Groundwater pesticides

  • Image, groundwater pesticides.

    Pesticides are commonly used in New Zealand to control insects, diseases, and weeds in primary industries. They can harm the environment and human health, and also affect New Zealand’s competitiveness of exports (many overseas markets want their food produced in an environmentally responsible way). We report on pesticide levels in groundwater. Pesticides can move through the soil and enter groundwater aquifers, which is an important source of drinking water in New Zealand. Nearly 40 percent of the community drinking water supplies around New Zealand are reliant on groundwater. Many individual rural households also rely on groundwater for their drinking water.

    We classified Groundwater pesticides as a case study.

    Key findings

    Data showed little health risk related to pesticide contamination, with sampled wells detecting either no pesticides (83.0 percent of wells) or mostly very low levels of pesticides (17.0 percent) in 2014. 

    • One of 153 sampled wells exceeded the maximum acceptable value (MAV) for drinking water ΜΆ Dieldrin was detected in a Waikato well at 7.5 percent above MAV.
    • Pesticides were detected in Northland, Auckland, Waikato, Gisborne, Tasman, and Southland, with no data available for Bay of Plenty and West Coast.
    • Pesticide levels in the previous four pesticide surveys (1998, 2002, 2006, and 2010) were similar to the 2014 survey. 

    Figure 1

    Definition and methodology

    Environmental Science and Research (ESR) coordinated a survey of pesticides in groundwater throughout New Zealand in 2014 (Humphries & Close, 2015). Well sampling was completed in 13 regions by regional and unitary councils. For this analysis, ESR also used results from 40 wells (from a total of 153) sampled in 2012 from the Waikato Regional Council. Samples were analysed for acidic herbicides and a number of organo-chlorine, organo-phosphorus, and organo-nitrogen pesticides.

    Wells were selected based on the importance of the aquifer to the region, known application and storage of pesticides in the area, and the vulnerability of the aquifer to contamination. The majority of selected wells were in unconfined aquifers (ie aquifers that are more vulnerable to contamination from land use). 

    Data quality

    Topic Classification   Relevance Accuracy 
     Freshwater quality, quantity and flows  Case study

    Image, Partial relevance.


    Image, High accuracy.



    See Data quality information for more detail.


    Humphries, B, & Close, M (2014). National survey of pesticides in groundwater 2014. Prepared for the regional councils. ESR report number CSC 15003. Available from


    Published 27 April 2017


Related content

Access data files

Groundwater quality data


Related indicators

Groundwater quality 


Related links

Our fresh water 2017

Environment Aotearoa 2015


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