Resident Dave Brady said it seemed the Central Otago District Council’s planning around water provision was, at best, less than adequate.
Naseby town water came from the Hawkdun irrigation race — known locally as the Mt Ida irrigation race — a surface water source vulnerable to turbidity following rain.
When that happened the plant was shut down, treated water was supplied from reservoirs and a conserve water notice was put in place.
However, this summer had been cooler than previous years without any heavy rainfall, Mr Brady said.
And still there were issues with the local supply.
A conserve water notice for the township issued late last year "due to high demand on the water network" remains in effect in Naseby.
"This time there has been no major weather events to disrupt raw water sources via the Mt Ida water race," Mr Brady said.
"Temperatures have been generally mild and there have been sufficient spring rains to make garden and lawn watering negligible."
Naseby had a permanent population of about 130 which grew dramatically during the summer, particularly at Christmas and New Year.
It had been estimated that the summer population grew to about 2500 to 3000 people, compared to the 120 to 140 permanent residents.
"Some say that Naseby has a higher residential capacity than Ranfurly and there have been a number of new dwellings built over the last few years which increases demand pressure on the potable water supply," Mr Brady said.
Tourism was increasingly important to the Maniototo economy and Naseby was promoted by the council as the area’s "jewel in the crown".
"It would seem counter-intuitive to have a tourism focus for the economy but not ensure that the infrastructure is there to support it."
The council should be investigating a raw water dam next to the treatment plant to ensure a consistent supply of water during significant weather events and alternative water sources, Mr Brady said.
"We remain on a conserve water notice, despite the township being its usual busy summer self and a good supply of clear, non-turbid, raw water in the Mt Ida water race."
Council Three Waters group manager Julie Muir said conserve water notices were a common method used across the country to encourage wise water use during high demand periods.
The Naseby notice was issued due to the treatment plant having to operate at full capacity during the holiday time, Ms Muir said.
All council water forecasting and planning for Naseby was based on peak population.
There had been an average of six new connections on the Naseby network each year for the past five years, less than 2% a year, which was negligible.
However, the treatment plant ran continuously for a few weeks during the peak period which increased the risk of supply interruptions if there was a minor plant outage or burst in the network, Ms Muir said.
Increased water storage would not make any difference when the plant was operating at full capacity.
"This would be the equivalent of putting a bigger bucket on the end of a tap and expecting more water to come out of the same tap."
A second ultraviolet unit would be installed in the Naseby plant by mid-year which would enable increased flow through the plant and allow reservoirs to be refilled more quickly
"This will have the same impact as putting a bigger tap in place."
Work on using a nearby pond for up to six day’s raw water storage was progressing but investigations had shown the infrastructure cost of sourcing alternative groundwater sources was prohibitive, Ms Muir said.
Mr Brady said it was encouraging that the council was adding the second ultraviolet unit and settling pond, something the community had been asked for.
