The Layered Geology of Australia web map service is a seamless national coverage of Australia’s surface and subsurface geology. Geology concealed under younger cover units are mapped by effectively removing the overlying stratigraphy (Liu et al., 2015). This dataset is a layered product and comprises five chronostratigraphic time slices: Cenozoic, Mesozoic, Paleozoic, Neoproterozoic, and Pre-Neoproterozoic. As an example, the Mesozoic time slice (or layer) shows Mesozoic age geology that would be present if all Cenozoic units were removed. The Pre-Neoproterozoic time slice shows what would be visible if all Neoproterozoic, Paleozoic, Mesozoic, and Cenozoic units were removed. The Cenozoic time slice layer for the national dataset was extracted from Raymond et al., 2012. Surface Geology of Australia, 1:1 000 000 scale, 2012 edition. Geoscience Australia, Canberra.

In the southern half of Australia, recent droughts and predictions of a drier future under a number of climate change scenarios have led to the search for innovative strategies to identify more secure water supplies for regional communities and industries, while also delivering environmental benefits to threatened river systems. These issues are of particular concern in the Murray-Darling Basin (the Basin), where the recent Millennium Drought (late 1990's - 2010) adversely affected many communities, industries and the environment. It has long been recognized that one of the areas with the greatest potential to contribute water savings in the Basin is at the Menindee Lakes Storages (MLS), located on the lower section of the Darling River in far western New South Wales. The MLS provide the main (up to 2,050 GL) water supply storage in the lower Murray-Darling River system, and play a significant role in meeting South Australia's water requirements. The shallow nature of the MLS, which are located in a hot, windy, semi-arid environment, results in an average evaporation loss across the MLS of 420 GL per year. Changing the management of the MLS to reduce these evaporative losses and provide enhanced water security for Broken Hill is possible, but Broken Hill's water supply would need to become less reliant on the MLS. To address these issues, in 2008 the Australian Government commissioned studies to reduce evaporation and improve water efficiency at the MLS, secure Broken Hill's water supply, protect the local environment and heritage, and return up to 200 GL to the Basin. As part of a broader suite of scientific and technical investigations, the Broken Hill Managed Aquifer Recharge (BHMAR) project was tasked with assessing the viability of Managed Aquifer Recharge (MAR) and/or groundwater extraction options to provide improved drought security for Broken Hill (Lawrie et al., 2012). An initial scoping study assessed options within a 150 km radius of Broken Hill, while Phase 1 of the BHMAR project narrowed the search to an area of the Darling Floodplain near Menindee. Based on the findings of these scoping studies, the BHMAR project was subsequently tasked with identifying and assessing: - Alternative groundwater-related water supply options for Broken Hill that could provide enhanced drought security for periods up to 3 years (~30 GL), within 50 km (later reduced to a radius of 20km) of existing water and energy infrastructure at Menindee on the River Darling Floodplain; - Groundwater resources and potential MAR opportunities that could provide enhanced drought security for regional communities and industries (e.g. agriculture and mining). To this end, a larger area (~7,500 km2) of the Darling Floodplain has been studied. Data acquisition utilised a phased approach, and was guided by the two main project objectives, and the requirement to address very specific scientific and technical questions embedded with national MAR guidelines. Initially, a data acquisition program was designed to map and assess groundwater resources and MAR opportunities in 4 main aquifers: - Shallow (0-30m) alluvial (unconfined) sand aquifers associated with the Darling River and it's Anabranches (Coonambidgal Formation and Menindee Formations); - Intermediate depth (30-100m) Pliocene Calivil Formation and Loxton-Parilla Sands (semi-confined to confined) aquifers. These were the primary target; - Deeper level (180-250m) Renmark Group Formation (confined) aquifers; - Shallow (<100m) Palaeozoic (Devonian and older) basement aquifers, in buried basement palaeo-topographic highs (sandstone, weathered zone and fractured rock aquifers).

AGSO has tried to make the information in this product as accurate as possible. However, it does not guarantee that the information is totally accurate or complete. Therefore, you should not rely solely on this information when making a commercial decision. Geology of the Tantangara 1:100 000 mapsheet. Dataset not fully attributed. The purpose of the dataset is for incorporation into a Murray-Darling Basin-wide geology dataset.

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Surface-groundwater connectivity in many of Australia's major river systems is poorly understood, often due to a paucity of relevant spatial and temporal data. The Broken Hill Managed Aquifer Recharge (BHMAR) study in the Darling Floodplain involved identification and assessment of potential MAR targets and groundwater resources over a large area (>7,500 km2) of the Darling Floodplain. In addition to the acquisition of new geoscientific datasets (airborne, ground and borehole geophysics), and complementary hydrogeological and hydrochemical studies, a bore monitoring network was established to monitor the groundwater response to river leakage. Pressure loggers were installed in 40 bores to monitor groundwater levels in the shallow unconfined Quaternary aquifers, deeper semi-confined Calivil Formation and confined Renmark Group aquifers. Pressure monitoring of bore responses was complemented by periodic hydrochemical sampling of the groundwater in the monitoring bores and by analysis of temperature data collected from data loggers. 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. 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 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 north of Lake Menindee which confirms lake leakage to the aquifer at this site, as previously inferred from AEM data. A pressure response of 0.1-0.9m was evident in certain Renmark aquifer bores which may relate to both connectivity and transient hydraulic loading associated with the flood. The monitoring confirms the importance of episodic flood events to the recharge of the alluvial aquifers, as supported by groundwater major ion chemistry and stable isotope data. In places, there is a degree of hydraulic connectivity between the aquifers and understanding surface water-groundwater dynamics is essential in assessing water resources in the Darling floodplain system.

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