Browsing by Author "Iverach, CP"
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- ItemAccumulative evidence highlighting that the Narrabri and Gunnedah formations are mythical(National Centre for Groundwater Research And Training, 2017-07-12) Kelly, BFJ; Cendón, DI; Iverach, CP; Harris, SJ; Hankin, SIThe Narrabri and Gunnedah Formations, used to describe the valley-filling sedimentary sequences in portions of the Murray-Darling Basin, have never been formally defined. The hydrogeological evidence for naming these formations is reviewed in the context of modern sedimentary models. Are we using the right architectural model? Hundreds of lithological logs from the Murrumbidgee, Namoi, and Gwydir catchments are used to examine the evolution of each alluvial aquifer. For each depth interval, the catchment-wide proportions of coarse (gravel, sand) and fine (silt, clay) sediments is determined. Sediment size distributions are then examined in the context of past climates and the conceptual inland fluvial model for distributive fluvial systems. Vertical hydraulic connectivity is examined using new hydrogeochemical data and nested groundwater hydrograph sets. All systems show the core features of aggradational distributive fluvial systems. The valley-filling sequences for all catchments examined transitioned from high energy wet environments at depth, dominated by sand and gravel deposits, through to the modern-day low-energy silt and clay dominated depositional environments. Gravel and sand deposits dominate in the proximal portion of the catchment, and low energy silt and clay deposits dominate in the distal portions. The apparent existence of the Narrabri and Gunnedah Formations is due to changing sediment grain size proportion and channel fill sand connectivity. Both the facies and hydrograph analyses show that semi-confining layers are only local. Extensive hydrogeochemical data from the Namoi catchment show continuity of mixing between basement and surface inflows. All catchments have many sedimentary architectural features consistent with the distributive fluvial system model, and reflect changing climate throughout the Neogene and Quaternary. Use of the Narrabri and Gunnedah Formation nomenclature, which has been incorporated into the National Aquifer Framework, is not supported by either the sedimentological, hydrograph or hydrogeochemical record.
- ItemAssessing connectivity between an overlying aquifer and a coal seam gas resource using methane isotopes, dissolved organic carbon and tritium(Nature, 2015-11-04) Iverach, CP; Cendón, DI; Hankin, SI; Lowry, D; Fisher, RE; France, JL; Nisbet, EG; Baker, AA; Kelly, BFJCoal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ13C-CH4), groundwater tritium (3H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater δ13C-CH4 versus CH4 concentration, in association with DOC concentration and 3H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity. © The Authors. This work is licensed under a Creative Commons Attribution 4.0 International Licence. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons licence, users will need to obtain permission from the licence holder to reproduce the material.
- ItemAssessing connectivity between an overlying aquifer and a coal seam gas resource using methane isotopes, dissolved organic carbon and tritium(National Centre for Groundwater Research And Training, 2015-11-03) Iverach, CP; Cendón, DI; Hankin, SI; Lowry, D; Fisher, RE; France, JL; Nisbet, EG; Baker, AA; Kelly, BFJCoal seam gas (CSG) production can have an impact on groundwater quality and quantity in adjacent or overlying aquifers. To assess this impact we need to determine the background groundwater chemistry and to map geological pathways of hydraulic connectivity between aquifers. In south-east Queensland (Qld), Australia, a globally important CSG exploration and production province, we mapped hydraulic connectivity between the Walloon Coal Measures (WCM, the target formation for gas production) and the overlying Condamine River Alluvial Aquifer (CRAA), using groundwater methane (CH4) concentration and isotopic composition (δ13C-CH4), groundwater tritium (3H) and dissolved organic carbon (DOC) concentration. A continuous mobile CH4 survey adjacent to CSG developments was used to determine the source signature of CH4 derived from the WCM. Trends in groundwater δ13C-CH4 versus CH4 concentration, in association with DOC concentration and 3H analysis, identify locations where CH4 in the groundwater of the CRAA most likely originates from the WCM. The methodology is widely applicable in unconventional gas development regions worldwide for providing an early indicator of geological pathways of hydraulic connectivity. © The Authors.
- ItemAssessing the hydraulic connection between fresh water aquifers and unconventional gas production using methane and stable isotopes(European Geosciences Union, 2015-04-12) Iverach, CP; Cendón, DI; Hankin, SI; Lowry, D; Fisher, RE; France, JL; Nisbet, EG; Baker, AA; Kelly, BFJUnconventional gas developments pose a risk to groundwater quality and quantity in adjacent or overlying aquifers. To manage these risks there is a need to measure the background concentration of indicator groundwater chemicals and to map pathways of hydraulic connectivity between aquifers. This study presents methane (CH4) concentration and isotopic composition, dissolved organic carbon concentration ([DOC]) and tritium (3H) activity data from an area of expanding coal seam gas (CSG) exploration and production (Condamine Catchment, south-east Queensland, Australia). The target formation for gas production within the Condamine Catchment is the Walloon Coal Measures (WCM). This is a 700 m thick, low-rank CSG resource, which consists of numerous thin discontinuous lenses of coal separated by very fine-to medium-grained sandstone, siltstone, and mudstone, with minor calcareous sandstone, impure limestone and ironstone. The thickness of the coal makes up less than 10% of the total thickness of the unit. The WCM are overlain by sandstone formations, which form part of the Great Artesian Basin (GAB). The Condamine Alluvium fills a paleo-valley carved through the above formations. A combination of groundwater and degassing air samples were collected from irrigation bores and government groundwater monitoring boreholes. Degassing air samples were collected using an SKC 222-2301 air pump, which pumped the gas into 3 L Tedlar bags. The groundwater was analysed for 3H and [DOC]. A mobile CH4 survey was undertaken to continuously sample air in and around areas of agricultural and unconventional gas production. The isotopic signature of gas from the WCM was determined by sampling gas that was off-gassing from a co-produced water holding pond as it was the largest emission that could be directly linked to the WCM. This was used to determine the source signature of the CH4 from the WCM. We used Keeling plots to identify the source signature of the gas sampled. For the borehole samples these plots assume that there are only two sources of CH4, each with a unique isotopic signature. When the two sources mix in varying proportions they will plot along a straight line in the Keeling plot. Geometric mean displacement was used to fit a regression line and determine the intercept value. Within the Keeling plot, samples clustered according to their 3H and [DOC] values. One cluster is associated with near surface biological processes, while the other cluster can be attributed to gas sourced from the WCM. This indicates that in places there is hydraulic connectivity between the WCM and the overlying Condamine Alluvium. The results from this case study demonstrate that measuring 3H activity, [DOC] and CH4 concentrations in combination with CH4 isotopic analysis can provide an early indicator of hydraulic connectivity in areas of expanding unconventional gas development. © Author(s) 2015. CC Attribution 3.0 License.
- ItemBaselining lower Namoi groundwater and evaluating Pilliga CSG developments(University of New South Wales, 2018-12) Kelly, BFJ; Cendón, DI; Iverach, CPHydrochemical and isotopic results reveal that there are distinct differences in the groundwater chemistry with depth throughout the Lower Namoi Alluvium (LNA). This is due to varying recharge processes, as well as the evolution of the groundwater chemistry through the system. Na-HCO3 - type groundwater is dominant throughout the study area, increasing in concentration with depth. Locally, in areas where the alluvial sediments have a higher proportion of clay, the groundwater is more saline because of evapotranspiration processes and is classified as Na-Cl-type groundwater. Groundwater residence time (an indicator of age) is correlated with distance from the river channel for near surface samples, and with depth due to increased proportional input for the Great Artesian Basin (GAB). Where the groundwater is enriched in Na+, it is most likely the result of mixing between the Na+-rich GAB groundwater and surface-sourced water (river leakage, floodwater recharge, and areal recharge (including irrigation deep drainage)). The weathering of silicate minerals and cation exchange processes in the shallow alluvium with a higher clay content may also contribute to the enrichment of Na+ in the LNA. High activities of tritium (3H) in the shallow aquifer close to the river corridor highlight the importance of river leakage and flood associated recharge to total aquifer recharge. Modelling the mixing of various water types using a box model mixing approach shows that large floods are the biggest contributor to the renewal of the near-river shallow groundwater. Our calculations also show that minor recharge occurs into the shallow groundwater proximal to Namoi River in years when the region experiences average rainfall. Isotopic data (36Cl/Cl, 14C and 3H) indicate that the residence time of the groundwater is highly dependent on the proportion of groundwater sourced from surface recharge and input from the GAB in each location. The Lower Namoi alluvial groundwater in the study area is a mixture of groundwater of different origin mainly: a) a young component with residence times of < 70 years associated with periodic flooding and; b) groundwater that is potentially hundreds of thousands of years old, mostly derived from outflow from the GAB units. 6 Methane is ubiquitous throughout the alluvium, with the concentration increasing significantly with depth. The CH4 isotope data suggest that the CH4 in the LNA is biologically produced, with varying degrees of microbial oxidation occurring. Our results, coupled with CH4 data collected from formations underlying the GAB (primarily the Hokissons coal seam) by Eastern Star Gas (ESG 2008-2011) suggest that mixing of groundwater in the LNA with water from the GAB has influenced both the occurrence of CH4 in the alluvium (hence the increased concentration and lighter isotopic signature with depth), and the processes acting on the CH4 once it has reached the LNA. Microbial community analyses of the alluvial groundwater show 3 distinct changes in composition with depth. These changes with depth are related to the changing geochemical environment through the vertical profile of the LNA, because of multiple recharge inputs. There are significantly less methanogens in the groundwater than suggested by the CH4 concentration, indicating that in situ production is not the primary source of CH4 to the alluvium. Comprehensive details on the biogeochemical results from this project are published in: Iverach C.P; Cendón D.I.; Meredith K.T.; Wilcken K.M.; Hankin S.I.; Andersen M.S.; Kelly B.F.J, (2017) A multi-tracer approach to constraining artesian groundwater discharge into an alluvial aquifer, Hydrology and Earth System Sciences, vol. 21, pp. 5953 - 5969, http://dx.doi.org/10.5194/hess-21-5953-2017
- ItemBiogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures(European Geosciences Union, 2017-04-26) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJGeochemical and microbiological indicators of methane (CH4) production, oxidation and migration processes in groundwater are important to understand when attributing sources of gas. The processes controlling the natural occurrence of CH4 in groundwater must be characterised, especially when considering the potential impacts of the global expansion of unconventional gas production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition ( 13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer that directly overlies coal measures targeted for unconventional gas production in Australia. A combination of geochemical and microbiological groundwater samples were collected from private irrigation boreholes. The groundwater was analysed for the major ions, water stable isotopes ( 2H and 18O), the isotopic composition of dissolved organic carbon ( 13CDOC) and dissolved inorganic carbon ( 13CDIC). Quantitative realtime PCR was used to determine abundances of bacterial and archaeal 16S rRNA gene targets and functional gene targets in the groundwater. Measurements of CH4 indicate that there is biogenic CH4 in the aquifer, however microbial community analysis indicates that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of DIC and, as well as the concentration of SO2-4 , indicate limited potential for methanogenesis insitu. Microbial community analysis also showed that aerobic oxidation of CH4 is occurring in the alluvial aquifer despite the absence of a microbial pathway to produce the CH4. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the freshwater aquifer, is the upward migration of CH4 from the underlying coal measures. © Author(s) 2016. CC Attribution 3.0 License.
- ItemBiogeochemical constraints on the origin of methane in an alluvial aquifer: evidence for the upward migration of methane from underlying coal measures(European Geosciences Union, 2017-01-17) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJGeochemical and microbiological indicators of methane (CH4) production, oxidation and migration processes in groundwater are important to understand when attributing sources of gas. The processes controlling the natural occurrence of CH4 in groundwater must be understood, especially when considering the potential impacts of the global expansion of coal seam gas (CSG) production on groundwater quality and quantity. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition (δ13C-CH4), to determine the processes acting upon CH4 in a freshwater alluvial aquifer that directly overlies coal measures targeted for CSG production in Australia. Measurements of CH4 indicate that there is biogenic CH4 in the aquifer; however, microbial data indicate that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC), as well as the concentration of SO42−, indicate limited potential for methanogenesis in situ. Microbial community analysis also shows that aerobic oxidation of CH4 occurs in the alluvial aquifer. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the freshwater aquifer, is the upward migration of CH4 from the underlying coal measures. © Author(s) 2017. This work is distributed under the Creative Commons Attribution 3.0 Licence.
- ItemConstraining source attribution of methane in an alluvial aquifer with multiple recharge pathways(Elsevier B. V., 2020-02-10) Iverach, CP; Cendón, DI; Beckmann, S; Hankin, SI; Manefield, M; Kelly, BFJIdentifying the source of methane (CH4) in groundwater is often complicated due to various production, degradation and migration pathways, particularly in settings where there are multiple groundwater recharge pathways. This study demonstrates the ability to constrain the origin of CH4 within an alluvial aquifer that could be sourced from in situ microbiological production or underlying formations at depth. To characterise the hydrochemical and microbiological processes active within the alluvium, previously reported hydrochemical data (major ion chemistry and isotopic tracers (3H, 14C, 36Cl)) were interpreted in the context of CH4 and carbon dioxide (CO2) isotopic chemistry, and the microbial community composition in the groundwater. The rate of observed oxidation of CH4 within the aquifer was then characterised using a Rayleigh fractionation model. The stratification of the hydrochemical facies and microbiological community populations is interpreted to be a result of the gradational mixing of water from river leakage and floodwater recharge with water from basal artesian inflow. Within the aquifer there is a low abundance of methanogenic archaea indicating that there is limited biological potential for microbial CH4 production. Our results show that the resulting interconnection between hydrochemistry and microbial community composition affects the occurrence and oxidation of CH4 within the alluvial aquifer, constraining the source of CH4 in the groundwater to the geological formations beneath the alluvium. © 2019 The Author(s). Published by Elsevier B.V. Open Access - CC BY licence
- ItemDetecting connectivity between an overlying aquifer and a coal seam gas resource using methane isotopes, dissolved organic carbon and tritium(Association of Australian Cotton Scientists, 2015-09-09) Iverach, CP; Cendón, DI; Hankin, SI; Lowry, D; Fisher, RE; France, JL; Nisbet, EG; Baker, AA; Kelly, BFJThere is public concern that coal seam gas (CSG) production will affect groundwater quality and quantity in overlying aquifers used to support irrigation, stock and domestic water supplies. To assess this risk there is a need to map pathways of hydraulic connectivity using geochemical and isotopic measurements. We demonstrate that measurements of methane (CH4) concentration and isotopic composition, dissolved organic carbon (DOC) concentration and tritium (3H) activity data highlight potential pathways of hydraulic connectivity between the Walloon Coal Measures (WCM – the target formation for CSG production) and the Condamine Alluvium, south-east Queensland, Australia. At 19 locations, both groundwater and degassing air samples were collected from irrigation bores. Degassing air samples were pumped into 3 L Tedlar bags. This air was analysed for both its methane concentration and isotopic signature. The groundwater was analysed for 3H and [DOC]. To determine the isotopic signature of the WCM, CH4 ambient air samples were collected adjacent to CSG coproduced water holding ponds. We use isotope mixing plots to identify the isotopic source signature of CH4 in the air samples from the degassing irrigation bores and those adjacent to CSG water holding ponds. Within the mixing plots samples graph along clear trend lines, which allows gas sources to be assigned. These trends in the mixing plots indicate potential local hydraulic connectivity between the WCM and the overlying Condamine Alluvium.
- ItemDetecting hydraulic connection between fresh water aquifers and coal seam gas production using the isotopes of carbon in methane(University of New South Wales and Australian Nuclear Science and Technology Organisation, 2015-07-10) Iverach, CP; Cendón, DI; Hankin, SI; Lowry, D; Fisher, RE; France, JL; Nisbet, EG; Baker, AA; Kelly, BFJNot provided to ANSTO Library.
- ItemGroundwater hydrographs in the Namoi and Gwydir catchments: an assessment of groundwater level change(University of New South Wales, 2019) Kelly, BFJ; Cendón, DI; Iverach, CPNot available
- ItemGroundwater residence time in the Condamine River Alluvial Aquifer (SE-QLD)(National Centre for Groundwater Research And Training, 2017-07-11) Cendón, DI; Iverach, CP; Hankin, SI; Kelly, BFJMany gigalitres of groundwater have been extracted from the Condamine River Alluvial Aquifer (CRAA) since the 1960s. These groundwater withdrawals have stressed the system and locally altered the groundwater flow paths. Isotopes can provide powerful insights into recharge pathways, flow direction, and the sustainability of groundwater withdrawals from alluvial aquifers. To address some of the regional groundwater concerns we must characterise alluvial groundwater residence time. A total of 31 groundwater samples were collected from privately owned irrigation bores and Qld-DNRM government monitoring bores in the region between Condamine Plains and Dalby. Parameters analysed included: 3H, 14CDIC, 222Rn, 87Sr/86Sr, δ13CDIC, water δ2H and δ18O, sulfate δ34S and δ18O as well major, trace and REE elements. Distance from primary recharge areas (rivers) provides the main control on groundwater residence time in the CRAA. This is supported by the following observations: 1) Groundwater between the Condamine River and its northern branch has low TDS (~400 mg/L), is Na-HCO3-type and has detectable 3H, indicating a proportion of modern recharge (<70 years); 2) Groundwater east of the northern branch has higher TDS (~700 mg/L) and is Na-HCO3- -type with increasing eastern inputs. No 3H is detected and 14C shows sub-modern groundwater (~500 years); 3) Groundwater along the eastern and western boundaries of the alluvium or samples retrieved from the Walloon Coal Measures (WCM) have high TDS (1,250-19,770 mg/L) and are Na-Cl-type. Residence times in the upper WCM increase along the flow path to the west from modern to 32,000 years on the western side. Groundwater residence time distributions provide a visualisation of recharge processes and delineate areas where groundwater withdrawals are less sustainable within the CRAA.
- ItemHydrochemical apportioning of irrigation groundwater sources in an alluvial aquifer(Elsevier B. V., 2020-11-20) Scheiber, L; Cendón, DI; Iverach, CP; Hankin, SI; Vázquez-Suñé, E; Kelly, BFJRiver floodplains sustain irrigated agriculture worldwide. Despite generalised groundwater level falls, limited hard data are available to apportion groundwater sources in many irrigated regions. In this paper, we propose a workflow based on: hydrochemical analysis, water stable isotopes, radiocarbon contents and multivariate statistical analysis to facilitate the quantification of groundwater source attribution at regional scales. Irrigation water supply wells and groundwater monitoring wells sampled in the alluvial aquifer of the Condamine River (Queensland, Australia) are used to test this approach that can easily be implemented in catchments worldwide. The methodology identified four groundwater sources: 1) river/flood water; 2) modified river/flood water; 3) groundwater recharged through regional volcanic materials and 4) groundwater recharged predominantly through sands and/or sandstone materials. The first two sources are characterised by fresh water, dominant sodium bicarbonate chemistry, short residence time and depleted water stable isotope signatures. Groundwater sources 3 and 4 are characterised by saline groundwater, sodium chloride chemistries, enriched water stable isotopes and very low radiocarbon contents, inferred to correspond to long residence times. The majority of wells assessed are dominated by flood water recharge, linked to decadal >300 mm rainfall events and associated flooding in the region. The approach presented here provides a groundwater source fingerprint, reinforcing the importance of floodwater recharge in the regional water budgets. This apportioning of groundwater sources will allow irrigators, modelers and managers to assess the long-term sustainability of groundwater use in alluvial catchments. Crown Copyright © 2020 Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND licence
- ItemIrrigation bore water in the Condamine Catchment: baselining groundwater quality and assessing pathways of hydraulic connectivity(Geological Society of Australia, 2014-07-07) Martel, L; Cendón, DI; Hankin, SI; Iverach, CP; Kelly, BFJThe expansion of coal seam gas production adjacent to the irrigation farming districts in the Condamine Catchment has raised concerns about the impact of gas production on groundwater in adjoining aquifer systems. To assess the risk, and to be able to detect any future changes in groundwater properties, existing groundwater chemistry data sets need to be updated and expanded. Historically, the testing of groundwater chemistry in the Condamine Catchment has focused on the Queensland Government groundwater-monitoring network, but it is unlikely that these samples come from the same sand and gravel bodies from which the irrigation bores extract groundwater. We report the result of 20 groundwater samples collected from bores that supply irrigation water for cotton and other crops. These samples were collected in January 2014 at the end of the pumping season, when the aquifer system is at peak stress for the year. We compare the major ion chemistry recorded in the irrigation bores to that measured at selected sites from the QLD government groundwater-monitoring network and with historical results reported in the literature. A hydrochemical facies analysis of these data provides one assessment of the likelihood of hydraulic connectivity between the Walloon Coal Measures, other bordering Great Artesian Basin formations and the valley filling sediments of the Condamine Alluvium. The results highlight variation in groundwater chemistry within the Condamine Alluvium, particularly in the Cecil Plains and Dalby regions, where there are signs of water mixing. As a result, further research into the area to explain the baseline data sets would provide a better understanding of hydraulic connectivity and the potential effects of CSG on the groundwater.
- ItemA multi-tracer approach to constraining artesian groundwater discharge into an alluvial aquifer(European Geosciences Union, 2017-11-28) Iverach, CP; Cendón, DI; Meredith, KT; Wilcken, KM; Hankin, SI; Andersen, MS; Kelly, BFJUnderstanding pathways of recharge to alluvial aquifers is important for maintaining sustainable access to groundwater resources. Water balance modelling is often used to proportion recharge components and guide sustainable groundwater allocations. However, it is not common practice to use hydrochemical evidence to inform and constrain these models. Here we compare geochemical versus water balance model estimates of artesian discharge into an alluvial aquifer, and demonstrate why multi-tracer geochemical analyses should be used as a critical component of water budget assessments. We selected a site in Australia where the Great Artesian Basin (GAB), the largest artesian basin in the world, discharges into the Lower Namoi Alluvium (LNA), an extensively modelled aquifer, to convey the utility of our approach. Water stable isotopes (δ18O and δ2H) and the concentrations of Na+ and HCO3− suggest a continuum of mixing in the alluvial aquifer between the GAB (artesian component) and surface recharge, whilst isotopic tracers (3H, 14C, and 36Cl) indicate that the alluvial groundwater is a mixture of groundwaters with residence times of < 70 years and groundwater that is potentially hundreds of thousands of years old, which is consistent with that of the GAB. In addition, Cl− concentrations provide a means to calculate a percentage estimate of the artesian contribution to the alluvial groundwater. In some locations, an artesian contribution of up to 70 % is evident from the geochemical analyses, a finding that contrasts with previous regional-scale water balance modelling estimates that attributed 22 % of all inflow for the corresponding zone within the LNA to GAB discharge. Our results show that hydrochemical investigations need to be undertaken as part of developing the conceptual framework of a catchment water balance model, as they can improve our understanding of recharge pathways and better constrain artesian discharge to an alluvial aquifer. © Author(s) 2017. This work is distributed under the Creative Commons Attribution 4.0 Licence.
- ItemShallow groundwater recharge and residence time in two separate flood plains along an aridity gradient in South Queensland, Australia(National Centre for Groundwater Research And Training, 2015-11-03) Cendón, DI; Kelly, BFJ; Larsen, JR; Hankin, SI; Hughes, CE; Meredith, KT; Hollins, SE; Iverach, CPFertile floodplains in headwater Darling-Murray catchments like the Condamine have endured profound physiographic changes over the last ~150 years, including the onset of intensive agriculture and groundwater abstraction since the 1960s. This has placed groundwater within alluvial aquifers under stress, raising allocation concerns and triggering salinity problems in some areas. Approximately 1,000 km west, across a decreasing rainfall gradient (659 mm/yr at Dalby to 198 mm/yr at Ballera), the Cooper Ck floodplain (near Ballera) is still in pristine condition and provides an ideal example of arid zone hydrological processes. This study compares groundwater from two alluvial systems with an emphasis on understanding groundwater recharge processes under various climatic conditions. Groundwater was collected from the Condamine alluvium in 2014 from 30 irrigation and monitoring wells. Groundwater was collected from the Cooper Ck alluvium between 2008 and 2011, from piezometers installed along a transect between major waterholes. All bores were sampled for major, minor/trace elements, water stable isotopes (δ18O and δ2H), δ13C in dissolved inorganic carbon, 3H, 14C and sulfate isotopes (δ34S δ18O) in selected samples for both study areas. The groundwater dataset was complemented with available long term rainfall data. Both locations showed that groundwater had depleted isotopic signatures consistent with recharge associated with large floods. Also in both locations groundwater defined well-correlated evaporation lines (R2>0.95), consistent with mixing with other sources. Groundwater near main channels contained 3H and 14C consistent with modern recharge, however, in the Cooper Ck modern recharge appeared restricted to areas like channel confluences. This study has implications for understanding how to sustainably use groundwater resources and the role of floods in recharging floodplain aquifers. Comparing the two sites provides a snapshot of how the Condamine could respond to increased aridity.
- ItemThe use of the hydrogeochemistry and multivariate statistical methods as a tool for groundwater management. Condamine River Alluvial Aquifer (CRAA), Australia(Copernicus Publications, 2018-04-08) Scheiber, L; Iverach, CP; Kelly, BFJ; Cendón, DI; Vázquez-Suñé, EThe alluvial aquifers of the Condamine River near Dalby have been increasingly used since the 1960s as a water resources to support Irrigated agriculture of mainly cotton and grain crops. Groundwater abstraction from the underlying Condamine River Alluvial Aquifer (CRAA) supplies 30% of the irrigation water (Dafny and Silburn, 2014). Over the past decade, Coal Seam Gas (CSG) exploration and production has expanded rapidly in the Queensland portion of the Surat Basin (SB), targeting the underlying Walloon Coal Measures (WCM), with tenements to multiple companies along the western flank of the Condamine Plain. To produce the gas, groundwater will be extracted in large quantities, depressurising the WCM. There is concern that the zone of depressurisation will impact the groundwater levels within the CRAA. In the last decade, great efforts have been made to improve hydrogeological conceptualization and modeling. The rapid expansion of CSG exploration and production in Australia has generated controversy within the public who are concerned about the impact on adjacent aquifers used to support irrigated agriculture, stock and domestic water supplies. The proximity of gas extraction to aquifers used for irrigation or domestic water supply is common to many CSG production sites globally. To address these concerns there has been increased research within the region to improve our understanding of aquifer connectivity and the regional water balance. To solve the uncertainties about the impact of CSG exploitation on the groundwater of the adjacent aquifers is necessary to have a robust conceptual model to understand the hydrological dynamics and hydrochemical processes. Most cases, spatial and temporal variability of groundwater chemistry is the result of mixing processes between different water sources. Understanding the mixing processes which take place between several groundwater inputs or groundwater with other water bodies is crucial for groundwater management. Mixing calculations have been successfully applied in many hydrogeological setting to improve the conceptual model and understanding the origins of groundwater compositions. The main aims of this work are to improve the knowledge of the hydrogeologic system in the Condamine alluvium and to investigate the possible impacts of CSG exploration and production to the Condamine Alluvium. To attain these objectives, this study applies a methodology based on multivariate statistical methods for computing the mixing ratios of different water sources (end-members) in several observation points to evaluate the potential impacts. This included the identification and chemical characterization of the recharge sources (end-members), the evaluation of the mixing proportions for each sample, the quantification of the geochemical processes undergone, and the evaluation of CSG exploitation effects. Mixing ratios are computed using MIX code developed by (Carrera et al., 2004). MIX code is based on the maximum likelihood algorithm to estimate the mixing ratios taking into account the uncertainty of the end-members and mixed samples. Building a robust conceptual model together with the application of multivariate statistical methods will serve as a useful tool for groundwater management. © Author(s) 2018. CC Attribution 4.0 license.
- ItemWhere do the methanogens live? New insights into the origin of methane in the Condamine River alluvial aquifer(National Centre for Groundwater Research And Training, 2017-07-11) Iverach, CP; Beckmann, S; Cendón, DI; Manefield, M; Kelly, BFJThere is considerable debate about the origin of methane (CH4) in aquifers surrounding coal seam and shale gas exploration and production. Numerous processes control the natural occurrence of CH4 in groundwater. To determine the origins of CH4 in an aquifer both the geochemical and microbial community need to be characterised, however this is rarely done. We use geochemical and microbiological data, along with measurements of CH4 isotopic composition (δ13C-CH4), to determine the processes acting upon CH4 in the Condamine River Alluvial Aquifer, a freshwater aquifer that directly overlies coal measures targeted for coal seam gas production in Australia. Groundwater samples for geochemical and microbiological analyses were collected from private irrigation boreholes in the Condamine Catchment. The groundwater was analysed for the major ions, water stable isotopes (δ2H and δ18O), the isotopic composition of dissolved organic carbon (δ13CDOC) and dissolved inorganic carbon (δ13CDIC). Quantitative real-time PCR was used to determine abundances of bacterial and archaeal 16S rRNA gene targets and functional gene targets in the groundwater. Measurements of CH4 concentration and isotopic composition suggest that there is biogenic CH4 in the aquifer, however microbial community analysis indicates that there are no methanogenic archaea in the groundwater. In addition, geochemical data, particularly the isotopes of DIC and, as well as the concentration of SO42-, indicate limited potential for methanogenesis in situ. Microbial community analysis also showed that aerobic oxidation of CH4 is occurring in the alluvial aquifer despite the absence of a microbial pathway to produce the CH4. The combination of microbiological and geochemical indicators suggests that the most likely source of CH4, where it was present in the deeper freshwater aquifer, is the upward migration of CH4 from the underlying coal measures.