Regional Information- Ground Water

Around the world groundwater is a major source of the fresh water and in Australia is accounts for approximately 20% of the counties total water use.  Groundwater is a vital resource in NSW where the volume of groundwater is estimated to be 5 billion million litres.  This is more than 200 times the storage capacity of all of the water supply dams in the Sate and enough to fill Sydney Harbour 10 times.

Groundwater, or bore water, is naturally occurring water that is found below ground level.  The area below ground where the water is stored is called an aquifer.  To extract this water, bores are drilled into the ground, in the case of sand-based aquifers, shallow spear points can be used or wells are another way of extracting groundwater.

On the Central Coast there is a mix of both hard rock and sand aquifers which generally produces a good quality of water.  The quality of the water in an aquifer depends on a number of factors including:

  • The original source of the water – rain, snow etc…
  • How long the water has been held underground – water can be stored under the ground for thousands of years
  • The structure of the aquifer – confined or not, the rock type
  • The quality of water entering the aquifer from the surface – is there contamination or not 


Figure 1: Groundwater Well (Source: Wyong Shire Council) 

Depending on the above factors the water that is extracted can be of very high or very low quality.  High quality water such as spring water can be drunk straight from the source with little to no treatment whereas low quality may have high levels of salt and minerals in it and requires treatment before it can be used.

On the Central Coast we have five borefields (an area which contains one or more borehole) consisting of 19 individual bores.  These are located at:

  • Braithwaite Park
  • Mangrove Creek Weir
  • Mardi
  • Ourimbah Creek
  • Somersby Water Treatment Plant

Between all of the boreholes approximately three million litres of drinking water a day is produced.  There are also two additional borefields located at Woy Woy and Narara which consist of 17 individual bores which came online April/May 2007.  These boost total groundwater supplies in the region to around nine million litres a day.  The total cost for all seven borefields is $29 million.

In addition to the above bores which are suitable for drinking water purposes on the Central Coast there are also 27 other groundwater bores which, following extensive testing were found to be unsuitable for drinking water purposes.  These bores supply water to irrigate sporting fields and flush public amenity blocks across the region.

Table 2:  The Borefields


Current average supply per day (million litres)



Mangrove Weir








Woy Woy







Woy Woy is located on a sandy substrate with coffee rock (hard impenetrable rock) and the boundary layer and is the largest borefield on the Central Coast.  It includes 13 bores, 6.5km of underground pipeline and a new water treatment plant at Gosford City Council's Woy Woy Depot.  It has the capacity to deliver an average of 3.8 million litres of fresh drinking water a day which represents around 4 per cent of the aquifer's estimated total capacity.  This is enough to supply around 7,000 households based on current usage levels.  The Narara borefield includes four bores, 6km of underground pipeline and a booster water pump station.  It has the capacity to deliver up to 2.2 million litres of water a day.

Figure 2:  A playing field being irrigated by groundwater  (Source: Wyong Shire Council)

All groundwater resources in Australia are State controlled.  This means in NSW, groundwater is managed by the NSW Department of Water and Energy (formally The Department of Natural Resources).  It is this Department that is responsible for setting overall policy and issuing of all commercial licenses to extract groundwater.  The key requirement is that the Councils collect a vast array of data including everything from environmental impacts through to detailed hydrogeological information.  This data is then used by the Department to determine an appropriate annual groundwater extraction and allocation for each groundwater bore that's been established on the Central Coast.  At any time, in assessing this data, the Department can direct the Councils to alter or increase its bore monitoring systems or pumping regimes.  It can also request the shut down of individual bores or entire borefields.

The Department of Water and Energy operates a licensing/registration program with the specific objective of sustaining the State's groundwater resources by managing them effectively.  As part of this program it is required that the installation of all domestic bores must be carried out by experienced installers that hold a current drillers licence issued by the Department.  By registering your bore or spear point you can help prevent inappropriate installation and use of bores as well as provide protection for all groundwater users and the actual groundwater resources.

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