As the big drought in Auckland continues and severe water restrictions are more likely this summer, Bernard Orsman looks at the role suburban rainwater tanks play to help households and the environment.
After much dilly-dallying and a severe drought, Auckland Council is starting to take suburban rainwater tanks seriously.
Mayor Phil Goff this week announced the council is scrapping resource consent fees for suburban tanks and considering making them a requirement for new developments.
Tomorrow councillors will get a heads-up on scrapping archaic and costly barriers to installing rainwater tanks after a warning from MetService, that the city's water shortage has been pushed to "critical".
MetService's forecast for a drier-than-normal spring and a strong ridge of high pressure preventing rain in Auckland raises the stakes for a summer of severe water restrictions.
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Suburban rainwater tanks are not a silver bullet - historically there are few applications - but they give people another water supply to water the garden, wash the house and car and feed through the toilet system. They also take pressure off the city's stormwater system.
Rainwater tanks are compulsory on most new houses in Sydney to meet a mains water saving target of 40 per cent.
In Auckland, rural areas and the Hauraki Gulf islands rely on water tanks but the council and Watercare have shown little interest in suburban rainwater tanks since the Super City was formed in 2010.
A council report on the benefits and barriers of rainwater collection tanks in February this year included a "people's panel" survey that found high interest in tanks but people were put off by the high cost and difficult consenting process.
The report said the cost of a tank varied from $500 to $4500, depending on size. Installation costs are between $6100 and $7100 for a 500-litre tank for outdoor use and toilet flushing.
The council poorly promotes and provides little guidance on installing rainwater tanks, and ties people in red tape, the report found.
Under the Unitary Plan, rain tanks higher than 1m are deemed a building and require a resource consent. This captures modern slimline tanks that sit flush against a house.
Then there is the cost of resource consent, including an upfront deposit, which can be more than the cost of the tank itself, plus an administrative charge of $250. Maintenance costs are about $165 a year, according to the report.
The economic benefits of rain tanks are marginal at best. Because suburban water tanks cannot be used for drinking water, they can only save about half of the average household water bill of $970 a year. In some cases, it would take more than 20 years to pay them off.
The report, by the council's Healthy Waters stormwater division, said rainwater tanks could help households during a drought if water is stored during rainy periods. Furthermore, they could help the city's water challenges, particularly if installed on a large scale and across catchments.
Faced with a crisis, councillors will begin tomorrow to scrap the need for consents and look at incentives for installing rain tanks. This will require a change to the Unitary Plan - a lengthy process.
Council planning chairman Chris Darby says the council has to wear criticism for the crisis it finds itself in, saying the drought is a near repeat to the middle of last year when nature came to the rescue with heavy rain in late winter and spring.
He backs suburban rainwater tanks, saying they win on two fronts.
"They store water during extreme rainfall to take pressure off the stormwater system and provide water during drought," he said.
Darby believes Watercare is fixated on big-ticket solutions and dismissive of tanks, possibly because every tank means less revenue.
He believes innovative solutions at the council have been worked up by staff - he only found out about the Healthy Waters rainwater tank report after some probing - but sealed off by senior managers.
Darby said Auckland gets 1.25 metres of rain a year and although it is not of a drinking standard, it can meet more than half of household demand.
"It seems to be a pretty obvious place to go. There has been resistance and now I hope we are starting to look at the urgency of valuing that rainfall and not just using it for residential supply but also addressing the flooding challenges," he said.
Goff, too, has said it makes sense to capture rainwater, saying a change in thinking is long overdue.
Watercare played down the value of suburban rainwater tanks in hot and dry summers when peak demand is up to 560 million litres of water a day.
"Peak demand typically occurs in February when it is hot and dry. It's also when people's rain tanks typically run dry and they turn to the metropolitan supply for water."
Watercare said rain tanks can be useful when average demand is around 440 million litres of water a day, which helps the dams fill up over the winter months.
Councillor Daniel Newman, who has worked for Watercare, said dealing with consenting issues to install water tanks is a modest suggestion.
The bigger issue, he said, has been the planning failure to address water security and transport while tackling the housing crisis.
"Packing in housing, whether townhouses, apartments, greenfield subdivisions and infill housing has triggered more and more demand for services that we simply do not have.
"Warning of chronic infrastructure deficits were ignored when preparing the Auckland Unitary Plan," said Newman.
This issue was picked up in the Healthy Waters report, which said population growth and intensification will increase pressure on the city's waterways.
By 2048, many areas in Auckland will have an impervious area of more than 40 per cent and some areas will have up to 60 per cent. Stormwater management calls for on-site stormwater measures where imperviousness is greater than 15 per cent.
The report said rain tanks could help with stormwater run-off, flooding and degraded river and stream health.