Working to slay a green lake monster for nearly 50 years

It’s a deep green monster and calls Okanagan Lake home.

If left to its own devices, it would become so strong it would stop a boat in its track, grinding the motor to a halt.

No, we’re not taking about the Ogopogo.

Eurasian watermilfoil is the target of relentless efforts to keep Okanagan Lake a top recreational area.

And keeping the water clear of the invasive weed is a year-round effort.

“It’s bad for the environment. It grows in large quantities, forms mats on the surface of the water, disturbs aquatic habitat,” James Littley, Operations and Grants Manager at the Okanagan Basin Water Board (OBWB), told Kelowna10.

“It can create a no swimming area [and it] grows so thick that it can actually stop a power boat motor from rotating.”

Milfoil arrived in the Okanagan in the 1970s. By 1974, it had spread to nearly every lake in the valley.

The weed can create algae blooms, which kills native fish due to the lack of oxygen in water. Growth can spike during flooding, as more nutrients from the watershed go into the lake.

From around Oct. 1 to April 1, the OBWB controls the growth by de-rooting milfoil in five lakes throughout the Okanagan.

The bottom of the lake is rototilled, similar to how farmers do it on land. When done annually, it can slow down the growth of the invasive plant.

A large red paddle wheel driven barge with a rototilling head helps to slay the plant.

The tiller can be operated in depths of up to 4.5 metres.

“During the winter, it’s a dormant plant anyway, so it’s not going to spread and grow while we’re doing this in cold temperatures,” he explained.

After the roots are tilled, they float to the surface where they are either consumed or biodegrade before spring.

The OBWB works with permits from the provincial and federal government to make sure they are being ecofriendly and not tilling in fish spawning locations, as they don’t want to harm aquatic life.

In the summer, a different method is used to dispose of the weeds since they reestablish through fragmentation, meaning any part of the weed in the water can keep growing.

Littley said the machine used in the summer is similar to the winter one, but instead of a rototiller, it has a cutting edge and a conveyer belt that trims and collects the milfoil.

“[It’s] just like cutting your lawn with a bag on. We cut it down to about five feet below the water surface,” he said.

The collected milfoil is typically donated to orchards and gardens to be used as compost since it’s rich in phosphorus and nitrogen.