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“Water, water everywhere nor any drop to drink…”

“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. Water Cycle annual fluxes. RAIN 110. RAIN 390. Evaporation. 70. 430. Runoff. 40. Ocean. Land. Water.

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“Water, water everywhere nor any drop to drink…”

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  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. Water Cycle annual fluxes RAIN 110 RAIN 390 Evaporation 70 430 Runoff 40 Ocean Land

  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% = 10,665km3 (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 15 0.4 Zaire/Congo 3.5 1.3 Tundra rivers 5 0.2 21% of Global Runoff is not useable

  6. 1990 Global water use and consumption

  7. Different Water Withdrawals Min. flow

  8. The past

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

  10. Population, water withdrawals & irrigation

  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. Increase in irrigated land area

  13. World land use 1700 - 2000

  14. Rice yields in Japan 600 - 2000

  15. Irrigated Area Vs World Population 1950 – 2000

  16. The Future

  17. World Population(middle estimate)

  18. Population Growth and Water Needs

  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. Santa Barbara story • 1970s drought • Water only $0.47/m3 - severe W shortage! • Desalination plant and pipe line built • 1996: Water now expensive - $1.55/m3 • 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?

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