Conference Report on Milwaukee Workshop…

                               Conference Report on Milwaukee Workshop



                                              Workshop Title:
                        Climate Change and the Great Lakes Water Ecology:
                       What Are the Potential Impacts, and What Can We Do?


                                               June 15, 2001



                                      Morning Presentations

How will climate change affect weather patterns and lake levels in the Great Lakes region?
Peter Sousounis, University of Michigan, and Brent Lofgren, Great Lakes Environmental Research Lab,
NOAA


Evaluating changes in synoptic patterns is tantamount to understanding regional climate change. To date, the
synoptic evaluations that have been done regarding climate change output from General Circulation Models
have been restricted mainly to examining changes in storm tracks across large areas (e.g., the Atlantic Ocean).
In this presentation, we looked at output from the Canadian Coupled Climate Model (CGCM1) and the
Hadley Coupled Climate Model (HadCM2), which were used as part of the U.S. National Assessment of
Climate Change. We examined potential changes, relative to present conditions, in synoptic patterns, as well
as changes in temperature, precipitation, and lake levels over the Great Lakes region toward the end of the 21st
century.


Both models show a decrease in the number of extremely cold days, an increase in the number of extremely
hot days, and an increase in precipitation for the ­future--particularly for heavy precipitation (e.g., > 12.5
mm) events. Both models show a decrease in surface windspeed and an increase in the number of days with
an easterly wind component. Both models exhibit decreases in cyclone numbers for the future. The Canadian
Model shows a general decrease in the number of moderately strong cyclones and decreases in each month.
The Hadley Model shows a slight increase in the number of strong cyclones but a greater decrease in the
number of weak ­cyclones--especially during the spring. The Canadian Model exhibits significant decreases
in the number of anticyclones in summer and significant increases in fall, but the model does not exhibit any
systematic changes in terms of intensity. The Hadley Model shows a slight increase in the number of weak
anticyclones but a greater decrease in the number of strong anticyclones. Most of the decreases occur during
the ­summer--so that the seasonal distribution is more uniform.


In addition, the net effects on lake levels of the Great Lakes because of future changes in temperature and
precipitation as simulated by the Canadian Model and the Hadley Model are quite different. The CGCM1
yields a drop in the level of Lakes Michigan and Huron of 0.72 m (2.4 feet) by 2030 and 1.38 m (4.5 feet) by
2090. On the other hand, using the results of the HadCM2, the same lakes rise by 0.05 m (0.2 feet) by 2030
and 0.35 m (1.1 feet) by 2090.
All of the changes are consistent with changes in the general large-scale flow patterns. An understanding of
all these synoptic changes provides richness and a more conceptual understanding of how climate change may
affect the Great Lakes region.



How might future climate affect lake temperature, mixing, algae, and small invertebrates?
John Lehman, University of Michigan


Forecasting future conditions of the Great Lakes in response to climate change puts scientists in an uncom-
fortable role. The most confident prediction is that ecological surprises will emerge. The living communities
of our lakes have intimate and complex two-way linkages to the physical and chemical world, and many of
the linkages still await discovery.


The challenges of projecting future ecological conditions arise mainly from our incomplete understanding of
the present state and the ways that biota can respond. Different visions of future climate generated by alterna-
tive climate models lead us to anticipate fundamental changes in the physical environment of the lakes. Water
temperatures will be higher, the lakes will not mix deeply for as long as they do now, and more ultraviolet
light will strike the water surfaces. We understand that deep mixing resets important elements of the biologi-
cal and chemical clockwork of the lakes, and that temperature changes the speed of these clocks. To date, the
direct responses of organisms to climate variables have received most or all of scientists' attention. We need to
remain alert to the far-reaching consequences of ecological complexity. We do not yet know enough, for
example, to project how temperature, mixing, UV light, and biological processes will interact to affect toxic
metals like mercury that become concentrated up a food chain. We do not yet know exactly which new
species will establish themselves in the lakes and which existing species will be eliminated, or what new or
invigorated parasites will emerge. Our ecological knowledge does warn us about the types of surprises that
will occur. But current theory is no substitute for a strong program of observation and interpretation of Great
Lakes ecology as an insurance policy and early warning system for future environmental problems.



The lakes are changing: Do fishes care about climate change?
John Magnuson, University of Wisconsin-Madison


All aspects of a fish's life such as survival, growth, and habitat choice are dependent on water and water
temperature, both of which are directly affected by climate warming. Warming alters the amount of thermal
habitat suitable for coldwater fishes (trout), coolwater species (perch and walleye), and warmwater fishes
(bass and bluegill). In streams, ponds, and shallow lakes in the Great Lakes region, warming scenarios reduce
habitat for coldwater and coolwater fishes but increase habitat for warmwater species. In deeper lakes that
thermally stratify in summer, such as Lake Mendota and Lake Michigan, warming increases the amount of
thermal habitat for all three thermal groups of fishes. However, coldwater habitat suitable for coldwater fishes
is degraded by loss of oxygen in deeper water; this loss is severe in the shallower or more productive lakes
such as Mendota and could be severe in the larger lakes such as Lake Michigan if thermal stratification
became more permanent. Warming also is expected to increase the invasion of warmwater fishes into the
Great Lakes and the streams and inland lakes of the region. Invasions of warmer water fishes would move
progressively northward, and extirpations of coldwater and coolwater fishes in the streams and inland lakes
would become progressively more common initially in the southern part of the region. The invasions would
result in species interactions that can accelerate the rate of extirpations. For example, in Ontario's inland
lakes, the arrival of warmwater basses (usually by stocking) results in the loss of minnow species. Fishes are
an excellent indicator of the expected changes from global warming because they are sensitive to water
temperature and interactions with the northward migration of fishes; they also are highly valued by people.



Implications of climate change in the Laurentian Lakes: What can the African Great Lakes tell us?
Harvey Bootsma, University of Wisconsin, Milwaukee


The African Great Lakes are similar in size to the Laurentian Great Lakes, but they experience a much
warmer climate. Thus, they can provide clues as to what changes might be expected in the Laurentian Great
Lakes if the regional climate warms. Two notable aspects in which tropical large lakes differ from temperate
large lakes are hydrology and lake circulations, which in turn affect nutrient cycles, algal production, and fish
production.


Although the African Great Lakes experience annual rainfall similar to that of the Laurentian Great Lakes,
greater evaporation rates under warm conditions result in reduced outflow. This reduction in outflow has
implications for lake levels, contaminant retention, and hydroelectricity generation. Deep tropical lakes also
tend to be permanently stratified. Observations in the African Great Lakes suggest that permanent stratifica-
tion of the Laurentian Great Lakes would result in lower deep-water dissolved oxygen concentrations, large
changes in the cycling of nitrogen and phosphorus, and greater inter-annual variability of plankton and fish
production.
          Question and Answer Panel Discussion: Morning Session

Question 1: John Higgins, The Nature Conservancy

When building climate change models based on mean values, you often see very similar degrees of
fluctuation, as in the models just shown. But people working with climate change models and
hydrologic changes are often very interested in the variance, since the predicted change in variance
could be greatly increased with climate change. For example, though the lake level highs and lows
have not changed dramatically in Lake Huron and Lake Michigan over the last 70 years, the vari-
ance of changes is larger than the difference of highs and lows. So, I'm wondering if you've devel-
oped any variance in your models to allow for more extremes to result from the models.

Response: Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA

Hopefully in the next year, daily data will be used more as inputs into hydrologic models to incorpo-
rate a little bit more of the change in variability that is projectedby the GCMs. But how reliable the
projected change in variability will be is a question worth asking. Another question to ask is: "What
kind of analyses will we want to do with this variance data?" Specifically, what time scales will we
look at? Are we interested in looking at storm activity on a weekly scale? Are we interested in
looking at lake level rise over a five-year period? All of these kinds of analyses will require a lot of
data handling, so these questions will need to be considered

Question 2: George Stone, Milwaukee Area Technical College

What is the "shelf life" of the Canadian and Hadley models? How often are they revised?

Also, it seems as though we've had an unusually cool, wet spring in the Great Lakes region. Is
there any evidence thus far that that has had any effect on lake levels?

Response: Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA

Actually, the Hadley Center has recently come out with a new version of its model, the HADCM3, for
which the results have begun to be published. Interestingly, the results of this new model agree
more closely with the Canadian Climate Center model that we have been using. One of the major
changes of this new Hadley model is in its handling of atmospheric aerosols that reflect sunlight,
and [the model now] ends up projecting warmer temperatures into the future [than before]. What-
ever the newest model is, that is the one that is essentially considered to be the best.

As for the recent low temperatures and high precipitation rates, such trends need to build up over a
couple of years to create a significant change.

Question 3: Thomas Johnson, Large Lakes Observatory, University of Minnesota Duluth

The modeling results look promising for fishing on Lake Superior, since availability of prey increases
with rising temperatures. I am interested in knowing to what extent fish production in the Great
Lakes is linked to phosphorus input to the lakes. Has anyone done a very simplistic comparison of
overall fish productivity in the Great Lakes and the overall phosphorus levels?

Response: John Magnuson, University of Wisconsin-Madison

If you add phosphorus to a point and have increased algal and subplankton productivity, you get the
classic bottom-up effect. If you compare lakes, about half of the variability is often associated with
this kind of bottom-up effect, so you would expect phosphorus availability to play a role. Years ago,
Dick Ryder developed an index of fish yields from lakes that consisted of a simple ratio of total
dissolved solids (which would include nutrients), divided by mean depth. That simple ratio explained
a lot behind the yields of fish in lakes around the world. So, it is well established that those bottom-
up effects are real. If it goes up and up, you begin to get a change in status--for example, if the
deep waters get anoxic (oxygen depleted), then the whole framework will change. But I haven't
seen anything presented today that suggests that the waters are going to go anoxic in a hurry.

Question 4: Thomas Johnson, Large Lakes Observatory, University of Minnesota Duluth

One of the reasons that I am asking about phosphorous in Lake Superior is that its bedrock is
different from that of the other Great Lakes. Because Superior doesn't have limestone and therefore
doesn't have the high total dissolved solids, I'm wondering what kind of impacts warming might
have on it.

Response: John Magnuson, University of Wisconsin-Madison

These models that I presented are very simple. If you began to include the whole food web and
productivity and some of the feedbacks, you would get a lot greater variety of scenarios. Both
because of its shape and runoff of nutrients into the area, Superior will remain a low-productivity
lake, even with a lot of activities going on. I would imagine that of all the Great Lakes, Superior is
the one that is most susceptible to a food web shortage.

Response: John Lehman, University of Michigan

Just because a lake is low in total dissolved solids, that doesn't mean that it can't become
ibritrophic, and that was the reason for choosing these lakes for nutrient experiment work. Inputs of
nutrients from the watershed will be largely controlled by anthropogenic processes, and we don't
know what the future holds for population migrations and how inputs will change. Another dimen-
sion to look at is the lake geometry index--a geometrical factor that has a fair bit of predictability.
Lake geometry affects whether or not lakes will form strong thermal stratification and become
depleted of oxygen in the deep layers. And, of the Great Lakes, Superior and Ontario are the most
susceptible to forming strong thermal stratification and deoxygenation according to that ratio. So, it
will be interesting to see if the predictions of these mixing models hold up and if the duration of
thermal stratification in Lake Superior increases faster than that of the other lakes.

Question 5: Lon A. Couillard, City of Milwaukee, Milwaukee Waterworks

What is the potential effect of climate change on algal blooms? How might it affect the water quality
for domestic water producers?

Response: Art Brooks, University of Wisconsin-Milwaukee

There has already been an increased abundance of some algal species growing on rocks along the
shores of Lake Michigan, which are likely explained (at least in part) by warmer water temperatures.
Generally, in warmer water, there tend to be greater numbers of cyanobacteria--bluegreen algae
that do somewhat better under lower nitrogen levels, since they can fix their own [nitrogen] from the
atmosphere. So, we might see some changes in this respect.

Response: John Lehman, University of Michigan

Increased duration of thermal stratification will lead to a relative loss in the number and success of
the diatom species, which are opportunistic, fast-growing clean water algae. However, diatoms
cannot tolerate high rates of loss, so an increased duration of thermal stratification may lead to their
replacement by either colonial greens--which may not present much of a problem other than filter
clogging--or by colonial or filament-forming bluegreens--which can present more of a problem, in
terms of taste, odor, and general nuisance.

Response: Harvey Bootsma, University of Wisconsin-Milwaukee

One must consider the multiple effects that climate change will have. Warming will affect algae
production and composition. But as changes in thermal structure and stratification occur, some
modeling suggests that production will actually decrease, because the longer stratified period does
not allow nutrients to get to the surface water. What we might expect to see is different effects in
near versus offshore areas. Offshore areas are more dependent upon annual mixing to bring up
nutrients, whereas near-shore areas may be more responsive to inputs from catchments (where
surface runoff is gathered). Therefore, even with constant nutrient inputs, near-shore areas will be
more responsive as temperature increases.

Response: Art Brooks, University of Wisconsin-Milwaukee

We have talked about some of the hydrologic effects and the fact that water levels may drop, which
means that most intakes would be drawing in more surface water than deeper water, which in turn
may mean that more productive water will come in, due to the physical factors.

Response: John Magnuson, University of Wisconsin-Madison

A paper was written on year-to-year variation of water clarity in Lake Mendota and what the statisti-
cal explanatory variables did over the last 30 years or so. It was found that water clarity was equally
influenced by three things--all three of which will be influenced by climate change:
(1) Runoff--which will probably increase due to increased precipitation;
(2) Stability of the water column--where the warmer the water--the warmer the summer--the less
erosion of the deeper nutrient waters there will be during the summer, ultimately resulting in less
upwelling or internal reloading of phosphorus; and
(3) Population size of daphnia--a herbivore that feeds on phytoplankton. Daphnia varied based on
the abundance of fish that [feeds on] them. In the eastern part of Great Lakes, we have a number of
very effective warmwater zooplanktivores--the probability that they would become dominant in our
systems would increase under a warmer climate.

Question 6: Patty Glick, National Wildlife Federation

Has anyone looked into how reduced lake levels may affect species that rely on lake shores for
breeding and other purposes?

Response: Art Brooks, University of Wisconsin-Milwaukee

Based on aerial photographs of the Mink River, we have seen great variations on the extent of
wetland areas along the coast. The photos revealed that the wetlands increased and decreased by
several orders of magnitude over a 10-year period, ranging from a trickling stream to a wide flooded
wetland area. Since climate change will only exaggerate the natural variations that already occur,
the implications of climate change on wetland production and nursery areas are very significant.
This will affect productivity.
Response: John Magnuson, University of Wisconsin-Madison

John Brazner at the EPA lab in Duluth would be a good resource person to speak to regarding the
effects on lake shore species.

Other effects to consider may be the within-year variations. For example, if water levels were to
drop rapidly, fish species that spawn in the sand and the gravel might be stranded--but that would
have to be fairly fast-moving water level drops. During the winter, fishes like the whitefish spawn on
rocks just below the high water mark, and if there were a large loss of water in the winter, one might
expect exposure of the ice settling on them. But I think those [effects] are unlikely, though it will
depend on how big the variation is.

Response: John Lehman, University of Michigan

Another potential impact would be from a change in ice scouring that can occur during the winter--
during the modification of shallow water habitat.

Question 7: Patty Glick, National Wildlife Federation

Do researchers know how natural variations of lake shore levels affect different populations of
species over decades? For example, do we know how water level fluctuations affect different
populations of species, such as impacts on hatching rates?

Response: Art Brooks, University of Wisconsin-Milwaukee

I suspect that some work has been done on that, though I am not familiar with any such research.
Certainly, inter-annual variations such as the extent of ice cover, the duration of spring mixing, and
other things of that nature would affect phytoplankton production.

Response: John Lehman, University of Michigan

We haven't analyzed numbers specifically in that way. There is anecdotal evidence in terms of
some invertebrate species development; for example, we know that fast-growing species that do
well in warm water are successful members of the fauna during unusually warm years--but no
systematic review has been done.

Response: John Magnuson, University of Wisconsin-Madison

In the fish literature, there are correlates of year-class reproductive success in some species that
are related to climatic factors that may be linked to water levels, but they may not actually be di-
rectly caused by the water levels. For example, walleye usually do better in situations where there
is more runoff in the spring, and perch have higher reproduction in springs that are warm and dry
instead of springs that are cold. Sorting out the exact causes for high or low productivity would be
difficult.

Question 8: Dave Michaud, Wisconsin Electric Power Co.

Given the demonstrated effects of zebra mussels in the near-shore area on phytoplankton and
maybe even on benthos, would it be difficult to discern the effects of climate change in the next 30
years from the effects of zebra mussels and other exotic zooplankton that are already causing
damages? How hard is it going to be to discern global climate impacts from exotic impacts?
Response: John Magnuson, University of Wisconsin-Madison

Discerning the causes and impacts of climate change from all other variables is difficult, but scien-
tists enjoy trying!

Question 9: Dave Michaud, Wisconsin Electric Power Co.

Based on recent observation from being a large water user along the western coast, I can tell you
that we have had to spend almost $10 million dealing with the zebra mussel, both in terms of direct
and indirect impacts. Given the tremendous impacts that have occurred in the near-shore area from
one species alone, I have serious doubts as to whether we can even begin discerning subtle
changes in trophic-level dynamics, when there are monster invaders causing so many changes.

Response: John Lehman, University of Michigan

But climate change and invasive species are not necessarily independent issues. Changes in the
physical environment, such as temperature and mixing, in many ways facilitate the introduction of
exotics and will increasingly continue to do so. Lots of introductions are occurring all of the time, but
we only notice the catastrophic ones that affect us. But, as mixing patterns change and the vertical
extent of warm water changes, deep water intakes that are currently unaffected by the zebra mus-
sels, thanks to cold temperatures, may be affected in the future when the water warms. So there
may be an interaction between climate change and exotic species in the future.

Response: Art Brooks, University of Wisconsin-Milwaukee

Another unknown that should be considered in the Great Lakes is the fact that these are managed
systems, yet managers of the lakes have not paid any attention to climate change projections and
are continuing to practice the same behaviors. If they decide to put more salmon or trout in the lake,
that could change the whole mix as well. So we are not just looking at a random input of exotics, but
maybe a purposeful input of exotics that scientists have minimal control over.

Response: John Magnuson, University of Wisconsin-Madison

Though zebra mussels are no doubt a pressing issue for the hydroelectric industry, and climate
change may not influence the industry in the same way, climate change may influence how you
place inputs, or the efficiency of your cooler system.

The navy has already started thinking about how they would deal with military issues in an ice-free
Arctic! This demonstrates the long-term investment time for which some people are, and must, think
about to protect certain interests. So, the only thing that I can encourage people to do is not to get
too caught up in dealing only with the most pressing issues of the day, but also to think about some
longer term problems that will affect them in the future.

Response: Harvey Bootsma, University of Wisconsin-Milwaukee

Certainly, introduction of exotics does make it very difficult to predict what will happen in the future.
But, as mentioned earlier, though phosphorus inputs can explain about 50 percent of the variability
in primary production and other top-down mechanisms also influence this variability, that does not
mean that it is not useful to look at the relationship between phosphorus and chlorophyll. In the
same respect, despite variability and the complexity of factors that affect lakes, it is still worth
considering the potential impacts of climate change on lakes. There are fundamental physical
factors that we need to know about lakes as a result of climate change. Even though there will be
other changes superimposed on these climate change-related impacts, our ability to predict the
results of exotics is improved by fundamental background data that will allow us to better know how
systems will change over time.

Question 10: Alberto Vargas, Wisconsin Coastal Management Program

What are the next steps that should be taken to further the climate change debate? What is the role
of science? Do we need to refine predictions? Provide economic assessments for different sce-
narios? Based on what newspapers are saying, the discussion is not so much centered on whether
or not climate change is happening, but on the economic implications.

Response: Peter Sousounis, University of Michigan

What we have learned from the first assessment is that we need to expand on three major areas:
(1) we need a better understanding of the inter-annual/decadal variability of systems from year-to-
year, not by mean; (2) we need to conduct more interdisciplinary studies; and (3) we need eco-
nomic answers. For the latter need, since stakeholders have the best idea of how weather may
affect their industry, scientists need to foster better relationships with stakeholders and provide them
with the necessary information for them to determine the economic answers.

Response: John Magnuson, University of Wisconsin-Madison

We need to know what the impacts may be and what potential adaptive strategies can be adopted.
Most people do not propose adaptive strategies but simply believe that we'll just have to cope with
whatever changes result. Also, the climate system needs more work. For example, the U.S. needs
to know more about its carbon budget--where are the sinks? Are there adaptive mitigation mea-
sures to be taken in agricultural, forestry and/or lake management to increase carbon storage? We
also need to keep providing policymakers with information to allow them to develop an action
strategy on climate change at the international level. So, there is clearly a large role for communica-
tion and education--lots of priorities!

Response: John Lehman, University of Michigan

Studies have revealed that there is much uncertainty and a great need to fill in the gaps in our
scientific knowledge. For example, maybe we need to know more about seasonality of maximum
rates of primary production. Therefore, in addition to exploring the socio-economic side of the
problem, we also need to know how good a job we are doing at putting the right numbers into our
equations. An example of uncertainty worth further interdisciplinary research is the variation in cloud
cover during the day and night. Cloud cover variability can have a huge impact on climate and
lakes. These impacts, which could have huge effects on projections, cannot be deciphered from the
GCMs but will need to come out of mesoscale models. But right now we don't much data on cloud
cover, so these impacts are still largely unknown.

Question 11: Jo Sandin, The Milwaukee Journal Sentinel

How will we be able to find out variability in cloud cover between day and night, now that the Na-
tional Oceanic and Atmospheric Administration (NOAA) has replaced humans with machines that
are not capable of monitoring cloud cover? Nobody is looking out the window anymore, because we
are not paying anyone to do it. Do we know if it will be cloudier in Milwaukee?
Response: Peter Sousounis, University of Michigan

It is hard to pay observers 24 hours a day. Remote sensing does actually have some advantages. It
allows more spatial cover over remote areas of the lakes and the algorithms used to interpret
satellite data are getting better and providing more accurate numbers for cloud cover. On the whole,
satellite-derived cloud cover is probably doing a better job than human observers could. The algo-
rithms are compared to mesoscale output, which will help refine both. Using this newly refined
information, we hope to obtain better estimates of how cloud cover will change the picture.

Response: Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA

The problem with remote sensing is that it eliminates the temporally homogenous record at any one
point of cloud cover that one would get by using a consistent method of measurement. In most
cases, one would want an overlap of several years, but some things, such as cloud base height, are
not necessarily measured by satellites. A similar problem has arisen with the elimination of river flow
measurement sites maintained by the U.S. Geological Survey, which has occurred at some sites in
the Great Lakes basin over the last few years.

Question 12: Patty Glick, National Wildlife Federation

Despite the many uncertainties that exist in the current science on global warming, there is very
little uncertainty that human activities are causing the Earth to warm. Yet, by constantly talking
about uncertainty, policymakers hone in on the different layers of scientific uncertainty and then do
not act. As scientists, do you feel comfortable conveying so much uncertainty, knowing that the
declaration of uncertainty causes policymakers to delay action?

Response: John Magnuson, University of Wisconsin-Madison

As scientists, we must say what we feel confident about and what we feel uncertain about, or we
are lying and cheating. Policymakers need to decide if, in the face of uncertainty, we should act
conservatively or take the risk-prone approach. What people have discovered in the past is that we
would have been well off to have taken the risk averse strategy--known as the precautionary
principle. So, most scientists would tell policymakers that if you're looking at an uncertain future,
you should take the cautious approach. Science only plays a certain role in deciding policy. As
scientists, our role is to reveal the uncertainty to force political debate on important environmental
issues. Scientists can only reduce uncertainty; they cannot eliminate it.

Comment: George Stone, Milwaukee Area Technical College

An important part of risk assessment is to ask the question, "What are the consequences?" There is
uncertainty about contracting or not contracting a disease, but that does not cause people to forgo
inoculation. Likewise, we do not know when or where earthquakes are going to occur, but that does
not prevent us from passing building codes and construction requirements to prevent casualties and
costs if an earthquake does occur. I think this kind of approach, where you take not only probability
into account, but also the severity of the consequences, is important for policymakers to consider.
                                     Afternoon Presentations

What are the potential impacts of Lake Michigan water levels on drinking water production, quality,
and demand?
Roger Johnson and Bill Soucie, West Shore Water Producers Association


More than 40 drinking water plants in four states draw on Lake Michigan as a water source. All of the plants
have water intakes that extend from about 900 feet (40 m) to upwards of 15,000 feet (4.5 km) into the lake.
The intake structures typically rest in 10 -50 feet (5-15 m) of water.


High- and low-water levels affect water plants differently. However, most water plants are designed to with-
stand 100-year historic high and low lake levels. Some water plants built in the late 1800s have actually
persevered through these extremes and continue to pump water today. High water levels pose the greatest
challenge to shoreline water plants. The combination of elevated lake level and wave action makes these
facilities particularly vulnerable to flooding. In contrast, lower lake levels would provide increased protection
for these utilities. Lake levels below 100-year historic lows may decrease the ability of some water producers
to draw enough water from the lake to meet customer demand. Deeply submerged intakes facilitate water
conveyance through intakes to pumping stations. Shallow water limits water withdrawal. If customer demand
then exceeds the ability to withdraw water, some intakes may require extension.


Water quality changes during high and low lake level extremes are difficult to identify. The major water
quality factors that treatment plants work with today are water temperature, turbidity (suspended solids), and
microbiological quality factors. These factors also change more often than other water quality factors. New
water temperature extremes may pose a few challenges. Colder winter water may lead to increased ice
formation on intakes and a decreased ability to supply water. Warmer summer water may lead to increased
algal blooms and the resulting taste and odor events. Taste and odor problems would increase treatment costs.
Turbidity and microbiological changes already fluctuate greatly during the year, especially for near-shore
shallow intakes. Although water plants are designed specifically to handle these extremes, slightly increased
usage of coagulants and disinfectants may be anticipated.


Changes in climate also may affect public water demand. Water production typically increases by more than a
factor of two during the hot summer months. Extended dry and hot weather results in maximum water de-
mand since irrigation increases. If treatment plants are unable to produce sufficient quantities of water,
demand will have to be reduced or water supply increased. Increasing the supply would most likely involve
increases in water rates.


Overall, water providers are cautiously confident that the climactic changes anticipated for the 21st century
will not dramatically affect our ability to supply drinking water to the communities we serve. However, we
will continue to monitor lake levels and water quality closely to assure production of high-quality water in
sufficient quantities.
What are the challenges and opportunities facing commercial fishermen?
Ted Eggebraaten, Wisconsin Commercial Fishing Association, Door County Chapter


Chubs, whitefish, lake trout, yellow perch, and rainbow smelt are important commercial fishes harvested in
the Great Lakes. Species are harvested at various depths and times of the year, using a variety of gear types
and techniques. Gill nets, trap nets, and pound nets are the most common gear used in the region, though
trawls and trap nets are still used by some. Historically, natural cycles cause variability in fish populations,
but invasive species have caused the most significant changes to local fish populations. Whether climate
change will affect Great Lake fisheries for better or worse is unknown.


Climate change will bring warmer water, which will affect species composition and lead to a greater
introduction of exotic species. Depending on the market value of the fishes that thrive under warmer
conditions, climate change will either hurt or help the fishing industry. Changes in water clarity also will
affect fishing practices and catch levels, if nets become more visible at shallower levels. Improved water
quality from zebra mussels has allowed whitefish to detect gill nets and swim deeper in order to avoid them.
Because gill nets can go no deeper than 150 to 180 feet, problems could result if climate change produces a
significant further increase in water clarity. In addition, greater water clarity allows predatory birds, such as
cormorants, to hunt more fish and create added competition for fishermen. Other possible changes include
lower lake levels that could lead to dredging in order to maintain the use of existing docks, and shifts in
prevailing winds, which could affect fishing dramatically (with more easterly winds resulting in decreased
fish catches and more westerly winds resulting in increased catches). On a positive note, reduced ice cover
would facilitate fishing during the winter months. How the fishing industry will change and adapt under
climate change remains to be seen.



Water quality and public access: Who's watching the waterfront?
Eric Skindzelewski, President, Lake Shore Fishermen Sports Club


The Lake Shore Fisherman's Sports Club has worked to achieve greater public access to lake shores and
clean water for about 20 years. After confronting countless barriers and eventually paying high costs for
legal representation without achieving results, the club decided to embark on a major outreach campaign to
win public support. The club conducted workshops and educational seminars about public access, and
conducted a successful campaign to inform government at various local, state, and national levels about the
need for greater public access.


After 15-20 years of this outreach, the club prevailed. A state park was established and a boardwalk con-
structed; public access to piers and many lakefronts was awarded; children now are allowed to ice fish in
county parks; and laws were passed to ensure that there are enough fish for the public to enjoy. Other
notable accomplishments of the club include improvement of boat ramps and the provision of fishing pole
holders and other amenities for the public, all paid for by the local government and donations from the
public. Today, the club supplies videos on water safety to children and holds educational workshops in
parks twice each year, fostering the enjoyment and care of water resources and the natural environment.
Approximately 80,000 children and 40,000 elderly have attended the seminars.


What are the potential impacts of climate change on fresh water recreational fishing opportunities in
the United States?
Susan Herrod Julius, USEPA


As greenhouse gases accumulate in the atmosphere and alter the climate, rising temperatures, changes in
precipitation, and changes in other weather patterns are likely to affect ecological processes and ecosystem
services. Among the systems and organisms affected may be a variety of fish species. The potential negative
impacts on fish species and the popularity of recreational fishing led to an EPA-sponsored research project
that examined the potential impacts of climate change on fish species survival and the consequent impacts on
future recreational fishing opportunities. The study modeled the effect of temperature changes on habitat
conditions in various geographic areas and the subsequent effect on the ranges of fish species. An economic
model in the second step of the analysis projected changes in recreational fishing behavior based on measures
of habitat changes and fishes estimated by the thermal model. Results were expressed as changes in total days
spent fishing for each class of fish (cold, warm/cool, rough). The annual damages represented by lost fishing
opportunities were calculated using values per day spent fishing for each class of fish developed from a series
of recreational fishing valuation studies.


The modeling results showed that 21 of 48 states would lose at least one of the 31 fish species studied in the
analysis. More than 75 percent of the scenarios that were modeled resulted in economic costs associated with
climate change being significantly larger than benefits (on the order of about $239 million in losses per year),
indicating that the costs will likely outweigh any benefits for recreational fishing. Using very conservative
assumptions, cold water fishing losses were estimated at $1.3 to 3 billion per year (1993 dollars). This model-
ing exercise is a first attempt to characterize and assess the economic impacts of climate change in the Great
Lakes region and provides a sense of the magnitude of the problem.
         Question and Answer Panel Discussion: Afternoon Session

Question 1: Jonathan Higgins, The Nature Conservancy

In the analysis of water and air temperatures that fed into Susan's work on the potential economic
impacts of climate change on fresh water recreational fishing opportunities in the U.S., were warm-
versus cold-dominated systems split out, or was a mean value used?

Response: Susan Julius, U.S. EPA

A mean value was used in the analysis.

Question 2: Jonathan Higgins, The Nature Conservancy

I'm wondering if groundwater-dominated systems may buffer against climate change impacts to
some extent, given their colder, more stable water. Are our predictions about the decimation of cold-
water species in groundwater-dominated streams really as extreme as the projections discussed
today?

Response: Art Brooks, University of Wisconsin-Milwaukee

Groundwater follows mean annual temperatures, so it would still be affected, though there may be a
greater lag time in its response to ambient temperatures.

Response: John Magnuson, University of Wisconsin-Madison

Modeling of groundwater-fed streams under the scenario of a doubling of carbon dioxide has been
done, and, though they have not indicated 100 percent loss like the work presented today, they did
end up with considerable shortening of stream miles that are cold water. I also wonder if any of the
streams monitored by the USGS are actually trout streams.

Response: Susan Julius, U.S. EPA

These were just a sample of streams, they were not discerned--so some may be trout streams.

Response: John Lehman, University of Michigan

There is also a confounding influence of stream hydrograph performance as a function of whether
or not fish species are groundwater fed or surface water fed. That is something dealt with in an
assessment by David Allen, at the University of Michigan, where some attention was paid to the
issue of cold water fish in groundwater-dominated systems. That may be a source worth consulting.

Question 3: Jonathan Higgins, The Nature Conservancy

I have seen that assessment and it really does not address the question of to what extent the
hydrologic performance will affect species. I am interested in the conservation angle, in terms of
what potential degree of impacts will result for different types of systems, and what spatial configu-
rations we will have to take into account when spending conservation dollars. Are there certain
streams systems that might naturally be buffered from climate change, based on water sources?
Response: John Lehman, University of Michigan

The final steady state solution is still going to be towards warmer groundwater temperatures, though
it may take a longer time to get there. If it is a variance issue, you might be able to see the buffering
work, which is an excellent topic for further analysis.

Question 4: Art Brooks, University of Wisconsin-Milwaukee

In Susan's economic analysis on recreational fishing, five of the species considered were exotic
species. How did that fit into your economic calculations, when it came to stocking those fish?

Response: Susan Julius, U.S. EPA

The numbers were not costs of stocking. Essentially, they are estimates of what a person is willing to
pay to spend a day fishing for that type of fish. We did not look at any issues concerning the mainte-
nance of fish populations. The economic analysis looks at what people value the most, without
differentiating between native and exotic or what will survive best.

Question 5: Art Brooks, University of Wisconsin-Milwaukee

Looking into the future, what might the costs be of maintaining suitable fisheries, of re-stocking
systems, or stocking something else?

Response: Susan Julius, U.S. EPA

We did not look at how costs might change in terms of stocking, or any issues related to maintaining
fish populations. As for the costs of maintaining fisheries, this analysis did not assess that. That
would be an excellent to look at further. As it is now, they introduce new stocks of species into sys-
tems during the summer months, for the sole purpose of fishing, and then the fish die by the end of
the season. One would presume that they will probably adapt their stocking practices; I do not know.

Question 6: Peter Sousounis, University of Michigan

Is it possible to take some aspects of algorithms used for the economic assessment on fishing and
apply them to other industries? Are there some general thought processes developed that can be
applied to future analyses for other industries?

Response: Susan Julius, U.S. EPA

Our economic models were specifically developed for fisheries, but the general thought processes
used could apply.

Response: John Furlow, U.S. EPA

General methodologies for conducting economic assessments are being developed by a group at
Colorado State University. Focused on gateway communities bordering the Rocky Mountain National
Park, they are looking at what it is that brings tourists into the area, at what the economic benefits are
to the community, and then assessing how the local economy will be affected if any changes occur to
the natural resources base. For example, what will the economic impacts be if there are no more
buffalo or elk? The study looks at willingness to pay, travel costs, etc., and this type of economic
analysis--though not necessarily widely respected--is fairly well developed.
Response: Susan Julius, U.S. EPA

Another thing to consider is that even if you argue with the numbers of the economic analysis, it
offers at least one attempt to estimate what the impacts will be, to get a sense of the magnitude of
the problem. Before conducting the analysis, we first looked at all the activities that can be mea-
sured in terms of market or non-market data, and then checked if we had enough economic data to
connect changes in activities with economic impacts. Recreational fishing is one of the few catego-
ries for which we had enough data linking climate to changes in species of interest, and then to the
economic value of those changes.

Comment: Michelle DePhilip, The Nature Conservancy

To add to that, an economic analysis was conducted by the University of Illinois in Chicago on the
economic value of the natural resources in southern Lake Michigan. The analysis estimated the
individual value of different fish species and then calculated what people would pay for the natural
resources of the area.

Question 7: Mike Rau, Wisconsin Gas Water Services

Has there been a study done on warming, taking into account possible population trends that may
change in the Great Lakes region, given that people like to live in places that are warm and by
water? For example, Florida is a prime destination for people. Has any study looked at the eco-
nomic impacts of these types of future population trends in the area?

Response: Susan Julius, U.S. EPA

That is a really good question. I do not believe that that's been done yet, but there are ways for that
to be studied, using economic modeling approaches that look at all the variables that determine
where people live and why--and it is very much weather-related

Response: Peter Sousounis, University of Michigan

It is indeed a very interesting question. At the start of our assessment, we were provided with
socioeconomic and population data projections for 2030 and 2050. However, those population
projections do not account for the interaction between variations in population trends and a warming
climate. They were straight, independent population projections.

Question 8: Art Brooks, University of Wisconsin-Milwaukee

The Chicago workshop in March was concerned more with water levels, and the shipping industry
had figures showing that for every inch that the lake drops, they must offload "X" hundred tons of
iron ore from ships. In other words, they directly equated lake levels with economic impacts. Have
water producers looked at increased pumping costs and the use of more effective chemical reac-
tions to clean water under certain processes? Do you keep track of the pumps as they are running
to monitor the amount of horsepower used to draw in water?

Response: Roger Johnson, West Shore Water Producers Association

For some of the lakes, the horsepower must be increased to get the volume that they want. Often,
what happens is that the level over the intakes is less, decreasing the amount of water that can be
taken in. Therefore, it costs a lot more to increase the horsepower, plus it also reduces the volume
of water that they can take into the plant.
Question 9: Art Brooks, University of Wisconsin-Milwaukee

Do you keep track of the pumps as they are running to monitor the horsepower used to draw water
in? If so, do you see a difference in kilowatts consumed in 1986, when water levels were at an all-
time record high, compared to now, when they are at an all-time record low?

Response: Roger Johnson, West Shore Water Producers Association

I do keep track of pumping, because it is one of our highest costs. The last three years, we have
had a very wet spring. At my plant, which is different than those in the Chicago area, the pumps are
at the bottom of the lake. We monitor the kilowatt-hours per million gallons of production, and that
hasn't changed over the years.

Questions 10: Jeanne Bisanz, University of Michigan

Do you estimate demand? In the short and/or long-term?

Response: Roger Johnson, West Shore Water Producers Association

Yes, we do estimate demand--usually broken down by month and by temperature. As the tempera-
ture increases, people's use of water increases. April, May, and June are the highest water-use
months, when everyone waters their lawn. By July and August, people are less excited about
watering lawns, so water use decreases. We are really dependent on forecasts, and where we are
going to be in terms of our production of water use. We estimate over a five-year time frame, though
it is hard to predict. For example, we more or less base our production on population projections,
based on average use of water per day, per person, as well as industrial usage. But this can be
difficult to predict with any degree of accuracy, if a big water user comes into the area or moves out.

Questions 11: Jeanne Bisanz, University of Michigan

Do the West Shore Water Producers supply any farms with water?

Response: Roger Johnson, West Shore Water Producers Association

No, we don't supply farms. We only supply residential and industry uses.

Questions 12: Lon Couillard, Milwaukee Water Works

If global warming warms summer climate in the Great Lakes region, we will likely be reluctant to
switch our plants to desert plants. Could that increase our irrigation demands and affect our water
consumption?

Response: John Magnuson, University of Wisconsin-Madison

Even the people in Phoenix who have desert gardens, water them at the same rate that they would
grass!

Question 13: John Lehman, University of Michigan

It seems to me that there were concerns about days with high turbidity and high contamination
related to a weather event, as well as about taste and odor events related to algal production of
particular kinds of species. If there were a way to get a handle on the frequency and probability of
those kinds of events in the future, would that be useful to you? Or is that outside of the manage-
ment and planning sphere that you engage in?

Response: Roger Johnson, West Shore Water Producers Association

That would certainly be useful. As algal blooms increase, so too do taste and odor problems, which
require expensive changes to systems. Different methods used to rid water of bad tastes and odors,
such as granular-activated carbon and powder-activated carbon, cost about $0.60 to $0.80 per
pound. The more chemicals we must use, the higher are our costs, and the more it ends up costing
the consumer.

Question 14: John Ferland, U.S.EPA

Is there any correlation between changes in temperature to changes in algal blooms and use of
carbon or ozone treatments to rid water of bad tastes and odor?

Response: Roger Johnson, West Shore Water Producers Association

We can run tests that measure odor-free water against raw water, and based on how high the
threshold odor number is, we can determine how many pounds of carbon will be needed to clean it.
We can also run tests to determine the concentration of bluegreen algae, which help us predict
changes in the taste and odor of water and in what it will cost us per million gallons produced.

Question 15: John Ferland, U.S.EPA

Have your costs to rid water of bad tastes and odors over the last years increased at all?

Response: Roger Johnson, West Shore Water Producers Association

Our carbon costs have increased over the last three years.

Question 16: John Ferland, U.S.EPA

Is the cost increase because of a change in use of carbon or because of a change in the cost of
carbon?

Response: Roger Johnson, West Shore Water Producers Association

The cost increase for carbon is due to the increased odor in water that costs more to clean.

Comment: Art Brooks, University of Wisconsin-Milwaukee

A comment for people who work on the water all of the time: some of the best records that we have
of long-term changes in the lakes are from water producers. For the last 75 years, they have col-
lected this data, counting phytoplankton every day, until the zebra mussels appeared and [then the
water producers] unfortunately stopped. I urge you all not to stop looking at shifts in algal popula-
tions! It may prove to be very useful to you at some time in the future.

Question 17: Brent Lofgren, Great Lakes Environmental Research Laboratory, NOAA

I have a question for Art Brooks regarding spring phytoplankton blooms being triggered by light
availability. In a worldwide conference I participated in a short while ago, they seemed to indicate
that phytoplankton blooms are triggered by temperature thresholds, not light.
Response: Art Brooks, University of Wisconsin-Milwaukee

In Lake Michigan, algal blooms begin when temperatures are still 4 degrees or less, so my opinion
is that they are triggered by light. Maybe in other lakes they may be triggered by nutrients or tem-
peratures; I don't know.

Response: John Lehman, University of Michigan

Certainly, the growth trigger will vary by type of algae. Diatoms, which are very successful in the
Great Lakes--particularly in Lake Michigan, are extremely capable of growing in cold temperatures
at low average light intensities. About 50 years ago, it was demonstrated that even without cold
temperatures, light can cause full blooms in some types of algae.

Question 18: John Lehman, University of Michigan

The presentation on commercial fishing illustrated a really nice interface between some knowledge
of natural history and environmental issues. Is there not some aspects of the cormorants' biology
and feeding biology or production that we really need to know more about in terms of their future
impact on future fishing?

Response: Ted Eggebraaten, Wisconsin Commercial Fishing Association, Door County Chapter

Certainly, there is a lot more that we need to know about. But as a gill netter, I rely on my net being
invisible. With algal blooms, our production goes way down, because by the end of February or
early March, algae rolls along the bottom the lake and gets stuck on our nets, making the nets
visible to fish, so they swim around them. I don't know if a change in algal species will affect us,
since there is much variability among species, with some getting caught in nets more than others,
and some being more visible than others. If one species of algae finds something it really likes (like
the zebra mussels), and then really blooms, then the impacts on the commercial fishing industry
may be big.

Question 19: John Higgins, The Nature Conservancy

Are commercial fishermen looking for potential alternative methods for fishing? For example, are
you looking at other large lake fisheries that might have some of the same conditions that our lakes
may have in the future? Do you have any idea of what those techniques might be and how they
would affect you?

Response: Ted Eggebraaten, Wisconsin Commercial Fishing Association, Door County Chapter

Commercial fishing is constantly evolving and progressing. We will always use new materials and
try new methods. I experiment with at least a half dozen new techniques over the course of the
year. Fishing and fishermen are very adaptable, we constantly try new things, which is what has
kept us alive in many ways. It could be that our production times may be compressed; for example,
maybe we will fish only during spawning season or at other opportune times of the year.

Question 20: Jeanne Bisanz, University of Michigan

How many commercial fishermen would you say are at Lake Michigan?

Response: Ted Eggebraaten, Wisconsin Commercial Fishing Association, Door County Chapter
There are probably about 90 license holders in Wisconsin, most of whom are concentrated in
groups. So, in Wisconsin, there are maybe about 40 to 60 operations of commercial fishing. Michi-
gan probably has about the same number, and there are a couple in Illinois also.

Question 21: Patty Glick, National Wildlife Federation

This question is for Harvey Bootsma: Do you have any ideas of what the future impacts from cli-
mate change will be for the African Great Lakes? Are there any projections for them?

Response: Harvey Bootsma, University of Wisconsin-Milwaukee

There is some evidence of climate change in the African Great Lakes, though not to the same
extent or magnitude as that seen in temperate areas. In looking at Lake Tanganika and Lake
Malawi, we know that a small change in temperature will result in large changes in thermodynamics
and stratification. Lake Tanganika is only about 1 degree warmer than Lake Malawi, but its ther-
mocline is about 100 meters, whereas the thermocline is about 200 meters in Lake Malawi.

Response: John Magnuson, University of Wisconsin-Madison

With increased stability of the thermocline, one researcher recently found that there was less mix-
ing. There was some evidence that the deep waters were warming up from geothermal heat.

Question 22: Patty Glick, National Wildlife Federation

Are the African Great Lakes also relied upon as fishing resources as the Great Lakes are here?

Response: Harvey Bootsma, University of Wisconsin-Milwaukee

Yes. While angling is not very popular in Africa, fishing for food is. Lake Malawi has thousands,
possibly tens of thousands, of fishing operations on it. The emphasis is a little different than here,
with less emphasis on commercial fishing and much more so on subsistence. Seventy-five percent
of the protein from local peoples' diets is from fish. The economic factor is greater in Lake Victoria,
though, as it is the source of one-quarter of the freshwater fish from all of Africa, much of which is
imported to Europe and elsewhere.

Question 23: Patty Glick, National Wildlife Federation

Will commercial fishing operations in Africa be able to adapt to climate change the way the commer-
cial industry here will? Or will they be more adversely affected?

Response: Harvey Bootsma, University of Wisconsin-Milwaukee

It depends on the change. If it was a fairly simple change, like a change in gear type, then that may
be okay. But tradition is just as important as practicality over there, so tradition may slow the pro-
cess of change in fishing practices.

Question 24: Art Brooks, University of Wisconsin-Milwaukee

We have representatives of two energy suppliers here, and I'm wondering if they have any ideas
about what the economic impacts of warmer lake temperatures will be in terms of less gas or
electricity sold for heating water versus the additional costs of pumping.
Response: David Michaud, Wisconsin Electric Power Co.

In terms of water temperature, clearly there is an impact because most utilities with operations on
the lake use a very high volume cooling. The efficiency cycle in power plants is linked directly to
water temperatures. Systems have been designed based on expected variabilities in water tempera-
tures, keeping historical high and low temperatures in mind. But if temperatures change significantly,
or even by a few degrees Fahrenheit, it can drastically affect the efficiency of the steam cycle. As the
water warms at nuclear plants on a per unit basis, you can lose anywhere between 15 and 30
megawatts of output on a given day, just because of a few degrees Fahrenheit increase in tempera-
tures. And engineers know this. Yet, if this were to occur on a permanent basis, cumulatively around
the lake, the net loss would be hundreds of megawatts for plants using this kind of cooling. You
would basically have to replace that generation with something else--independent of low flow and
population increases. So, it is an issue.

Low water levels may also cause problems. If water levels fall below a certain point, all of a sudden
large circulating water pumps will be in-taking air or cavitating--which would have a monstrous
effect on efficiency. Those types of things were not thought about in 1986, when people were con-
cerned about preventing inundation. Now, we're worried about the opposite.

In the water levels game, there are winners and losers. On the positive side, you get less erosion
and less flooding. On the negative side, dredging and other factors can be big money items, not to
mention the environmental effects.

In terms of planning for demand, you plan by population projections. But if temperature increase is
added to the mix, in addition to increased demand from consumption--from air-conditioning, etc.--
things get difficult. In the case of plants that use cooling towers, efficiency cycles will take a hit from
higher ambient temperatures, and those lost megawatts will have to be produced in some other way.
This would affect the planning cycle for providing essential energy. As you can see, it is not just the
energy industry affecting climate, but climate change will produce positive feedbacks that exacer-
bate the problem.

Response: Mike Rau, Wisconsin Gas Water Services

On a smaller scale, warmer lake temperatures will decrease energy use for water heaters.

Question 25: John Furlow, U.S. EPA

Do the electric utilities use the lakes to vent hot water after you cycle it through? Do you worry about
there being regulations on thermal pollution to prevent you from using the lakes to vent hot water?

Response: David Michaud, Wisconsin Electric Power Co.

In the 1970s, people were concerned about the cumulative effect of venting hot water, so the utilities
did a large number of studies around the lake to see if it would heat the near-shore area in any
significant way. First of all, nuclear plants generally warm water more than coal plants. But, after
looking at the plumes or spheres of influence in an area of 3 square miles, the envelope of this
warmwater area was about 1 degree Celsius above ambient temperatures--and fluctuated through-
out the day. On a surface area basis, the thermal enrichment was not significant, considering that
Lake Michigan is about 22,000 square miles, so people decided that there are more important
issues on which to focus their concern. Quite frankly, any regulations on this might force people to
go to closed-cycle cooling, where water is taken into cooling towers, evaporated, and then water
leaves the basin, all of which would cause even more problems.
Question 26: John Magnuson, University of Wisconsin-Madison

But this mixing zone issue could be a bigger problem in some of the older plants on small rivers?

Response: David Michaud, Wisconsin Electric Power Co.

Absolutely. For utilities on the Great Lakes, thermal enrichment is probably inconsequential, but that
is not the case on small rivers, where [the] area of impaction can occupy the entire cross-section of a
river. Thermal blockage of migratory patterns of fish can occur in these cases. Fortunately, there are
not many power plants built on limited resources like that, and are not likely to be in the future, either,
for these reasons.

Comment: Harvey Bootsma, University of Wisconsin-Milwaukee

The City of Toronto has actually looked at pumping hypolimnetic water (water that lies below the
thermocline, is noncirculating and remains perpetually cold) for cooling of the city, and there was
some concern that that would heat Lake Ontario. So, physical modeling was done to determine if this
would be the case, and it was found that it would not have a measurable effect on the thermal struc-
ture of the lake.

Question 27: John Higgins, The Nature Conservancy

I have a question about water withdrawn from lakes. Cities like Chicago, for example, take a lot of
water out of the lake, process it, and it eventually goes down into the river drainage. While I do not
think that this volume of water is actually that large, is this going to be an issue for the public? Will
there be public concern about water being withdrawn from the lake