Using 14C and 3H to delineate a recharge 'window' into the Perth Basin aquifers, North Gnanagara groundwater system, Western Australia

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dc.contributor.authorMeredith, KTen_AU
dc.contributor.authorCendón, DIen_AU
dc.contributor.authorPigois, JPen_AU
dc.contributor.authorHollins, SEen_AU
dc.contributor.authorJacobsen, GEen_AU
dc.date.accessioned2013-04-16T00:36:43Zen_AU
dc.date.available2013-04-16T00:36:43Zen_AU
dc.date.issued2012-01-01en_AU
dc.date.statistics2013-04-17en_AU
dc.description.abstractThe Gnangara Mound and the underlying Perth Basin aquifers are the largest source of groundwater for the southwest of Australia, supplying between 35 and 50% of Perth's potable water (2009–2010). However, declining health of wetlands on the Mound coupled with the reduction in groundwater levels from increased irrigation demands and drier climatic conditions means this resource is experiencing increased pressures. The northern Gnangara is an area where the Yarragadee aquifer occurs at shallow depths (~ 50 m) and is in direct contact with the superficial aquifer, suggesting the possibility of direct recharge into a generally confined aquifer. Environmental isotopes (14C and 3H) and hydrochemical modelling were used to assess the presence of a recharge ‘window’ as well as understand the groundwater residence time within different aquifers. Forty-nine groundwater samples were collected from depths ranging from 11 to 311 m below ground surface. The isotopic variation observed in the superficial aquifer was found to be controlled by the different lithologies present, i.e. quartz-rich Bassendean Sand and carbonate-rich sediments of the Ascot Formation. Rainfall recharge into the Bassendean Sand inherits its dissolved inorganic carbon from the soil CO2. Organic matter throughout the soil profile is degraded by oxidation leading to anoxic/acidic groundwater, which if in contact with the Ascot Formation leads to enhanced dissolution of carbonates. Hydrochemical mass balance modelling showed that carbonate dissolution could contribute 1–2 mmol kg− 1 of carbon to groundwaters recharged through the Ascot Formation. The corrected groundwater residence times of the Yarragadee aquifer in the northern part of the study area ranged from 23 to 35 ka, while waters in the southeastern corner ranged from sub-modern to 2 ka. Groundwater ages increase with distance radiating from the recharge ‘window’. This study delineates a recharge ‘window’ into the commonly presumed confined aquifers of the Perth Basin, highlighting the need for appropriate sustainable management. Crown Copyright © 2011 Published by Elsevier B.V. All rights reserveden_AU
dc.identifier.citationMeredith, K., Cendón, D. I., Pigois, J. P., Hollins, S., Jacobsen, G. (2012). Using 14C and 3H to delineate a recharge ‘window’ into the Perth Basin aquifers, North Gnangara groundwater system, Western Australia. Science of the Total Environment, 414, 456-469. doi:10.1016/j.scitotenv.2011.10.016en_AU
dc.identifier.govdoc4201en_AU
dc.identifier.issn0048-9697en_AU
dc.identifier.journaltitleScience of the Total Environmenten_AU
dc.identifier.pagination456-469en_AU
dc.identifier.urihttp://dx.doi.org/10.1016/j.scitotenv.2011.10.016en_AU
dc.identifier.urihttp://apo.ansto.gov.au/dspace/handle/10238/4554en_AU
dc.identifier.volume414en_AU
dc.language.isoenen_AU
dc.publisherElsevier B. V.en_AU
dc.subjectCarbon 14en_AU
dc.subjectGround wateren_AU
dc.subjectWestern Australiaen_AU
dc.subjectTritiumen_AU
dc.subjectAquifersen_AU
dc.subjectIsotopesen_AU
dc.titleUsing 14C and 3H to delineate a recharge 'window' into the Perth Basin aquifers, North Gnanagara groundwater system, Western Australiaen_AU
dc.typeJournal Articleen_AU
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