Many 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.
River 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. ; This research was funded by the Cotton Research and Development Corporation, Australia, Grant Number UNSW1401. The authors would like to thank Lucienne Martel for her assistance with sample collection. We would also like to thank all cotton growers who provided access to their irrigation water supply wells and the staff at the Queensland Department of Natural Resources and Mines (Toowoomba, Office) who facilitated at short notice access to the government groundwater monitoring wells. Dr. Matthias Raiber (CSIRO) is also acknowledged for conversations and assistance in the field during sampling. Chris Dimovski, Barbora Gallagher, Robert Chisari, Henri Wong, Brett Rowling and Vlad Levchenko from ANSTO are also acknowledged for their constant logistic and analytical support. Laura Scheiber and Enric Vázquez-Suñé would like to thanks Spanish Ministry of Science and Innovation (Project CEX2018-000794-S). The authors also thank Lisa Williams for editing and proofreading the manuscript. ; Peer reviewed
This is the final version of the article. Available from the publisher via the DOI in this record. ; The Surface Ocean CO2 Atlas (SOCAT) is a synthesis of quality-controlled fCO2 (fugacity of carbon dioxide) values for the global surface oceans and coastal seas with regular updates. Version 3 of SOCAT has 14.7 million fCO2 values from 3646 data sets covering the years 1957 to 2014. This latest version has an additional 4.6 million fCO2 values relative to version 2 and extends the record from 2011 to 2014. Version 3 also significantly increases the data availability for 2005 to 2013. SOCAT has an average of approximately 1.2 million surface water fCO2 values per year for the years 2006 to 2012. Quality and documentation of the data has improved. A new feature is the data set quality control (QC) flag of E for data from alternative sensors and platforms. The accuracy of surface water fCO2 has been defined for all data set QC flags. Automated range checking has been carried out for all data sets during their upload into SOCAT. The upgrade of the interactive Data Set Viewer (previously known as the Cruise Data Viewer) allows better interrogation of the SOCAT data collection and rapid creation of high-quality figures for scientific presentations. Automated data upload has been launched for version 4 and will enable more frequent SOCAT releases in the future. Highprofile scientific applications of SOCAT include quantification of the ocean sink for atmospheric carbon dioxide and its long-term variation, detection of ocean acidification, as well as evaluation of coupled-climate and ocean-only biogeochemical models. Users of SOCAT data products are urged to acknowledge the contribution of data providers, as stated in the SOCAT Fair Data Use Statement. This ESSD (Earth System Science Data) "living data" publication documents the methods and data sets used for the assembly of this new version of the SOCAT data collection and compares these with those used for earlier versions of the data collection (Pfeil et al., 2013; Sabine et al., 2013; Bakker et al., 2014). Individual data set files, included in the synthesis product, can be downloaded here: doi:10.1594/PANGAEA.849770. The gridded products are available here: doi:10.3334/CDIAC/OTG.SOCAT-V3-GRID. ; Research vessel Tiglax in Columbia Bay, Alaska, is shown on the website for SOCAT version 3. The Columbia Glacier can be seen at the head of the bay, as well as calved ice from the glacier. The photo was taken by Wiley Evans. Pete Brown (National Oceanography Centre Southampton, UK) designed the SOCAT logo. IOCCP (via a US National Science Foundation grant (OCE-124 3377) to the Scientific Committee on Oceanic Research), IOC-UNESCO (International Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization), SOLAS and IMBER provided travel and meeting support. Funding was received from the University of East Anglia (UK), the Bjerknes Centre for Climate Research (Norway), the Geophysical Institute at the University of Bergen (Norway) and the University of Washington (US). The US National Oceanic and Atmospheric Administration (NOAA) made important financial contributions via the Climate Observation Division of the Climate Program Office, the NOAA Ocean Acidification Program, the NOAA Pacific Marine Environmental Laboratory (PMEL), the NOAA Atlantic Oceanographic and Meteorological Laboratory (AOML) and the NOAA Earth System Research Laboratory. Funding was also received from Oak Ridge National Laboratory (US), PANGAEA® Data Publisher for Earth and Environmental Science (Germany), the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research (Germany), the Antarctic Climate and Ecosystems Cooperative Research Centre (Australia), the National Institute for Environmental Studies (Japan) and Uni Research (Norway). Research projects making SOCAT possible included the European Union projects CarboChange (FP7 264879), GEOCARBON (FP7 283080) and AtlantOS (633211), the UK Ocean Acidification Research Programme (NE/H017046/1; funded by the Natural Environment Research Council (NERC) and the Departments for Energy and Climate Change and for Environment, Food and Rural Affairs (Defra)) and the UK Shelf Sea Biogeochemistry Blue Carbon project (NE/K00168X/1; funded by NERC and Defra). Numerous government and funding agencies financially supported SOCAT, notably the Australian International Marine Observing System, the U.S. Geological Survey, the National Aeronautics and Space Administration (NASA) (US), the European Space Agency, the German Federal Ministry of Education and Research (BMBF projects 01LK1224J, 01LK1101C, 01LK1101E, ICOS-D), the Japanese Ministry of the Environment, the Royal Society of New Zealand via the New Zealand–Germany Science and Technology Programme, the Norwegian Research Council (SNACS, 229752), the Swedish Research Council (project 2004-4034) and the Swedish Research Council for Environment, Agricultural Sciences and Spatial Planning (Formas, project 2004- 797). This is PMEL contribution number 4441. Finally, we thank the two anonymous reviewers for their thoughtful, constructive and insightful reviews
