Domestic and Industrial Use
Approximately 70 per cent of the population of New Zealand is served by public water supply piped systems. Apart from a small proportion which relies on Government-owned water supplies, the remaining population obtain their water from private sources, such as springs, streams, shallow wells, artesian bores, and roof catchments. On a national basis, there is no shortage of water for present or likely future uses. In some districts, however, such as arid Central Otago and the larger urban areas, water is not available where it is wanted, and so must be obtained from distant sources to meet the demand. In addition, although rainfall is generally abundant and evenly distributed throughout the year, some districts suffer from seasonal drought conditions which cause temporary shortages of water. This condition applies particularly to the hill country on the east coast of the North Island and in the northern part of the South Island.
The supply of a safe and wholesome water to the urban population depends on one of the largest and certainly one of the most important industries in the country. The demand for water varies considerably from one locality to another and from season to season, but the average daily demand for each person served by a public supply generally falls within the range of 50 to 90 gallons. This represents an annual usage of something like 100 tons of water for every man, woman, and child. Fortunately water is one of the cheapest commodities available to the public, the cost being about 6d. a ton delivered into each household every day of the year. The total amount of water delivered by urban water supply systems averages about 120 million gallons a day, but rises to about 200 million gallons a day in mid-summer.
Public supplies of water are obtained mainly from rivers and streams with their sources in bush-covered upland catchments, while only about 20 per cent are drawn from groundwater sources. The water obtained from surface sources, while originally of good quality, is deteriorating as catchment cover is destroyed by wild animals such as deer, pig, and opossum, and as the upland areas become developed for pastoral and agricultural purposes. These areas are also becoming more accessible to the public and increasingly used for recreational purposes by trampers and others, with consequent greater risk of water contamination. Thus many supplies, once reasonably safe, now require treatment to ensure their suitability for public consumption.
The Department of Health in 1960 adopted the “International Standards for Drinking Water” issued by the World Health Organisation as a basis for assessing drinking-water quality. In 1961 the Department made a survey of over 200 public and Government water supplies serving 70 per cent of the country's population, and graded each supply against these international standards. The survey indicated that only 44 of the individual supplies, serving 35 per cent of the total population on public supplies, could qualify for an “A” grading (“Good”). A further 87 supplies, serving 41 per cent of the total, were graded “B” (“Doubtful – better operation and possibly better treatment and/or other improvements required”), while the remaining supplies, serving 24 per cent of the population, were regarded as unsatisfactory.
Industries, especially those concerned with food processing and pulp and paper production, have a high demand for water. The meat and other food industries have seasonal demands, whereas the pulp and paper industry uses something of the order of 40 million gallons a day throughout the whole year. The latter industry, which is located in proximity to the exotic forests some distance from towns and cities, has its own independent water supplies. Some of the meat-processing plants are sited near centres of population and may draw their water requirements form public supplies, but the remainder have their own sources. The total national requirements for the meat industry is some 50 million gallons a day in the peak summer period.