Groundwater contamination

Well water is drawn from the groundwater resources, and groundwater originates from precipitation. As this water moves down from the surface to recharge aquifers it can be affected by a range of human activities, e.g.:

• Leaching of chemicals/seepage of contaminated storm water at the land surface
• Discharges from septic tanks/underground fuel storage below ground level

The quality of groundwater is also influenced by its interaction with soil and rocks. While this interaction can help remove surface man-made contaminants, there are some naturally derived contaminants that can also impact groundwater quality.


How to minimise the risk

The best way to manage your drinking water supply is to avoid likely sources of contamination. This diagram provides a few tips for best practice.

Direct signs of a contaminated water supply can be observed in its colour, odour, taste or cloudy appearance but there are other contaminants such as bacteria, nitrate and arsenic that cannot be seen.


Test your water

The best way to check for potential water quality issues is to collect a water sample and have this tested by an independently accredited IANZ laboratory, which you can find here:

What to look for

The graphic below lists some parameters and the problems they cause. For more information go to and search for groundwater bores.

Who looks after the water?

• Territorial local authorities (TLA) like district or city council for large water supplies
• Water suppliers for small water supplies
• Private landowners/self-suppliers that own their household water supply


Who is responsible?

• Regional councils for the management of source catchments (under the Resource Management Act)
• Water suppliers for the water supply from the point of abstraction to the property (under the Health Act)
• Self-suppliers are covered by the Building Act 2004, which requires any building intended for use as a dwelling house to have an adequate and convenient supply of water that is potable. Self-suppliers have to ensure themselves that their water is safe.


The information on this page is available as a downloadable brochure here. Further reading is available at (search: household water supplies). Advice around particular contaminants, individual water supply wells and groundwater quality is available from:

Health Protection Officers  
Public Health South - Dunedin
Private Bag 1921, Dunedin 9054
Ph: 03 476 9800

Public Health South - Queenstown
PO Box 2180, Frankton, Queenstown 9349
Ph: 03 450 9154

Environmental Health Officer  
Dunedin City Council Ph: 03 477 4000
Queenstown Lake District Council Ph: 03 441 0499
Central Otago District Council - Alexandra Ph: 03 440 0056
Waitaki District Council - Oamaru Ph: 03 433 0300 or 0800 108 081
Clutha District Council - Balclutha Ph: 03 419 0200 or 0800 801 350
Groundwater Scientists  
Otago Regional Council Freephone: 0800 474 082
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