What is groundwater?
Groundwater is water that is held beneath the ground surface and it can be found just about everywhere.
The capacity or ease to access groundwater, and the quality of that water can vary widely depending on the natural geology. That portion of a groundwater system that can yield productive volumes of groundwater is known as an aquifer.
Water enters a groundwater system through a process called recharge. Recharge can occur by direct rainfall infiltration, overland or flood flows, from rivers and lakes and from irrigation. In the short term, the amount of water that can be taken from a groundwater system depends on how easily water flows through the aquifer. In the longer term it depends on the amount of recharge the aquifer receives.
Groundwater is a highly valuable resource, especially in the dry and highly variable climate of NSW. During the wetter years, surface water is the main supply of water to many parts of rural NSW. During times of drought, groundwater is commonly used as an alternative source for both agricultural and town water uses.
Approximately 11% of all water used in NSW comes from groundwater sources. It is used for drinking water, irrigation, watering stock, and domestic and industrial purposes. For more than 200 towns in NSW, groundwater is the principal source of water supply. An estimated 13% of the groundwater used in NSW goes to domestic and stock purposes. Overall, agriculture is the largest user of groundwater in NSW with the greatest volume being used for irrigation. This does however vary from one area to another.
Gunnedah Basin ~ 1,260 GL
Gloucester Basin ~ 2 GL
Clarence-Moreton Basin ~ 18 GL
For example, groundwater use in the Gunnedah Basin area totals some 1260 gigalitres mostly drawn from the high-yielding alluvial aquifers that exist from the Liverpool Plains to west of Narrabri. The bulk of this water is used for irrigation, with only small percentages used for town water supply and mining and an even smaller volume used for stock and domestic purposes. This pattern is similar in all large inland alluvial aquifers in NSW. Smaller volumes are used in the areas east of the Great Dividing Range. For example in the Clarence-Moreton Basin (18 gigalitres) irrigation is the main use, and in the Gloucester Basin (2 gigalitres) groundwater is mainly used for mining purposes.
The pattern of groundwater use is therefore variable from year to year. The chart below shows the volume of metered groundwater use since 1999/2000 in NSW. Note the large reduction in use during the very wet years from 2010 to 2012.
Managing groundwater impacts
To preserve groundwater resources for the long term it is critical to balance the competing needs of the environment and water users. Water Sharing Plans establish rules for sharing water between the environmental needs of the river or aquifer and water users, and also between different types of water use such as town supply, rural domestic supply, stock watering, industry and irrigation. The groundwater Water Sharing Plans for those groundwater systems closest to the surface are shown in the interactive map at the top of this page.
The NSW Aquifer Interference Policy defines the regime for protecting and managing the impacts on NSW’s water resources from all extractive use other than that for town water supply.
There are three key parts to the policy:
- All water taken must be properly accounted for.
- Consideration must be given to the potential impacts on water table levels, water pressure and water quality.
- Planning for measures in the event that impacts are greater than predicted
In addition, there are established standards for the construction on groundwater bores in NSW. In regard to the deep groundwater bores the NSW Code of Practice on Coal Seam Gas Well Integrity sets constructions standards to ensure aquifers are protected from cross-aquifer or surface-borne contamination.
Groundwater is an important resource for many towns, industries and irrigators who rely on groundwater extraction to support their activities. Also, many landholders rely on groundwater for domestic and stock use. Groundwater is also important for the environment, as it supports some ecosystems and provides baseflow to rivers.
Over-extraction or contamination of groundwater can have serious, long-term and sometimes permanent impacts on the groundwater system. This may ultimately reduce the volume and quality of water available for the users and ecosystems that depend on this groundwater.
That is why the NSW Office of Water operates an extensive groundwater monitoring network of over 5000 bores at more than 3000 locations. There are multiple monitoring bores ('nests') at some of these sites which enable the groundwater levels and pressures at a range of depths to be monitored. The majority of bores are in shallow (20 metres to 150 metres) alluvial groundwater systems that are used for drinking water and irrigation. Monitoring bores are also deployed where other groundwater management issues exist, such as highly saline water tables or sensitive groundwater dependent ecosystems.
Data from our extensive monitoring network have been loaded into our new groundwater data archive. These data are regularly used and analysed often in conjunction with computer-based groundwater modelling to ensure that the resource is used and managed sustainably.
This new extensive groundwater database also provides bore construction data from around 135,000 water supply and monitoring bores across NSW. This includes information on the depth of each bore, the rock types that have been drilled, the depth of water bearing zones intersected by the bore, the depth to water and the estimated bore yield.
Groundwater Quality Monitoring video
As part of the NSW Office of Water’s role in managing the state’s groundwater resources, the impact of groundwater use is analysed by our hydrogeologists to ensure the resource is protected and used sustainably. This analysis is provided in groundwater assessment reports which show facts and figures on groundwater use, changes to groundwater levels, pressure and water quality. Information is also provided on water management metrics on water licensing and trading.
Groundwater and coal seam gas
Water and Coal Seam Gas video
In response to community concern about the potential effect of coal and gas activities on groundwater resources the NSW Government has introduced stringent new measures including legislation, policies, plans, guidelines and codes of practice to ensure that protection of our groundwater resources.
These new measures include:
- Introduction of an Aquifer Interference Policy
- Ban on the use of BTEX chemical in CSG activities
- Ban on the use of evaporation ponds to dispose of produced CSG water
- Capped amount of water that can be taken by exploration activities without a licence at 3 megalitres per year
- Commissioning the NSW Chief Scientist and Engineer to undertake a comprehensive review of the CSG industry, and water monitoring requirements
- New Codes of Practice for well integrity and fracture stimulation
- Establishing the independent EPA as the lead environmental and health regulator of the CSG industry
- Introduction of the NSW Gas Plan to reset CSG development in NSW, and ensure that exploration and production is undertaken on our terms
More information on water and coal seam gas is available here
If you would like to find out more about how groundwater is managed in NSW go to – www.water.nsw.gov.au