Shallow groundwater is relatively accessible in Perth and its use on gardens reduces the demand on valuable potable scheme water. Activities removing large volumes of groundwater require an abstraction licence from the Department of Water but household bores in the metropolitan area do not usually require a licence. The number of bores in an area depends on:
- Depth to the water table
- Difficulty of access – areas closer to the coast have fewer bores due to the cost of drilling into limestone and the risk of saline intrusion
- Chance of success- bores are fewer in some eastern suburbs in areas of clay or granite where bore yields are generally lower
To assess suitability for a garden bore in the metro area refer to the Dept. of Water’s ‘Perth Groundwater Atlas’.
Although groundwater may be readily available, it should still be considered a precious resource. Excessive use can result in groundwater draw-down where over pumping can lower the water table to undesirable levels in some areas and be detrimental to the environment. Care should be taken near sensitive environments such as wetlands.
In some areas where there has been excessive clearing of natural vegetation and a rise in the water table, bores can be beneficial in preventing further ground level rises and minimising the need for drainage. It is important to encourage efficient bore use among consumers so a waterwise irrigation system should be installed which only waters enough to meet the garden’s needs. Overuse of a bore can result in groundwater draw-down, nutrient loss and saltwater intrusion (in coastal areas).
Application of bore water
Bore water can be applied either via sprinkler systems or drip irrigation. When considering the use of bore-water for any drip irrigation system it is always recommended that an analysis is made of a water sample from the bore prior to installation of such a system.
Bore water in many areas of the South-West of WA contain concentrations of dissolved iron which, when oxidised, can clog drip emitters over time.
Manufacturers do not recommend the use of drip irrigation where the levels of dissolved iron exceed 0.5 parts per million. Some high output drippers, however, may be used with higher levels than this- refer to manufacturers for their recommendations. Periodic maintenance will be required – cleaning filters and flushing driplines.
Garden Bore users in Perth and Mandurah are permitted to water between 6pm and 9am on three days of the week depending on the last digit of the house or lot number. Winter sprinkler bans currently apply to bore users in Perth, Mandurah and some parts of the South West.
