Water supply in the Wellington region involves the provision of drinking water services in the Greater Wellington region of New Zealand.
Water supplies to the Wellington metropolitan area meet the requirements of the Health Act and conform with drinking water standards. However, for some of the towns in the Kāpiti Coast and Wairarapa regions, there have been occasional non-conformances with the required standards for drinking water quality and safety.
The challenges for managing the three waters in the Wellington region include the deteriorated condition of pipelines in the Wellington metropolitan area. The pipelines are in significantly worse condition than those in other large networks nationwide, and there has been a recent history of serious failures. As at 2023, around 44% of the treated water is lost through leaks. The water supply to the region is also at significant risk during a severe earthquake, although some projects are underway to improve resilience.
Asset ownership and service provision
The three waters assets in the Wellington metropolitan area are owned by five councils: Wellington City, Hutt, Upper Hutt and Porirua city councils, and the Greater Wellington Regional Council. However, the water assets of these councils are managed by an infrastructure asset management company, Wellington Water. From 1 October 2019, Wellington Water also became the asset manager of the water assets of the South Wairarapa District Council.
Wellington Water is jointly owned by all six councils.
The assets in the region covered by these six councils includes 6,300 km of pipes, 138 reservoirs, 249 pump stations and four drinking water treatment plants.
Three waters services for the remaining parts of the Greater Wellington region are provided by the Kāpiti Coast District Council, the Carterton District Council and Masterton District Council.
Asset management and investment planning
Benchmarking data published by Water New Zealand as part of their 2018/19 National Performance Review showed that capital expenditure on three waters assets in the Wellington region is well below the average of the expenditure on networks in most other major centres. Approximately 200 kilometres of the city's pipes were laid before the outbreak of World War I, and more than half of all the city's pipes will need replacing in the coming three decades. $578 million is required to fix a backlog of existing issues as at 2020. The forecast costs for new investment just to cope with expected population growth range from $2 billion to $4.5 billion.
Wellington city councillors commented at about the same time that the city was already spending a third of its annual budget on water systems. Councillor Sean Rush said that prioritisation of expenditure had to change from age-based replacement to where the consequences of failure would be the worst.
In May 2021, the Wellington City Council approved a 10 year plan that included expenditure of $2.7billion on water pipe maintenance and upgrades in Wellington city, and an additional $147 to $208 million for plant upgrades at the Moa Point wastewater treatment plant.
In June 2021, a report released by Wellington Water gave estimates for investments in water infrastructure that could be required to meet forecast population growth to 2050. The report indicated that total new investment for growth could reach $3.6billion. The estimated cost of upgrade per new dwelling varied widely across the region, from $70,000 to $520,000.
In 2023, a meeting of regional leaders was held to review projected shortfalls in the supply of water. Options under consideration included installation of universal water metering to contain demand, continued emphasis on finding and repairing leaks, and constructing new water storage. It was reported that around 44% of the region's treated water supply is lost through leaks.
Regional water supply networks The supply of reticulated drinking water is regulated under the Health Act, and suppliers are registered and subject to a testing regime. The registered water suppliers for the Greater Wellington region are listed in annual drinking water quality reports published by the Ministry of Health.
Supplier Region/ Town Population Greater Wellington Water Wellington metropolitan area – bulk supply 350,000 Hutt City Council Lower Hutt 95,469 Kāpiti Coast District Council Ōtaki 5,700 Kāpiti Coast District Council Paekākāriki 1,665 Kāpiti Coast District Council Waikanae, Paraparaumu, Raumati 35,800 Porirua City Council Porirua 46,444 Upper Hutt City Council Upper Hutt 34,650 Wellington City Council Wellington City 165,126 Carterton District Council Carterton 4,200 Masterton District Council Masterton 19,000 Ōpaki Water Supply Association Ōpaki 1,500 South Wairarapa District Council Featherston 2,580 South Wairarapa District Council Greytown 1,952 South Wairarapa District Council Martinborough 1,505 This table omits several small supplies serving populations less than 1,000.
Water sources for Wellington metropolitan area Water supply for the Wellington metropolitan area comes from three sources:
Hutt River Wainuomata and Ōrongorongo rivers Waiwhetu aquifer
There are times each year, particularly during summer months, where the total demand is greater than can be supplied from these sources. There are two large storage lakes that can be used to supplement the supply during these periods.
Hutt River catchment
The Hutt river water supply catchment covers almost 9,000 hectares of bush-clad mountains and valleys at the southern edge of the Tararua Forest Park and adjoining the Kaitoke Regional Park. Rainwater from tributary streams flows into the Hutt River and is intercepted at a weir at Kaitoke, north of Upper Hutt. The water is then strained to remove sticks, leaves and silt, and piped through tunnels to the Te Mārua Water Treatment Plant. Up to 150 million litres of water per day may be diverted from the Hutt River, provided an adequate flow is maintained downstream of the weir. The Hutt water supply catchment provides about 40 percent of the water used in the Wellington metropolitan area each year.
Macaskill storage lakes
There are two large storage lakes at Te Mārua – the Macaskill Lakes. These lakes are filled from the Hutt River intake when the water is clean and there is sufficient flow available. Stored water is pumped from the lakes into the treatment plant when there is not enough water in the river to meet public demand. The storage lakes are also used to meet demand when the river is too dirty – after heavy rainfall – or when it is in flood and the intake is closed to prevent rocks and gravel from entering the intake pipes.
The Macaskill Lakes are 17.3 metres deep and have a combined usable capacity of approximately 3,350 million litres, or enough to meet average water use for around 23 days.
Building the lakes was first proposed in 1975. The construction of the two lakes proved difficult because of weather and on-site conditions, resulting in cost increases and litigation. There were also problems with leaks after completion, leading to further litigation.
Wainuomata/Ōrongorongo rivers The Wainuomata/Ōrongorongo water supply catchment area lies within the Remutaka Ranges to the east of Wainuiomata. The collection area covers 7,600 hectares, and includes the Wainuiomata Water Collection Area. Five low dams (weirs) with intake pipes provide water from the rivers to the Wainuiomata Water Treatment Plant. These catchment areas provide approximately 20% of the water used in the Wellington metropolitan area each year. Water from the Wainuiomata treatment plant is piped to the Hutt Valley through the Wainuiomata Tunnel, an abandoned road tunnel that was converted in 1980 to a utilities tunnel.
Waiwhetu aquifer
The Waiwhetu artesian aquifer is a zone of water-retaining sand, gravel and boulders beneath the Hutt Valley. Water from the Hutt River starts to flow underground around Taita Gorge. From Melling southwards, the water becomes naturally pressurised beneath a layer of hard clay. This pressurised zone is estimated to be up to 70 metres thick at its western edge against the Wellington Fault, and 20 metres thick at the eastern edge of the harbour. The aquifer extends under Wellington Harbour and supplies several hundred fresh water springs in the harbour floor.
Water takes more than 12 months to pass through the aquifer to wells where it is extracted for distribution via the water network. Extraction is monitored and controlled to minimise the risk of saline intrusion. The Waiwhetu Aquifer provides around 40 percent of the annual water supply.
The Te Puna Wai Ora (Spring of Life) in Buick Street, Petone provides unchlorinated water from the aquifer free to the public. In April 2017 the fountains at Te Puna Wai Ora and the Dowse Art Museum were shut down after returning positive results for coliforms. The fountains were reopened to the public after the installation of filtration and UV treatment.
Water sources for remaining areas The water sources for the South Wairarapa District Council area are the Waiohine catchment for Featherston, the Kuratawhiti Street bore for Greytown residents, and the Herricks bore field for users in Martinborough.
Water supplies for the Kāpiti Coast region are sourced from combination of bores and surface water from the Waikanae River.
Water supply for the Carterton district comes from the Kaipatangata Stream and two underground bores.
Masterton's drinking water is sourced from the Waingawa River, about 10 km west of Masterton.
Consumption, losses and metering During a prolonged dry spell in November 2017, Wellington Water reported that weekend consumption in the Wellington metropolitan area reached 171 million litres for the day – around 30 million litres more than a typical day, and the highest November daily consumption in five years. Wellington Water called on consumers to cut back on their water use, and make sure they observe garden watering restrictions.
A National Performance Review published by Water New Zealand for the 2019 financial year showed that daily residential consumption in the Wellington metropolitan region was about 226 litres per person. By way of comparison, daily residential water use in Auckland and Tauranga was significantly lower at about 156 and 189 litres per person respectively. Both Auckland and Tauranga have water metering in place for all residences, but in Wellington only around 1% of residential supplies are currently metered.
The same National Performance Review also compares water losses between supply networks. The 2019 review for Wellington shows that despite having a higher than average system pressure, the water losses (reported as an infrastructure leakage index), were lower than average, and approaching a threshold where action to reduce losses even further could be uneconomic unless there are shortages.
However, in 2023 Wellington Water reported that around 44% of the region's treated water supply is lost through leaks. For Upper Hutt city, Wellington Water reported that 52% of the drinking water supplied was being lost through leaks. An Upper Hutt councillor claimed that the state of the water network in the city was the result of decades of under-investment, and that the city was currently only replacing 1.5 km (0.93 mi) of water mains each year. The Upper Hutt mayor Wayne Guppy disputed the claims and said that he had "no confidence" in Wellington Water and its advice.
In their submission to a Wellington City Council Water Committee, Wellington Water warned that "current water consumption and a growing population will lead to water shortages by 2040".
Water meters In March 2020, it was reported that Wellington City Council was considering installing water meters for all domestic consumers. At the time of that report, only 1,200 residential properties in Wellington were using water meters.