Groundwater resources

2016

Groundwater systems are important in providing water resources for much of the country, and are subject to the pressures of climate (McFarlane et al. 2012), development and growth. Groundwater is also an important and often overlooked component of aquatic ecosystems, both by itself and in conjunction with surface water.

Groundwater and surface-water interconnections have myriad hydrological and ecological effects, and disconnection of groundwater from surface water has potential implications for ecological function and resilience. For example, an investigation of the disproportionately high reductions in streamflow arising from reduced rainfall in Western Australia found that, when groundwater was connected, it played a key role in streamflow generation (Kinal & Stoneman 2012). Groundwater was an effect magnifier; the contribution of connected groundwater to streamflow generation was mostly indirect and magnified other streamflow-generating processes, such as surface run-off and throughflow. As connectivity decreased, this magnifying effect declined.

Even as late as 2012, saturated groundwater ecosystems were considered one of the ecological research frontiers (Larned 2012), with many unexplored processes and issues. Research issues included:

  • field and access logistics
  • ecosystem boundaries and other spatial information
  • habitat, taxonomic and biogeographic knowledge.

This new assessment summary area is based largely on the national integrated information sources available from the Bureau of Meteorology, aided by state-level analysis and reporting. Supporting information came from investigations associated with the Bioregional Assessment Programme that aim to improve understanding of the potential impacts of coal-seam gas and large coal mining developments on water resources and water-related assets.

Available data

Nationally collated groundwater data were not available for consideration and inclusion in SoE 2011, although at that time significant investments were being made in the collation and assessment of groundwater data. These were driven by both the growing interest in coal-seam gas exploration and production, and the Bureau of Meteorology’s commitment to extending the national water information focus under the ground.

Spatial and informational heterogeneity is a challenge in assessing groundwater observations across Australia. Each state and territory uses localised terminology to describe hydrogeological units (e.g. sediments and rocks with similar hydraulic characteristics), causing problems for cross-jurisdictional regions such as the Great Artesian Basin and the Lake Eyre Basin bioregions. Since 2011, the Bureau of Meteorology has led development of a National Aquifer Framework, used for consistent naming and grouping of hydrogeological units across Australia.

The National Aquifer Framework is used to standardise terminology in the Bureau’s National Groundwater Information System (NGIS)—Australia’s national groundwater information system. The NGIS is a specialist spatial database containing a broad range of groundwater information contributed by states and territories. It contains more than 850,000 bore locations across Australia, with associated lithology logs, bore construction logs and hydrostratigraphy logs. For some areas, 2D and 3D aquifer geometries are also available.

The NGIS forms a large component of a national suite of groundwater information products available from the Bureau; the others are Australian Groundwater Insight, Australian Groundwater Explorer and the Atlas of Groundwater Dependent Ecosystems. The Insight tool provides broadscale, nationally consistent information on groundwater, including hydrogeology, entitlements, management plans and zones, and levels and trends. The Explorer supports in-depth examination of bore locations, bore logs, groundwater levels and landscape characteristics, including visualisation, analysis tools and data download. Finally, the Atlas shows ecological and hydrogeological information on known groundwater-dependent ecosystems, and ecosystems that potentially use groundwater.

Additional resources exploring the state and trend of groundwater resources are available from some states and territories, often tied to local resource management planning and monitoring. The South Australian Government, for example, has implemented a robust and consistent method to report on State Natural Resource Management Plan 2012 targets, using a report card approach. The report cards provide statewide information on the condition of natural resources and their management. The information is also presented at the scale of natural resource management (NRM) regions. In total, 56 report cards summarise statewide information, and 242 are regional snapshots of the same information. For groundwater assessment, the report cards provide summary assessments that focus on groundwater extraction, annual rainfall, current salinity and changes in groundwater level for the past 12 months. The report cards include traffic-light indicators of aquifer condition at the scale of groundwater management units.

Recent additions to the CSIRO-led national series of water resource and yield assessments have used a range of approaches to consider groundwater. In the Flinders (Petheram et al. 2013a) and Gilbert (Petheram et al. 2013b) assessments, for example, groundwater was not assessed as a resource. Instead, the assessments focused on the potential for groundwater processes and, hence, associated ecological processes, to change under irrigation development. Elsewhere, in the Pilbara assessment (McFarlane 2015), significant attention was paid to groundwater-dependent ecosystems and their ecological, cultural, social and tourism values.

A major recent initiative to improve groundwater information and understanding in selected areas is the Australian Government’s Bioregional Assessment Programme. The bioregional assessments focus on areas across Queensland, New South Wales, Victoria and South Australia, specifically the Lake Eyre, Gippsland, Sydney and Northern Sydney basins, and the Clarence–Moreton and Northern Inland Catchments bioregions. The assessments provide a risk analysis that identifies areas where potential impacts are likely, or unlikely, to occur. They consider potential impacts, particularly focusing on regional-scale and cumulative impacts, of coal-seam gas, and open-cut and underground coalmining developments. They produce a range of products, including registers of data and water-dependent assets, conceptual models, outputs of numerical and analytical models, and descriptive reports. The assessments have limited reporting on the impacts of recent development, but, in terms of groundwater levels and trends, they do offer the opportunity to clearly set baseline conditions and to identify the types of changes in condition that may occur, thereby informing ongoing monitoring programs.

Surface-water drainage divisions have been used elsewhere in this theme as the assessment components, and Australia’s water resource assessments consider groundwater in this context. Alternative organising approaches for assessment are to consider the principal or other hydrogeology (Figure WAT14), or possibly groundwater management units. However, the challenges of undertaking assessment across multiple hydrogeological layers in one area, along with the desire for spatial consistency across condition assessments, led to selection of the surface drainage divisions as the assessment components. Within these areas, the assessment considers the range of groundwater aquifer layers for which information is available.

Groundwater level status is available in the Groundwater Insight tool for many of the more than 800,000 bores in the national database. Trend information is also available for many of the bores that are monitored on a regular basis, and that meet criteria for both frequency and continuity of monitoring. Levels are categorised by percentile, based on a 20-year water level history; below average conditions are below the 25th percentile, above average conditions are above the 75th percentile, and average conditions are in between.

Regional results

Carpentaria Coast bore information mostly comes from upper aquifers, and from two primary regions: the Roper River in the Northern Territory and the Mitchell–Coleman river system in Queensland. More than 100 bores had timeseries data, with some 70 having sufficient data to support a 5-year trend analysis. Of these, around 40 showed a rising trend, 20 were stable, and the remainder showed a declining trend. Water level status was mostly average, with an equal minor mix of below average and above average levels.

Groundwater data for the Lake Eyre Basin come mostly from the Diamantina–Georgina rivers system, with a small number of sites in the Cooper Creek – Bulloo system to the east of the basin. Reasonable coverage of upper, middle and lower aquifers is available. Sixty sites supported decile analyses of levels, with just over half having below average values and one-third being average. Of the 48 sites with sufficient data for timeseries trends, 27 were declining, and the remainder were equally distributed between stable and rising trends. This counters some of the information available from the mid-term review for stage 3 of the Great Artesian Basin Sustainability Initiative (Sinclair Knight Merz 2013), which reported anecdotal evidence of increasing bore pressure and increasing flow from bore springs. Similarly, a recent water resource assessment for the Great Artesian Basin (Smerdon et al. 2012) indicated that, when considering the 20 years up until 2010, there was clear evidence of recovery of groundwater levels arising from bore-capping and water-piping activities.

More than half of the bore timeseries available from the national information system are for bores in the Murray–Darling Basin, with bores in all 28 of the Basin’s river regions. More than 7000 of the 10,400 sites are for upper aquifers, and the remainder are evenly split between middle and lower aquifers. More than 5000 bores have sufficient data to support decile analyses of water level, with most showing average levels, and the remainder fairly evenly distributed between below average (1202 bores) and above average (1231 bores). Groundwater trends were mostly (3429 out of 5518) rising, with slightly more than 1500 bores stable and nearly 600 declining.

The North East Coast division is well represented, with groundwater data for most areas south of Cairns. Data are available for nearly 5000 sites, with 3500 of these reporting on the upper aquifers and 3600 reporting on water level status. Of the 5000 sites, 2000 had above average water levels, and most of the rest were in the average range. Clusters of below average values are evident near Atherton and west of Toowoomba, and clusters of above average levels occur near Ayr, near Bowen, near Mackay, inland of Bundaberg, west of Toowoomba and at North Stradbroke Island. Groundwater trends are largely rising (50 per cent) and stable (37 per cent), with clusters of rising trends around Toowoomba and inland of Bundaberg.

No groundwater observations are available in the national database for the North Western Plateau. Only a small set of bore data is available for the Pilbara–Gascoyne division, all but 3 of which are in the Greenough River region, to the south. Most bores have average to above average levels, with trends mostly stable.

Nearly 1000 bores have data available across the South Australian Gulf division, the bulk of which are located towards the coast, south of the Lake Torrens – Mambray Coast river region. Nearly 750 bores have sufficient data to support decile analysis, with around 43 per cent of bores above average and 38 per cent in the average range. Trends are available for 800 bores, and are mostly rising (322 bores) or stable (349 bores). A minority are declining.

Although 300 bores are recorded in the national database for the South East Coast (New South Wales) division, fewer than 25 have data suitable for analysis; these are dominated by average groundwater level status and stable trends.

The South East Coast (Victoria) division has been the focus of considerable groundwater investigation, being a trial area for development of a standardised groundwater information model and database (Sinclair Knight Merz 2009). More recently, it has been an area for investigation of a multi-annual timeseries analysis approach to assess the effects of pumping and climate drivers on groundwater levels (Shapoori et al. 2015). Data from more than 1500 bores are available, mostly for the upper aquifers, spread from the Mitchell–Thomson river region in the east to the Millicent Coast at the Victoria – South Australia border. Average range groundwater levels exist for 46 per cent of bores, and the remainder are evenly distributed between above average and below average levels. Trends are reported for 1259 bores, with the majority being stable.

Bores within the South West Coast division are located predominantly in the coastal and near-coastal regions, mostly between Busselton and Joondalup–Yanchep. Levels are in the average (54 per cent) or below average ranges (38 per cent), with trends mostly being stable or declining. Very few bores show a rising trend.

There are 165 bores reported in the South Western Plateau division, all of which are in the Gairdner River region, and most of which are east of Penong, thereby limiting the relevance of the bore information for the whole division. Of the 95 bores supporting decile analysis of levels, nearly two-thirds have groundwater levels in the average range. Trends are reported for 130 sites, with most being stable during the past 5 years.

The Tanami–Timor Sea Coast division has data available for 263 bores, most of which are in the Adelaide, Daly, Finniss and Victoria River – Wiso river regions. Data are available for a good range of lower, middle and upper aquifers, with a significant majority of bores showing levels in the average range. Trends are less evenly distributed, with 53 per cent of bores having a rising trend, 27 per cent stable and 40 per cent declining. A small cluster of rising trends is evident west of Katherine.

Six bores from Tasmania have timeseries data available in the national database, although around 2000 bores are included in the NGIS. Data in the national database are currently insufficient to support reporting of either levels or trends, although work to increase available data is progressing.

Argent RM (2016). Inland water: Groundwater resources. In: Australia state of the environment 2016, Australian Government Department of the Environment and Energy, Canberra, https://soe.environment.gov.au/theme/inland-water/topic/2016/groundwater-resources, DOI 10.4226/94/58b656cfc28d1