28 February 2022
Media: Local Democracy Reporter
Topic: Lake weed stranding at lakefront
Enquiry
I'm writing a story about the build-up of lake weed around the Rotorua lakefront and the smell it has brought with it, filing today.
I've cc'd both councils as some questions may be more appropriate for one or the other and I think it will save forwarding of queries if the two councils can please divide up the questions as appropriate.
I would like comment on, for the story:
- What has caused the build-up of lake weed on the lakefront? When did it first begin to build up?
- How much has it cost to clear up so far and how much more cost is expected (if it has cost both councils please let me know the cost to each separately). What does clean up entail?
- How much longer is it likely to be before the weed is cleared and the smell abates?
- How much weed has been collected (in kg or tonnes) and how much more is there to collect?
- Has the lakefront boardwalk/redevelopment been any hindrance/challenge to clean up efforts (some have suggested this on social media) and if so in what way?
- What happens to the weed after it is collected? Where does it go and can it be used as compost?
- What are the ecological/environmental effects of the build-up of lake weed - I've heard of people seeing dead fish in the water, is this related?
- Are there any possible impacts to human health from the lake weed?
- Is there some way the build-up of lake weed can be prevented or mitigated by either council?
- How many reports/complaints about build-up and or smell have both councils received from the public?
Response
From Sport, Recreation and Environment Manager Rob Pitkethley
The build-up on shore and in the shallow areas around the lake edge was caused by the effects of ex-sub-tropical Cyclone Dovi, during which Rotorua experienced 80+ kmph northerly winds. This resulted in large amounts of weed breaking off and washing up along the lake edge
Where access for the weed harvester is an issue (shallow areas) the weed will remain until it blows back into the lake where it will naturally break down, or it will dry out on the shoreline. It’s likely that the odour will abate as it either moves away from shore or completely dries out.
It has not been a problem. In the past, the weed would have washed up in the same way, with some coming ashore, but the majority being left in the shallow edges of the lake.
It is estimated that the current cost to remove the weed up to now is approximately $15,000.
Please note: costs may increase with any ongoing work that is required.
Rotorua Lakes Council has collected 29 truckloads or 260m3 approx.
The weed has been taken to an old composting yard where it will dry out and decompose. Due to the levels of heavy metals in the weed it’s not suitable for home composting.
*Reporter was referred to BOPRC to provide more information about weed growth in the lake, potential for ecological/environmental effects and future prevention or mitigation
*Reporter was referred to Toi Te Ora Public Health regarding any impacts on human health