Water, Air and Climate Change Branch
WATER QUALITY
Eurasian
Watermilfoil in British Columbia
This
brochure has been produced to answer the more frequent enquiries
received by the Ministry of Environment, Lands and Parks
(now called Ministry of Water, Land and Air Protection)
on Eurasian watermilfoil and to provide you with general
information on related water management concerns.
What
is the Problem?
Aquatic
plants are an important part of the biology of our lakes
and other water bodies. They provide food, habitat and
rearing areas for a wide variety of organisms. Vegetation
helps to stabilize lake bottoms and aerate the water.
However, some aquatic plants, such as Eurasian watermilfoil,
also can have undesirable effects, especially when
they are
too
abundant
or become
established
in unwanted locations.
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In British
Columbia, problems caused by Eurasian watermilfoil include:
- growing
and spreading rapidly
- invading
and replacing native plant communities
- obstructing
swimming, boating, waterskiing and fishing
- reducing
the appeal of beach areas due to the accumulation of plant
debris
- impeding
flood control, water conservation, drainage and irrigation
works
- reducing
the economic benefits of tourism where dense growth limits
recreation
Eurasian
watermilfoil is not native to North America. It was first observed
in British Columbia in 1970 in Okanagan Lake. The plant has spread
since to Shuswap and Mara Lakes, to Christina and Champion Lakes
in the Kootenays, to all the main lakes in the Okanagan Valley
and to numerous water bodies in the Lower Mainland. Also, isolated
populations were discovered on Vancouver Island in 1985, and
in Nicola Lake in 1991.
Many uninfested
water bodies in these areas and elsewhere in British Columbia
remain susceptible to the introduction of this plant.
How Does it Grow and Spread?
Eurasian
watermilfoil is a perennial, which grows from a fibrous root system
on a variety of bottom types. During the spring and summer
months, when growth is rapid, plants may reach the water surface
from depths exceeding five metres.
Floating
plant fragments produced by waves and boaters are spread
by water currents, making the plant difficult to contain.
New
plants develop when the fragments sink, rooting best in protected
locations.
Boats and
boat trailers carrying plant fragments are thought to be the
most common form of spread from one water body to another.
Management
Management
strategies currently in use in British Columbia include:
- preventive
efforts (e.g. surveillance of non-infested areas and public
information to discourage spread, particularly by boaters)
- placing
bottom coverings on new populations to prevent lake-wide infestations
- root
removal (maintenance of priority areas by rototilling or
shallow water cultivation)
- harvesting
(cosmetic control by cutting the plant below the water surface)
What Can You Do?
- Reduce
spread of watermilfoil and other aquatic weeds by clearing
all plant
material from boats, motors, trailers, wet wells and anchors.
Dispose of plants far away from water bodies.
- Learn
how to identify Eurasian watermilfoil.
- Report
suspected new infestations to any BC Water, Land and Air
Protection office.
- Contact
local authorities and seek expert advice when concerned about
aquatic plant problems in your community.
Originally
published in June 1993
updated: November 18, 2004
