Huka Falls in Taupō - the headwaters of the Waikato River. Photo / 123RF
Aucklanders could be drinking treated sewage in just a few decades, according to a confidential agreement that will see it stop relying on the Waikato River for its water supplies.
The kawenata, reached between Watercare and Waikato-Tainui iwi in December, would see the Super City progressively slow the taps from the river, while investigating alternative supplies including recycled wastewater and desalination plants.
The agreement was part of Watercare gaining support from the iwi for its application to take another 150 million litres a day (MLD) from the river, making up a total consented maximum of 300MLD. The bid is currently open for consultation.
Hamilton City Council has already indicated it will "conditionally oppose" the application, and Waikato Regional Council has also voiced concerns.
If approved, the take would make Watercare easily the largest water user on the river, surpassing Wairakei Pastoral Ltd - an estate mostly made up of dairy farms - which has consent to take just under 153MLD.
Watercare currently pumps 175MLD out of the river - which includes an emergency allocation from Hamilton City Council of 25MLD - making up well over a third of the total 440MLD used on average by Auckland's 1.6 million residents and 40,000 businesses.
The rest comes from storage dams - the largest in the Hūnua Ranges and smaller in Waitākere Ranges- and smaller sources including aquifers.
Watercare has long seen the river as the most reliable and cost-effective future source for the city's water needs - largely because it does not rely on immediate rainfall - and in 2013 it lodged a resource consent application to take another 200MLD, estimated to provide water needs until at least 2060.
While under its planning - taking into account population growth, demand and climate change - any of the extra supply would not be needed until 2026, a public battle over Waikato River water broke out last year, as Auckland endured its driest start to the year on record, and storage lakes neared record lows.
With water restrictions introduced for the first time in decades and public pressure building, Auckland Mayor Phil Goff urged Waikato Regional Council to process the consent from 2013, which he said was lagging in the queue with around 100 other applications ahead.
That led to a spat between regional leaders, with Auckland accused of "queue-jumping", criticism of the RMA process, and even talk of Auckland paying for water.
Eventually, Environment Minister David Parker stepped in, deeming the consent application a matter of national significance, meaning it would be fast-tracked and considered by a Board of Inquiry under the Environmental Protection Agency.
But that move came with concern from Waikato-Tainui and Waikato Regional Council, along with industry and businesses and environmentalists, about the impact it would have on the already severely degraded and over-allocated waterbody.
After months of negotiations, a confidential agreement was reached between Watercare and Waikato-Tainui in December, with the iwi supporting the consent application while requiring a "reduction over time" in Auckland's reliance on the Waikato River for its municipal water supply.
This started with Watercare reducing its original application from 200MLD to 150MLD, reflecting Waikato-Tainui's special relationship with the river as outlined in the Waikato-Tainui Raupatu Claims (Waikato River) Settlement Act 2010.
The agreement also implies - provided the consent is granted - seeking "alternative solutions" sooner than planned, and establishing a trust through which to fund restoration projects along the awa.
Watercare refused to provide the Herald a copy of the agreement, stating it was "confidential", nor comment for the article, citing the current consultation process.
Waikato-Tainui also declined to comment.
Auckland Mayor Phil Goff said the agreement meant the Waikato River meeting a significant portion of demand growth for the nearer-term future, and providing time to plan for and commission another large water source.
"Waikato-Tainui has stated that restoration and protection of the awa is at the heart of the agreement, and that it balances the needs of the communities with the needs of the awa for future generations," Goff said.
The extra take would not jeopardise other users, and not have a detrimental effect on the environment, he said.
"It would reduce water levels on the Waikato by less than 2cm at a point where 16 billion litres of water a day flows past the Tuakau intake and out to sea."
The trust established would fund projects to clean up the river's water quality, which is heavily affected by urban and rural run-off - much of it upstream from Auckland's intake.
Seed funding for the trust was $1.5 million and further funding for remediating poor water quality in the Waikato will be forthcoming, Goff said.
Work would likely support activities such as stream bank stabilisation, riparian planting and monitoring and research programmes.
Auckland Council was developing a water strategy with input from Watercare about future long-term options, Goff said.
"Desalination currently is prohibitively expensive, although with new technology may become cheaper in the future.
"Recycling of wastewater to guarantee purity is also more expensive than drawing water from the Waikato but could provide a guaranteed source of water for the future."
Watercare and the council were also working on conserving and fixing leaks, with work in the past few years already saving around 5 million litres a day.
The council was also encouraging greater use of rainwater, for example by removing charges for resource consents, but longer term these were not seen as being viable water sources due to their dependence on rainfall, like the storage dams.
The new water source will be needed progressively from 2026, according to Watercare.
This is to keep up with population growth that will see Watercare customers increase from 1.48m people in 2020 to 2.2m in 2055.
Watercare expects annual average water usage to increase from 432.9MLD in 2020 to 638.8MLD by 2055.
Consultation documents discussed five options to provide Auckland with the 150MLD needed over the next 35 years: the Waikato River, purified recycled wastewater, desalinated water, increasing dam supplies, and rainwater tanks.
Watercare's preferred option is to increase the amount of water taken from the Waikato River, increasing its current consented take from 150MLD to 300MLD.
A report prepared by Beca found that compared to other large-scale options like recycled water and desalination plants it was much cheaper, and less carbon-intensive.
And due to existing infrastructure it would also be much faster to implement, making it the only option that would enable Watercare to ensure security of supply during a drought between 2025-2027, and meet peak demand by 2028.
The estimated capital cost for the Waikato A 75MLD WTP and associated transmission of water is $200-$290m, while that for the Waikato A 150MLD WTP and associated transmission is up to $830m (predominantly for a new pipeline and reservoirs).
While favouring this approach, Watercare would also commit to investigate the potential direct and indirect purified recycled water "large scheme" options for potential implementation in the late 2030s to meet ongoing growth in demand.
Watercare asserts its extra take from the Waikato River would not impact on other water-users, and its impacts on the environment would be "less than minor".
However, consultation documents showed Waikato-Tainui representatives said Watercare doubling its take from the river was their "least favoured option" due to the impacts on the mauri, life-supporting capacity.
They supported the application ultimately due to "timing constraints involved in seeking to meet Auckland water supply demands", but indicated that other options such as wastewater reuse should be considered as future water supply options.
The application would also have to fit in within the Waikato Regional Plan, which provides specific allocation limits at various points of the river based on ecological, cultural and recreational values.
Hamilton City Council recently voted to "conditionally oppose" the take in its submission, meaning it would have a chance to address the Board of Inquiry during the hearing about future water issues.
Waikato Regional Council voiced no opinion in the consultation documents, leaving any position up to elected councillors, but chair Russ Rimmington reportedly believes Auckland shouldn't be getting another drop from the river. He declined to comment for this article.
Waikato Regional Council had been working with existing and aspiring consent holders to ensure water use was justified. This had reduced allocation pressure and freed up about 181MLD, and in turn removed the "queue" meaning applications could now be processed based on need rather than "first in, first served".
Other major water users including Fonterra, Horticulture NZ and Mercury Energy also expressed concerns about how the application would affect other applications and future water demands.
Fish and Game and the Department of Conservation reported concerns over environmental impacts but withheld their views on the application.
A high-level concept design by Beca has been developed for Watercare of three purified recycled water schemes involving an Advanced Water Treatment Plant (AWTP) process at either Rosedale or Māngere WWTP.
The schemes would start at producing 75MLD, scaling up to 150MLD at a cost of between $840m and $1.9b.
This option would need a change in Government regulation to allow treated sewage to be used as a water supply, meaning the timeframe for implementing a scheme was difficult to determine but estimated at least 15 years.
Other major factors to consider was "community resistance and cultural concerns".
"There is currently no certainty about the willingness of central government to progress such a change, and the timeframe in which this could be achieved, particularly given the likelihood of community resistance and cultural concerns in relation to purified recycled water as a drinking water source," report authors said.
"Community resistance would seem particularly likely if purified recycled water was
pumped directly into the treated water network (as with the Rosedale or Māngere direct
potable reuse options) and is also likely to be significant with an indirect use option."
Similar schemes are used in about 35 cities around the world, and have been in parts of the United States since the 1960s. Even Thames Water in London is looking into it.
However, most are at much lower levels than proposed for Auckland, generally from 2-27MLD.
Other approaches include recharging aquifers with purified recycled wastewater, adding another layer of filtration.
In Perth - which has seen dramatic decreases in rainfall due to climate change - about 14 billion litres of recycled water is added to the city's aquifers every year, with work to double capacity due for completion next year.
Another proposal was a desalination scheme located at the Rosedale Wastewater Treatment Plant.
A concept report by Beca involved involve a pipeline running about four kilometres out to sea and new treated water storage facilities at Schnapper Rock.
Desalination was deemed much more costly that the Waikato River take, with an estimate for the first 75 MLD stage $1.4 billion, while the second stage cost estimate is a further $380m.
It was by far the most energy-intensive and had the largest carbon impact, and would require hundreds of millions of litres of extra, undrinkable water, to be discharged each day.
This option would also need a change in regulations which could take up to 10 years, and another 10 years to implement the scheme.
Consultants suggested raising all 10 storage dams by 10 to 15m, which could see an extra 73MLD for the city.
However, it would likely have the highest environmental impact, displacing ecosystems in the process.
"Construction and operation of the raised dam would result in significant environmental
effects, particularly on indigenous biodiversity and habitats and on freshwater systems.
"Notwithstanding any other measures to avoid, minimise and remedy effects, substantial
offsets and/or compensation would still be required."
While it would be much less costly, at $117m-$135m, and less time-consuming, around 5 to 8 years, there were limited options to scale up to the level of supply required.
It also offered no increased diversity in supply as it would still rely on rainwater.
Beca also investigated rainwater tanks. Its report concluded that if approximately 270,000 small, medium and large rainwater tanks were installed within new and existing properties by 2055, the average yield would be expected to be between 15MLD and 30 MLD.
This would come with a total capital cost of $1.623 billion.
"While use of rainwater tanks is technically feasible, they would not provide the water
required to meet the supply/demand balance requirements," the report found.
There was also "significant uncertainty" associated with implementation of this option (in terms of timing and uptake) and with the ongoing contribution that such tanks would provide (due to maintenance and tank management requirements).
Also like increasing dam supply, rainwater tanks relied on rain, and with climate change m it was not seen as the most reliable source.
One issue seemed harder to agree on than most - how big the crowd was.