Perspectives of the World’s
Freshwater Resources under
Global Change
Presentation by Olivia Roithmeier
Part of the modul: Physical
fundamentals of Global Change
www.geo.de
Content of presentation
 Background facts
 Different driving forces (without climate change)
 Climate change effects
 Perspectives of fresh water resources under global change
Our blue water planet earth
 app. 1.4 billion km³ water: 96.5% in oceans  71% of earth surface
 only 2.5% sweet water:
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69% stored in glaciers and ice coverings
30% in underground groundwater
0.3% surface sweet water (permafrost, lakes, swamps, rivers)
0.001 % in the atmosphere
 water distribution and state of aggregation is irregular in time and
space due to it's physical-chemical characteristics and existing
geographical conditions
Mean annual precipitation on continents
Lozan et al, 2006
Distribution of water among continents
 continental precipitation is
higher than evaporation from
continents, difference is runoff
 app. 41.000 km³ H2O/yr
transported into oceans by
river's (28.000 km³ surface
water, 13.000km³ groundwater)
 mean duration of water vapor
in the atmosphere: 10 days
WBGU 1997
(Sweet) water - Source of life on earth
 besides air to breath most essential for living: all plants and animals
need water for chemical-physical-physiological processes
 combination “necessary for living but rare available“ makes water to
a valuable resource:
» 66% of extinct species were living in sweet water
 provides important functions:
» natural (e.g. necessary for life, space for living, transportation
medium, earth formation by erosion)
» cultural (e.g. food production, drinking, cleaning, use as energy
exchanger, waste disposal)
How to provide the demand?
 actually app. 8% of this renewable resource sweet water used
» 69% agriculture
» 23% industry
» 8% households
 huge regional differences: 96% of industrial water used in North
America and Europe
 up to 40.000 embankment dams are employed; daily a new one build
 all dams combined: fivefold the world river volume
 three quarter of natural runoff is regulated anthropogenic in North
America, North Asia and Europe
 sediment transport has increased 5x by land use (app. 45 billion t)
Water use per capita
Daily water use (liters) per
capita of households
USA
301
Japan
285
Switzerland
263
Germany
145
India
25
Sudan
19
Lozan et al, 2006, changed
 daily water demand in
Brandenburg approx. 90 l per
day and capita
(Märkische Allgemeine Zeitung, „Die
Havel fließt rückwärts“, 01.08.2006)
Water stress: today
 app. 33% of the world’s population in countries under ‘water-stress’
 app. 1 billion people without access to safe drinking water
 50% of developing countries suffering on water-related hazards
 worldwide only 5% of house sewage cleaned developing countries:
90% of unclean water directly into surface waters
 21st century increasing population  changed patterns of water use
 increase of future pressures on water
» e.g. we consume 8 times more water than our grandparents did
and with app. 8.5 billion peoples in 2025 we will have 1/3 sweet
water less per capita
Perspectives of sweet water availability
Atlas der Globalisierung
Important driver's effecting sweet water
resources (without climate change)
 population growth (provided same use per capita and year as 1990):
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most increasing demand in Africa and parts of Asia (often ≥ 2x)
in North America, Oceania and China up to 40%
in South America up to 60%
in Europe mainly stable, partly decreasing
 today more than 900 billion people chronically malnourished, will
increase if global crop does not enhanced for 60% till 2010
 agriculture (provided no change in conditions of cultivation)
» 2025: 18% increased water removal compared to 1995 (2x to 1970)
» in spite of this increase, the proportion of agricultural water use will
decrease on global scale to 56% = -19% compared to 1995
Important driver's effecting sweet water
resources (without climate change)
 households: world-wide increase up to 2–3% with huge differences
» high increase in Africa, Asia; decrease in Europe, South America
» changed lifestyle linked with enhanced individual demand: today
water demand in India 25l/capita/day; tourist centers around
Mediterranean 1000l/capita/day
 industry: triples till 2025, main reason of increasing water demand
 even without climate change water stress is expected to increase,
especially in Central Asia, North Africa, the drier parts of China
Example: water stress and population growth
 app. 1.4 billion people currently live in watersheds with less than
1000m³ water/person/year
people (millions) living in water-stressed watersheds in absence of
climate change (percentage of global population in parentheses)
A1/B1
A2
B2
1995
––
1368 (24)
––
2025
2882 (37)
3320 (39)
2883 (36)
2055
3400 (39)
5596 (48)
3988 (42)
2085
2860 (37)
8065 (57)
4530 (45)
Schellnhuber et al 2006
Water stress and climate change projections
 WBGU-Analysis comparing the of actual water cycle with a
simulated climate based upon doubled CO2-equivalent-content
» in a warmer climate more precipitation will fall on land,
especially in high latitudes and parts of the tropes and subtropes
» in contrast, effected by lower precipitation will be big parts of
Brasilia, South-West Africa, west and north of Australia
 Conclusion
» it seems that the anthropogenic climate changes will increase the
water cycle, simultaneously there will be huge regional
differences between who is how affected
» climate change has the potential to increase water resource
stress by increasing flood risk in some areas and increasing
shortage risk in others
Water stress and climate change projections
 magnitude vary between climate models but consistency in:
» many parts of the world: precipitation in winter fallen as snow will
fall as rain whilst run off rapidly into rivers rather than be stored on
the surface
» runoff: increase in high latitudes of North America, Siberia, Eastern
Africa, Eastern Asia while decrease in much of Europe, Middle East,
Southern Africa, parts of North and Latin America
 By the 2050s
» increased water stress by climate change especially under A2
population growth in Europe, around the Mediterranean, parts of the
Middle East, Central/Southern Africa, the Caribbean, parts of Latin
and North America
» “decrease“ in water stress by increased river flow in some regions but
increased river flow mean not necessarily reduced water-related
problems (higher flows occur during the high flow season increased
flooding risk; without enough reservoir storage this “more“ water is
not available for the dry season)
WBGU
WBGU 1997
WBGU 1997
Regional risks for hydrosphere
 water shortage by increased demand/removal: Africa, parts of West Asia, North-
West of China, parts of Pakistan and Mexico, West/South of India, western coast of
USA and North-East Brasilia
» overuse of ground water: e.g. Ogallala-Aquifers in USA
» overuse of fossil ground water: e.g. Yemen, India, South East Asia
» water discharges for irrigation: drying of the Aral lake or Everglades
» salt water intrusion into deltas and coastal aquifers as consequence of overused
ground and surface water: e.g. in Israel, China, Gulf of California
 water shortage by decreasing quality of water
» Africa salination, sedimental transport in rivers
» North America and Europe  nitrate and biocides of agriculture (surface
water eutrophication), contamination by industry (toxins, acidification)
» South America  high bacterial/organic contamination
» Middle East  salination by agriculture, salt water intrusion
» East and South Asia  organically pollution, pesticides, eutrophication
Effects of GHG mitigation on water stress
 increase of 2°C above the 1961–1990 mean by 2055
» increased water stress for 500-1000 million (A1/B1 population
projection), for 800-2200 million (A2 pop. proj.) and for 7001100 million (B2 pop. proj.), depending on climate model
 assumption of stabilization at 550 ppm: app. reduction of people
faced with increased water stress by 15- 25% by 2025 and by 25-40%
thereafter
 These calculations are mean values on global scale not respecting the
often substantial geographic variations!
Perspectives of fresh water resources under
global change
 climate change: most important and geographically extensive physical driver
» likely alter magnitude and timing of water stress
» effects on water resources depend on spatial pattern and rate of climate change
 several drivers (demographic, economic, social, physical) can change exposure to
water related hazards, access to water, future water supply and thus influence
changes in global water resources, too
 2050s: app. two times more would be adversely affected by climate change (under the
most populous A2 population growth projections compared to the lowest)
 climate policies reducing GHG emissions can reduce the impacts of climate change on
water resources stresses without eliminating them
 550 ppm stabilization: reduces people adversely affected by climate change to 30-50%
 one of the major future risk factors  increased demand of mega-cities and large
population centers, e.g. in India and China (may have broad implications for
environmental flows of water in major rivers of China, India and Tibet)
 The impact of climate change on future water resource availability depends to a very
large extent on the future state of the world and particularly on the numbers of people
potentially exposed to water shortage.
Some ways out of water crisis
 increasing awareness for this problem and possible solutions, incl.
that everyone can and must change behavior, not only industry
 increasing efficient use of water (e.g. removed water: 55% used and
45% loss by transport or evaporation) including technical and
knowledge transfer to implement this
 increase re-use of water and diminish first use
 improved supply with “healthy“ water
 adaptation to changed (time and space) precipitation pattern
 if water is used by more than one state (intercontinental lakes, sea,
rivers) the states must cooperate with each other to prevent water
conflicts escalating
Sources of literature
 Schellnhuber et al.,
2006_Avoiding dangerous
climate change
 Lozan et al., 2006_Enough water
for all ?
 WBGU 1997_Wege zu einem
nachhaltigen Umgang mit
Süßwasser
 Atlas der Globalisierung, Le
Monde diplomatique,
2006_Sauberes Wasser –
knappes Gut
www.geo.de, aurora/laif
Comments for Olivia Roithmeier
from Manfred Stock
1.
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