QUALITY OF FRESHWATER
(A Canadian
Perspective)
Water quality would suffer
from the projected impacts of climate change. Poor water quality effectively
diminishes the availability of potable water, and increases the
costs associated with rendering water suitable for use.
Changes in water quantity and water quality are inextricably
linked. Lower water levels tend to lead to higher pollutant concentrations,
whereas high flow events and flooding increase turbidity and the flushing of
contaminants into the water system. Box 2 lists some of
the main water quality concerns facing different regions of the country.
Warmer air temperatures would result in increased
surface-water temperatures, decreased duration of ice cover and, in some cases,
lower water levels. These changes may
contribute to decreased concentrations of dissolved oxygen, higher
concentrations of nutrients such as phosphorus, and summer taste and odour
problems.
River flows are expected to become more variable in the
future, with more flash floods and lower minimum flows. Both types of
hydrological extreme have been shown to negatively affect water quality.
Climate change may also affect the quality of
groundwater. For example, reduced rates
of groundwater recharge, flow and discharge may increase the concentrations of
contaminants in groundwater. Saltwater
intrusion into groundwater aquifers in coastal regions is another concern,
although Canadian research on this topic is limited. In southern Manitoba, future
changes in precipitation and temperature may cause groundwater levels in some
parts of the Red River basin to decline faster than
others. These changes would affect the
flow in the aquifer, and possibly shift the saline-freshwater boundary beneath
the Red River valley, so that the groundwater
in some areas may no longer be drinkable.
BOX 2:
Main water quality concerns across Canada
|
Region Water
quality concern |
|
|
Atlantic
|
Saltwater intrusion in groundwater aquifers
Water-born health effects from increased flooding
|
|
Quebec
|
Upstream shift in saltwater boundary in the Gulf of St. Lawrence
Water-borne health effects from increased flooding and
sewer overflow
|
|
Ontario
|
Degradation of stream habitat
Water-borne health effects
Volatilization of toxic chemicals
|
|
Prairies
|
Summer taste/odour problems in municipal water supply
Stream habitat deterioration
|
|
British Columbia
|
Saltwater intrusion due to rise in sea level and increased
water demands
Water-borne health effects from increased floods
Increased water turbidity from increased landslides and
surface erosion
|
|
Arctic and the North
|
Rupture of drinking water and sewage lines from permafrost
degradation
Rupture of sewage storage tanks from permafrost
degradation, and seepage from sewage storage lagoons
Increased turbidity and sediment loads in drinking water
|
