Hydrogeological investigations in two pediplain basins at Lanyon, in the southern Tuggeranong Valley of the ACT, have identified areas which require remedial drainage for urban development. The rocks of the central Lanyon area consist of faulted Silurian dectic to rhyolitic ash-flow tuffs and interbedded sediments. Significant storage and transmission of groundwater occurs in well developed sets of open tensile fractures which formed in response to at least two reversals in regional principal stress directions during epeirogenic uplift and erosional unloading. Hydrogeological parameters measured in the field and laboratory included infiltration capacities, effective proosities, and hydraulic conductivities. From these data a predictive model for drain spacings is developed for all hydrogeological populations and for any given rainfall event. Constraints on locations of drains are also identified. It is recommended that a sufficient number of bores and piezometers be preserved after urban development to adequately assess changes to the groundwater regime.

Legacy product - no abstract available

Geomorphic landscape features and associated surface materials are fundamental to groundwater recharge processes as they form the first layer through which surface water passes before it becomes groundwater. Different surface materials exhibit different water-holding capacity and hence permeability characteristics. In the Broken Hill Managed Aquifer Recharge project, surface-materials mapping in conjunction with geomorphic mapping, has assisted hydrogeological investigations, including recharge predictions, salinity hazard and the identification of potential infiltration basins. Prior to landform identification, LiDAR DEM data was levelled using trend surfaces to eliminate regional slope (~20m). As a consequence of this, an ArcGIS interactive contour tool could be used to identify specific breaks in elevation associated with landform features. Multivariate image analysis of elevation, high resolution SPOT and Landsat-derived wetness further enhanced the contrast between geomorphic elements to confirm mapping boundaries. While specific landforms can be characterised by particular surface materials, these sediments can vary within a single geomorphic feature. Consequently, SPOT multispectral satellite imagery was used to identify surface materials using principal component analysis and unsupervised classification. This approach generated 20 classes; each assigned a preliminary cover/landform attribute using SPOT imagery. Field data (surface and borehole sample, and observations at shallow pits) were used to refine the classification approach. Interactive mapping using a de-trended DEM provided a rapid, effective and accurate alternative to time consuming manual landform digitisation. The combination of these two new products - surface-materials and geomorphic maps - has assisted in the identification of potential recharge sites and naturally occurring infiltration sites.

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.

This progress report from South Australian Department of Mines and Energy, Water Resources Commission of New South Wales, Geological Survey of New South Wales, Rural Water Commission of Victoria, Department of Industry, technology and Resources Victoria, and Bureau of Mineral Resources. This project is a long-term study which is being under taken jointly by the bodies listed above. It is coordinated by a Steering Committee comprising members of those organisations. The primary aim of the Project is to improve the understanding of the groundwater regime of the Murray Darling basin by examining it as a single entity, unencumbered by State boundaries. Since a knowledge of the geology of an area is basic to the understanding of groundwater occurrence, a geological study of the basin is an essential part of the Project and, as a consequence, it will also be possible to make an assessment of other mineral resources.

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.

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.

Legacy product - no abstract available

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.

Integrating surface water and groundwater sampling with pore fluid analysis of cored sediments, combined with fuzzy-k means (FCM) cluster analysis, provides a novel, relatively simple but powerful tool to interpret groundwater processes. This methodology has been applied to a study of shallow (<120m) alluvial aquifers in the Darling River floodplain, Pore fluids were extracted from sediments from 100 sonic-cored bores, and together with surface and groundwater samples, provided a hydrochemical dataset with over 1600 samples and 25 analytes. The FCM cluster analysis used analytes that were present in at least 60% of samples and resulted in samples being classified into eight classes (or hydrochemical facies). Pore fluids and groundwaters with the greatest affinity to the surface water samples were easily identified. In this way, sites with significant active recharge, principally by river leakage, were mapped. Downhole plots of the pore fluid FCM classes provided additional insights into groundwater processes. Comparing the FCM classification of pore fluids within the target (semi)confined aquifer with those from the overlying clay aquitard and shallow aquifer allowed the assessment of vertical inter-aquifer leakage. The FCM cluster analysis also assigns indices to each sample as indicators of how well it relates to each of the eight classes. A simple recharge index was calculated from these FCM indices. This novel approach has provided invaluable new insights into groundwater processes and has assisted greatly with assessing groundwater resources and managed aquifer recharge options.