Any effort to replenish a shrinking Canterbury Lake would require a costly new resource consent - and there's no guarantee it will be approved.

The Ashburton District Council heard expert advice at a workshop on Lake Camp on Wednesday.

Locals have been pleading for help to top up the lake with a diversion from the nearby Balmacaan Stream.

But this action requires a resource consent - which the council will discuss next week.

Speaking in front of a packed public gallery, Ashburton mayor Neil Brown described the workshop as a fact-finding mission for the council with different experts gathered.

Environment Canterbury surface water science manager Elaine Moriarty said the region is dry, which was impacting the lake’s levels.

Even with a diversion in place, there wasn't sufficient water to flow down it, she said.

“It’s sad to see it but it’s not an unnatural event”.

When asked if the lake could completely dry out, Moriarty said "it was not an imminent event” as the lake has a deep centre.

DOC’s Geraldine operations manager Tony Preston said the situation was just natural fluctuations and lake levels should eventually return to normal through natural processes, he said.

“Nature is taking its course."

The workshop covered the consenting requirements to reinstate a diversion – the cost of which was unknown.

It would require ecological, hydrology, wildlife and environmental impact reports, as well as a seperate process of getting apporval for an easement from DOC.

When Fish and Game surrendered the consent in 2020 it was facing a $50,000 cost to make the diversion compliant.

Fish & Game Central South Island chief executive Steve McKnight said restoring a diversion would require a new structure at a new location because of how the stream was scoured out after 2021 flooding.

“Don’t put it where the old one was.

"That diversion point is no longer fit for purpose."

After almost two hours, Mayor Brown said a report would come to the council meeting on Tuesday where the next steps would be discussed.

Mayor Brown had visited the site and said “it would take some engineering to get that water lifted back up again to flow [into the diversion]”.

The council have plenty to ponder from the workshop, and also the knowledge that the community is calling for action, ahead of their discussion on Tuesday.

A petition, calling for action ‘to save Lake Camp from draining away’, has received 1635 signatures.

The land around Lake Camp is a recreation reserve owned by the Department of Conservation but vested in the Ashburton District Council to administer.

The expert panel at the workshop included representatives from Environment Canterbury, the Department of Conservation and Fish and Game. ECan chairperson Peter Scott also attended.

By Jonathan Leask