How much water is Wellington losing?

Saturday, 30 December 2023

A burst water pipe in Marjoriebanks Street, Mt Victoria.

Nicholas Boyack investigates how water leaks are measured and includes some facts and figures, which show the magnitude of the problem facing the region.

When Wellington Water held a recent “summit” to reinforce how serious the looming water crisis is, a surprise fact emerged. Upper Hutt was losing more than half the water in its pipes to leaks.

Mayor Wayne Guppy subsequently rejected the claim that his city was the leakiest in the region, arguing Wellington Water lacked credibility.

Boxing Day shoppers dodge a leak on Lambton Quay near Stout Street.

Wellington Water’s chief drinking water advisor, Laurence Edwards, says the organisation is committed to accurately assessing how much water is being lost.

Without universal water meters, however, producing an accurate figure was not straight forward. For a long time, Wellington Water had relied on a “very small” number of manually read meters.

It used the small sample to provide an estimate for average household water use.

That came with “a large range of uncertainty” and in 2021 Wellington Water installed 16 “small area meters” to monitor residential water use and to provide councils with more accurate data.

Wellington Water is upgrading the Te Mārua Water Treatment Plant to increase the supply of water to the region.

Wellington Water had been collecting and collating that information, and Edwards said it now had much better data.

“We now have a good sample of data … and this, along with our further analysis, shows that the approach we had been using previously underestimated water loss from the network.”

In Upper Hutt’s case that resulted in an increase from 21% to 52%.

Upper Hutt mayor Wayne Guppy disputes the claim that the city is losing 52% of its water due to leaky pipes.

That does not, however, mean Upper Hutt is losing more water than previously. It just means that the figure for Upper Hutt was previously underestimated, he said.

The improved measuring system showed that Porirua was actually losing 41%, rather than the previously estimated figure of 27% and for Wellington City, the figure changed from 26% to 41%.

Edwards said that Wellington Water’s approach had been independently reviewed and audited.

“Our approach is also based on UK reporting guidance where this approach has been used for over 20 years.”

Wellington Water wants Wellingtonians to use less water.

He said, however, that getting truly accurate data could only be achieved by installing universal residential water meters.

The amount of water being lost was due to ageing infrastructure, resulting from historical underinvestment by councils. Getting councils to take the situation seriously, however, was not easy.

The Post recently reported that Upper Hutt had 269 km of pipes needing replacing within 30 years. It is currently replacing leaky pipes at 1.65km per year.

The estimated unbudgeted cost of replacing Upper Hutt’s pipes is $500m.

A burst pipe sends huge plume of water spouting over Aro St.

Last month, Guppy responded to questions about how the council would fund the work required by rejecting the advice given by Wellington Water.

He accused Wellington Water of only presenting “gold plated” options.

Earlier this month, Greater Wellington chair Daran Ponter wrote to the metro mayors giving them an ultimatum to respond, by January 31, with evidence of a commitment to water meters in their long term plan.

Ponter believed there was no point installing costly new storage facilities until councils committed to water meters and renewing leaky pipes.

The region is currently losing the equivalent of 30 Olympics swimming pools a day.

Wellington Water by the numbers

$30b: That’s what Wellington Water says it needs to spend over the next 30 years to bring infrastructure up to scratch.
$2b: The capital cost of installing meters, reducing leaks and increasing storage.
$2b-$4b: The capital cost of increasing the supply of drinking water but not fixing the leaks or installing water meters.
$261m: The total cost of capital projects completed by Wellington Water for the year until the end of June.
One in four: The chance of Wellington running out of water this summer.
64 billion litres: The volume of drinking water delivered to the Wellington region in the year to June 2023.
$300m: The estimated cost of installing universal water meters for the four metro councils.
150,000: The estimated number of extra people in the region, over the next 30 years, for whom Wellington Water has to provide infrastructure.
296: The number of leaks fixed in the week of November 24.
47: The number of leaks fixed in the week before Christmas.
$7.7b: The value of three water assets managed by Wellington Water.
40 litres per day: The amount you can save by having a 2-minute shower.
Four: Level 4 water restrictions would mean two-minute showers, a weekly load of washing per person, and a total ban on outdoor water use.
220 million litres per day: The amount of water that can be supplied in winter. In summer that could fall to 170 million litres. With Wellingtonian using as much 205 million litres that leaves a large potential shortfall.
2543 km: The region's drinking water network is largely 30 to 100 years old and made up of 2543km of pipeline, the equivalent distance of flying from Wellington to Sydney.