It was reported last month that a rainfall event after a prolonged dry period had elevated nitrate levels in the scheme to 40mg/l, and figures provided this week showed the levels were now at 45mg/l.
The Waimate District Council is continuing to carry out regular sampling at the water source, with samples independently tested by an accredited laboratory.
Chief executive Stuart Duncan said the council also had an online nitrate probe to monitor nitrate levels in real time.
"Simply put, we are keeping very close tabs on the situation."
The council assured the community the water remained safe to drink, and was still compliant with the Drinking Water Standards for New Zealand, which set a maximum acceptable level of 50mg/l for nitrates.
Alternative water supply tanks are available at the Glenavy Hall, Morven Hall, Glenavy Fishing Camp and Glenavy School.
Domestic self suppliers are advised to get their water tested.
Nitrate is a water-soluble molecule made of nitrogen and oxygen. It is naturally found in plants and many foods and is tasteless and odourless.
While it is naturally occurring in the environment, it can also enter the environment by other pathways including chemical fertilisers and various land uses.
The council said it would continue to monitor and advance the work associated with future denitrification.
Daily checks of the nitrate levels were in place and should the situation worsen, the council would provide updates to residents through its new notification service, NotifyMe, as well as via Facebook and the council’s website.
