Water Skiers Call For Review Of Lake Hood Closure

Tuesday, 13 May 2025, 6:17 pm
Article: Jonathan Leask - Local Democracy Reporter

Users of a popular Canterbury recreational lake are calling for a review of the closure process after undertaking their own water testing.

Lake Hood, near Ashburton, has been closed since April 3 due to health warnings sparked by toxic algae.

Water Ski Lake Hood secretary Janeen Donaldson said they had independent water testing carried out and claims the results show there was no justification for closing the ski lane.

“Minimal testing didn’t justify a full lake closure, and further testing confirms that.

“The main lake and ski lane have never tested above health warning level, so there is no reason for them to still be closed.”

The group is asking for the main lake and ski lane to be re-tested, and if cleared, reopened until “water testing evidence justifies closure”.

Ashburton District Council chief executive Hamish Riach is standing firm that the closure “was necessary to protect the public from the high level of risk”.

The council's decision to close the man-made lake came after two people were poisoned by the toxic algae before a health warning was placed on the lake on March 20. This included a jet skier.

Riach reiterated the decision was due to “continued, clear evidence of an algal bloom across various areas of the lake”.

However, Donaldson said an independent water test of the ski lane, taken after the lake's closure, confirmed the ski lane was not at health risk levels.

The results were 0.000069 total cyanobacteria, “nowhere near” the 10mm3/L that triggers a health warning, she said.

The club is calling for authorities to reevaluate their approach to closing the lake, as they claim the results disprove the risk-based closure due to algal bloom spread.

Environment Canterbury water and land science manager Dr Elaine Moriarty said the worst-affected area is tested based on visual assessments.

This summer, that was the ski lane on three occasions (January 23 and 30, and February 5), reaching the amber level (between 3-6mm3/L), she said.

“When the lake entered the warning in March, we tested at different points of the lake, as this was where the algal blooms were most visible.

“This doesn’t mean that the ski lane wasn’t affected, or wasn’t above warning levels, it just means it wasn’t the worst affected area and therefore not selected for sampling.

“Because algal blooms move and shift across water bodies, we can’t rule out higher concentrations elsewhere.”

Recent ECan testing showed cyanobacteria in the lake had dropped significantly this month.

However, Moriarty said two consecutive tests needed to show cyanobacteria levels are less than 0.5mm3/L.

Cyanobacteria scums were also visible in April, which can prolong a warning, she said.

Donaldson argued there are two land masses, and over a 1km between the canals and the ski lane, “plus a huge volume of water, over 100 hectares of main lake in which to dilute any algae spread”.

“Lake Hood is distinct from many other lakes in that it has three very different bodies of water, all with unique water flows.

“It needs to be tested and considered as three specific areas.”

Donaldson said the club felt the council closed the lake based on limited information.

The closure, and its timing before the week-long national championships, had widespread repercussions for water skiing, other lake users, residents and businesses.

"It’s just not good for Ashburton.”

However, Riach said the whole lake is treated as one water body, including the ski lane.

“The protocol cannot be changed as the lake is one water body, unless the three areas were physically separated.”

The councillors have asked for an issues and options report on Lake Hood in April.

Riach said the report will only cover the issues facing the lake and the options for council to manage the water.

“What we’re hearing from the community is that we need to continue to focus our efforts on the water quality, rather than the closure decision.”

He expects the report to land “with enough time before elections”, which occur in October.

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

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