Browsing by Author "Habermehl, MA"
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- ItemReply to Comment on “Uranium series dating of Great Artesian Basin travertine deposits: Implications for palaeohydrogeology and palaeoclimate” by Uysal et al. (2019).(Elsevier, 2020-01-01) Priestley, SC; Karlstrom, KE; Love, AJ; Crossey, LJ; Polyak, VJ; Asmerom, Y; Meredith, KT; Crow, R; Keppel, MN; Habermehl, MATonguc Uysal and co-authors (this issue) propose that at least some of the U-series ages reported by Priestley et al. (2018) and Ring et al. (2016) provide minimum ages of movement at the Norwest Fault Zone in central Australia resulting from significant CO2 production due to mantle degassing related to active tectonics. We thank Tonguc Uysal and co-authors for their discussion on the role of tectonics and CO2 degassing in travertine precipitation and note that we had previously published (and agree with) the importance of mantle degassing as a source of CO2 that closely interacts with palaeohydrogeologic and palaeoclimatic forcings in explaining the rate and distribution of travertine deposition in the southwestern Great Artesian Basin (GAB) of central Australia. Based in part on western U.S. analogues (Crossey et al., 2016; Karlstrom et al., 2013a), we proposed and explored a model for these processes and their implications for the GAB in previous publications (Crossey et al., 2013; Karlstrom et al., 2013b) whereas Priestley et al. (2018) focused more specifically on palaeoclimate implications. Crown Copyright © 2019 Published by Elsevier B.V
- ItemSustainability of groundwater under climate change(International Atomic Energy Agency, 2003-05-19) Airey, PL; Henderson-Sellers, A; Bradd, J; Chambers, SD; Hughes, CE; Habermehl, MAOne of the key commitments from the plan of implementation of the World Summit on Sustainable Development Johannesburg 2002 was to 'develop integrated water resources management and water efficiency plans by 2005'. In this paper, a detailed concept will be presented for assessing the sustainability of groundwater in warm arid and semi-arid areas challenged by climate change. The IAEA Global Network of Isotope Precipitation (GNIP) database is fundamental to the development of the concept which will be extended to the evaluation of climate change models. The concept will be evaluated with data from three recharge areas in the Great Artesian Basin, as well as aquifers in Central Australia, in the far north of the country and in Victoria. Experimental work is currently being extended to the Murray-Darling Basin. The role of the GNIP in the evaluation of climate change models is illustrated with data from the Amazon. Groundwater sustainability is achieved through balancing exploitation of the resource with recharge. As groundwater exploitation raises issues of demand management beyond the scope of this paper, the focus will be on recharge. Surface water infiltration is dependent on total rainfall within the intake areas, the seasonal distribution of rainfall, the rainfall intensity and the antecedent landscape conditions. Variation in total rainfall can be predicted without recourse to isotope data. However, effective recharge will only occur if the total monthly rainfall exceeds a threshold value. The above-mentioned concept involves predicting these threshold values from GNIP and groundwater isotope data. The evaluation of the concept with field data, and its incorporation into a predictive tool are the central themes of this paper. Four stages are involved: Stage 1: Correlating isotope depletion and the total monthly rainfall Analysis of the GNIP data from continental stations shows a widespread trend towards increasing stable isotope depletion with increasing monthly average rainfall. Stage 2: Matching stable isotope levels in groundwater with those in rainfall with monthly totals exceeding a threshold value The stable isotope levels in groundwater is generally depleted relative to that in mean average rainfall at recharge. The groundwater levels match those in rainfall provided the monthly intensity reaches a threshold value. This value, which may be expressed as a percentile of all monthly data for the GNIP station, is interpreted as the threshold value for effective recharge. The difference between the stable isotope ratios in groundwater and in the mean rainfall is called the 'groundwater depletion'. Stage 3: Correlating the 'groundwater depletion' with aridity. It will be shown with reference to data from Australian aquifers that the 'groundwater depletion' correlates with a defined 'aridity index'. Stage 4: Development of the predictive tool: The above mentioned correlation is the basis of a tool which may be applied to a) assessing groundwater sustainability, b) predicting soil moisture in the root zone and thus contribute to agricultural sustainability and c) evaluating climate change models. a) Groundwater sustainability: Climate change leads to variations in the 'aridity index' and hence to variations in the threshold intensity for effective recharge (Stage 3 above). Climate changes may be modelled numerically, assessed through correlations with sub-global parameters such as ENSO (El Nino Southern Oscillation) Index or simply postulated as scenarios. Reliable knowledge of predicted changes to effective recharge, would provide decision makers with additional time to adjust the groundwater exploitation rate consistent with the long term sustainability of the resource. b) Sustainability of the agricultural and pastoral industries: Variations in soil productivity depend on a number of factors including moisture levels in the root zone. Predictions of the soil moisture levels will depend on the temporal variation of the effective recharge (above), the water balance and the residence time distribution of the water. The use of isotopes to establish a water balance at a site in the Darling basin has been demonstrated. c) Evaluation of climate models: The use of isotopes to evaluate climate change models has been demonstrated in the Amazon basin. The principles will be extended to arid and semi arid areas using isotopic data in age dated groundwater as a probe for variations in effective recharge and therefore in the aridity index. The concept will be illustrated with data from the Great Artesian Basin and the Mereenie Sandstone aquifer in Central Australia. On-going project work will be focussed on ANSTO's contribution to the Murray-Darling Water Basin Study through the GEWEX (Global Energy and Water Cycle Experiment) Hydrometeorological Panel and the IAEA Coordinated Research Program Isotope Tracing of Hydrological Processes in Large River Basins, 2002-2004. The Organisation is also contributing to the Integrated Climate System Study (ICSYS) initiative of the IAEA/WCRP (World Climate Research Programme). © The authors.
- ItemUranium series dating of Great Artesian Basin travertine deposits: implications for palaeohydrogeology and palaeoclimate(Elsevier, 2018-01-15) Priestley, SC; Karlstrom, KE; Love, AJ; Crossey, LJ; Polyak, VJ; Asmerom, Y; Meredith, KT; Crow, R; Keppel, MN; Habermehl, MATravertine deposits precipitated by groundwater discharging from the Great Artesian Basin (GAB) are widespread in central Australia and have the potential to provide a record of palaeohydrogeology and palaeoclimate. The GAB is one of the largest artesian basins in the world and a relationship between travertine deposits and recharge sites has potential importance regarding the time and position of past climate events, given that the travertines growth forms from precipitation discharge. We sampled numerous travertine sites in the southwest section of the GAB as a first approach to test this relationship. U-series dating of the travertine deposits reveal that spring discharge has likely been episodic for the last several hundred thousand years. Spring travertine deposition occurred episodically around 465 ± 50 ka, 370 ± 20 ka, 335 ± 15 ka, 285–240 ka, 185 ± 10 ka, 160–150 ka, 110–100 ka and during the past 30 ka. The periodicity of travertine ages observed with simultaneous deposition at multiple locations, argues for regional palaeohydrologic controls. Comparison of the travertine deposit ages with climate proxies in Australia shows that elevated travertine deposition rates are synchronous with wet periods in both central and southern Australia. Due to the large size of the GAB and that the recharge zones extend over multiple climatic regions of Australia, the times of travertine deposition are interpreted to represent times of high rainfall regionally. This study shows that the travertine deposits of central Australia provide a datable archive of past climate and hydrogeology of importance for understanding the groundwater evolution of the Great Artesian Basin, and that further more comprehensive studies are warranted. © 2018 Elsevier B.V.