Authors / CoAuthors
Gibson, D.L. | Magee, J.W. | Tan, K.P. | Lawrie, K.C. | Clarke, J.D.A. | Brodie, R.S. | Abraham, J.
Abstract
A new integrated, multi-scale geophysical and hydrogeological approach has been used to map shallow (<100m) aquitards in alluvial sediments beneath the Darling River floodplain. The 3D mapping approach uses a regional-scale airborne electromagnetics survey over an area of 7,500km2, integrated with targeted ground electrical surveys and borehole lithological, geophysical (induction, gamma and NMR), hydrogeological and hydrogeochemical data obtained from a 100 borehole (7.5km) sonic drilling program. This multi-scale mapping approach has confirmed the near-ubiquitous presence of a relatively thin (5-10m) Blanchetown Clay overlying Pliocene fluvial sediments containing the principal aquifer of interest (Calivil Formation). The aquitard properties of the Blanchetown Clay are demonstrated by hydrograph responses in overlying and underlying aquifers, by wetting profiles observed in drillcore, moisture data obtained from cores, NMR and gamma logging, laboratory permeameter measurements on cores, and hydrogeochemical data. This integrated mapping approach has revealed variations in aquitard extent and thickness, with a complex sub-surface distribution. Variations in the elevation of the top of the Blanchetown Clay (20-80m AHD ) are attributed partly to neotectonics. The study has also revealed that the aquitard forms a major barrier to recharge and discharge. Where absent (through erosion by the Darling River system, non-deposition, or facies change to fluvial sand), local recharge has resulted in previously unrecognised resources of fresh to slightly brackish water in the underlying semi-confined aquifer. Where present, it could form an effective cap for managed aquifer recharge schemes. More broadly, this study highlights the importance of understanding detailed floodplain sedimentology to alluvial groundwater management.
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nonGeographicDataset
eCat Id
73639
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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- GA PublicationAbstract
- ( Theme )
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- hydrogeology
- ( Theme )
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- groundwater
- ( Theme )
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- marine
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2012-01-01T00:00:00
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[-33.159278, -31.814781, 141.958071, 143.284724]
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