A new computer modelling project is being launched to track how invasive lakeweed moves around Lake Rotorua, as agencies step up efforts to tackle frustrating weed washups impacting local communities and lakefront areas.
Toitū Te Whenua Land Information New Zealand (LINZ) has commissioned Earth Sciences New Zealand — formerly NIWA — to develop the model, which aims to better understand how weed travels across the lake during changing weather and storm conditions.
LINZ Leader Biosecurity Tracey Burton says the work is designed to provide stronger scientific data to improve future weed control efforts.
“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 will combine weather information including wind speed, temperature, humidity, solar radiation, and lake inflow and outflow data to simulate water movement throughout Lake Rotorua.
Researchers will then compare the model against real-world observations gathered from a monitoring buoy already operating on the lake.
Scientists will pay particular attention to storm events linked to major weed washups, allowing them to trace where the weed likely originated within the lake system.
Burton says understanding how lakeweed moves could help agencies target the weed beds most responsible for shoreline washups.
“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,” she says.
LINZ is the primary funder of aquatic weed control across the Rotorua lakes and works alongside Te Arawa Lakes Trust, which represents the lake owners and helps deliver the control programme.
Decisions around treatment sites are made collectively through the Bay of Plenty Aquatic Pest Coordination Group, which includes LINZ, Te Arawa Lakes Trust, Rotorua Lakes Council, Toi Moana Bay of Plenty Regional Council, the Department of Conservation, and Eastern Fish and Game Council.
However, Burton warns the modelling is not a quick fix.
“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,” she says.
She says treatments can fail when algae blooms are present or when weed is too dirty for herbicide spraying to work properly.
The project comes as concerns continue around lake health, environmental management, tourism impacts, and maintaining the cultural and recreational value of Rotorua’s waterways.
