Groundwater quality, state, 2014-18

11 June 2021: A revised version of this dataset has been published to correct the terminology used to compare nitrate-nitrogen values to the 3 g/m3 guideline value. The field name has been changed from “reference_condition” to “n_n_guideline”, and values in this field will now be either “Does not exceed” or “Exceeds”, instead of “Meets” or “Does not meet”.

​

20 July 2020: We corrected the data about drinking water standards for E. coli and nitrate-nitrogen in the key findings for groundwater quality.

For the five-year period 2014‒2018:

• 68 percent of 364 sites failed to meet the E.coli drinking water standards (changed from 98 percent of 145 sites failed to meet the E. coli drinking water standards)
• 19 percent of 433 sites didn’t meet nitrate-nitrogen standards (changed from 28 percent of 403 sites failed to meet the nitrate-nitrogen drinking water standards).

This indicator measures groundwater quality in New Zealand’s aquifers and how it is changing over time, based on measurements made at monitored sites. We report on nitrate-nitrogen, ammoniacal nitrogen, dissolved reactive phosphorus, chloride, conductivity and Escherichia coli (E. coli) including:

• median values for the period 2014–18
• nitrate-nitrogen median values compared to a guideline value of 3 grams per cubic metre (g/m3). This value is defined as a concentration that indicates groundwater has been influenced by industrialised agriculture and is highly likely to have been impacted by human activity (per Morgenstern & Daughney, 2012 and Daughney & Reeves, 2005).
• the proportion of samples from each site that have concentrations of nitrate-nitrogen or E. coli in excess of the Maximum Acceptable Values for protection of human health (Ministry of Health, 2018).

More information on this dataset and how it relates to our environmental reporting indicators and topics can be found in the attached data quality pdf.