Damon Mcknight
Australia's diverse geography includes arid regions like the Outback and coastal areas, which present unique challenges when it comes to water resource management. One of the largest underground freshwater resources in the world, the Great Artesian Basin, lies beneath parts of Queensland, the Northern Territory, South Australia, and New South Wales. This basin is an important water source, providing the only source of fresh water for much of inland Australia. Groundwater is found in aquifers, which are geological formations able to store and transmit water. Australia has various types of aquifers, including alluvial aquifers formed by river sediments, coastal aquifers formed by wind and water deposits along the coast, and fractured rocks like granite that can store and transmit water. To effectively manage water usage and ensure essential services during droughts, Australia has adopted the use of underground water maps, which provide detailed insights into the distribution, quality, and availability of groundwater across the country.
| Characteristics | Values |
|---|---|
| Largest groundwater basin in Australia | Great Artesian Basin |
| Location of Great Artesian Basin | Underlies 22% of the Australian continent, including Queensland, the southeast corner of the Northern Territory, northeastern South Australia, and northern New South Wales |
| Size of Great Artesian Basin | 1,700,000 square kilometres (660,000 square miles) |
| Amount of groundwater in the Great Artesian Basin | 64,900 cubic kilometres (15,600 cubic miles), or 65 million GL |
| Temperature of water in the Great Artesian Basin | 30 to 100 °C (86 to 212 °F) |
| Water storage in Australia | Geological formations called aquifers, which vary depending on the diverse geology of the country |
| Types of aquifers | Alluvial aquifers, coastal aquifers, fractured rocks, sedimentary basins, palaeovalleys, and karst |
| Importance of groundwater | Critical during droughts when surface water dries up |
| Use of underground water maps | Provides critical information for drought management, helps locate and manage water usage, and guides the construction of water infrastructure |
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What You'll Learn
Locating underground water in Australia's diverse landscapes
Australia's diverse landscapes present unique challenges when it comes to locating and accessing underground water. The country's vast geography encompasses arid regions like the Outback, coastal areas, and varying geological formations, all of which influence the availability and characteristics of groundwater.
One of the most significant sources of underground water in Australia is the Great Artesian Basin (GAB). This basin is one of the largest underground freshwater resources in the world, spanning almost 1.7 million square kilometres, or over one-fifth of the Australian continent. The GAB provides the only source of freshwater for much of inland Australia, including parts of Queensland, the Northern Territory, South Australia, and New South Wales.
The water in the GAB is held in a sandstone layer, formed during the Triassic, Jurassic, and early Cretaceous periods. This sandstone layer is covered by a confining layer of marine sedimentary rock, which helps to trap the water. To access the water, boreholes are drilled down to the sandstone layer, and the pressure of the water often forces it up without the need for pumps.
However, uncontrolled water flow from bores and bore drains has led to issues such as reduced water pressure and volume, threatening groundwater-dependent ecosystems and limiting access to artesian water. Additionally, up to 95% of water can be wasted through evaporation and seepage, even in well-maintained drains. To address these issues, the Australian Government has initiated programs like the Great Artesian Basin Sustainability Initiative and the Improving Great Artesian Basin Drought Resilience program, which aim to coordinate funding and improve management of the basin.
Underground water maps, or groundwater maps, have become an essential tool in Australia's water industry. These high-resolution maps provide detailed insights into the distribution, quality, and availability of groundwater across the country's diverse landscapes. They help water industry professionals manage water resources effectively, ensuring sustainable use and drought resilience. By using these maps, engineers and planners can also determine the most suitable locations for water infrastructure projects, such as pipelines and treatment plants, based on the availability of groundwater.
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Understanding aquifers and their characteristics
Aquifers are formed from a variety of different rock types and sediments, including gravel, sandstone, conglomerates, and fractured limestone. Porous rocks, such as sandstone, can yield hundreds of gallons of water per minute, even when lying thousands of feet below the surface. The porosity and permeability of rocks generally decrease as their depth below the land surface increases, due to the weight of the overlying rocks.
Aquifers can be categorised as confined or unconfined. A confined aquifer has an impermeable barrier above it, which prevents the water level from rising any higher. In contrast, an unconfined aquifer has no such impermeable layer, allowing the water level to rise in response to recharge. Unconfined aquifers are also known as water table or phreatic aquifers, as their upper boundary is the water table. Perched aquifers are a type of groundwater that occurs at a higher elevation than a regionally extensive aquifer, and they are smaller than unconfined aquifers. Confined aquifers are typically deeper than unconfined aquifers.
Aquifers are an important source of water for human use, with groundwater serving a variety of purposes, including irrigation and drinking water supply. However, aquifers can become depleted if water is extracted at a faster rate than it can be replenished through precipitation. This depletion has been exacerbated by expanding agricultural irrigation, which has also led to groundwater contamination due to excessive pesticide and herbicide use.
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The importance of groundwater maps
Groundwater maps are an essential tool for understanding and managing Australia's water resources. They provide a comprehensive overview of the country's groundwater distribution, enabling informed decision-making and sustainable water resource management. Here are several reasons why groundwater maps are of paramount importance:
Understanding Groundwater Distribution
Groundwater maps, such as the National Hydrogeological Inventory developed by Geoscience Australia, offer a detailed understanding of Australia's major groundwater-bearing basins and geological provinces. By mapping these basins, such as the Great Artesian Basin, the largest groundwater basin in Australia, maps provide a visual representation of the location and extent of groundwater resources. This information is crucial for water resource management and planning, helping identify areas with abundant groundwater and those facing scarcity.
Supporting Water Security and Sustainability
With Australia facing water security challenges, particularly in arid and rural regions, groundwater maps are vital for ensuring sustainable water use. By providing data on groundwater levels, recharge rates, and extraction points, maps assist in monitoring and managing groundwater resources. This information guides policies and initiatives to protect and conserve groundwater, ensuring its availability for current and future generations.
Informing Land-Use Planning and Development
Groundwater maps are essential for land-use planning and infrastructure development. They help identify areas suitable for agriculture, urban development, or industrial activities based on the availability and quality of groundwater. Additionally, maps can reveal potential environmental impacts of extracting groundwater in specific regions, helping to minimise ecological risks and preserve groundwater-dependent ecosystems.
Facilitating Groundwater Exploration and Research
Groundwater maps serve as a foundation for further exploration and scientific research. They provide baseline data for hydrogeologists and researchers to study groundwater dynamics, recharge mechanisms, and the interaction between groundwater and surface water. This knowledge is crucial for improving water management practices and developing strategies to address water scarcity.
Enabling Community Engagement and Stakeholder Collaboration
Groundwater maps play a pivotal role in fostering community engagement and collaboration among stakeholders. By visualising the communities and industries that rely on groundwater, maps raise awareness of the significance of groundwater resources and the need for collective stewardship. This understanding encourages cooperation between various levels of government, community organisations, and local communities in managing and conserving groundwater resources.
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The Great Artesian Basin
The water of the Great Artesian Basin is held in a sandstone layer formed during the Triassic, Jurassic, and early Cretaceous periods. During this time, much of inland Australia was below sea level, and the sandstone was covered by a layer of marine sedimentary rock, trapping water in the sandstone aquifer. The eastern edge of the basin was uplifted with the formation of the Great Dividing Range, while the western side was shaped by the Central Eastern Lowlands and the Great Western Plateau. Recharge water enters the rock formations from high ground near the eastern edge and gradually flows towards the south and west.
However, the Great Artesian Basin faces challenges due to water extraction, which exceeds the rate of recharge. There are concerns about depletion and chemical damage, with significant water wastage occurring through evaporation, seepage, and uncontrolled water flow from bores and bore drains. To address these issues, the Australian government has implemented initiatives such as the Great Artesian Basin Sustainability Initiative and the Improving Great Artesian Basin Drought Resilience program, aiming to improve basin management and drought resilience.
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Managing groundwater during droughts
Groundwater is one of a nation's most important natural resources. It is a source of drinking water for the majority of the rural population. Managing groundwater during droughts is critical, and understanding the effects of droughts on aquifers can help shape management decisions.
Droughts have severe impacts on the economy, society, and the environment. They also impact groundwater levels and vice versa. Groundwater levels are dependent on recharge from precipitation, so when a drought occurs, it can impact the water levels below ground. The water level in an aquifer that supplies a well is not constant and can be affected by seasonal variations in rainfall and pumping rates. If a well is pumped faster than the surrounding aquifer is recharged, water levels in the well can be lowered. This can happen during a drought due to the extreme deficit of rain.
Since aquifers can be extensive, usage from one well can influence other wells miles away. Groundwater that supplies wells also feeds streams during low flow, so pumping from a well may cause water levels in streams to be lower.
Research has found that groundwater recovery times exceeded the lag times. Shallow aquifers take about three years, on average, to recover the storage lost during a multiyear drought. For 85% of droughts, groundwater levels spanning multiple aquifer systems recovered within 10 years. However, the return of rainfall does not guarantee that a depleted aquifer will recover to its previous levels.
In Australia, the Great Artesian Basin is an important water resource and must be carefully managed. It is one of the largest underground freshwater resources in the world and provides the only source of fresh water through much of inland Australia. The basin is an important water supply for cattle stations, irrigation, and livestock and domestic purposes. Boreholes are drilled down to access the water, and the pressure often forces it up without pumps. However, uncontrolled water flow from bores and bore drains reduces water pressure and volume, threatening groundwater-dependent ecosystems and limiting access to artesian water.
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Frequently asked questions
Underground water maps, also known as groundwater maps, show the distribution and flow of water beneath the Earth’s surface. These maps provide detailed information about the location and quality of groundwater resources, which can be used to plan and build infrastructure such as pipelines and treatment plants.
The geology of Australia is diverse, therefore the types of aquifers vary. Examples include:
- Alluvial Aquifers: formed of sediments such as gravel, sand, and silt deposited by rivers or other running water.
- Coastal Aquifers: deposits of sand formed along the coast by wind and water.
- Fractured Rocks: fractures and fissures within impermeable rock that can store and transmit water.
- Sedimentary Basins: large areas with thick layers of sedimentary rock such as sandstone or siltstone.
The Great Artesian Basin (GAB) is one of the largest underground freshwater resources in the world and is Australia's largest groundwater basin. It lies beneath parts of Queensland, the Northern Territory, South Australia, and New South Wales. It provides the only source of freshwater for much of inland Australia.
To access water from the Great Artesian Basin, boreholes are drilled down to a suitable rock layer, and the pressure of the water often forces it up without the need for pumps.
The main challenge is that recharge rates are much lower than current extraction rates. Uncontrolled water flow from bores and bore drains reduces water pressure and volume, threatening groundwater-dependent ecosystems and limiting access to artesian water. Many bores are also unregulated or abandoned, resulting in considerable water wastage.
