Know more about your bore

To understand your bore and how you can better manage your water use, you should first find your bore using the 'Know your bore' tool.

With this tool, you can:

• find out which water resource your bore is pulling from
• review your bore report/statement the department has on file.

To help you understand your statement of bore, read how to read this statement PDF (359.5 KB).

If your bore information is incorrect

If your bore information is incorrect, send us an email with following updated information:

• bore number
• owner name
• contact phone
• contact email
• details needing updating.

If you have any questions or need help, contact the Water Resources Division on 08 8999 4455.

Bores are a narrow hole drilled down into an aquifer to extract groundwater.

Bores, like any plumbing device are subject to degradation and even failure.

This can be due to age or improper design.

Domestic bores are typically lined with 150mm steel or PVC pipe to prevent the hole from collapsing.

The pipe is perforated with slots opposite the aquifer to allow water to enter.

Special borehole pumps are placed in the bore with their inlet located at some distance above the slots.

When the pump is turned on it causes a localised cone shape drawdown of the water table around the bore.

The cone gradually expands away from the bore until a balance is reached between the amount of water pumped and the rate of inflow from areas of the aquifer surrounding the cone.

A domestic bore would typically influence the surrounding area by a few tens of metres.

When the pump is turned off the water table gradually returns to close to its original level.

Information about most bores is registered with Water Resources Division. This information includes:

• registered bore number (all bores in the NT have a unique registered bore number)
• depth and type of construction
• location of screens/slots
• water quality at the time of construction.

Being aware of the signs of bore failure will allow you to plan for a:

• new or extended bore
• temporary contingent water supply.

Signs of bore failure

The following are signs of bore failure:

• pump spurts (water and air)
• no water
• change in water quality
• discoloured water or sediment/sand in water
• reduced pressure/pumping rate (less sprinklers running than previous)
• pump switches off (overheat sensor).

Possible causes of bore failure

Types of bore failure can be many and varied.

You should know them so you can monitor and maintain your bore.

These include:

• improper design such as:
  • design of bore screen
  • design of gravel pack
• faulty construction such as:
  • wrong placement of bore screen
  • improper jointing of pipe and bore screen
  • inadequate development
• faulty operation such as:
  • over pumping
  • poor maintenance
• mechanical failure such as:
  • shearing and collapse due to excess load
  • lodging of foreign objects, including pump components
• corrosion
• incrustation
• interference between bores
• adverse aquifer conditions like:
  • lowering of water table
  • deterioration of water quality.

Possible bore issues

Low water levels are not the only reason for bore failure or inefficiency.

Low water levels contribute to and result in the any of the following.

• Improper design - The use of inappropriate materials or improperly placed screens/slots can cause bore failure.
• Borehole instability - Damaged casing and screens, borehole wall collapse due to, corrosion or excessive water flow in the bore.
• Biofouling - Installing and pumping a bore in some aquifers can increase the amount of oxygen and nutrients in the water. Bacteria such as iron-fixing bacteria, can thrive under these conditions. This is quite common in bores throughout the Darwin rural area.  For more information, read the iron fouling in groundwater factsheet PDF (173.1 KB).
• Corrosion - Some aquifers are slightly acidic and can eventually corrode metal bore casings.
• Over pumping - This is the most common issue that leads to premature bore problems. It not only depletes the groundwater, but it rapidly increases the rate of corrosion, incrustation and biofouling related issues.  It can also increase the amount of sediment particles moving toward the bore causing plugging of the screens or perforated casing where water flows into the bore.

Many problems with bores can be fixed either by the way they are operated or with maintenance.

In some cases the option may be to drill a new bore, reconstruct or deepen the existing one.

The first actions you need to consider include:

• reduce your water usage
• reduce your pumping rate if possible - pumping tests are recommended
• lower the pump if possible
• have the bore cleaned to remove sand and silt as well as encrustation in the slots.

For more information, read looking after your bore PDF (974.0 KB).

Contact Water Resources Division on 08 8999 4455 or send an email to waterresources@nt.gov.au