Water, water everywhere nor any drop to drink

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 Earths water is fresh
• 2/3 of fresh water (1.73) exists as ice
• remainder 0.77 10,665 km3 (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 Earths 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?