Ashburton’s mayor is looking at potential fixes for Lake Hood’s toxic algae problem, but the council has been warned there’s “no magic wand or silver bullet”.
The Ashburton District Council closed the popular recreation lake on April 3 after two people reported being poisoned by toxic algae, including a jet-skier who fell into the water.
It followed a health warning being placed on the lake on March 20 due to the risk posed by cyanobacteria toxins.
Ashburton Mayor Neil Brown said the council has been inundated with suggestions for how to fix the lake.
“Everyone has one idea on how to fix it, and they are all different.
“What we need to do is take a look at the viable and financially feasible options.”
The mayor has asked the head of Ashburton council to prepare a report on the issues and options for the man-made lake before the council made a decision on spending money.
During a recent meeting, council chief executive Hamish Riach cautioned “there is no magic wand or silver bullet” option.
“The report will make it clear there are no guarantees that any money spent will result in the outcome that the community and council desires.
“There is always risk with whatever initiative might find approval.”
Mayor Brown said the council, which took over management of the lake in June 2024, already added a second canal off the intake and introduced a weed harvester, “but it didn’t help enough”.
The council had explored other options, including adding a second outlet at the southern end of the lake to help circulation, estimated to cost around $250,000, he said.
The council has been working with Environment Canterbury on the ability to divert more water from the Hakatere/Ashburton River and feeding that water back into the river at the other end. There is also the possibility of a device to divert water into the canals to improve flow, Brown said.
None of those options are budgeted, but Brown pointed to the council’s reserve contribution account having around $7 million.
“The lake is a reserve.”
That means a solution could be funded without impacting rates, he said.
Since the health warning and subsequent lake closure, the council has been inundated with “offers from all around the world for potential solutions to the problem”, Brown said.
The difficulty would be be working out the options with the greatest chance of improvement, he said.
It would be Riach’s job to “sort the chaff out from the hay and bring those options to us”.
Councillor Rob Mackle said he believed the only answer is more water and that using the $7m on other options “will only cause a ripple”.
Mackle has previously suggested using unused stockwater to feed into the Hakatere/Ashburton River and then divert that allocation into the lake.
“We own that allocation. We just need to get it by ECan and iwi.
“ECan could not restrict that flow, or they could a little bit, but not completely on most years. It would have continual flow without them pulling the plug on us which causes the problem we have at the moment.”
Riach said the council has been discussing a variation to the water take consent with ECan and it will be included in the report.
According to data from ECan, the minimum flow restrictions on the Hakatere/Ashburton River were not fully implemented this summer, meaning the take from the river to the lake was not closed at any point, but was reduced for no more than seven days between January and the end of March.
The council will sometimes close the intake if the river is full of sediment after a heavy rain or if the intake needs repairs.
LDR is local body journalism co-funded by RNZ and NZ On Air.
