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Ontario and the Great Lakes.docx


Department
Geography
Course Code
GEOG 2011A/B
Professor
Wendy Dickinson

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Lake Levels
The International Joint Commission:
The binational agency established under the Boundary Waters Treaty of 1909
between Canada and the U.S
Responsible for regulation of flows on the St. Mary’s and the St. Lawrence Rivers
Lake Michigan flows to Lake Huron through the Straits of Mackinac.
Michigan and Huron standing at the same elevation.
No artificial controls on the St. Clair and Detroit Rivers that could change the
flow from the Michigan-Huron Lakes system into Lake Erie.
Outflow of Lake Erie via the Niagara River is uncontrolled except for some
diversion through the Welland Canal
Further regulation by engineering systems could not be justified in light of the
cost and other impacts *** one inch (two and a half centimeters) of water on the
surface of Lakes Michigan and Huron amounts to more than 36 billion cubic
meters of water (about 1,260 billion cubic feet).***
Lake Processes
Stratification: layering of water in the lakes due to density changes caused by
changes in temperature.
The density of water increases as temperature decreases until it reaches its
maximum density at about 4° Celsius (39° Fahrenheit)
Thermal stratification, or the tendency of deep lakes to form distinct layers in
the summer months.
Deep water is insulated from the sun and stays cool and more dense, forming a
lower layer called the 'hypolimnion'
- High productivity just above the hypolimnion
- Hypolimnion has less sunlight and is therefore less productive
- Hypolimnion lacks oxygen in central basin of lake erie b/c of
decomposition o organic matter
Surface layer called the 'epilimnion'.
- Supports most life in lake
- Rich in oxygen
Thermocline (middle layer) develops as summer progresses and temperature
differences increase between the layers in which a rapid transition in
temperature occurs.
Fall surface waters cool, become denser and descend, displacing deep waters
and causing a mixing or turnover of the entire lake
Winter the temperature of the lower parts of the lake approaches 4° Celsius
(39° Fahrenheit), while surface waters are cooled to the freezing point and ice
can form.

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Temperatures and densities change in spring, another turnover may occur.
However, in most cases the lakes remain mixed throughout the winter
Turnover is the main way in which oxygen-poor water in the deeper areas of the
lakes can be mixed with surface water prevents anoxia
Thermal bar holds pollutants near shore, they are not dispersed to the open
waters and can become more concentrated within the near shore areas.
Living resources
Plant material is consumed in the water by zooplankton, which grazes the waters
for algae, and on land by plant-eating animals (herbivores)
~ 180 species of fish indigenous to the Great Lakes.
Near shore fish: smallmouth and largemouth bass, muskellunge, northern pike
and channel catfish.
Open water fish: lake herring, blue pike, lake whitefish, walleye, sauger,
freshwater drum, lake trout and white bass.
Erie was the most productive warm and shallow
Superior was the least productive- deep
Overfishing, habitat destruction or the arrival of exotic or non-indigenous
species, such as the lamprey and the alewife, has lost many native fish species
Chapter 4: Concerns Today
Since about 1960, we realized the harsh implications of some human activities.
The largest categories of impact are pollution, habitat loss and exotic species
Agricultural development, forestry and urbanization caused streams and
shoreline marshes to silt up and harbor areas to become septic.
Domestic and industrial waste discharges, oil and chemical spills and the effects
of mining left some parts of the waterways unfit for water supply and recreation.
Pathogens
Historically, the primary reason for water pollution control was prevention of
waterborne disease.
Treating drinking water by adding chlorine, as a disinfectant
Humans can acquire bacterial, viral and parasitic diseases through direct body
contact with contaminated water as well as by drinking the water.
Closing affected beaches during the summer when the water is warm and when
bacteria from human and animal feces reach higher concentrations.
Combined sewers contribute to contamination problems during periods of high
rainfall and urban runoff
Sewage collection and treatment systems cannot handle volumes of storm and
sanitary flow untreated sewage, diluted by urban runoff, is discharged directly
into waterways.

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Expensive to replace combined sewers with separate sewers
Alternative s combined sewer overflow retention for later treatment (lower
costs than sewer separation)
Beach closures have become more infrequent with improved treatment of
sewage effluent
Eutrophication and Oxygen Depletion
Lakes characterized by biological productivity (amount of living material they
support)- mostly algae
Oligotrophic- lease productive
Mesotrophic- middle
Eutrophic most productive
Variables that determine productivity are temp. Light, depth, volume and
nutrients
Temps of tributes have increased b/c of removal of shade and some thermal
pollution
Nutrients/ organic material entered lake has increased with urbanization and
agriculture nutrient loading with phosphate detergents and inorganic
fertilizers
Phosphates in detergents are a problem when not regulated b/c increased
nutrients stimulates growth of green plants (algae) which eventually die and
decompose Organisms that decompose the plants use up the oxygen
dissolved in water near bottom
Without nutrient loading oxygen levels are maintained
Biochemical oxygen demand (BOD): depletion of oxygen through decomposition
of organic material
- generated from discharges from treatment plants and decaying algae
- big problem in central basin of Erie
- As BOD increases and O2 drops certain species of fish can be killed and
sludge, worms and carp replace them
Foggy water and increase in chlorophyll accompany accelerated algal growth and
indicate eutrophication
Erie was firs to develop eutrophication
O2 depletion in Erie 1920s
Controlling input of phosphorus could control eutrophication
Lower layer of central Erie (hypolimnion) can become anoxic and chemical
processes change “dead zone”
- Western less susceptible to anoxia b/c of wind and too shallow and eastern is
deeper with thicker hypolimnion
Belief that Erie was “dying” cladophors near beaches and turbid water
Toxic Contaminants
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