A summary report of the work programs, key findings and recommendations from the Palaeovalley Groundwater Project 2008-2012. Produced as the final deliverable product by Geoscience Australia for submission to the National Water Commission in June 2012. To be published by NWC as a Waterlines (on-line) report.

This project is a long-term study which is being undertaken jointly by South Australian, Victorian and New South Wales geological surveys and water authorities and by the Commonwealth Bureau of Mineral Resources, Geology and Geophysics. It is coordinated by a Steering Committee comprising members of those organisations. The Murray Basin is a geological structure with an areal extent of some 300 000 km2. In each of the three States, the basin sediments contain very large groundwater reserves. Where the groundwater has a low salinity it is increasingly being used for irrigation and town water supply purposes. In much of the basin, the water is suitable only for stock use and is extensively used for this purpose. In other parts of the basin, the groundwater is too saline for any use. There is a complex interaction between groundwater and surface water which may be beneficial, as in recharge areas in some parts of the basin, or harmful as in areas of saline groundwater discharge to rivers. In recent year, the states involved have stepped up the rate of assessment of the groundwater regime in the basin.

Legacy product - no abstract available

Sonic drilling is a relatively new technology that has been used successfully to obtain relatively uncontaminated and undisturbed continuous core samples with excellent recovery rates to depths of 206m in fluvio-lacustrine sediments of the Darling River floodplain in western NSW. However, there are limitations with the method. Sands, in particular, are disturbed when they are vibrated out of the core barrel into the flexible plastic sampling tube. There can be changes to moisture content, pore fluid chemistry and sediment mineralogy on exposure to the atmosphere, even when the samples are processed and analysed soon after collection. The option exists during drilling to encapsulate the core in rigid polycarbonate lexan tubes. Although this increases costs and reduces drilling rates, atmospheric exposure of the core during drilling is reduced to the ends of the lexan tubes before being capped. In addition, the tubes can be purged with an inert gas such as argon. Lexan coring is best carried out below the watertable as the heat from drilling dry clays can cause the polycarbonate to melt. In this study, lexan-encapsulated core samples were obtained for analysis of pore fluids (salinity, major ions, trace metals, stable isotopes) and mineral phases (XRD, XRF). The major advantage was the recovery of encapsulated and intact sediment intervals for determining hydraulic conductivity by centrifuge or falling head permeameter methods. By painting some tubes black, sand samples were also successfully obtained for optically stimulated luminescence (OSL) dating. Alternatively, opaque black lexan can be made to order by the supplier.

Submission to the Parliamentary Joint Committee on the Australian Capital Territory concerning the inquiry into long-term collection and disposal techniques for Canberra city waste. In Canberra, solid waste is disposed of in open dumps and sanitary landfill sites. A major environmental problem resulting from such practice is the pollution of groundwater by leachate, and the monitoring of groundwater pollution is an essential part of landfill management that must be continued long after a site is closed. The selection of landfill sites depends on the physical constraints of geology and hydrogeology, but planners do not always sufficiently consider the physical constraints in the selection of landfill sites. The success of a landfill site depends mainly on site selection,and must be supported by good site management techniques and groundwater-pollution monitoring procedures. In many communities, public authorities maintain good land-fill practice by setting high standards for landfill operators, and by controlling the site through regulations and the supervision of monitoring procedures.

In this study, 3D mapping using airborne electromagnetics (AEM) was used to site a monitoring bore network in the Darling River floodplain corridor. Pressure loggers were installed in over 40 bores to monitor groundwater levels primarily in the shallow unconfined Coonambidgal Formation aquifer, deeper (semi)confined Calivil Formation and confined Renmark Group aquifers. In 2010-11, the network provided the opportunity to monitor the groundwater response to flooding of the Darling River and the replenishment of the Menindee Lakes storages, following a period of prolonged drought. In this event, the Darling River at Menindee (Weir 32) rose from 1.59m in October 2010 and peaked at 7.16m in March 2011. A synchronous rise in groundwater levels varying between 0.5-3.4m was observed in the shallow unconfined aquifer near the river. Shallow groundwater levels also declined following the flood peak. Near-river groundwater levels in the Calivil aquifer rose between 0.2-1.3m and also by 4.0 m at a site near Lake Menindee. The latter confirms lake leakage into the aquifer at this particular site, as previously inferred by the AEM data. There was also a pressure response of 0.1-0.9m evident in certain Renmark aquifer bores near the river. The monitoring confirms the importance of episodic flood events to the recharge of the alluvial aquifers, as supported by groundwater chemistry and stable isotope data. Although some of the confined aquifer response may relate to transient hydraulic loading associated with the flood, the inference is that in places there is a degree of hydraulic connectivity between the aquifers.

In recent years there has been a significant increase in the level of interest in Australia in hydrogeological maps. However, only a limited number of such maps have appeared as yet and there are currently no agreed guidelines for legends. It was for this reason that the Groundwater Committee of the Australian Water Resources Council established a Working Group to develop guidelines, bearing in mind recent developments in computer-assisted cartography. The authors of this report were members of that Working Group. A definitive set of guidelines has yet to be accepted by the Groundwater Committee. This report is produced as a contribution to the debate on hydrogeological maps and the depiction of data on such maps.

The work presented is the outcome of a pilot program of 2 1/2 month's duration involving the preparation by Australian Groundwater Consultants (AGC) of a hydrogeological map of the Ballarat 1: 250 000 scale sheet, with accompanying explanatory notes. The pilot program was initiated by Bureau of Mineral Resources through funding provided by the Commonwealth Department of Resources and Energy,and was based on recommendations contained in a report to theDepartment by AGC on the National Groundwater Data Base Inventory 5 Year Forward Program. The pilot program report to BMR by AGC had three parts: volume 1 described the approach and methodology, the second part (volume 2) consisted of a copy of the Victorian Department of Industry, Technology and Resources (DITR) database used to compile the map, and the third part comprised the map and explanatory notes. In the present record the approach and methodology form part 1, and the explanatory notes and map part 2; only representative examples of the database files are included in part 1.

Traditional aquifer tests are an expensive and time-consuming method for obtaining hydraulic information. Furthermore, in many environments, it is becoming increasingly difficult to obtain environmental clearances to dispose produced waters. In this study, the Nuclear Magnetic Resonance (NMR) method was evaluated to provide data on hydraulic conductivities (K) and transmissivities (T) of sediments within the Darling River Floodplain, Australia. NMR data were acquired every 0.5 m using a slim-hole logging system in 26 sonic cored wells to a depth of ~70 m. KNMR can be estimated from the NMR measurements using the Schlumberger-Doll Research Equation: KNMR = C x ?2 x T2ML2, where is the NMR effective porosity, T2ML is the logarithmic mean of the T2 distributions, and C is a formation factor related to tortuosity. Prior to the calculation of the KNMR, the NMR data were classified into five hydraulic classes ranging from clay to gravely-coarse sand using the core, geophysical, mineralogical, and hyperspectral logs. In selected zones aquifer tests were conducted to provide constraints on the K and T of the formations. Least-squares inversion was used to solve for the optimum C values for each of the hydraulic classes versus the aquifer test obtained T. Comparisons between laboratory permeameter measurements and KNMR indicated correspondence within two orders of magnitude. The borehole NMR method provides a rapid way of estimating the near continuous variations in K through a sedimentary sequence, while also providing useful estimates of K at a scale not achievable using traditional aquifer testing methods.

Seawater intrusion (SWI) is a problem globally due to changes in catchment water balances and rising sea levels. The northern coastline of Australia is an area of incipient SWI hazard; however, there is limited understanding of the characteristics of SWI. This study undertook a regional TEMPEST AEM survey of the Darwin coastal plains over the Koolpinyah Dolostone (KD) aquifer, to inform understanding of SWI in this important urban and peri-urban water source. Calibration and validation of AEM data involved sonic and rotary mud drilling, borehole geophysical and geological logging, and laboratory analysis of lithologies, pore fluids and groundwater samples. The AEM data provide greater spatial detail of critical elements of the hydrostratigraphy, and map a complex SWI interface in 3D. A potential SWI hazard to the main producing aquifer has been identified, with SWI ingress through preferential flow paths mapped along structural corridors. There is also extensive leakage of saline groundwater beneath the tidal Adelaide and Mary River floodplains. The existing regional hydrogeological model requires major revision to incorporate the significant weathered zones and salt stores, more restricted extent of dolostone in the aquifer,, and preferential recharge zones and groundwater flow paths to the KD aquifer identified through this study. Assessment of SWI risk to the groundwater resource requires additional hydrodynamic data targeted using the AEM data, and incorporation of results within a predictive groundwater model. The study demonstrates the value of regional, AEM surveys in understanding SWI proceses in karstic aquifers, particularly in data-poor, inaccessible or environmentally sensitive areas.