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“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…” 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 • 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
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
Different Water Withdrawals Min. flow
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
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
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)
Conclusions • not enough water overall – there will be problems • so solutions have to be more or less local • New technology • Litigation • War?