Groundwater

Groundwater is sourced from below the earth's surface and includes water from bores, spear points (shallow installations), springs or wells. Groundwater can be used for many purposes, however water quality is variable. Groundwater may contain disease causing microorganisms which can cause illness. Some groundwater supplies in Victoria have been found to contain high levels of chemical contaminants, such as arsenic, which can cause illness in people who drink the water. Some salts that occur naturally in water, including sulfate and nitrate, can be harmful if they are present in large quantities. Other dissolved salts can make the water hard. This may result in scale build-up and corrosion in pipes, which can release harmful metals such as lead and copper into the water.

Hazards to groundwater quality

Groundwater quality can be influenced by factors such as the time of year, depth, catchment area and land uses, and aquifer characteristics.

Groundwater can be contaminated by a range of sources including:

• sewage
• waste (including animal waste)
• agricultural run-off (such as pesticides and fertilisers)
• industrial run-off and pollution
• flooding
• seepage from rubbish tips
• polluted stormwater
• chemical spills
• contaminated surface waters
• high levels of naturally occurring chemicals and radioactive substances.

Managing health risks

The risks to health will depend on the type and concentration of contaminants in the groundwater, also how often, for how long and in what ways people are exposed to the water (for example drinking, inhalation, or skin contact).

Disease causing microorganisms found in water supplies can cause diarrhoea, vomiting or other gastrointestinal illness. Some of these microorganisms can also lead to more serious illnesses, even death. The people most at risk from unsafe water are the elderly, young children, pregnant women and people with weakened immune systems.

Groundwater is not as reliable as reticulated (mains) water. Where a mains water supply is available, that should always be used for drinking. When mains water is not available it is important to choose the next best source of water. Treatment may be required to ensure the alternative water supply is safe for drinking.

Residents in areas where contamination is likely (for example areas of previous industrial use) should not use groundwater for domestic purposes, such as irrigation of fruit and vegetables, bathing or use in spas and swimming pools.

Groundwater should only be used if the bore is well maintained and the water quality is suitably high. Water from shallow bores is not recommended due to the risk of contamination.

Nitrates in groundwater can pose a risk to bottle-fed babies. If you are considering using groundwater to prepare infant formula, you should contact your maternal and child health nurse or family doctor first.

Landowners should complete a water supply management plan and regularly assess water quality risks from microbiological, chemical and radiological sources.

Maintaining bores

Make sure the bore is protected from:

• surface run-off
• channel water
• irrigation water
• leakage from sewer pipes or septic tanks
• stormwater and greywater drainage
• shallow underground seepage
• inundation from flooding.

The bore should be properly cased, with an above-ground well-head. If possible, store drinking water in an above-ground tank rather than an underground tank.

To avoid the risk of cross connections, make sure mains drinking water plumbing is separated from all other plumbing or pipe systems, and that all pipe joints are properly sealed.

Information on the licensing, construction and protection of bores and groundwater sources can be obtained from the Department of Environment, Land, Water and Planning website.

Managing groundwater

Managing groundwater should include understanding the groundwater supply from the source through to the point of use.

It is important for users of groundwater to understand the risks and the intended use of the groundwater supply. Groundwater may need to be disinfected to remove harmful microorganisms prior to use however disinfection does not remove chemicals, algal toxins or radiological contaminants that maybe present.

Landowners or individuals can contact local water agencies to provide general information on local groundwater characteristics to better understand their water supply source.

Key water agency websites have information on bore licensing and maintenance, including Southern Rural Water, Goulburn-Murray Water and Grampians Wimmera Mallee Water.