020406080100AntimonyBromodichloromethaneNitrate and nitriteNitrateManganeseFluorideTrihalomethanesLeadArsenicCopperDichloroacetic acidTrichloroacetic acidHaloacetic acidsNickelProportion of people receiving drinking water which met individualchemical standards in New ZealandBy chemical, year ended June 2017, % of population in assigned zonesProvider: Ministry of Health

Proportion of people receiving drinking water which met individual chemical standards in New Zealand

By chemical, year ended June 2017, % of population in assigned zones


Some zones, with their contributing plants, will have multiple chemicals assigned, so the total may not equal the sum of determinands.
Chemical determinands are not regularly monitored in all supplies, but are assigned to specific supplies where treatment or water characteristics indicate levels may approach health limits.


Water supply: in this context, it refers to a distribution zone, which is all or part of a reticulated supply for which the water is expected to be of consistent quality throughout. While smaller communities usually have a single distribution zone, larger communities may have two or more. Size groupings of supplies are therefore based on the population served by each zone.
Large Zones; 2,957,000 people in 74 zones, each with over 10,000 people. Serves 78% of the report population.
Medium Zones: 295,000 people in 41 zones, each with 5001 to 10,000 people. Serves 8% of the report population.
Minor Zones: 487,000 people in 257 zones, each with 501 to 5000 people. Serves 13% of the report population.
Small Zones: 75,600 people in 289 zones, each with 101 to 500 people. Serves 2% of the report population.
All Supplies: 3,815,000 people in 661 zones.

Bacteriological achievement: determined primarily using Escherichia coli monitoring
Protozoal achievement: based on monitoring the effectiveness of the treatment processes used to remove or inactivate Cryptosporidium.
Chemical achievement: assessed for those supplies that have been identified as containing chemicals that require monitoring (known as Priority 2 determinands).
Overall achievement: assessed on the basis of Escherichia coli and chemical monitoring. There is no requirement to directly monitor for protozoa in the Standards.

Monitoring: provides a check that the water safety plan is operating satisfactorily, and indicates whether remedial action is required.
Provision of drinking water: a requirement to take all practicable steps to ensure the adequacy of supply and in the event of an interruption, planned or otherwise, to take appropriate action.
Source protection: Protection of source waters reduces the number and concentrations of contaminants that the water treatment system has to deal with.
Records: the keeping of records assists water suppliers and drinking-water assessors in determining whether a supply meets the requirements of the Act and achieves the Standards.
Complaints: consumer concerns about drinking-water quality, which often relate to the aesthetic properties of the water (taste, odour and appearance).
Remedial action: appropriate actions in the event that monitoring reveals contamination of the water and that the Standards are breached.

Data calculation/treatment

Population figures are rounded to the nearest thousand (nearest hundred for small supplies).

Data provided by

Ministry of Health

Dataset name

Annual Report on Drinking-water Quality 2017



How to find the data

At URL provided, select "Annual Report on Drinking-water Quality 2016–2017 (docx, 391 KB)" from the right-hand column. The data can be found in tables throughout the document, which we have pasted into a spreadsheet for internal processing purposes.

Import & extraction details

File as imported: Annual Report on Drinking-water Quality 2017

From the dataset Annual Report on Drinking-water Quality 2017, this data was extracted:

  • Sheet: Table 6
  • Range: C5:G19
  • Provided: 75 data points

This data forms the table Health - Drinking water quality achievement for individual chemicals Year ended June 2017.

Dataset originally released on:

June 29, 2018

About this dataset

This data describes drinking-water quality for all registered networked drinking-water supplies that served populations of more than 100 people (the supplies) from 1 July 2016 to 30 June 2017 (the reporting period), representing 3,699,000 people (the report population). It describes how drinking-water supplies met the requirements of the Drinking-water Standards for New Zealand (the Standards) and their progress towards meeting the requirements of the Health Act 1956, as amended in 2007 (the Act).

Method of collection/Data provider

Information on drinking-water quality was obtained from drinking-water assessors employed by district health board public health units, using questionnaires that sought data relating to water supply quality, monitoring and management. The information was collected at the level of the distribution zone. Two surveys were used to gather information.
The first survey sought information about the microbiological and chemical quality of the drinking-water, water treatment processes in use, the means used to demonstrate achievement against the Standards, and the status of water safety plans. This survey utilised the online Water Information New Zealand (WINZ) database.
The second survey sought information relating to the management of the supplies by drinking-water suppliers, in terms of the requirements of the Act that will eventually apply to water suppliers. The completed spreadsheets were returned to ESR for compilation and analysis.