While it could pump water as a last resort, people would have to boil it once it came out the tap, the council said.
Greymouth is experiencing its fourth-driest January and December on record, and the second- or third-warmest.
Some have never seen the Grey River so low, and consequently for the first time since the bores were sunk into the river at Coal Creek in 2001, they are not drawing enough water to meet demand.
As water restrictions remain in place — and could continue into March — council managers are meeting daily.
Group manager operations Aaron Haymes said there was no simple solution, such as diverting the river or pumping water.
He explains: Gravel in the Grey River, brought down over thousands of years, acts as a great filter, and cleans the water. At the bottom of the bores are pumps, which draw in water. It then goes into a treatment area, to ensure it is safe to drink. When there is plenty of water in the river there is literally downward pressure, which means the pumps work well. But as the water table has dropped, the pumps do not work as well.
Mr Haymes said the bores could not be sunk any deeper, as there was harder sandstone further down.
If water was pumped straight from the river it would not have been “cleaned” by the gravel filtration, and people would have to boil it.
“The standards are very, very high. We are in touch with the regulator [Taumata Arowai], as it’s not business as usual.”
Diverting the river could help as it would get the water flow closer to the bores.
“There is a shingle fan we may be able to cut away. We are having a meeting to talk about it.”
However, the risk of that was damaging the gravel filter and increasing turbidity (impurities), he said.
“Gravel is our friend.”
Mr Haymes said he had heard from locals that they had never seen the river so low.
Meanwhile, the council is still trying to bring the disused Runanga bore online. That bore at Sids Road, Coal Creek, was never commissioned because the Ministry of Health refused to authorise it, he said.
However, it was not a quick job and could take a couple more weeks, Mr Haymes said.
Meanwhile, Niwa records for Greymouth dating back to 1947 show this December was the fourth-driest December on record (93mm of rain or 37% of normal).
It was only surpassed by December 1960 (70mm), 1980 (65mm) and 1955 (60mm).
So far, January 2023 has been the fourth-driest January on record (70mm of rain so far) — December 1961 (59mm), 1997 (58mm), and 2022 (52mm).
“Since there will likely be some minor rainfall between now and the end of the month, there’s a chance that the January ranking drops a bit,” meteorologist Ben Noll said.
The driest summers (December to February) on record for Greymouth rank as: 1973 (336mm), 1972 (337mm), 2015 (369mm) and 1961 (391mm).
So far this summer Greymouth has had 163mm.
“I also had a look at some older, historical data that we hold for Greymouth that showed the summers of 1900, 1934, 1930, and 1947 as being extremely dry.”
Mr Noll said it was also the third-warmest December on record in Greymouth, and January 2023 was so far the second-warmest January.
It was due to a record strong marine heatwave off the West Coast, which he said was influenced by climate change, as well as the effect of the La Nina dry, easterly winds.
“Greymouth is currently experiencing dry to very dry conditions according to Niwa’s drought index; this is most likely to intensify over the coming weeks, reaching ‘extremely dry’ in parts of the region, or one category below drought.”
There was 20mm of rain in Greymouth on Thursday while yesterday remained dry. MetService is forecasting rain from tomorrow through to Thursday but how much will fall, and whether it will help river levels and ease the need for water restrictions, remains to be seen.