Small coastal aquifers seriously at risk after weekend rain provides little relief

Kaikohe received 1.4mm and Kerikeri recorded 0.4mm of rain over the weekend. Photo / File

Northland's small coastal catchments may become the next victims of the region's unrelenting drought as the Northland Regional Council prepares to issue water shortage directions in 23 communities.

Water and waste manager Ali McHugh warned that the regional council is likely to restrict water to essential use only – meaning reasonable household domestic and stock welfare needs – in these coastal areas "in the very near future".

"More than two dozen aquifers are nearing, or quickly heading towards, their lowest groundwater levels on record and this could cause problems for many of our small coastal communities," she said.

"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."

Small, shallow coastal groundwater systems will likely drop to significantly lower levels than would normally be seen during the next two to three months, bringing the real risk of saltwater 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 before a bore water supply could be used again.

McHugh urged people to save all the water they can 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."

Minor rain over the weekend made next to no difference to the ongoing drought, providing little relief to the region.

Water St in Whangārei recorded the most rainfall with 11.8mm, followed by Cape Reinga with 8.8mm and Onerahi Aiport with 7.8mm.

Kaikohe only got 1.4mm and Kerikeri 0.4mm. 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.

Coastal aquifers sensitive to saltwater 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

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