Taking Waikato water does not mean Auckland can return to its wasteful old ways

Monday, 23 August 2021

The Waikato River and the location where Auckland draws water into its pipeline

OPINION: The boosting of Auckland’s water supply from July with an extra 50 million litres a day from the Waikato River should have ended the city’s drought worries, correct?

Actually no. Or at least not yet as the juggling act with the city’s dams and other smaller supplies means the glass is still half-full, and filling only slowly.

Since Auckland’s water dams bottomed out at 42 per cent in early 2020, in the wake of a record dry summer and two below-average winters, $224 million has been spent boosting the city’s supply.

Fifteen million litres a day are coming from recommissioned smaller supplies such as bores and a dam, along with 75 million litres a day in two steps from the Waikato River – together equal to 21 per cent of current demand.

* Auckland's water crisis was a good thing

* Auckland drought: How just thinking about water made the difference

22-05-20 Stuff Image David White/Stuff.The Upper Nihotupu Dam in Parau. Auckland worst drought has seen dam levels fall to record lows.DROUGHT WATER WATERCARE

Along with that boost consumption has fallen sharply, partly due to low level restrictions on outdoor use but mainly due to a huge effort by larger users, including Auckland Council, to be smarter.

So with the river now able to supply 56 per cent of Auckland’s current winter needs, why is it supplying less than half and why are the dams continuing to be drained rather than filled to the brim for summer?

Juggling Auckland’s 10 dams, clustered in the western and southern ranges, and a handful of small supplies such as bores is not simple.

Each of the dam groups has a bare minimum outflow that must be maintained to avoid complicated shutdowns, meaning the first almost 140 million litres a day has to come from the dams.

The Waikato River’s two separate plants can on paper supply 225 million litres a day but the need for maintenance, cleaning and not running plants at full tilt for long periods, means 190 million litres a day is more realistic.

Watercare’s new $145 million water treatment plant boosting the take from the Waikato River.

Other tweaks mean the small Waitākere Dam is also being run, simply because it is full and overspilling would be a waste.

Watercare took water from Western Springs lake for use by commercial users not needing drinking-standard water.

The end result is that the council’s company, Watercare, does not expect the dams to rise to 100 per cent before the expected hit from a dry summer.

The collection of resource consents which Auckland currently holds for Waikato water also means the volume it takes could drop from the current 225 million litres a day, to 175 million litres a day in summer, if the river level falls.

One of the consents, for 100 million litres a day, is valid only between May and September and beyond that only while river levels remain above their median flows.

That would leave the only backup being a “loan” of 25 million litres a day from Hamilton City Council from October to April, providing river levels don’t fall too low.

All of this is a juggling act that was not so critical when Auckland’s seasonal weather was “normal”.

However, with the warning drought in 2019 that ended without anyone being alarmed, the real drought of 2020, and continuing long-range forecasts picking at best normal rain tending drier-than-normal, it could be well into 2022 before the dams fill, if they do.

This need not be alarming. The restrictions of 2020 and the scramble to reduce waste of precious treated drinking water highlighted how wasteful and water-reckless Auckland had become.

The Waikato River water will keep Auckland out of trouble, especially if the unconditional 150 million litres a day take is granted by a fast track board of inquiry hearing.

But the river won’t be enough to allow Auckland to return to its wasteful old ways and won’t avert the need to do far more to conserve whatever water falls from the skies.