Drinking Water for New Zealand
Managed by ESR for the Ministry of Health. Data extracted from the National WINZ Database.
The Ministry of Health, through the provision of standards, guidelines and other tools, ensures that an appropriate infrastructure is present in New Zealand to support the provision of clean and safe drinking-watter to communities. Underlying the standards and processes is the Health (Drinking-Water) Amendment Act 2007.
Three organisations are concerned with the provision of safe and wholesome drinking-water to any particular community in New Zealand, one at the local level, one regional and one with a national perspective.
At the local level, the typical supply in this Register is owned by a territorial local authority (TLA) such as a district or city council. They extract the source water, run the treatment plant to remove risks or contaminants, and pipe the water to your door. Under the Drinking-Water Standards for New Zealand 2005, they are expected to test the water regularly to demonstrate that it is safe. If you are unhappy with your water supply, your first step should be to contact them.
The drinking-water standards were produced by the Ministry of Health, which has a national function to ensure appropriate regulations are in place. The Ministry of Health does not check on the local authorities directly, but instead works at the regional level through the District Health Boards (DHBs). Each DHB is expected to oversee the TLAs in its area and ensure (audit) that they maintain appropriate water quality. In a serious health risk situation, the DHB can, through the health districtís Medical Officer of Health, order a water supply to close, but generally it works effectively through persuasion rather than coercion. You can discuss health aspects of your drinking-water with your DHB if you have concerns. DHBs also report to the Ministry so that a national picture (such as this Register) can be maintained of the state of all community drinking-water supplies.
Drinking-water responsibilities of of the DHBS are undertaken by Drinking-Water Assessors (DWAs). Formerly this work was covered by Health Protection Officers, but the Health (Drinking-Water) Amendment Act 2007 provides for the more specialised DWA role.
The simplest water supply is just a well with a pipe from it, or a pipe from a river or lake, perhaps with a pump and storage tank. More commonly though, as a population increases, a treatment plant is required to remove actual or potential contaminants and ensure the water delivered is safe to drink. The most common treatment is chlorination, where a chemical compound is mixed with the water to kill any bacteria from the source. This treatment will also maintain some degree of residual "resistance" to any subsequent bacterial entry to the water while it is in the pipework. Other treatment processes include coagulation (making fine particles drop out), filtration and the removal of other contaminants. Removal of cloudiness is important because chlorination is not as effective otherwise.
The water is transported to users through a network of pipes, known as the reticulation or distribution system. In larger cities, some suburbs may be supplied differently from others. Additional pumping may be required to suburbs on the hills, or the city may be subdivided, with one plant supplying to one part but not to another. For a complex situation like Dunedin City, at least eight areas can be identified as having water different to their neighbouring suburbs.
The different components of a water supply are listed in the Register, with lines to indicate how they are connected. The terms used are formally defined in the glossary. Here is a brief summary:
Community: The people served by the supply.
Zone: (or Distribution Zone) That part of the town or community receiving water of similar quality. For a small supply, that means "everywhere". For larger supplies, it may be only part of a town or city. By definition, parts receiving different water will be in different zones.
Plant: The treatment plant supplying the water. In some situations where no treatment is given, a nominal plant is defined as where the water is pumped from or merely gathered together. In others, the treatment plant will have highly technical operations with extensive automated control and monitoring of water quality.
Source: The river, groundwater, or other source from which the water is taken. About half of New Zealandís drinking-water is pumped from the ground, with the remainder coming from surface sources.
In the Register, each of these components is on a separate line and each component has its own code, which is unique in New Zealand. The lines are ordered so that you can see which plants and sources supply each zone.
Chemical contamination of New Zealand supplies is always a risk, but usually it is a very small one. Most chemicals mentioned in the Drinking-Water Standards for New Zealand 2000 specify levels likely to cause adverse effects only after prolonged periods of exposure, so, with some exceptions, chemicals are not the main area of concern unless there is a major chemical spillage.
Throughout the world (and New Zealand is no exception) by far the most common problems arise from microbiological contamination of the source waters. Animal, bird and even human effluent, introduced in one way or another upstream from a water supply, can make that water unfit for consumption. Bacteria have always been of major concern, while protozoa such as Giardia and Cryptosporidium are increasingly being highlighted as causing ill health through drinking-water.
There are two ways of minimising the risk from these microbiological contaminants:
The most successful approach is to use both of these, and to regularly monitor the water quality to demonstrate that any risks are being controlled. Good systematic and ongoing risk management is important.