Locals hoping to fix Canterbury's shrinking lake

Geoff Horrell has a long affinity with the much-loved Ashburton Lakes — he even caught his first rainbow trout at Lake Camp in 1957.

Now Horrell is joining the growing community chorus calling for action to reverse Lake Camp's declining water levels.

"I haven't seen it that low,'' Horrell said. "Something has to be done."

Horrell's been raising concerns about the water levels associated with the Balmacaan Stream diversion with authorities since early 2022, after its resource consent ended in November 2020.

The consent allowed Fish and Game to divert water from Balmacaan Stream to top up Lake Camp but since November 2022. However, with no consent in place, concerns have been raised about the lake's water levels. Detractors say local authorities are simply caught up in bureaucratic red tape.

There are costs involved in applying for a new consent — perhaps a five-figure sum — and no guarantee it would be approved.

Although local authorities say Lake Camp is prone to natural fluctuations, and has been relatively stable in terms of ecological health since 2007.

Horrell, 85, recently trekked 2km up the hill to investigate the state of the historic Balmacaan Stream diversion.

The stream now sits "at least 2 metres lower" than the original concrete intake that remains intact, he said.

"Some people have obviously been up there trying to move a few big stones around to dam it but that's not going to cut it.

"Even if it did, one good rain would wash it out."

Flooding in 2021 scoured the stream, meaning and "it will take a lot more than a few stones and probably a lot of red tape to fix it".

Horrell has suggested another cheap solution could be piping the water to the natural tarn, a lake on the hill.

A one-week trial of re-establishing a diversion would also be enough to prove its benefit for Lake Camp, he said.

Horrell's sentiments are echoed by Duncan Humm, a Mt Somers deer farmer, who also hiked up to take a look at the diversion.

The management of Lake Camp mirrors the historical management of Greenstreet Creek where people have been augmenting water to successfully manage and protect biodiversity, along with amenity values of Lake Camp he said.

While he admits he isn't fully versed on the details of the former Balmacaan Stream diversion resource consent, he still believes it should be easy for Environment Canterbury and the Department of Conservation to allow ongoing management based on the historical success.

"I have to wonder if consent should even be required as the water fundamentally doesn't leave the catchment, or even leave the shingle fan where Lake Camp is at the base of.

When he walked up the path, he saw obvious areas that benefit from water moving to Lake Camp.

"I think of these areas as like a battery that holds onto water that benefits the ecosystem which is of benefit in dry years."

There must be a pragmatic and timely solution, Humm said.

"I estimate it wouldn't be a huge amount of work for a bulldozer or excavator to push some shingle around on the Balmacaan fan to allow water to reach the intake."

Environment Canterbury said creating a diversion from Balmacaan Stream to Lake Camp would require resource consent and that someone would need to hold that consent.

Surface Water science manager Elaine Moriarty said because previous consents were surrendered in November 2020, there were none that could be taken over.

Any new application would need to be considered against the regulatory framework, including water regulations, plus consider the impacts of the proposed activity on the environment.

Department of Conservation Geraldine operations manager Tony Preston said most of the section of Balmacaan Stream nearest Lake Camp, and the concrete structure formerly used as an intake for the diversion, sat on Department of Conservation-managed public conservation land.

Most of the channel previously used to carry the diverted water to Lake Camp was on private land and not administered by the Department of Conservation.

"Diverting the water without a permission from the Department of Conservation would be a breach of the Conservation Act, which prohibits the interference or damage of any historic or natural feature in any conservation area."

Modifying the stream without resource consent may also be unlawful under the Resource Management Act.

"If we were to find diversion work that had been done without a permission, we would seek to return the stream to its natural state, in discussion with Environment Canterbury," Preston said.

Environment Canterbury's Moriarty said Lake Camp has been relatively stable in terms of ecological health since 2007.

"Because of Lake Camp's depth, it is more resilient to natural fluctuations in water levels."

She said historical aerial photography and satellite imagery showed the level of the lake has varied significantly in the past, while the diversion was in place.

"Images from 2006 highlight a low water level in the lake, similar to the current level."

Preston reiterated that the water levels at Lake Camp were primarily a recreational issue.

"We have no evidence the water level is worsening the health of the lake."

LDR is local body journalism co-funded by RNZ and NZ On Air.

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