1. “Water, water everywhere nor any drop to drink…” Talk by Ron Oxburgh Hong Kong 11January 2002 Material derived from many sources but particularly from Postel et al., Science,1996

2. 2 Water Cycle annual fluxes RAIN 110 RAIN 390 Land Ocean Evaporation Runoff 70430 40

3. 3 Water only 2.5% of the Earth’s water is fresh 2/3 of fresh water (1.73%) exists as ice remainder 0.77% = 10,665 km 3 (rivers, lakes, swamps & atmosphere) all human extraction is from runoff much is inaccessible uncertainty in estimates

4. The Present

5. Inaccessible Water % Global Runoff % global popln. Amazon 150.4 Zaire/Congo 3.51.3 Tundra rivers 50.2 21% of Global Runoff is not useable

6. 6 1990 Global water use and consumption

7. Different Water Withdrawals Min. flow

8. The past

9. 9 Global water withdrawals over time, per cap. & total US

10. 10 Population, water withdrawals & irrigation

11. 11 Irrigation driven by food needs much of Earth’s surface too steep, too cold or too dry for cultivation irrigation allows cultivation in some dry areas & enhances yield in others BUT irrigation water is CONSUMED at present is 80% of consumption significant energy for pumping

12. 12 Increase in irrigated land area

13. 13 World land use 1700 - 2000

14. 14 Rice yields in Japan 600 - 2000

15. Irrigated Area Vs World Population 1950 – 2000

16. The Future

17. 17 World Population (middle estimate)

18. Population Growth and Water Needs

19. 19 What next? Water not where needed - population growth in ‘wrong’ places Climate change Novel resources ? –desalination - expensive in energy –Ice –Pipe-lines -water expensive to transport

20. 20 Santa Barbara story 1970s drought Water only $0.47/m 3 - severe W shortage! Desalination plant and pipe line built 1996: Water now expensive - $1.55/m 3 demand drops to 61% of pre-drought level desal. plant unnecessary (now only as back- up)

21. Conclusions not enough water overall – there will be problems so solutions have to be more or less local New technology Litigation War?