A computer model is being developed to help better understand how lakeweed moves around Lake Rotorua, supporting future weed management and control efforts.
Toitū Te Whenua Land Information New Zealand (LINZ) has commissioned Earth Sciences New Zealand (formerly NIWA) to carry out the modelling.
LINZ Leader Biosecurity Tracey Burton says the work aims to help reduce the impacts of weed washups along the lake’s shoreline.
“We know how frustrating weed washups have been for the Rotorua community, particularly following storm events, and we hear and share that frustration,” Burton says.
“This modelling is about giving us better information so we can make more effective decisions to address the issue.”
The model uses weather data such as wind speed, air temperature, solar radiation and humidity, along with river inflows and outflows to simulate how water moves around the lake.
Earth Sciences New Zealand will test the accuracy of the model against observations from a monitoring buoy on the lake.
Researchers will focus on storm events when weed wash‑ups have occurred, allowing them to backtrack where the weed has likely come from within the lake.
“By understanding how the weed travels, we can better target control efforts to the weed beds that are most likely contributing to washup events along the Rotorua foreshore,” says Burton.
LINZ is the primary funder of aquatic weed control across the Rotorua lakes and work in partnership with Te Arawa Lakes Trust (the lake owners), who deliver the control programme. Decisions on which lakes and sites are treated, are made through the Bay of Plenty Aquatic Pest Coordination Group (APCG), which brings together multiple agencies to take a collective, evidence-based approach.
Members of the APCG include Te Arawa Lakes Trust as lake owners, LINZ, Toi Moana Bay of Plenty Regional Council, Rotorua Lakes Council, the Department of Conservation, and Eastern Region Fish and Game Council.
Burton cautions that the modelling is not a standalone solution.
“This is no magic bullet. Lake Rotorua is notoriously difficult to manage weed in, as conditions need to be just right for herbicide treatments to be effective. When those conditions aren’t met, the herbicide simply doesn’t work.”
Unsuitable conditions include times when algae blooms are present or when plants are too dirty for the spraying to be effective, she says.
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