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National
Infrastructure Unit
Publication

Infrastructure: Facts and Issues: Towards the First National Infrastructure Plan

Drinking Water

Description

Background and history

181. We are currently seeking further information on this.

Assets

182. The estimated replacement cost of (territorial authority-managed) drinking water-related infrastructure in New Zealand is $11 billion.[46]

183. Metropolitan councils have far fewer individual water schemes than provincial and rural councils, but have a much greater length of reticulation. This reflects the more intense development in metropolitan areas. The table that follows indicates these differences.

  Metropolitan Provincial Rural
Average number of schemes 4 (max 12) 8.4 (max 24) 7.4 (max 23)
Length of reticulation (km) - extrapolated 17,400 14,500 4,500

Source: DIA Water network infrastructure report

184. The estimated capacity of the surveyed water supply systems totals 668 million cubic metres per annum. The capacity utilisation rates range from 22 per cent to 92 per cent and, on average, is 56 per cent. This is the average utilisation over the year. There are seasonal peaks for both water supply and water demand.[47]

Analysis

185. Most of the country's largest urban areas have reliable, quality water supplies. For example:[48]

  • The new supply pipeline from the Waikato River should be adequate to provide the foreseeable needs of Auckland city, although there are some distribution problems due to the location of growth nodes in the northern part of the region.
  • Wellington city and Hutt city are well served by supplies from the Wainuiomata catchment, the Hutt River (run-of-river as well as storage at Te Marua) and the Hutt aquifer.
  • Christchurch city has an excellent high-volume management supply from groundwater.
  • Dunedin's municipal water take comes from a number of small surface streams that tend to dry up in summer and that have minimum flow requirements to protect instream values. This suggests that further supply infrastructure may need to be developed in the future.

186. Water supplies in provincial and rural councils are more variable.

187. There are some areas of New Zealand where population growth pressures and increased demand from other users are creating pressure on drinking water supplies, particularly during drought periods. The 2009-2019 Long Term Council Community Plans (LTCCPs) indicate a number of areas where water supply has been identified as a significant issue. Examples include:

  • Pressure on the municipal supply from both domestic and industrial users in the Tasman district has prompted the commissioning of a feasibility study on a pipeline from the Motueka Plains through Tasman, Ruby Bay and Mapua to the Waimea Plains, eventually linking into the Tasman District Council reticulation system;
  • The Kapiti Coast District Council has a history of water supply issues and is currently considering various water storage and pipeline[49] options; and
  • Councils indicating that they are looking to increase capacity through the construction or enlargement of existing reservoirs.

188. Many territorial authorities introduce either voluntary or active hosing restrictions in drought period to control water use. Volumetric charging is also used by a number of councils.

189. In some regions, tourism has a sizable seasonal impact on drinking water demand (and conversely, on the need to treat wastewater). As a consequence, higher infrastructure capacity is required than would otherwise be needed to meet the requirements of the local community. Some councils indicate the population in some of these areas may increase by over 200 per cent during peak times. For example, the population of Whangamata increases by 650 per cent from 2145 to 21000 in the peak season, and the population in Tekapo increases by 250 per cent from 300 to 1050. The absolute numbers may not be large, but the potential cost impact on small residential towns in the peak season, could be significant.

190. A demand management project involving the Ministry for the Environment, the New Zealand Water and Wastes Association and Local Government New Zealand is now under way to assist water utilities throughout the country to introduce appropriate demand management measures.

Drinking water quality

191. The 2004 Ministry of Economic Development Stocktake[50] noted that new drinking water standards (DWSNZ) proposed at that time by the Ministry of Health would require many territorial authorities to upgrade their water supply infrastructure and management systems. This was particularly an issue for many smaller rural councils and a small number of metropolitan councils, where surface water sources were subject to minimal treatment.

192. Progress has been made in improving the quality of drinking water and wastewater infrastructure. In 2003, 68 per cent of New Zealand’s population received water that was known to comply with the bacteriological requirements of the drinking water standards. By 2008, this had increased to 80 per cent. The graph that follows shows the increasing levels of drinking water supply registration, and improved levels of compliance with drinking water standards (with respect to bacteria).

Trend in bacteriological compliance at the distribution zone
Trend in bacteriological compliance at the distribution zone.
Source: Ministry of Health, Annual Review of Drinking-Water Quality In New Zealand, 2006/07(reproduced)

193. Despite the availability of a government subsidy, the substantial cost of new infrastructure to meet the increased water quality standards mandated by the Ministry of Health remains a significant issue for many councils. Small rural-based councils typically have the greatest issue with the standards as their smaller water schemes (of which they may have a large number) may supply as few as 10 to 50 properties.

194. There is some debate about the appropriateness of the drinking water quality standards. The costs and benefits of the standards are currently under review.

Notes

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