up to approximately 3500 to 4000 m. Overlying the basin sedimentary sequences within the Clarence-Moreton bioregion (the eastwards draining part of the basin) are five major catchment systems (Lockyer Valley, Bremer/Warrill, Logan/Albert in Queensland, and the Richmond and Clarence river catchments in NSW), which host important alluvial groundwater and surface water resources that are intensively used for irrigation. In addition, these catchments host significant assets such as groundwater-dependant ecosystems (e.g. springs and wetlands). In order to predict the potential impacts of depressurisation associated with coal seam gas extraction from the Walloon Coal Measures (major target of CSG exploration in the Clarence-Moreton Basin), an accurate understanding of the links between different components of the hydrological system is essential. Prior to the development of numerical models, it is critical to describe potential connectivity pathways between deep and shallow aquifers, as well as interaction between groundwater and surface water. In order to assist with the development of reliable conceptual models that describe these interactions and constitute a road map to bioregional assessments, we have constructed a 3D geological model from elevation (DEM), stratigraphic, seismic and lithological data using GoCAD (Paradigm) 3D geological modelling software. The 3D geological model represents the major alluvial, sedimentary and volcanic aquifers and aquitards of the Clarence-Moreton bioregion. It helps to develop a more realistic understanding of the aquifer system behaviour, particularly if integrated with complementary data sources such as water level or hydrochemical data, and it will provide the geometric framework for the groundwater numerical model. The 3D geological model highlights the structural complexity of the Clarence-Moreton Basin, with significant vertical displacements of major basin units of several hundred meters registered along major regional fault systems, and abutments of stratigraphic units against basement ridges or pinching out of units observed in different parts of the basin. These observed structural features and the geometric characteristics of aquifers/aquitards can have a significant influence on potential connectivity pathways. For example, the thinning of the Gatton Sandstone against the underlying Woogaroo Subgroup at the basin margin in the Lockyer Valley results in upwards seepage of groundwater from the Gatton Sandstone into the alluvial aquifer, and this upwards discharge probably also feeds wetlands located along the northern margin of the Gatton Sandstone.
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    Multi-isotope studies investigating recharge and inter-aquifer connectivity in coal seam gas areas (Qld, NSW) and shale gas areas (NT)
    (CSIRO Publishing, 2020-05-15) Suckow, A; Deslandes, A; Gerber, C; Lamontagne, S; Mallants, D; Davies, P; Taylor, A; Wilske, C; Smith, S; Raiber, M; Meredith, KT; Rachakonda, PK; Larcher, A; Wilkes, P; Prommer, H; Siade, A; Barrett, D
    Large sedimentary basins with multiple aquifer systems like the Great Artesian Basin and the Beetaloo Sub-Basin are associated with large time and spatial scales for regional groundwater flow and mixing effects from inter-aquifer exchange. This makes them difficult to study using traditional hydrogeological investigation techniques. In continental onshore Australia, such sedimentary aquifer systems can also be important freshwater resources. These resources have become increasingly stressed because of growing demand and use of groundwater by multiple industries (e.g. stock, irrigation, mining, oil and gas). The social licence to operate for extractive oil and gas industries increasingly requires robust and reliable scientific evidence on the degree to which the target formations are vertically and laterally hydraulically separated from the aquifers supplying fresh water for stock and agricultural use. The complexity of such groundwater interactions can only be interpreted by applying multiple lines of evidence including environmental isotopes, hydrochemistry, hydrogeological and geophysical observations. We present an overview of multi-tracer studies from coal seam gas areas (Queensland and New South Wales) or areas targeted for shale gas development (Northern Territory). The focus was to investigate recharge to surficial karst and deep confined aquifer systems before industrial extraction on time scales of decades up to one million years and aquifer inter-connectivity at the formation scale. A systematic and consistent methodology is applied for the different case study areas aimed at building robust conceptual hydrogeological models that inform groundwater management and groundwater modelling. The tracer studies provided (i) in all areas increased confidence around recharge estimates, (ii) evidence for a dual-porosity flow system in the Hutton Sandstone (Queensland) and (iii) new insights into the connectivity, or lack thereof, of flow systems. © CSIRO 2020
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    Multi-tracer approach to investigate groundwater recharge and aquifer connectivity in the Clarence-Moreton and eastern Surat basins in southeast Queensland
    (National Centre for Groundwater Research And Training, 2015-11-03) Raiber, M; Feitz, A; Cendón, DI; Suckow, A
    The Walloon Coal Measures (WCM) in the Clarence-Moreton and the Surat basins in QLD and northern NSW contain up to approximately 600 m of mudstone, siltstone, sandstone and coal. Wide-spread exploration for coal seam gas (CSG) within both basins has led to concerns that the depressurisation associated with the resource development may impact on water resources in adjacent aquifers. In order to predict potential impacts, a detailed understanding of sedimentary basins hydrodynamics that integrates geology, hydrochemistry and environmental tracers is important. In this study, we show how different hydrochemical parameters and isotopic tracers (i.e. major ion chemistry, dissolved gas concentrations, δ2H and δ13C of CH4, δ13C-DIC, δ18O, δ2H, 87Sr/86Sr, 3H, 14C and 36Cl) can help to improve the knowledge on groundwater recharge and flow patterns within the coal-bearing strata and their connectivity with over- or underlying formations. Dissolved methane concentrations in groundwaters of the WCM in the Clarence-Moreton Basin range from below the reporting limit (10 μg/L) to approximately 50 mg/L, and samples collected from nested bore sites show that there is also a high degree of vertical variability within the aquifer. Other parameters such as 3H, δ13C & 14C in DIC collected along assumed flow paths are also highly variable, which indicates local groundwater flow cells rather than regional flow. In contrast, 87Sr/86Sr isotope ratios of WCM groundwaters are very uniform and distinct from groundwaters contained in other sedimentary bedrock units. This suggests that 87Sr/86Sr ratios may be a suitable tracer to study hydraulic connectivity of the Walloon Coal Measures with over- or underlying aquifers, although more studies on the systematic are required. Overall, the complexity of recharge processes, aquifer connectivity and within-formation variability confirms that a multi-tracer approach is required to understand aquifer connectivity in these sedimentary basins.
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    Noble gas tracers: improving the understanding of groundwater recharge and flow systems in Australia
    (American Geophysical Union (AGU), 2019-12-14) Deslandes, A; Suckow, A; Gerber, C; Wilske, C; Mallants, D; Raiber, M; Meredith, KT
    Australia has several large sedimentary basins, including the Great Artesian Basin (GAB), one of the largest aquifer systems in the world, which has a long history of groundwater extraction for stock, agriculture and urban water supplies. With the recent onset of exploration and development for coal bed methane and shale gas and the extension of existing and approval of new mining operations, there is a need to characterise recharge processes and flow dynamics in these complex aquifer systems to assess cumulative impacts, develop policy for groundwater use and underpin the social licence to operate for extractive industries. We present examples of two sedimentary basins where noble gas tracers have been used in combination with other environmental tracers and show how the noble gas tracers provided critical insights into groundwater system understanding. In the eastern recharge areas of the GAB, 14C and 36Cl results highlighted the existence of two different flow areas with very different recharge mechanisms. Although these isotope systems yielded the qualitative results in a relatively straightforward manner, the isotopes 85Kr and 81Kr provided much more reliable results than 14C and 36Cl, for which detailed geochemical corrections were needed, and the application of noble gases therefore helped to reduce the conceptual uncertainties associated with previous ‘conventional’ tracer studies. The Beetaloo Sub-Basin, located in the Northern Territory, contains aquifer systems that cover hundreds of square kilometres. The karstic and heterogeneous structure of the shallow aquifers, and associated recharge characteristics that are variable in season, latitude and local structures, poses many challenges for the characterisation of groundwater flow and recharge. Conventional tracers demonstrate obvious contradictions such as an increase of 14C down the hydraulic gradient, and modern waters according to the gas tracers CFC, SF6 and H1301, combined with negligible tritium. The noble gases provided insights into the recharge mechanisms, elucidating the challenges within the rest of the dataset, and suggest that 39Ar might be very useful as it covers a unique age range that is important for better understanding the system.
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    Strontium isotopes in the atmosphere, geosphere and hydrosphere: developing a systematic “fingerprinting” framework of rocks and water in sedimentary basins in eastern Australia
    (Elsevier, 2024-11-15) Raiber, M; Feitz, AJ; Cendón, DI; Flook, S; Suckow, A; Schöning, G; Hofmann, H; Martinez, J; Maas, R; Kelly, BFJ
    Understanding the connection between aquifers, aquitards, and groundwater-dependant ecosystems remains a key challenge when developing a conceptual hydrogeological model. The aim of this study was to develop a systematic strontium isotope (87Sr/86Sr) fingerprinting framework of rocks and water within the sedimentary Surat and Clarence-Moreton basins (SCM basins) in eastern Australia – an area of extensive coal seam gas development and high potential for aquifer and groundwater-surface water connectivity. To do this, new groundwater samples (n = 298) were collected, analyzed and integrated with published data (n = 154) from the basins' major sedimentary, volcanic and alluvial aquifers, including the major coal seam gas target, the Walloon Coal Measures. Samples were also analyzed from rainfall (n = 2) and surface water (n = 40). In addition, rock core samples (n = 39) from exploration and stratigraphic wells were analyzed to determine the range of Sr isotope composition from host rocks. The analyses of cores demonstrate a distinct and systematic contrast in 87Sr/86Sr between different hydrogeological units. This confirms that all major hydrogeological units have a narrow range with unique 87Sr/86Sr population characteristics that are useful for guiding conceptual model development. Comparison with selected hydrochemical and groundwater age tracers (14C and 36Cl) suggests only limited changes of 87Sr/86Sr from recharge beds to the deeper parts of the basins or with a decrease in natural 14C and 36Cl tracer content along flow paths. Stream sampling during baseflow conditions confirms that 87Sr/86Sr in surface waters are similar to those of the underlying bedrock formations. We demonstrated that 87Sr/86Sr analyses of rocks and water provide a powerful hydrostratigraphic and chemostratigraphic fingerprinting framework in the SCM basins, enabling reliable assessments of plausible aquifer and groundwater-surface water interconnectivity pathways. Applied in other complex multi-aquifer sedimentary basins in Australia, and globally, a similar approach can help to constrain conceptual hydrogeological models and facilitate improved water resource management. © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY - NC 4.0 license.