Growing water scarcity in agriculture – future challenge to global water security

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!

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