Water for what, where and how much ?

1. Water for what, where and how much? Alexander J.B. Zehnder Water Resources, AI-EES Acknowledgment Hong Yang Junguo Liu

2. 6 great challenges in the water area Water infrastructure(distribution & collection) Good water quality fora growing population Water induced disasters Disaster protection Distribution betweenhumans and ecosystems Solution for waterconflicts and fairwater share for all Enoughfood for all

3. Rain 100% ET Grassland ET Cropland Evaporation Run-off Infiltration ET Forest River & Lakes Evaporation Green Water ~65% Blue Water ~35% Blue and green water

4. Annual water requirement per person Sufficient > 1700 m3 Water stress 1000 - 1700 m3 Scarcity 500 - 1000 m3 Extreme scarcity < 500 m3 From Falkenmark & Widstrand, 1992

5. Dailyrequirements liter/person Annual requirements m3/person Purpose 3 - 9 1 - 3 Drinking water Personal hygiene,sanitation, and cooking 30 - 50 11 - 18 80 - 250 30 - 90 Other household needs Services 20 - 400 8 - 140 20 - 400 8 - 140 Industries Social good and human right Economic good Water requirements for people,services, and industry From Zehnder et al. 2003

6. Annual water requirement per capita forhousehold, services, industrial activities (average 2000–2009)

7. Estimated annual world water use totaland by sector 1900–2000 From Postel, 1992

8. Water needed to produce1 kg of plant material (dry weight) Sorghum 250 Liter Corn 350 Liter Clover 460 Liter Wheat 500 Liter Potatoes 636 Liter Cucumber 713 Liter Alfalfa 900 Liter Rule of thumb: For 1kg of bread 1m3 water is needed Partially from Muller, 1974

9. 1.2 1.0 0.8 0.6 0.4 0.2 1 2 3 4 5 6 7 8 Relationship of crop water productivity (cwp)to grain yield Irrigated Dryland Crop water productivity (kg/m3) Y=0.259X – 0.016X2 R2=0.88 From: Musick et al. 1994 Grain yield (ton/ha)

10. Crop water productivityof 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

11. Meat production Animals convert 5 to 15 % of the energy content of plant material into meat. The average is 10 percent. Rule of thumb: 10 times more water is needed per unit of energy from meat than from plants

12. Annual per capita water needs for foodto cover 2500 kcal a day 20% meat: 1200 - 1500 m3 Vegetarian: 600 - 1000 m3

13. Water availability in Israel in cubic meter per person and year (average 2000–2006) Internal surface & groundwater 110 Fossil groundwater 26 External surface and groundwater 147 Desalination and recycling 81 Total 361 Rain-fed agriculture 101 Import of crops 795 Import of meat and dairy products 75 Total virtual water import870 Overall 1,332 From: Aquastat FAO, FAOstatWRI, Yang et al., 2007 and Liu et al., 2009

14. Virtual water as part of a country‘s water resource Israel ET ~8.4 Rain 9.2 Discharge 0.5 External supply 1.03 Virtual water imp. approx. 6.0 Recycling 0.35 Virtual water exp. approx. 0.35 Fossil groundwater 0.2 Desalination 0.21 ET 1.3 Rain 1.7 from Malaysia 0.58 Singapore Recycling 0.52 Desalination 0.15 Virtual water imp. approx. 4.0 Discharge 0.34 Run-off 0.15 Numbers are in km3/yr

15. Situation 2000 From Zehnder, 2002

16. Virtual water export Big Five From Liu et al. 2009

17. no data -15 - 0 15 - 20 -100 - -50 0 - 5 20 - 30 -50 - -25 5 - 10 30 - 60 -25 - -15 10 - 15 Net virtual water trade by country(average over the period 2000–2006) Unit: cubic km From Yang et al. 2007

18. Water flux and reservoirs in Alberta (average 2004-2009) 340 Rain Numbers are km3 or million dam3 233 Boreal forest Grass Land Rivers out 130 Virtual water export 17 26 25 5 Rivers in 74 Evaporation Municipalities & Industries Agriculture Virtual water import 1 15 Groundwater Water reservoirs: Glaciers 30-55 Groundwater: alluvial 18-57 Lakes 200 buried channels 49-392 Soil moisture 1,225-1,637 bedrock 171-5,600

19. Agricultural water consumption in Alberta (average 2004-2009)

20. Agricultural Virtual Water Export from Alberta (average 2004-2009) VWE million m3 0-50 50-100 100-200 200-500 500-1,000 >1,000

21. Situation 2030 From Zehnder, 2002

22. Projection of water availability From Zehnder, 1999

23. Future? – models used and interpretation

24. Impact of climate change on crop production (wheat, maize & rice) 2030 Increase with high confidence Decrease with high confidence Increase/Decrease mix Increase with low confidence Decrease with medium confidence 2090 Decrease with low confidence Increase with medium confidence Liu et al., in prep.

25. Impact on crop production in North America 2030 2090 Increase with high confidence Decrease with high confidence Increase/Decrease mix Increase with low confidence Decrease with medium confidence Decrease with low confidence Increase with medium confidence Liu et al., in prep.

26. Food production and climate change: 2030 Liu et al., in prep.

27. Food production and climate change: 2090 Liu et al., in prep.

28. Challenges & Conclusions • If we use water wisely there will be sufficient water for even 9 billion humans. • Climate change may have globally less of a negative • effect on food production but we need to feed 2 billion • humans more. • Economic and political dependence in the water and virtual water (food) sector is growing. • Virtual water must become an integral part of future • water management decisions. • Geopolitical efforts are needed to allow the principle of national food self-sufficiency to be abandoned. • Only if these challenges are met there will be in the future water for all.

29. Thank you all !