This Regulatory Review investigates, analyses and reports on the extent to which the legislation, regulation and policy of the Australian jurisdictions (as at July 2009) adopt the key elements of groundwater quality protection set out in the Guidelines for Groundwater Protection in Australia (ARMCANZ and ANZECC, 1995) (Groundwater Guidelines), an element of the National Water Quality Management Strategy, Australia.

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Surface and groundwater resources in Australia face intensifying pressures from significant population growth in the coastal fringe, and prolonged droughts in the southern half of the continent. Recently, and most significantly, new additional pressures on groundwater systems have emerged through the rapid expansion of new energy sources (coal seam gas, uranium, geothermal and carbon geo-sequestration) and existing mineral resources (including iron ore). These pressures are likely to be exacerbated by projected climate changes. The complexity and conflicts in the nexus between water, new energy, minerals, and food and fibre security require innovative approaches in science, management and policy. This is particularly the case in the context of Australia's inherent vulnerability to climate change and the likely emergence of a carbon economy. Quantification of the hydrological cycle and catchment water balances in Australia is limited by a lack of spatial and temporal data. This results in high uncertainties in model predictions. In surface hydrology and processes, recent advances have been made in attempts to quantify evapotranspiration and soil moisture, however significant uncertainties still exist and most water balance studies rely on 'estimates'. Likewise, while nationally consistent approaches to recharge and discharge mapping have been developed, large-scale mapping programs have yet to be implemented. Significant uncertainty also remains in the quantification of surface-groundwater interactions, particularly over the cycles of drought and flood. Climate predictions also still largely rely upon northern hemisphere-derived GCMs, with large uncertainties in down-scaling within the Australian landscape context.

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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Nauru, in the central Pacific Ocean, is a raised atoll capping a volcanic seamount arising from an ocean floor depth of 4300m. The land area is 22km, and the island rises to 70m above sea level. Drilling has proved dolomitised limestone of upper Miocene or younger age to a depth of 55m below sea level. Gravity and magnetic surveys indicate that the limestone probably overlies volcanic bedrock at a depth of about 500m. Reverse-circulation drilling and geoelectrical probes indicate that there is a discontinuous freshwater layer averaging 5m thick beneath Nauru. This is underlain by a mixing zone of brackish water, 60-70m thick. The exceptional thickness of the mixing zone is ascribed to high permeability of the karstified limestone. The forthcoming cessation of phosphate mining will mean a shortfall in water supply which will probably have to be met by the desalination of brackish water. Groundwater beneath the mined-out area, and the settled coastal terrace, is highly vulnerable to pollution, and waste disposal management needs to be considered in relation to groundwater protection.

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