NSW Health recommends that groundwater is not used for drinking, cooking and personal hygiene (including cleaning teeth and bathing) without testing and appropriate treatment including disinfection.
What is groundwater?
Groundwater is water that can be sourced from below the earth’s surface. Some of the rain that falls on the land seeps into the ground and can dissolve minerals on its way. Excess water in the soil seeps down until it reaches a level where the spaces within sediments or rocks are saturated with water. This is called the water table. Water in the saturated zone below the water table is called groundwater.
Groundwater moves very slowly, compared to rivers and streams, because it has to flow through small openings in layers of soil, sediment and rock. A rock or sediment layer that is capable of yielding useful supplies of groundwater is called an aquifer. Groundwater from aquifers can be brought to the surface by constructing bores or wells and installing a pump.
Safety of groundwater
In rural areas groundwater can be a safe and reliable water source. Water from bores, spearpoints (shallow bore installations), springs or wells may be of high quality if the source is well maintained and protected. However, groundwater can be contaminated with:
- animal wastes
- agricultural runoff (which may contain fertilisers and pesticides)
- polluted stormwater/floodwater
- industrial pollution
- seepage from rubbish tips and other chemicals.
- naturally occurring chemicals (e.g. arsenic)
- radioactive materials.
Some groundwater may also be affected by hardness, salinity and other naturally occurring chemicals.
Groundwater contamination can move from the original source of contamination over a wide area or very deep underground. Contamination can persist for a long time as groundwater moves slowly and often lacks the natural biological, chemical and physical processes that help cleanse surface water (e.g. sunlight).
The amoeba Naegleria fowleri has been identified where bore water is held in above-ground dams then piped over distances in above-ground pipes. Infections are very rare but are often fatal. Infection may occur when contaminated water goes up into the nose (including when people swim, dive or fall into water, or when children play under sprinklers or with hoses). Any water body that seasonally exceeds 30 degrees Celsius or continually exceeds 25 degrees Celsius can support the growth of Naegleria. Users should seek specialist advice on the use of chlorination to control Naegleria, which cannot survive in water that is clean, cool and chlorinated.
Users should check for groundwater contamination warnings issued by the NSW Environment Protection Authority (EPA) or other authorities.
Information on ground water quality is available from NSW Department of Primary Industries (DPI) Water.
To avoid or minimise water quality problems in groundwater:
- A groundwater source should be uphill and at least 250 metres from any wastewater disposal system such as a septic tank and trenches
- Avoid contamination, or provide treatment, where groundwater is in contact with surface waters (open wells) or where water flows freely from the surface down into the bore water (e.g. in limestone areas)
- Inspect the area around a groundwater supply regularly and protect it from surface contaminants. Bore heads and wells should be raised above ground level and sealed to avoid floodwaters and surface runoff flowing into the source.
- Only extract groundwater from a place where underground contaminants are unlikely. Avoid sites with known contaminants, including fuel storage tanks, heavy industry and intensive agriculture areas
- Where groundwater is stored in above ground tanks, tanks should be properly sealed and maintained to prevent the entry of birds and small animals. For more information on safe use and maintenance of water tanks refer to the NSW Health Rainwater Tank brochure.
The Public Health Act 2010 requires premises that serve the public or employees and have a private water supply (including bore water/groundwater) used for drinking, food preparation or personal hygiene must adhere to a quality assurance program and should comply with NSW Health’s Private Water Supply Guidelines.
NSW Health recommends that users of groundwater be familiar with the quality of their water. This can be done by testing the microbiological, chemical and radiological quality of the water. Water used for household purposes such as drinking, food preparation and personal hygiene (including cleaning teeth/oral hygiene and bathing) should meet water quality guidelines in order to protect you and your family’s health. Refer to private water supply testing service and DPI Water monitoring for more information on water quality and treatment.
Groundwater in urban areas (cities and towns)
NSW Health recommends that people use the public drinking water supply in urban areas for drinking, food preparation and personal hygiene (including cleaning teeth/oral hygiene and bathing) because it is filtered, disinfected and generally fluoridated. The quality of public water supplies is regularly monitored. People who choose to use private groundwater supplies for drinking, food preparation and personal hygiene (including oral hygiene) should be aware of potential risks associated with microbiological, chemical and radiological contamination.
Groundwater in urban areas is more likely to be contaminated by human activities such as chemical contamination from industry, leaking from underground fuel storage tanks, leaching from rubbish tips or land fill areas and seepage from sewerage systems or septic tanks. Some potential groundwater contaminants include:
- bacteria, viruses and protozoa
- chromium and other metals
- per- and poly-fluoroalkyl substances (PFAS)
- petroleum hydrocarbons.
What happens to groundwater once it is contaminated?
Groundwater contamination can move from the original source of contamination over a wide area or very deep underground. It is often difficult to know where the contamination has gone. Overlying soil, sediment or rock can hide the exact location of the contamination and present a substantial barrier to remediation efforts.
Contamination can persist for a long time as groundwater moves slowly and often lacks the natural biological, chemical, and physical processes that help cleanse surface water.
What are the health effects of contamination?
The risks to health will depend on the type and concentration of contaminants in the groundwater and also how often, for how long and in what ways people are exposed to the water (e.g. drinking, inhalation, or skin contact).
Sometimes there is not enough information to assess the health risks from contaminated groundwater. Where risks are known, public warnings are issued.
Residents in areas where contamination is likely (e.g. areas of previous industrial use) should not use groundwater for other domestic purposes, such as irrigation of fruit and vegetables or use in spas and swimming pools.
An alternative to using groundwater is to collect rainwater. A properly maintained rainwater tank can provide good quality water. For more information on maintenance and safe use of rainwater tanks see the NSW Health Rainwater Tanks information.