Nitrate contamination of groundwater is a concern for human health and the environment and reflects land use in the area.
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Waikato Regional Council monitors nitrate in groundwater to detect changes in contamination levels that may affect human health and the environment. We have two monitoring networks - a regional and a community supply network of wells.
Excessive nitrate and iron are the most common groundwater contaminants in the region.
Iron occurs naturally, but high nitrate levels indicate contamination from human activities. Nitrate levels are generally highest in shallow groundwater aquifers.
Nitrate contamination of groundwater is a concern for human health and the environment. High nitrate concentrations have been linked to a blood disorder in bottle-fed babies, known as ‘blue baby’ syndrome (or methaemoglobinaemia).
The effect of contaminated groundwater on our rivers and streams is also important. In the Hamilton Basin, up to 85 percent of the base flow of small streams comes from groundwater. Much of this water is already enriched with nutrients including nitrate. Find out more in our indicator of the sources of nitrogen in our rivers and streams.
Excessive nitrate concentrations in groundwater are related to land use activities, including:
Studies have shown that high use of nitrogen fertilisers on pasture can make the groundwater unsuitable for human consumption.
Levels of nitrate in groundwater vary a lot across the region. Areas where nitrate levels most commonly exceed drinking water guidelines are:
We have few records to indicate long-term nitrate trends. But long-term information from some schools supplies (since 1950s) indicates a steady increase in nitrate at these sites.
Remember that it is much easier to prevent groundwater contamination than to fix it.
Look after your well
Be careful with nitrogen fertiliser
Growing commercial vegetables
Reduce the amount of nitrogen leaching when growing vegetables commercially:
Remember that most Waikato soils are over-fertilised.
Find out more about soil management in Franklin district where areas of intensive agriculture such as commercial vegetable growing are damaging soils.
Learn more in our indicators that measure groundwater quality in the Waikato region, including nitrate and pesticide levels.
Follow the guidelines on pesticide use in Growsafe(external link), the New Zealand Standard for Agrichemical Users' Code of Practice.