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CLIMATE CHANGE AND
WATER RESOURCES:
GLOBAL AND LOCAL IMPACTS
Situation now..
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Global Water Crisis
Over 1 billion people don't have access to clean drinking water; more than
2 billion lack access to adequate sanitation; and millions die every year
due to preventable water-related diseases.
5 million people – mainly children – die every year from preventable,
water-related disease is surely one of the great tragedies of our time.
over 34 million people might perish in the next 20 years from water-related
disease
hundreds of billions of dollars are needed to bring safe water to everyone
who needs it. Since international water aid is so paltry, many of these
experts claim that privatization of water services is the only way to help the
poor.
are solutions to the global water crisis that don’t involve massive dams,
large-scale infrastructure, and tens or hundreds of billions of dollars. …
Water and Climate Change
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Climate change will lead to more precipitation - but also to more evaporation
Precipitation will probably increase in some areas and decline in others.
Changing precipitation patterns will affect how much water can be captured.
The drier the climate, the more sensitive is the local hydrology.
High-latitude regions may see more runoff due to greater precipitation.
The effects on the tropics are harder to predict.
Reservoirs and wells would be affected.
New patterns of runoff and evaporation will also affect natural ecosystems.
Rising seas could invade coastal freshwater supplies.
Reduced water supplies would place additional stress on people, agriculture,
and the environment.
Conflicts could be sparked by the additional pressures.
Improved water resource management can help to reduce vulnerabilities.
Drivers of change
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Change in
resources
Population
demand
for water
Change in
exposure
River flows ;
groundwater
quality
Wealth; equity
access
Water
resources
stress
Change in
vulnerability
Measures of stress
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Indicators of exposure
 Numbers
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Indicators of access
 Numbers
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affected by flood / drought
with access to safe water
Indicators of availability
 Resources
per capita
Estimating the future
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Future impacts depend on future climate and future
exposed population
Simulate water availability using a macro-scale
hydrological model
Construct climate change scenarios from global
climate models
Construct consistent scenarios for change in exposed
population
Effects of climate policy
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Rescale changes in runoff to different global
temperature changes
Calculate water stress indicators for different
temperature increases
“2 degree C target”
~0.8 degrees C above 1961-1990 mean by 2020
~1.2 degrees C above 1961-1990 mean by 2050
What to look for specifically?
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Precipitation amount
Precipitation frequency and intensity
Evaporation and transpiration
Changes in average annual runoff
Natural variability
Snowpack
Coastal zones
Water quality
Water storage
Water demand
Precipitation amount
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Will increase as global temperatures rise
Evaporation potential will increase because warmer atmosphere can
hold more moisture
For a one-degree Celsius increase in air temperature, the waterholding capacity of the atmosphere increases by 7 percent
What goes up – must come down
How much global average precipitation will increase? Not so certain
Models suggest: 1-2 percent per degree Celsius
Does not mean it will get wetter everywhere and year-round; some
get less; some get more
More rain over high-latitude land areas; less over equatorial
regions;
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Precipitation frequency and intensity
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On average: less frequent; more intense  floods
and droughts; consequences for water shortage
Why?
Local and regional rainfall rates greatly >
evaporation rates and depend on the convergence
of regional to continental scale moisture sources
Rainfall intensity should increase at same rate as
increases in atmosphere moisture (7% / degree C)
Evaporation and transpiration
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evapotranspiration:
From open water, soil, shallow groundwater, water stored on
vegetation
 Transpiration through plants
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Consistent prediction: increase total evaporation
One study: an increase/decrease in precipitation of
20%  runoff changing by ~ 20%; w/ no change in
precipitation, a 2 degree C increase in temp -> reduce
mean annual runoff by 4 to 12%. Thus – if temp
increased by 4 degree, precipitation would need to
increase by 20% to maintain runoff
Changes in average annual runoff
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Importance?
Depend on changes in temp and precipitation
Global message of increased precipitation does not
translate into regional increases in water
availability
Natural variability?
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Will not go away
Water supplies can change dramatically, and for
extended periods, even without anthropogenic climate
change
Temperature, snowpack, and runoff
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Very likely that a greater portion of winter
precipitation will fall as rain rather than snow
An increase in rain events would increase winter
runoff
But
Result in smaller snowpack accumulations
Warmer climate likely result in earlier melt season
Increase in winter or spring flows
May increase the risk of winter and spring floods
Coastal zones
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6.
IPCC (2001): sea-level rise
Lowland inundation and wetland displacement
Altered tidal range in rivers and bays
Changes in sedimentation patterns
Severe storm surge flooding
Saltwater intrusion into estuaries and freshwater
aquifers
Increased wind and rainfall damage in regions
prone to tropical cyclones
Water quality
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Flooding…
-> increased sediment and non-point source pollution
loadings in watercourses
Decline in streamflows and lake levels …
 nutrients and contaminants become more
concentrated in reduced volumes with longer water
residence times
-> reducing dissolved oxygen concentrations
-> Cold-water species (salmon, trout) susceptible to
warm-water temp
 increase salinity of surface water
Water storage
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Tradeoff between storing water for dry-period use
and evacuating reservoirs prior to the onset of the
flood season to protect downstream communities
Water demand
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Different rates of use in different climate zones
UK: a rise in temperature of ~ 1.1 d C by 2025 ->
increase in average per capita domestic demand of
! 5% + larger % increase in peak demands
Still
rising water demands greatly outweigh greenhouse
warming in defining the state of global water
systems to 202
IPCC: Freshwater resources and their
management. 2007
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The impacts of climate change on freshwater systems and their
management are mainly due to the observed and projected
increases in temperature, sea level and precipitation variability
(very high confidence)
Semi-arid and arid areas are particularly exposed to the impacts
of climate change on freshwater (high confidence).
Higher water temperatures, increased precipitation intensity, and
longer periods of low flows exacerbate many forms of water
pollution, with impacts on ecosystems, human health, water system
reliability and operating costs (high confidence).
Climate change affects the function and operation of existing water
infrastructure as well as water management practices (very high
confidence).
The negative impacts of climate change on freshwater systems
outweigh its benefits (high confidence).
IPCC: Impacts on hydrology and water
impacts (2001)
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Variation in streamflow and groundwater
recharge regionally and between scenarios
 Early snowmelt – therefore…
 Degraded water quality
 Increase in flood magnitude and frequency
 Increased demand for water (pop. growth &
economic development) globally
 High vulnerability in unmanaged systems
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Non-climatic drivers…
Current vulnerabilities correlated with climatic
variability
 Particularly:
precipitation variability
 Particularly where?
Surface waters and runoff generation
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Changes in river flows, lake and wetland levels depend
on (climatic factors):
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Changes in temperature, radiation, atmospheric humidity,
and wind speed:
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Potential evapotranspiration  offset small increases in
precipitation  further effect of decreased precipitation on
surface waters
Increased atmospheric carbon dioxide [ ]
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Changes in volume, timing and precipitation intensity
Alters plant physiology  affecting evapotranspiration
Lake size
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Decreased – due to human water use + climatic factors (Lake
Chad)
Leaf 'sweat glands‘ (stomata)
to worsen future flooding
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Regulate the amount of carbon dioxide taken up by the
plants during photosynthesis
Absorb and release moisture during transpiration
Tend to shrink when carbon dioxide levels rice
So – plants transpiring less  plants consume less water
 more water remains in the soil  more water runs
into the river
River flow increased by 3% worldwide
In the Med and South American: might ease the
damage from drought; Not so in Asia, Europe, and
North America
Groundwater
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Respond slower than surface water systems
Correlate more strongly w/ precipitation than w/
temperature
Temperature more important for shallow aquifers
Temperature more important in warm periods
Floods and droughts
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Climate may already have had an impact on floods
Droughts affect:
Rain-fed agriculture production
 Water supply for:
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 Domestic
 Industrial
 Agricultural
purposes
Other impacts
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Climate change is killing US forests
Mortality rates increased at an average of 3%
yearly
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Latest news
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Autumn rain down 90 percent in China rice belt
BEIJING (Reuters) - Large areas of south China are
suffering from serious drought, with water levels on two
major rivers in rice-growing provinces dropping to
historic lows, state media said on Tuesday.
Bangladesh says reaches all cyclone-hit areas
DHAKA (Reuters) - Relief workers and the Bangladesh
military on Tuesday reached the last remaining pockets
of the country devastated by a cyclone that killed
nearly 3,500 people along the Bay of Bengal.
Water quality
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Lakes and reservoirs: climate change effects primarily
due to water temp. variations (climate change or
thermal pollution)
 oxygen regimes, redox potentials, lake stratification,
mixing rates, biota development
 diseases – via drinking water or via consuming crops
irrigated with polluted water
¼ of global pop lives in coastal regions: water-scarce
+ rapid pop growth
 sea-level rise  increased saline intrusion 
reduction in freshwater availability
Be sure to read…
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http://www.ipcc.ch/pdf/assessmentreport/ar4/wg2/ar4-wg2-chapter3.pdf
Status of Med
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Fresh water resources in the Mediterranean are under increasing pressure in
terms of both quantity and quality.
Northern Mediterranean countries with higher, more regular rainfall also
face climate-induced natural hazards, flooding and water shortages in
basins susceptible to periodic drought. As a consequence, human and
natural systems sensitive to water availability and water quality are
increasingly stressed, or coming under threat. Those countries will have to
face water quality degradation and meet the increasing needs of
environmental protection and restoration.
In South and East Mediterranean counties where use is now approaching
hydrological limits, and the combined effects of demographic growth,
increased economic activity and improved standards of living have
increased competition for remaining resources. Water resources are
already overexploited or are becoming so with likely future aggravation
where demographic growth is strong. The Eastern countries will be more
sensitive to short term or structural shortages, in certain areas.
IPCC: Mediterranean nations face up
to threat of climate change
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Global warming threatens to wreak economic havoc
across the Mediterranean basin
IPCC 2007 reports issued in February and April:
Mediterranean basin would be hit especially hard by
mounting temperatures, which are predicted to rise
globally by 1.8 to 4.0 C (3.2 to 7.2 F) by the end of
the century
Threatened by rising seas:
Nile River Delta
 Venice
 Tunisian island of Jerba
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Climate change and water resources
in the Mediterranean
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http://www.iucn.org/places/medoffice/Documentos/cli
mate-change-mediakit_EN2.pdf
Status of fresh water resources in the Mediterranean
Fresh water resources in the Mediterranean are under
increasing pressure in terms of both quantity and
quality.
Northern Mediterranean countries susceptible to
periodic drought.
In South and East Mediterranean counties –water
resources already overexploited; more sensitive to short
term or structural shortages.
Mediterranean vulnerability to
climate change
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greater variability and extreme weather events,
wetter winters and drier summers and hotter
summers and heat waves.
affect the water demand, quality and watershed.
Pollution will be intensified by runoff
floods which will be higher and more frequent.
The changes in the frequency of extreme events
might be the first and most important change
registered in the Mediterranean.
Algeria..
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Significant exposure to recurring natural hazards
(e.g., floods, earthquake, drought) emphasises the
vulnerability of the poor population because of the
recurring social, financial and economic losses.
On November 2001, severe rains accompanied by
floods and mud-flows affected 14 villages in the
northern part of Algeria.
Damage and loss of property were considerable
across sectors, amounting to about US$300 million
(according to the Government sources).
Saudi Arabia
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Depletion of water resources due to climate change
Ground water levels dropping very quickly
Overall temperature increase of 0.5 to 2 degrees
Celsius in desert regions between 1976 and 2000.
Many deserts will experience a decline of 5 to 10
percent in rainfall in the near future
Restrict irrigation agriculture
Egypt: Nile Delta
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2.5% of Egypt’s land area (Nile delta and Nile valley)
suitable for intensive agriculture
50 km wide land strip less than 2 m above sea-level
Erosion of sand belt – increased since Aswan dam
Rising sea level…
Change the water quality
 Affect more fresh water fish
 Flood agricultural land
 Endanger recreational tourism
 Salinate essential groundwater
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Egypt
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For graphics see:
http://maps.grida.no/go/graphic/nile_delta_poten
tial_impact_o f_sea_level_rise
Latest IPCC report
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There is high confidence that by mid-century "many
semi-arid areas, for example the Mediterranean
basin, western United States, southern Africa and
northeast Brazil, will suffer a decrease in water
resources due to climate change."
Readings – a lot, yes
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Climate Change 2001: Working Group II: Impacts, Adaptation and Vulnerability,
Intergovernmental Panel on Climate Change, (IPCC, 2001):
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Chapter 4 - Hydrology and Water Resources
Chapter 6 - Coastal Zones and Marine Ecosystems
Chapter 18 - Adaptation to Climate Change in the Context of Sustainable Development and Equity
and from: Climate Change 2007: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to
the Fourth Assessment Report of the Intergovernmental Panel on Climate Change: Chapter 3 - freshwater
sources and their management
Climate change puts sea at risk
Tropical cyclones in the Mediterranean?
Global Water Resources: Vulnerability from Climate Change and Population Growth
Climate Change and Water Resources: A Primer for Municipal Water Providers
and, on Lebanon, The Impacts of Climate Change on Water Resources of Lebanon-Eastern
Mediterranean and for Lebanon’s policies on water Drought, Thirst, and Hunger.” (in Arabic). AlAdab Magazine. September 2007. and, some other climate change news:
Other readings:
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Friday, November 23rd, 2007: “We Are Now In The Danger Zone”: Leading Australian Scientist Tim Flannery
on Climate Change and How To Save the Planet
British companies band together to tackle climate change
Homework
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By Friday. Via Email.
2 page paper (no less, no more) on impact of
climate change on water resources of any country in
the region (either Med or Arab world)
Or
Summary of methodology of understanding impact
of climate change on water resources
Reference correctly