Small coastal aquifers seriously at risk; NRC

24 Feb 2020, 3:00 PM

Northland’s small coastal catchments are set to become the next victims of the region’s unrelenting drought, with the Northland Regional Council poised to issue water shortage directions in 23 communities.

Water and Waste Manager Ali McHugh warns that the regional council’s likely to restrict water to essential use only in these coastal areas “in the very near future”.  (Essential use is ‘reasonable’ household domestic needs and stock welfare needs.)

“More than two dozen aquifers are nearing (or quickly heading toward) their lowest groundwater levels on record and this could cause problems for many of our small coastal communities,” she says. “For those drawing water from bores in these areas, this means if they have not already, they may soon begin experiencing issues such as water becoming noticeably salty and other bore behaviour they have not encountered before.”

Ms McHugh expects the small, shallow coastal groundwater systems will drop to significantly lower levels than would normally be seen during the next two to three months, bringing the real risk of saltwater (or ‘saline’) intrusion into freshwater systems.

“There is a real risk that there will be water that’s unsuitable for drinking – or even no water at all – as shallow bores become unable to pump water and deeper bores are impacted by saltwater moving inland.” If too much saltwater intrusion occurs, it could take many months for things to improve to a point where a bore water supply could be used again.

On that basis, Ms McHugh urges people to save all the water they can (if they are not already doing so) and if possible, reduce pumping rates further.

“In these conditions, it’s best to pump slowly from a groundwater system into a tank, which allows more recovery time for the aquifer and acts as a buffer if any issues arise with the bore.”

Ms McHugh says in small coastal settlements heavily reliant on aquifers, most bore water is taken by private individuals as a ‘permitted activity’, meaning no resource consent is required to take reasonably small amounts to meet daily domestic and stock drinking water needs.

However, she says it’s important to remember that during drought conditions, most groundwater users are just as much at the mercy of the lack of rain those relying on surface (stream, water and lake) supplies.

Predicted low groundwater levels are driven by the very large rainfall deficit the region has experienced in the past 18 months, with rivers now below drought flows at 93% of the council’s flow monitoring stations.

The anticipated 14-day water shortage directions will restrict water use to “reasonable household domestic needs and stock welfare needs”.

Water will not be able to be taken for irrigation, garden watering (other than with recycled domestic water from laundries, kitchen and bathrooms) car washing, water blasting and filling swimming and spa pools during the term of the directions, which can be extended as required.

“We will be monitoring water use; and those found using non-essential water such as for swimming pools, washing boats, and irrigation, may find themselves facing enforcement action for breaching the water shortage directions,” says Ms McHugh.

The council recently issued a water shortage direction for the whole of the Awanui River catchment and has been issuing general advice about the dry weather, minimal rainfall and dwindling groundwater for months.

Ms McHugh says people who have a critical need to take water and are unclear about whether they can do so under a water shortage direction should contact the regional council on freephone (0800) 002 004.

She says coastal aquifers sensitive to saline intrusion are;

  • Russell/Tapeka
  • Ngunguru
  • Tutukaka
  • Matapōuri North and South
  • Taipā
  • Coopers Beach/Cable Bay/Mangonui
  • Whangaumu Bay
  • Kowharewa Bay
  • Church Bay
  • Pataua North and South
  • Bland Bay
  • Ōākura
  • Teal Bay
  • Moureeses Bay
  • Sandy Bay
  • Taiharuru Bay
  • Taupo Bay
  • Tauranga Bay
  • Whananaki North and South
  • Woolleys Bay
  • Matauri Bay
  • Te Ngaere Bay

Meanwhile, Ms McHugh says other aquifers also likely to be affected soon are;

  • Ruawai
  • Whatitiri/Poroti
  • Maungakaramea
  • Maunu/Maungatapere
  • Mangawhai
  • Tara
  • Kaikohe (for other groundwater users)
  • Glenbervie
  • Three Mile Bush
  • Matarau.