Minnesota Hunting Lake Undergoes Habitat Restoration
Ask the locals,
and they’ll be quick to tell you that Olson Lake in rural Minnesota was once a
shallow and flourishing duck habitat. Shots rang out every fall as hunters
bagged their limits of mallards, wood ducks, and Canada geese. But, in time,
prolonged high water levels—combined with runoff from agricultural fields, and
the introduction of invasive fish species—left the water in a turbid state,
resulting in a deep and mucky slough. Over the years, the waterfowl and other
wetland-dependent wildlife disappeared, leaving hunters to wonder what had ever
happened to all the ducks.
Now, in an effort
to restore Olson Lake to its former glory as a staging, breeding, and feeding
ground for migrating waterfowl, engineers and biologists from Ducks Unlimited
and the US Fish and Wildlife Service have teamed with Prinsco Inc. to re-habitat
the wetland and improve water quality.
Olson Lake is a
small, 140-acre lake, located just east of the small town of Raymond in west
central Minnesota. It is included in Minnesota’s list of “public waters,” and
much of the shoreline is surrounded by the native grass uplands of the US Fish
and Wildlife Service’s 440-acre Olson Lake Waterfowl Production
Area.
According to Jim
Streifel, project engineer for Ducks Unlimited, the lake was chosen for this
re-habitat project because, historically, it was always a very good waterfowl
lake. It was a shallow hemi-marsh with approximately 50% open water and 50%
emergent vegetation. However, because of changes within the watershed and
precipitation patterns, the water level became deeper during the 1980s, killing
off underwater vegetation that is critical to a duck’s
habitat.
In time, rough fish like bullhead, carp, and fathead
minnows were introduced to the lake, either by migration through manmade
drainage systems or by private bait dealers. Soon, these invasive species began
stirring up the water and feeding on invertebrates that help control the amount
of algae. The increased levels of algae blocked out sunlight and prevented
underwater vegetation from growing. Without that critical vegetation, the amount
of phosphorous in the water rose, leading to even higher algae blooms—a vicious
cycle.
Biologists from the US Fish and Wildlife Service and
Ducks Unlimited determined that the best solution to restoring Olson Lake’s
water quality and waterfowl habitat was to undertake a complete drawdown of the
lake.
“We’ve had tremendous success with projects like this
in the past,” says Steve Erickson of the Fish and Wildlife Service. “It’s based
on sound science that simulates a natural drought.”
According to Erickson, periodic droughts are healthy
to a shallow lake and are necessary for restoring waterfowl habitat. The
drawdown of Olson Lake will kill all invasive fish and dry out the muddy bottom.
Once the substrate is exposed to oxygen, seeds of native aquatic plants that
were previously “banked” in the mud will begin to germinate and grow,
stabilizing the organic soils and absorbing nutrients that would otherwise fuel
unwanted algae blooms.
Two construction alternatives were considered to
achieve the desired drawdown effect. The first was a water control structure
with an open channel outlet. However, because this model had the potential to
adversely impact downstream wetlands, the team decided on a gravity-flow piped
outlet instead.
For the pipeline design, various sizes and types of
pipe were considered. Project engineers chose a 24-inch-diameter pipe based on
the estimated length of time required to remove 3 feet of water from the lake.
Prinsco’s dual-wall ECOFLO high-density polyethylene pipe was selected based on
flow characteristics, ease of installation, economics, and eco-friendly recycled
pipe material. “It’s an environmentally friendly product, made from 50%
recycled material,” says Streifel. “So,
we’re using sustainable materials to create a sustainable duck habitat. A
perfect fit.”
“This is a great
opportunity to work together on a project that will benefit both the wetland and
its wildlife,” says Prinsco vice president Jamie Duininck. “I hope we can do
more projects together in the future.”
Work began on the
3,600-foot pipeline project on October 20, 2008. A water control structure was
installed on the east shoreline of Olson Lake, and the outlet pipe installation
was completed on October 31. The outlet pipeline was installed over a granular
base material and backfilled to the top of the pipe using a select pipe bedding
material.
The inlet into
Olson Lake used a 24-inch-diameter reinforced concrete pipeline, 60 feet in
length, with a sloped inlet section. Dewatering of Olson Lake began on November
3, 2008, and the inlet pipeline was completed on December
11.
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Extremely cold
weather set in during early December, causing thick ice to form, bringing an end
to the water drawdown. Investigation by the Fish and Wildlife staff determined
that ice had formed all the way to the lake’s bottom, ensuring a complete
winterkill of the lake’s fish.
Final and complete
drawdown will occur during the spring thaw. Erickson anticipates that the lake’s
exposed mudflats will be a smorgasbord for a wide variety of migratory birds
during the upcoming spring migration. “We anticipate seeing multitudes of
shorebirds and waterfowl using the area this spring,” he says. “Hopefully, the
success of the Olson Lake project will garner the public’s interest and support
for other similar opportunities in the region.”
After
one or two growing seasons, the lake will be allowed to re-flood through normal
precipitation and runoff. If warranted, the installed water control structure
will allow management of Olson Lake’s water levels in future years.
March-April 2009
Minnesota Hunting Lake Undergoes Habitat Restoration
Ask the locals,
and they’ll be quick to tell you that Olson Lake in rural Minnesota was once a
shallow and flourishing duck habitat. Shots rang out every fall as hunters
bagged their limits of mallards, wood ducks, and Canada geese. But, in time,
prolonged high water levels—combined with runoff from agricultural fields, and
the introduction of invasive fish species—left the water in a turbid state,
resulting in a deep and mucky slough. Over the years, the waterfowl and other
wetland-dependent wildlife disappeared, leaving hunters to wonder what had ever
happened to all the ducks.
Now, in an effort
to restore Olson Lake to its former glory as a staging, breeding, and feeding
ground for migrating waterfowl, engineers and biologists from Ducks Unlimited
and the US Fish and Wildlife Service have teamed with Prinsco Inc. to re-habitat
the wetland and improve water quality.
Olson Lake is a
small, 140-acre lake, located just east of the small town of Raymond in west
central Minnesota. It is included in Minnesota’s list of “public waters,” and
much of the shoreline is surrounded by the native grass uplands of the US Fish
and Wildlife Service’s 440-acre Olson Lake Waterfowl Production
Area.
According to Jim
Streifel, project engineer for Ducks Unlimited, the lake was chosen for this
re-habitat project because, historically, it was always a very good waterfowl
lake. It was a shallow hemi-marsh with approximately 50% open water and 50%
emergent vegetation. However, because of changes within the watershed and
precipitation patterns, the water level became deeper during the 1980s, killing
off underwater vegetation that is critical to a duck’s
habitat.
In time, rough fish like bullhead, carp, and fathead
minnows were introduced to the lake, either by migration through manmade
drainage systems or by private bait dealers. Soon, these invasive species began
stirring up the water and feeding on invertebrates that help control the amount
of algae. The increased levels of algae blocked out sunlight and prevented
underwater vegetation from growing. Without that critical vegetation, the amount
of phosphorous in the water rose, leading to even higher algae blooms—a vicious
cycle.
Biologists from the US Fish and Wildlife Service and
Ducks Unlimited determined that the best solution to restoring Olson Lake’s
water quality and waterfowl habitat was to undertake a complete drawdown of the
lake.
“We’ve had tremendous success with projects like this
in the past,” says Steve Erickson of the Fish and Wildlife Service. “It’s based
on sound science that simulates a natural drought.”
According to Erickson, periodic droughts are healthy
to a shallow lake and are necessary for restoring waterfowl habitat. The
drawdown of Olson Lake will kill all invasive fish and dry out the muddy bottom.
Once the substrate is exposed to oxygen, seeds of native aquatic plants that
were previously “banked” in the mud will begin to germinate and grow,
stabilizing the organic soils and absorbing nutrients that would otherwise fuel
unwanted algae blooms.
Two construction alternatives were considered to
achieve the desired drawdown effect. The first was a water control structure
with an open channel outlet. However, because this model had the potential to
adversely impact downstream wetlands, the team decided on a gravity-flow piped
outlet instead.
For the pipeline design, various sizes and types of
pipe were considered. Project engineers chose a 24-inch-diameter pipe based on
the estimated length of time required to remove 3 feet of water from the lake.
Prinsco’s dual-wall ECOFLO high-density polyethylene pipe was selected based on
flow characteristics, ease of installation, economics, and eco-friendly recycled
pipe material. “It’s an environmentally friendly product, made from 50%
recycled material,” says Streifel. “So,
we’re using sustainable materials to create a sustainable duck habitat. A
perfect fit.”
“This is a great
opportunity to work together on a project that will benefit both the wetland and
its wildlife,” says Prinsco vice president Jamie Duininck. “I hope we can do
more projects together in the future.”
Work began on the
3,600-foot pipeline project on October 20, 2008. A water control structure was
installed on the east shoreline of Olson Lake, and the outlet pipe installation
was completed on October 31. The outlet pipeline was installed over a granular
base material and backfilled to the top of the pipe using a select pipe bedding
material.
The inlet into
Olson Lake used a 24-inch-diameter reinforced concrete pipeline, 60 feet in
length, with a sloped inlet section. Dewatering of Olson Lake began on November
3, 2008, and the inlet pipeline was completed on December
11.
Extremely cold
weather set in during early December, causing thick ice to form, bringing an end
to the water drawdown. Investigation by the Fish and Wildlife staff determined
that ice had formed all the way to the lake’s bottom, ensuring a complete
winterkill of the lake’s fish.
Final and complete
drawdown will occur during the spring thaw. Erickson anticipates that the lake’s
exposed mudflats will be a smorgasbord for a wide variety of migratory birds
during the upcoming spring migration. “We anticipate seeing multitudes of
shorebirds and waterfowl using the area this spring,” he says. “Hopefully, the
success of the Olson Lake project will garner the public’s interest and support
for other similar opportunities in the region.”
After
one or two growing seasons, the lake will be allowed to re-flood through normal
precipitation and runoff. If warranted, the installed water control structure
will allow management of Olson Lake’s water levels in future years.