Just as tourists start to flood into the Okanagan for the start of beach season, the invasive aquatic weed, Eurasian Watermilfoil has decided to make an early appearance in valley lakes. As a result, calls to the Okanagan Basin Water Board (OBWB) have already started.

“Usually we are just starting to survey the lakes to see where the milfoil is growing under the water and where we need to start working,” says James Littley, Operations and Grants Manager for the OBWB. “But I received our first call last week about the weeds and then today I had a couple calls saying the weed had broken the surface of the lake and is starting to form mats. It is looking like a good year for milfoil, and that’s bad for the rest of us.”

In summer 1972, the provincial government partnered with the Water Board and started an intensive program to remove the newly introduced, invasive milfoil from Okanagan lakes. Early efforts focused on harvesting the weed, using everything from floating barges to hand-scythes and pitch forks. The early goal was eradication by any means necessary – trying chemicals, bottom-barriers, dredging, and hand-pulling. The program was handed over to the Water Board in 1998 and more recent control efforts have included research into breeding special weevils to eat the weed. Today, the Water Board employs three operators who spend 1000s of hours on the water every year to control the volume of the invader at our beaches, boat launches and marinas, at over 200 sites in the valley.

Some wave off milfoil as just a nuisance that tickles your toes when you swim, but milfoil is bad for just about everything in our lakes. Economically, uncontrolled milfoil has negative effects on tourism, and studies have shown that thick milfoil mats can lower lakefront property values by as much as 19%, noted Littley. Environmentally, milfoil robs oxygen from the water, increases water temperature, slows the flow at the mouths of rivers, and increases polluting nutrients in the water. It has also been linked to fish kills and loss of biodiversity. Just last year, a provincial study found the primary factor reducing the flow of Okanagan River out of Vaseaux Lake was milfoil growth.

Source: Okanagan Basin Water Board

“Just think about that,” added Littley. “The Okanagan River there runs at about 10,000 L per second in the summer – enough to fill an Olympic swimming pool in around four minutes – and milfoil is slowing it down.”