Report of the Council of Great Lakes Research Managers
4.3
CLIMATE CHANGE – UNDERSTANDING THE IMPACT OF CLIMATE CHANGE ON GROUND WATER
In recent years, the levels of the lakes have been declining,
4.3.1
Introduction
4.2
as drought and warmer winters have taken their toll.  The
T
lakes have dropped to their lowest point in 35 years (U.S.
4.3
he drainage basin of the five Great Lakes covers an
Water News Online 2002).  This reduction in water
area of 750,000 square kilometers, including almost
availability, added to the fact that many of our aquifers are
all of southern Ontario, some of northern Ontario,
being stressed by pumping, may result in an inadequate
and much of eight U.S. Great Lake states.  Within this
supply of ground water in some areas.  Ground water levels
drainage basin water from precipitation percolates through
in some aquifers have declined over large areas, such as the
the soil and is stored as ground water.  Recent estimations
aquifers outside Chicago, Illinois, near Milwaukee and Fox
indicate that the volume of ground water stored in the
River-Green Bay, Wisconsin, and near Toledo, Ohio
Great Lakes basin is approximately equal to that of Lake
(Grannemann et al. 2000).  Total ground water withdrawal
Michigan (Grannemann et al. 2000).  This ground water
in the Great Lakes region in 1995 was estimated to be 1,510
moves slowly, discharging into streams, wetlands and
million gallons per day (Solely et al. 1998).  Growing
eventually to the Grea Lakes.  On average, the lakes receive
populations and increasing demands on ground water
recharge waters from tributaries of roughly 3000 m3/sec
supplies create an ever increasing risk of depleting ground
from the U.S. side and 2300 m3/sec from the Canadian side
water supplies beyond rechargeable levels.
(IJC 1993).  Approximately 50 percent of that recharge may
be indirectly contributed by ground water (Grannemann et
al. 2000).
4.3.3
Climate Change Models
General Circulation Models
4.3.2
Stresses on Ground Water Supplies
in the Great Lakes Basin
General Circulation Models are computer programs
created to mimic the interactions of the atmosphere and
As population continues to grow in the Great Lakes basin,
land surface in producing weather and climate conditions.
stresses on freshwater supplies also increase.  Given that 39
Newer General Circulation Models often include an ocean
percent of the Great Lakes basin population uses ground
component to account for the oceans ability to moderate
water as their source for drinking water (IJC 1993), it is
temperatures and to hold carbon dioxide.  They are used to
clear that ground water sources need to be valued and
investigate the influence of possible climate forcing
protected both locally and regionally.  More importantly, 90
mechanisms, like increasing levels of CO2, and to suggest
percent of the rural population of Ontario relies solely on
past and future climates.
ground water to supply their residential needs (Piggott et
The use of General Circulation Models is limited by several
al. Unpublished Paper), thus protection of this life resource
factors.  First, our knowledge of the complex interactions
is exceedingly necessary.
within the climate system restricts the function of the
models.  Since we do not know all of the variables, we
cannot account for them in our models.  Second, because
General Circulation Models are designed to work over a
As population continues to grow in the Great Lakes
large-scale area, they do not account for small but signifi-
cant regional features.  The Great Lakes are not represented
basin, stresses on freshwater supplies also increase.
in many of the General Circulation Models, thus their
Given  that  39  percent  of  the  Great  Lakes  basin
affects are not included in the simulations.  Third, energy
population uses ground water as their source for
and moisture flow are averaged, not accurately represent-
ing the processes.  This can result in misrepresentations in
drinking water (IJC 1993), it is clear that ground
precipitation within the predictions.
water sources need to be valued and protected both
In determining the usefulness of the General Circulation
locally and regionally.
Models, the U.S. National Assessment of the Potential
Consequences of Climate Variability and Change compared
95