STATE OF THE GREAT LAKES 2005
WHAT ARE THE CURRENT PRESSURES IMPACTING LAKE MICHIGAN?
Current pressures on the Lake Michigan ecosystem include increasing use of groundwater by a growing basin
population, disruption of the aquatic food web, and habitat alteration.
Pressures
Increasing use of groundwater
For more than ten million people, Lake Michigan is
the source of water for drinking, industry, and many
recreational opportunities. Of all the Great Lakes,
Lake Michigan has the largest amount of
groundwater discharge (79 percent) as its water
source due to sand and gravel aquifers near the
shore. Because of increased use by Lake Michigan
basin communities, groundwater levels are now low
enough in the western basin that Lake Michigan
water can migrate into the groundwater, a reversal of
normal flow.
Fluctuating lake levels
Lake Michigan's water level fluctuates as part of
what is thought to be a 30-year cycle. In 2001, Lake
Michigan was measured at its lowest level since
1966, two feet below the long-term average. The
drop was more than 40 inches from record high
levels in 1997. In 2004, lake level was close to average
due to high rainfall.
Low lake levels increase the pressure on available
water resources, further complicating the
groundwater-surface water exchange problem. Low
lake levels can also impact the shipping and boating
industry. Cargo loads must be lightened, leading to
losses of up to $28,000 per trip, and many
recreational boat ramps become inaccessible. High
lake levels can cause shoreline erosion.
Disruption of the aquatic food web
Populations of the native bottom-dwelling
invertebrate Diporeia, a major food source for Lake
Michigan fish, are decreasing rapidly. The reason for
the decline is unknown but the impact on the
aquatic food web is expected to be severe. A multi-
agency research team is working to determine the
cause of the decline.
Lake Superior
Lake Huron
Lake Michigan
Lake Ontario
Lake Erie
Populations of native fish species are also in decline.
The yellow perch population remains low. Lake trout
populations have not recovered to the point of
natural reproduction and thus continue to be
restocked. Remnant populations of lake sturgeon
survive in the Great Lakes only in scattered areas,
including eight Lake Michigan tributaries. A lake
sturgeon restocking program has begun in Lake
Michigan.
A major potential threat to the food web is the
invasion of Asian carp species, voracious non-native
fish that threaten to enter Lake Michigan through the
Illinois River system from the Mississippi River.
These large carp species feed on plankton and would
compete directly for food with native organisms
including mussels, all larval fish, and some adult fish.
An experimental electrical barrier to prevent Asian
carp from entering Lake Michigan is in place across
the Chicago Sanitary and Ship Canal. The barrier is
located approximately 25 miles from Lake Michigan.
Habitat alteration
The increase in development pressure to alter
remaining Lake Michigan aquatic and terrestrial
natural habitats impacts the plant and animal species
that depend on these habitats. The largest collection
of freshwater sand dunes and beaches in the world
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LAKE MICHIGAN PRESSURES
are threatened by residential development, mining,
and episodic resurgences of E. coli and the
macroalgae Cladophora that reduce water quality and
restrict beach use.
Over the last two centuries, more than 60 percent of
Lake Michigan coastal and inland wetlands have
been destroyed, yet the pace of shoreline
modification and urban, industrial, and agricultural
development is increasing, threatening the remaining
12.9 million wetland acres. Although the basin's
forest resources are healthy overall, and reviews of
national forest plans are addressing management
issues, development pressures on forest resources
remain high. In urban areas, impervious surfaces
such as roads and rooftops are degrading lakes and
streams by increasing water temperature, runoff
volume, altering watershed hydrology, raising
ambient air temperatures, and reducing open space.
Current Actions
The Lake Michigan Watershed Academy provides a
combination of land-use planning tools, data, and
approaches to local planners to promote an
ecosystem approach and dialogue among decision-
makers. The ten Lake Michigan Areas of Concern
(AOC) are undergoing sediment remediation and
combined sewer flow/stormwater management
remediation, as well as habitat restoration. It is
expected that AOC remediation and restoration will
enhance opportunities for public interaction with the
Lake Michigan ecosystem.
Recovery plans are in place for Lake Michigan basin
rare species including the piping plover, Mine's
emerald butterfly,
and Kirtland's
warbler. Chicago is
also one of five
United States
signatory cities to
Piping plover at Indiana Dunes National Lakeshore.
Photo: U.S. EPA Great Lakes National Program Office.
the Urban Conservation Migratory Bird Treaty, a
long-term partnership to protect migratory birds. An
aggressive program to train whooping cranes to
migrate and return to nest in Wisconsin's Lake
Michigan wetlands is successfully underway. A series
of dam removals on the Milwaukee River has
increased habitats for diverse fish and insect
populations. For the first time in 100 years, a nesting
pair of bald eagles was documented on Indiana's
Lake Michigan shoreline in 2004.
Actions Needed
The following actions are needed to counter the
current pressures on the Lake Michigan ecosystem:
• Research to determine groundwater status and
groundwater-Lake Michigan interactions
• Research to determine the cause of Diporeia
population declines
• Research to determine the causes of Cladophora
blooms and E. coli outbreaks
• Research to determine the impact of invasive
species on the food web and natural habitats
• Construction of an additional barrier and
improvements to the existing barrier in the
Illinois River system to prevent Asian carp from
entering Lake Michigan
• Protection and restoration of natural areas,
migratory bird flyways, and unique biological
and geological features, especially wetlands
• GIS training for local officials who make land-
use decisions
Further Information
For further information related to the state of Lake
Michigan, refer to the State of the Great Lakes 2005
report which, along with other Great Lakes
references, can be accessed at
www.epa.gov/glnpo/solec. The Lake Michigan
Lakewide Management Plan 2004 can be accessed at
www.epa.gov/greatlakes/michigan.html.
02/06
EPA 905-F-06-911
IISG-06-04
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