Bore water is groundwater that has been accessed by drilling a bore into underground aquifers (water storages) and pumping to the surface. Aquifers may contain chemicals and micro-organisms that are potentially harmful. Some of these chemicals are naturally occurring (such as those present in soils and rocks) while others are a result of contamination.
Confined or deep aquifers are usually deep underground which helps protect the water source. These types of aquifers are usually covered by more than 20 meters of rock or clay which act as a natural filter preventing microbial contamination. Unconfined or shallow aquifers are not protected by thick layers, because they are closer to the surface above and are susceptible to both chemical and microbiological contamination.
Types of bores and the quality of water
Deep bores are usually used when the aquifer is 20 meters below the ground.
The microbiological quality of water in deep or confined aquifers is generally very good. The water quality will continue to be good if the bore is properly constructed, protected from entry of surface water and well maintained. Though its microbiological quality may be good, water in these aquifers can contain high concentrations of naturally occurring hazardous chemicals.
Before using a deep bore, obtain a chemical analysis of the water.
Due to shallow bores not being protected by thick layers of soil or clay, shallow bores are not generally recommended as a suitable source of drinking water, particularly in urban areas.
Using bore water
Depending on quality, the uses for deep bore water can include irrigation, livestock watering and clothes washing.
Bore groundwater may be deemed safe for drinking, cooking, filling swimming pools or watering edible plants such as home grown vegetables only after it has been fully tested by a specialist laboratory.
Particularly in urban settings and where mains water is available, the use of shallow bore water is not recommended because of the high likelihood of chemical or microbial contamination. If you have no choice but to use water from a shallow bore, testing requirements will be more intense than for water from a deep bore.
In general, water quality should be assessed with reference to the Australian Drinking Water Guidelines and the Australian and New Zealand Guidelines for Fresh and Marine Water Quality.
The land owner is responsible for the safety aspects of bore water.
It is not always possible to tell if bore water is contaminated. However, changes in appearance or odour can indicate contamination. If this occurs, owners are advised to check the integrity of the bore and to test water quality. If you suspect your water is contaminated, seek advice from your local council Environmental Health Officer.
Bore water quality may change over time. Therefore, after the initial analysis the bore water should be checked every 2 years and monitored by the owner for any undesirable changes in water quality. Shallow groundwater will need to be tested more frequently. More information is available on the Bore water testing page.
Installing a bore
When deciding on a location, there are a number of factors that can affect water quality including:
- Presence of possible sources of pollution such as proximity to septic tanks
- Previous land uses such as industrial use or waste disposal
- Physical features that could lead to contamination such as installation at the bottom of a gully where surface run-off could submerge it or installation in the path of industrial or stormwater drains.
A permit must be obtained before the construction of a bore because:
- certain locations may have temporary or permanent restrictions on new bores
- a bore is required to be installed by a licensed water bore driller.
You can apply for a permit through the Department for Environment and Water.
Preventing bore water contamination
Avoiding contamination is important because bore water that becomes polluted can be difficult and expensive to treat. Ways you can prevent your bore water from becoming contaminated include:
- keep septic tanks well maintained and don’t discharge septic waste within 50 metres of the bore
- avoid chemical spills or excessive use of chemicals such as fertilisers
- protect the bore from livestock access by erecting fencing to allow at least a 50 metre clear zone around the bore
- seal the bore to prevent surface water or shallow ground water from contaminating the ground water
- once the ground water is pumped to the surface, protect the water through properly maintained, enclosed water systems and storage tanks
- use backflow prevention devices
Failure to properly maintain and protect bores contravenes the requirements of the Environment Protection (Water Quality) Policy.