Monitoring groundwater quality

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Threats to our groundwater quality come from many sources and are referred to as either point (from specific locations) or non-point sources (from wider areas).

Point sources include:

  • septic tanks, leaking effluent treatment ponds and landfills
  • leaking underground fuel tanks and pipelines
  • mines and waste tailings
  • chemical storage areas and timber treatment sites
  • waste disposal sites, such as offal holes.

Non-point sources include:

  • pesticide and fertiliser applications
  • agricultural land use
  • application of wastes to land
  • saltwater intrusion.

What we are measuring

Waikato Regional Council monitors the state of groundwater quality in the Waikato Region for:

    • background condition
    • nitrates
    • pesticides.

Groundwater indicators

Waikato Regional Council regularly monitors and reports on the quality and availability of our region's groundwater. The following groundwater indicators summarise the results of our science and monitoring programmes, and provide a holistic report on the state of the region's environment:

      • Groundwater availability
      • Micro-organisms in groundwater
      • Pesticides in groundwater
      • Groundwater well construction
      • Nitrate in groundwater

Check out where we monitor pesticide and nitrate levels in the Region.

Waikato Regional Council also gets groundwater information from:

  • community groundwater supplies
  • investigations (chemical and microbial) and data provided through resource consent applications and compliance monitoring.

The table below lists the different contaminants we measure to determine groundwater quality in our Region and their maximum acceptable values (MAVs) for drinking water.

Contaminant Drinking water MAV standard1 Principal concerns
Nitrate 50 mg/l
(11.3 g/m3 as nitrate–N)		 Human health.
Nutrient enrichment of rivers and lakes
Arsenic 0.01 mg/l Human and animal health
Boron 1.4 mg/l Human and plant health
Bacteria
(indicators of disease–causing micro–organisms)		 Less than 1 in 100ml of sample Human health
Pesticides Chemical specific Human and animal health
Hydrocarbons Various Human health and ecology
Synthetic organic chemicals Chemical specific Human health and ecology
Heavy metals Metal specific Human health and ecology

What we have found

The most common chemical contaminants found in community water supplies with near or above the maximum acceptable values for drinking water are:

  • nitrate
  • arsenic
  • boron
  • metals produced from corroding pipes (for example, zinc and copper).

It’s natural to find high levels of arsenic and boron in geothermal areas (mainly Taupo), but nitrate contamination is the result of the way we use the land.

Check out the national drinking water standards on the Te Whatu Ora website (online publications).

Footnotes

  1. Ministry of Health. 2000: Drinking-Water Standards for New Zealand 2000. Ministry of Health, Wellington.