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“Water, water everywhere nor any drop to drink…” Talk by Ron Oxburgh Hong Kong 11January 2002...
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Transcript of “Water, water everywhere nor any drop to drink…” Talk by Ron Oxburgh Hong Kong 11January 2002...
“Water, water everywhere nor any drop to drink…”
Talk by Ron Oxburgh
Hong Kong 11January 2002Material derived from many sources but
particularly from Postel et al., Science,1996
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 km3 (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
6
1990 Global water use and consumption
Use Consumption
km3 pa km3 pa %Agriculture 2880 1870 65Industry 975 90 9Municipaities 300 50 17Reservoir losses 275 275 100TOTALS 4430 2285
Stream flow needs 2350 2350 100
Total as % of Runoff 62% 43%
Different Water Withdrawals
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0 2 4 6 8 10 12
distance km
rela
tive
prop
ortio
n of
flow
Series1
Series2
Min. flow
9
Global water withdrawals over time, per cap. & total
0
1
2
3
4
1940 1950 1960 1970 1980year
per cap, thou. m3/yr
Total thou. km3/yr
US
10
Population, water withdrawals & irrigation
0
1000
2000
3000
4000
5000
60001900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
YEAR
million &
km
3/y
r
0
50
100
150
200
250
300
million h
a
populn
Wat. withdraws
Irrigated areas
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
Growth in Irrigated land
0.00
50.00
100.00
150.00
200.00
250.00
300.00
1950 1960 1970 1980Year
mil. ha
Oceania
S.America
N.America
Europe
Asia
Africa
Increase in irrigated land area
13
World land use 1700 - 2000
Forest
Pasture
Crops
0
1000
2000
3000
4000
5000
6000
7000
8000
1600 1700 1800 1900 2000
year
million h
a
14
Rice yields in Japan 600 - 2000
Japanese rice production over time Mather & Chapman p82
t/ha600 0.6800 1
1000 1.61200 1.71400 1.81600 21800 2.51900 2.72000 6
0
1
2
3
4
5
6
7
600 800 1000 1200 1400 1600 1800 2000 2200time
ton
nes /h
a
Irrigated Area Vs World Population 1950 – 2000
0.00
50.00
100.00
150.00
200.00
250.00
300.00
0.0 1000.0 2000.0 3000.0 4000.0 5000.0 6000.0 7000.0
World Population, millions
Irri
ga
ted a
rea
s,
mill
ion h
a
17
World Population(middle estimate)
EuropeN. America
Latin Amer./Carib.
CHINA
INDIA
Rest of Asia
Africa
Oceania
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
1950 1975 2000 2025 2050
peo
ple
- m
illi
on
s
Population Growth and Water Needs
0
2000
4000
6000
8000
10000
12000
14000
km3
fres
h w
ater
6000 6500 7000 7500 8000 8500 9000
World Population, millions
Deficit
Available
Borrow
USE
Flow needs
Inaccessible
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)