Climate change futures: health, ecological and economic dimensions

While seawater desalinization is currently not costeffective,
it has gradually become cheaper, and as the
demand for safe water increases, it is likely that technological
advances will bring the cost down to a reasonable
level (Levin et al. 2002). Meanwhile, the
energy demands of this process are enormous, and
the fossil fuels that are used to desalinate water will
contribute greenhouse gases to the environment and
compound the problem. Solar desalinazation may be
a safe and less expensive method in the future.
THE FUTURE
CCF-I: ESCALATING IMPACTS
Changes in temperature and weather patterns due to
global climate change will have serious consequences
for drinking water supplies. Patterns of warmer air and
surface water temperatures, increased frequency of
extreme weather events, rising sea levels, increased
evaporation of surface water, decreased snowpack, and
earlier snowmelt all threaten to compromise the quantity
and quality of drinking water in many parts of the
world. These trends could result in regional drought conditions
and a decrease in seasonal runoff, intrusion of
saltwater into coastal aquifers, diminished aquifer
recharge, increased microbial growth and harmful algal
blooms, increased contamination of surface water, and
increased incidence of waterborne diseases. The chart
on page 87 describes the multiple effects of global climate
changes on water resources.
An increase in ambient air temperatures due to global
warming, as well as an increase in surface water temperatures,
will increase the amount of water residing in
the atmosphere as vapor, leading to a net loss in precipitation
and in the amount of surface water worldwide.
Increased evaporation could also lead to water stress
and drought conditions for arid regions that don't experience
an increase in precipitation (Levin et al. 2002),
and current climate models being used by the IPCC predict
decreased precipitation in many equatorial areas,
leading to a decrease in surface water source volume
and in groundwater recharge. The intensity and duration
of droughts in some regions of Asia and Africa have
already been observed to have had increased over the
last few decades (Albritton et al. 2001).
Warming will also lead to a rise in sea level, due to
glacial melt and thermal expansion. In coastal zones
that rely on shallow surface aquifers for drinking water,
this rise in sea level leads to saltwater intrusion into freshwater
aquifers, contaminating drinking water supplies.
Water availability in high-latitude and mountainous
regions is often characterized by heavy runoff and peak
stream flows in the spring due to snowmelt, followed by
a drier summer and fall. Winter precipitation falls mostly
as snow, and is stored until spring in snow pack instead
of immediately running off or filtering into the ground.
Warmer winters and earlier springs associated with climate
change will result in more winter precipitation
falling as rain, decreasing the accumulation of snow
pack. It is likely that warming will also alter the timing of
melting and peak runoff, resulting in an earlier and more
rapid spring runoff (Levin et al. 2002; Frederick and
Gleick 1999). These predictions are borne out by
observed changes in stream flow patterns around the
world; earlier peak runoff in the spring and increases in
fall and winter runoff are some of the most frequent
changes noted (Frederick and Gleick 1999). Agriculture
in these regions will be adversely affected, as spring
snowmelt often provides water for irrigation at a crucial
point in the growing season.
Because warmer temperatures and more extreme rainfall
patterns increase the frequency of WBDOs, it is likely
that waterborne disease will be an even more serious
health problem in the 21st century than it is today (Levin
et al. 2002).
Continued warming and more extreme weather patterns
are likely to have a marked and adverse effect on the distribution
and quality of drinking water worldwide. Water
shortages and water-related illnesses could become more
widespread and more frequent, putting enormous pressure
on watersheds, water delivery systems and health care systems.
Agricultural impacts could be severe, especially as
irrigation needs rise due to warmer global temperatures,
and hydroelectric power could be severely compromised
in many nations. Water shortages could lead to intense
competition and more violent conflicts, as demand rises,
aquifers and surface water bodies become depleted, and
changes in the hydrologic cycle make water supplies more
varied and unpredictable. While climate change impacts
on water resources are likely to be severe worldwide, they
will be far worse for developing countries with inadequate
infrastructure, resources and adaptive capacities.
CASE STUDIES 89 | NATURAL AND MANAGED SYSTEMS