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  • The map shows salt lake regions favourable for boron deposits. For a more detailed description of the selection method see Jaireth et al. (2013).

  • An inventory of saline water disposal basins, Murray Basin : volume 3 additional basins in South Australia, Victoria and New South Wales 1998.

  • The Ord Valley Airborne Electromagnetics (AEM) Interpretation Project was undertaken to provide information in relation to groundwater salinity management in the Ord River Irrigation Area (ORIA), and to assess the salinity hazard in areas of potential irrigation expansion. Salinity hazard maps were produced using an informed GIS-based approach. The salinity hazard maps combined AEM-derived maps of the shallow alluvial sediments, salt stored in the unsaturated zone and maps of groundwater salinity, with drilling data and maps of depth to the watertable. Hydrographic analysis showed that under current climate conditions, water tables were rising, and it was therefore assumed for GIS modeling purposes that water levels would continue to rise after land clearing and the onset of irrigation. It was also assumed that if shallow watertables developed at some time in the future, that salt accumulation through capillary rise (if within 2m of the surface) may lead to salinisation. This assumption was informed by prior geochemical modeling that inferred that if relatively modest groundwater salinity levels (>750 mg/l TDS) were evapo-concentrated that it may cause a significant salinity hazard to irrigated agriculture. Salinity hazard was assessed as high where there were significant quantities of salt stored in the alluvium in areas of shallow groundwater, and lowest where there is little or no salt stored in alluvium and groundwater tables are deep. The salinity hazard was forecast to be high to very high in the Mantinea Plain, Carlton Hill, Parry's Lagoon and lower Ord Floodplain areas. In the Knox Creek and Keep River Plains, the hazard was low in the north of the area, but moderate to high in the southern-central and areas of the southern Knox Creek Plain. In the priority development area (Weaber Plain), the salinity hazard was estimated to be highly variable.

  • The role of palaeovalley evolution in the manifestation of salinity across the Australian continent P.M. English1 & J.W. Magee1, 2 1Geospatial & Earth Monitoring Division, Geoscience Australia, GPO Box 378, Canberra, ACT 2601 Pauline.English@ga.gov.au 2Department of Earth & Marine Sciences, Australian National University, Canberra, ACT 0200 jwmagee@ems.anu.edu.au Networks of palaeovalleys characterise much of arid, semi-arid and sub-humid Australia, including widespread rangelands and agriculturally important regions. These ancient river valley systems are very commonly the focus of salinity across our landscape, both primary salinity (Quaternary salt lakes and associated saline landforms), and secondary salinity in regions that have been cleared for agricultural development in the last 150 years. The preservation of palaeovalleys is a legacy of the continents tectonic stability, low relief and slow erosion and sedimentation rates. Palaeovalleys drain all the cratonic blocks and extend from Precambrian basement uplands across Palaeozoic, Mesozoic and Cainozoic sedimentary basins. They are now largely filled with Tertiary, or older, sediments and are commonly blanketed with Quaternary lacustrine, alluvial or aeolian sediments, including saline sediments and salts. While the palaeovalleys and their sedimentary infill are relatively ancient (early to mid Tertiary) the groundwater systems they host have evolved during latest Tertiary and Quaternary times. Salt began to concentrate in these palaeovalley networks and surrounding hinterlands from as long as 350 000 years ago, in response to glacial-interglacial cyclicity driven by global climate regimes. More recent salt accumulation in the historic period is the consequence of hydrologic disequilibrium wrought by land clearing which has caused broad-scale mobilisation of ancient salt stores into topographic lower areas and waterways in agricultural regions. Sodium chloride (NaCl) is the dominant salt in the Australian terrestrial environment, in both the arrays of ancient salt lakes and in secondary salinised agricultural regions. This reflects the dominance of marine aerosol source of salts in our rainfall and the longevity of salt accumulation in the near-surface environment. The marine signature is further pronounced in the case of primary salinity occurrences, where calcium sulphate, or gypsum (CaSO4.2H2O), is prevalent across the inland landscape. The ubiquity and solubility of NaCl and its mobility in shallow groundwater systems accounts for the recurrence and concentration of salinity in palaeovalley systems in particular. The persistence of ancient palaeovalley networks and of marine-derived salts in the salinised Australian landscape forms the basis of comparisons with southern Africa, for example, where tectonism and a significantly higher proportion of terrestrially-derived salts predispose contrasting manifestations of salinity. Such comparisons provide some insight and a broad perspective relevant to Australias contemporary salinity issues.

  • Airborne electromagnetic (AEM) systems are increasingly being used for mapping conductivity in areas susceptible to secondary salinity, with particular attention on near-surface predictions (ie those in the top 5 or 10 metres). Since measured AEM response is strongly dependent on the height of both the transmitter loop and receiver coil above conductive material, errors in measurements of terrain clearance translate directly into significant errors in predicted near-surface conductivity. Radar altimetry has been the standard in airborne geophysical systems for measuring terrain clearance. In areas of agricultural activity significant artifacts up to five metres in magnitude can be present. One class of error, related to surface roughness and soil moisture levels in ploughed paddocks and hence termed the ?paddock effect?, results in overestimation of terrain clearance. A second class of error, related to dense vegetation and hence termed the ?canopy effect?, results in underestimation of terrain clearance. A survey example where terrain clearance was measured using both a radar and a laser altimeter illustrates the consequences of the paddock and canopy effects on shallow conductivity predictions. The survey example shows that the combination of the dependence of AEM response on terrain clearance and systematic radar altimeter artefacts spatially coincident with areas of differing land-use may falsely imply that land-use practices are the controlling influence on conductivity variations in the near surface. A laser altimeter is recommended for AEM applications since this device is immune to the paddock effect. Careful processing is still required to minimise canopy effects.

  • In a land management context, conductivity can be related to quantities such as salt store, ground water salinity, clay content, hydraulic permeability, degree of groundwater saturation or more generally to definition of regolith and bedrock units. These relationships open the way for the use of electromagnetic methods to measure subsurface conductivity. From the very early trials, efforts have been made to transform the measurements to conductivity. The real world presents a myriad of difficulties, that translate into errors and artifacts in 2D sections or 3D volumes produced from individual 1D conductivity transformation solutions. Reconciliation of AEM conductivity predictions with other spatial information presents a deceptively difficult challenge. A variety of improvements in the future will lead to a more accurate portrayal of conductivity in 3D.

  • The GILMORE Project (Geoscience In Land Management and Ore System Research for Exploration) is a pilot study designed to assess methodologies and technologies for identifying mineral prospectivity and dryland salinity in areas of complex regolith cover (Lawrie et al., 2000). The project area (100 x 150 km) lies in the eastern part of the Murray-Darling Basin in central-west NSW and straddles the Gilmore Fault Zone, a major NNW-trending crustal structure that separates the Wagga-Omeo and the Junee-Narromine Volcanic Belts in the Lachlan Fold Belt. Included in the project area are tributaries of the Lachlan and the Murrumbidgee Rivers. A critical aspect of this research was to develop databases and a GIS to enable researchers to view and analyse complex datasets and their inter-relationships in both two and three dimensions. The GILMORE Project GIS consists of 11 CDs in 2 volumes. Volume 1 is comprised of 5 CDs and contains airborne electromagnetic (AEM), magnetic and gamma-ray spectrometric geophysical datasets. These are included in point located (line) form as ASCII column format files, and in gridded form as ERMapper format grids. These data have already been released. Volume 2 comprises of 6 CDs containing data in ESRI\222s ArcInfo and ArcView for mat. Each CD has an ArcView Project accessing colour geophysical images (created in ERMapper), ArcInfo polygon, point and line coverages, ArcView shape files, with links to gif images, photos and .dbf files. The GIS will also be released in MapInfo format.

  • This study reports the findings of salt store and salinity hazard mapping for a 20-km wide swath of the Lindsay - Wallpolla reach of the River Murray floodplain in SE Australia. The study integrated remote sensing data, an airborne electromagnetics (AEM) survey (RESOLVE frequency domain system), and lithological and hydrogeochemical data obtained from a field mapping and drilling program. Maps of surface salinity, and surface salinity hazard identified Lindsay and Wallpolla Islands, and the lower Darling Floodplain as areas of high to extreme surface salinity hazard. In the sub-surface, salt stores were found in general to increase away from drainage lines in both the unsaturated and saturated zones. Beneath the Murray River floodplain, salt stores in both unsaturated and saturated zones are high to very high (100 to 300t/ha/m) across most of the floodplain. Sub-surface salinity hazard maps (incorporating mapped salt stores and lithologies, depth to water table and the hydraulic connectivity between the aquifers), identify Lindsay and Wallpolla Islands; the northern floodplain between Lock 8 and Lock 7; and northern bank of Frenchman's Creek as areas of greatest hazard. Overall, the new data and knowledge obtained in this study has filled important knowledge gaps particularly with respect to the distribution of key elements of the hydrostratigraphy and salinity extent across the Murray River and lower Darling floodplain. These data are being used to parameterise groundwater models for salinity risk predictions, to recalculate estimates of evapotranspiration for salt load predictions, address specific salinity management questions, and refine monitoring and management strategies.

  • Airborne electromagnetic (AEM) systems are increasingly being used for mapping conductivity in areas susceptible to secondary salinity, with particular attention on near-surface predictions (ie those in the top 5 or 10 metres). Since measured AEM response is strongly dependent on the height of both the transmitter loop and receiver coil above conductive material, errors in measurements of terrain clearance translate directly into significant errors in predicted near-surface conductivity. Radar altimetry has been the standard in airborne geophysical systems for measuring terrain clearance. In areas of agricultural activity significant artifacts up to five metres in magnitude can be present. One class of error, related to surface roughness and soil moisture levels in ploughed paddocks and hence termed the ?paddock effect?, results in overestimation of terrain clearance. A second class of error, related to dense vegetation and hence termed the ?canopy effect?, results in underestimation of terrain clearance. A survey example where terrain clearance was measured using both a radar and a laser altimeter illustrates the consequences of the paddock and canopy effects on shallow conductivity predictions. The survey example shows that the combination of the dependence of AEM response on terrain clearance and systematic radar altimeter artefacts spatially coincident with areas of differing land-use may falsely imply that land-use practices are the controlling influence on conductivity variations in the near surface. A laser altimeter is recommended for AEM applications since this device is immune to the paddock effect. Careful processing is still required to minimise canopy effects.

  • The map shows salt lake regions favourable for potash deposits. For a more detailed description of selection method see Jaireth et al (2013)