Alarm bells ring for aquifer users

Houhora farmer (and former Far North District councillor) Eric Wagener fears that taking water from the Sweetwater aquifer for Kaitaia could compromise the aquifer to the point where the industries that already depend upon it will be put out of business.

If that were to happen, he said, the cost would be multiplied by the loss of future potential for horticulture and cropping.

"The only thing that enables orcharding and cropping activity to take place in the unique Far North soils is the ability to access ground water on the Aupouri Peninsular," Mr Wagener said.

"Without substantial and dependable water supplies, these industries will die."

Key to the debate was how the aquifer was replenished. Engineers had expressed the view that sources included run-off from the Maungataniwha Ranges, but in general soils were poorly-draining, with maximum absorption of 10ml per square metre, only a small percentage of which would penetrate to any depth. Much would be taken up by plants, grasses, wind and sun.

Most people living on those soils knew that real soakage only occurred under very dry conditions, over about three months of the year.

"Why, if ground water is replenished from [the Maungataniwha ranges], is it found only in this area?" he asked.

"The aquifer is relatively narrow."

The effects of Aupouri Forest also sounded a warning.

"There is no doubt that in the Waiharara, Pukenui, Houhora area shallow groundwater levels fell dramatically with the advent of forestry growth," he added.

"Springs which in my parents' lifetime had never run dry even in the worst droughts disappeared, as did lakes and rivers in the sand dunes. Rivers flowing out on to 90 Mile Beach dried up, and springs we relied on for farm water disappeared.

"Since the current clear felling a lot of the springs are now flowing, and causing problems for orchardists, even with deep-draining/pan-breaking activity.

"One has to ask why the water doesn't disappear through the broken pan, into the sand to the deep aquifer.

"Years ago, because of spring depletion, we sank the first deep bore into the shell bed in the district. Before this no one knew that this aquifer existed. Most bores were shallow in comparison.

"This peninsular is noted for impervious sandstone layers. So again, how does this extensive aquifer become replenished if not from above?"

Tidal effectContractors who broke the deep sandstone for avocado orchards in the Houhora area had noted that groundwater did not fall once the pan was destroyed but rose and fell regularly, after the harbour tide rise and fall.

It stood to reason therefore that if soils in the greater Kaitaia area did not allow significant water penetration, and the Aupouri Peninsular had an impervious sandstone base, the aquifer most likely comprised filtered salt water.

"If this is the case, which I believe it is, then if this aquifer is subjected to massive extraction the filtering action through the sand media will not cope and the water will become brackish and useless for human, animal and food production," Mr Wagener said.

"Once again human folly will cause economic ruin. There are plenty of examples both here in New Zealand and worldwide which can attest to this truth.

"Current figures of the proposed extraction rate for Kaitaia exceed my rough estimate of the total agricultural/horticultural allowance. This agricultural/horticultural draw-off is for no more than three or four months of the year. There is no draw-off for at least eight months of the year, when the resource can be replenished by natural means.

"I am not an engineer and I am not calling into question the processes to date in the issuing of resource consent, as people can only form opinions on the information considered and situations assumed. I am just concerned that industries that have no alternatives could be at severe risk. Once the aquifer is compromised there is no way back."

The answer, for Kaitaia, would be to increase the capacity of the kauri dam, while tests needed to be undertaken to establish exactly how the aquifer was supplied.

Those tests should show the shape of the bedrock basin holding the groundwater, and whether that structure extended beyond the shoreline of either coast. That could indicate that the aquifer was fed from the sea.

"It is imperative for the security of the economic growth of the Far North that the aquifer is protected from indiscriminate use when alternatives are present for urban/city use, and there is no alternative supply for the economic growth of the Far North productive sector, in particular the Waiharara, Motutangi, Pukenui, Houhora area," he added.

"We have no real ability to dam water.

"It is imperative that the source of replenishment is known with certainty. Without that knowledge, development can exceed sustainable supply.

"I understand that the test bore in Kaitaia, when under test, ran dry. The replenishment was not sufficient to match the outflow. This should raise warning bells. It is not good enough to state 'We estimate,' or 'current studies indicate'. We need to actually know with a high degree of certainty all aspects of the sustainability of the resource."