Water for what, where and how much? Alexander J.B. Zehnder
Water Resources, AI-EES Acknowledgment Hong Yang Junguo Liu
Slide 2
6 great challenges in the water area Good water quality for a
growing population Enough food for all Water infrastructure
(distribution & collection) Solution for water conflicts and
fair water share for all Distribution between humans and ecosystems
Water induced disasters Disaster protection
Slide 3
Rain 100% River & Lakes Run-off Infiltration Evaporation ET
Forest ET Cropland ET Grassland Evaporation Green Water ~65% Blue
Water ~35% Blue and green water Blue water Green water
MobilityMobileImmobile Sources substitutionPossibleImpossible
Competitive usesManyFew or none Conveyance facilitiesRequiredNot
required Cost of useHighLow
Slide 4
Annual water requirement per person Sufficient>1700 m 3
Water stress1000 - 1700 m 3 Scarcity 500 - 1000 m 3 Extreme
scarcity< 500 m 3 From Falkenmark & Widstrand, 1992
Slide 5
Water requirements for people, services, and industry Purpose
Daily requirements liter/person Annual requirements m 3 /person
Drinking water 3 - 91 - 3 Personal hygiene, sanitation, and cooking
30 - 5011 - 18 Other household needs 80 - 25030 - 90 Services 20 -
4008 - 140 Industries 20 - 4008 - 140 Social good and human right
Economic good From Zehnder et al. 2003
Slide 6
6 Annual water requirement per capita for household, services,
industrial activities (average 20002009)
Slide 7
Estimated annual world water use total and by sector 19002000
From Postel, 1992
Slide 8
Water needed to produce 1 kg of plant material (dry weight)
Sorghum250Liter Corn350Liter Clover460 Liter Wheat500Liter
Potatoes636Liter Cucumber713Liter Alfalfa900Liter Partially from
Muller, 1974
Slide 9
9 Relationship of crop water productivity (cwp) to grain yield
12345678 0.2 0.4 0.6 0.8 1.0 1.2 Grain yield (ton/ha) Crop water
productivity (kg/m 3 ) Irrigated Dryland Y=0.259X 0.016X 2 R 2
=0.88 From: Musick et al. 1994
Slide 10
Crop water productivity of wheat (2000) < 0.25 0.25 - 0.5
0.5 - 0.75 0.75 - 1.0 1.0 - 1.25 1.25 - 1.5 From Liu et al.
2007
Slide 11
Meat production Animals convert 5 to 15 % of the energy content
of plant material into meat. The average is 10 percent.
Slide 12
Annual per capita water needs for food to cover 2500 kcal a day
20% meat: 1200 - 1500 m 3 Vegetarian: 600 - 1000 m 3
Slide 13
Water availability in Israel in cubic meter per person and year
(average 20002006) From: Aquastat FAO, FAOstat WRI, Yang et al.,
2007 and Liu et al., 2009
Slide 14
Virtual water as part of a countrys water resource ET ~8.4
Fossilgroundwater0.2 Desalination0.21 Virtual water exp. approx.
0.35 Virtual water imp. approx. 6.0 Rain9.2 Discharge0.5 External
supply 1.03 Israel Singapore Rain1.7 ET1.3 from Malaysia 0.58
Desalination0.15 Virtual water imp. approx. 4.0 Run-off0.15
Discharge0.34 Numbers are in km 3 /yr
Slide 15
Situation 2000 From Zehnder, 2002
Slide 16
Virtual water export From Liu et al. 2009 Big Five
Slide 17
Net virtual water trade by country (average over the period
20002006) From Yang et al. 2007 Unit: cubic km no data -100 - -50
-50 - -25 -25 - -15 -15 - 0 0 - 5 5 - 10 10 - 15 15 - 20 20 - 30 30
- 60
Slide 18
Water flux and reservoirs in Alberta (average 2004-2009) Rain
Boreal forest Grass Land Rivers in Rivers out Groundwater
Evaporation Agriculture Municipalities & Industries 340 233 25
26 15 5 74 130 Numbers are km 3 or million dam 3 Virtual water
export 17 Virtual water import 1 W ATER RESERVOIRS : Glaciers
30-55Groundwater: alluvial 18-57 Lakes 200 buried channels 49-392
Soil moisture 1,225-1,637 bedrock 171-5,600
Slide 19
19 Total amount of water in km 3 Water per capita and year in m
3 Water consumed in Alberta267,900 Virtual water exported175,150
Virtual water consumed AB92,750 Agricultural water consumption in
Alberta (average 2004-2009)
Slide 20
Agricultural Virtual Water Export from Alberta (average
2004-2009) VWE million m 3 0-50 50-100 100-200 200-500 500-1,000
>1,000
Slide 21
Situation 2030 From Zehnder, 2002
Slide 22
Projection of water availability From Zehnder, 1999
Slide 23
Models used HadCM3 (Hadley Centre Coupled Model, version 3), UK
CGCM2 (Coupled Global Climate Model version 2), Canada CSIRO2
(Commonwealth Scientific and Industrial Research Organization),
Australia Parallel Climate Model couples three models, USA
Scenarios A1FI - emphasis on fossil-fuels (Fossil Intensive). B2
local environmental sustainable Future? models used and
interpretation
Slide 24
Impact of climate change on crop production (wheat, maize &
rice) 2030 2090 Decrease with high confidence Decrease with medium
confidence Decrease with low confidence Increase/Decrease mix
Increase with low confidence Increase with medium confidence
Increase with high confidence Liu et al., in prep.
Slide 25
20302090 Impact on crop production in North America Decrease
with high confidence Decrease with medium confidence Decrease with
low confidence Increase/Decrease mix Increase with low confidence
Increase with medium confidence Increase with high confidence Liu
et al., in prep.
Slide 26
Food production and climate change: 2030 Liu et al., in
prep.
Slide 27
Food production and climate change: 2090 Liu et al., in
prep.
