Growing water scarcity in agriculture
- future challenge to global water security
By Professor Malin Falkenmark
Stockholm International Water Institute and Stockholm Resilience Center
Why agriculture?
70 times more water than households
3000 kcal/p d
/20 % anim prot
--> 3500 l/p d or 1300 m3/p yr.
Two partitioning points: - land surface - root zone
Analy&cal framework
Country water balance
Kenya
Water security - what risks to cope with?
Aim = successful management of water for
- food……….green+ blue
- humans…..blue
A. Green water risks B. Blue water risks C. Regional risks D. Global risks
A. Green water-related risks links to agriculture
Risk 1. Too little annual rainfall
* par&cular exposure of semi-‐arid zone
Rainfall changes around red line of critical importance for crop production impact
From IWMI 2007
Risk 2. Dryspells
0
1
2
3
4
1960 1970 1980 1990 2000Year
Dry
spel
l >1
4 d
ays
du
rin
g c
rop
sea
son Maradi
Zinder
Linear (Maradi)
Linear (Zinder)
Number of dryspells during crop season > 14 days
1
2
3
nat.green
degraded green nat blue
drought risk
fourfold African vulnerability
Risk 3. Droughts
famine
• huge water losses -‐ blue water loss -‐ green water loss
• poor root water
uptake Farming systems in Subsah. Africa
RAIN
1
2
3
green loss
plant uptake blue
losses water partitioning
Result: poor yields -‐ why?
B. Blue water-related risks
- competition - complexity
scale: 1 cube = 1 million cubic meter/yr 1 dot = 100 persons
Risk1. : When population grows water crowding increases
Risk 2: When demand grows
water stress increases
> 2000
1000-2000
600-1000
P/flow unit agr trade ---->
1900-2005
groundw ----->
(from Kummu et al)
irrig ----->
200 m3/p yr municipal/ industrial use
demand- driven
population driven
%
vulnerable triangle
1000 p/flow unit
Result: River basin closure
p/flow unit
C. Regional-scale risks
carrying capacity overshoot
Country food water availability 2050 cropland water, km3/yr
--> Blue
Blue+ green
% of world pop a. 46 % b. 14 % c. 21 % d. 19 %
Water requirement 1300 m3/p yr
Crrying capacity overshoot 2050
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25 % yield gap closure
bln people
3.0
4.4
1.5 3.3
4.1
1.5 3.7
3.6
1.5
3000 kcal/p d 20 % animal food
3000 kcal/p d 5 % animal food
2200 kcal/p d 5 % animal food
D. Global-scale risks
Planetary Freshwater Boundary
Bloodstream of the biosphere
Maximized cons use:
max 5000 km3/yr
Terrestrial Ecosystems
Atmosphere
Continents
Sea
Aquatic Ecosystems
Ecosystem
Goods/Services
Ecosystem
Goods/Services Society
a
c
.
.
Consumptive Use b .
Water Withdrawals
Waste Water Return Flows
Planetary Freshwater Boundary - env flow > 0
Water-security means coping with:
A. Green water risks: crop water deficiency dryspells, drought, aridification
B. Blue water risks: water crowding, water stress irrigation limitations, competing sectors environmental flow constraints, basin closure
C. Regional risks: carrying capacity overshoot food trade
D. Global risks: consumptive use constraints food, carbon-seq., fuelwood
Thank you!
www.siwi.org
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