The document discusses the need to set sustainable targets for humanity's water footprint. It proposes four main targets: 1) Keep water footprints within catchments at maximum sustainable levels, 2) Keep water footprints of products at reasonable levels based on best technology, 3) Keep water footprints of communities at reasonable levels based on fair shares by nation, and 4) Reduce risks related to water use in supply chains by limiting import dependency. Specific policies are suggested to implement the targets such as setting water caps by river basin and water benchmarks by product.

1. Targets for a sustainable water footprint
Arjen Hoekstra
www.ayhoekstra.nl

2. Aral Sea Basin, Central Asia
1989 2008
Water allocation
how much can we use?

3. Strawberries for export
California, USA
Top-6 water consumers California
1. animal feed
2. almonds & walnuts
3. residential areas
4. rice
5. grapes
6. cotton
Water allocation
to which purposes?
what are reasonable amounts?

4. Car driving on bio-ethanol
from sugarcane:
40-500 litre/km
Water allocation
who finally benefits?

5. Many countries have externalized
their water footprint to other countries
Water allocation
Global dependences

6. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels

7. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
Economic
efficiency
Keep WF of products to
reasonable levels

8. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
Economic
efficiency
Keep WF of products to
reasonable levels
Social equity Keep WF of communities to
reasonable levels

9. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
Economic
efficiency
Keep WF of products to
reasonable levels
Social equity Keep WF of communities to
reasonable levels
Political
security
Reduce risks related to water
use in supply chains

10. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target Means
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
WF caps by river basin (based on
available runoff, environmental water needs
& waste assimilation capacity)
Economic
efficiency
Keep WF of products to
reasonable levels
Social equity Keep WF of communities to
reasonable levels
Political
security
Reduce risks related to water
use in supply chains

11. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target Means
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
WF caps by river basin (based on
available runoff, environmental water needs
& waste assimilation capacity)
Economic
efficiency
Keep WF of products to
reasonable levels
WF benchmarks by product (based on
best available technology)
Social equity Keep WF of communities to
reasonable levels
Political
security
Reduce risks related to water
use in supply chains

12. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target Means
Environmental
sustainability
Reduce WF within catchments
to maximum sustainable levels
WF caps by river basin (based on
available runoff, environmental water needs
& waste assimilation capacity)
Economic
efficiency
Reduce WF of products to
reasonable levels
WF benchmarks by product (based on
best available technology)
Social equity Reduce WF of communities to
reasonable levels
Fair WF shares by nation
Political
security
Reduce risks related to water
use in supply chains

13. Targets to reduce humanity’s water footprint to sustainable levels
Source: Hoekstra and Wiedmann (2014) Humanity’s unsustainable environmental footprint, Science
Target Means
Environmental
sustainability
Keep WF in catchments to
maximum sustainable levels
WF caps by river basin (based on
available runoff, environmental water needs
& waste assimilation capacity)
Economic
efficiency
Keep WF of products to
reasonable levels
WF benchmarks by product (based on
best available technology)
Social equity Keep WF of communities to
reasonable levels
Fair WF shares by nation
Political
security
Reduce risks related to water
use in supply chains
Max. degree of import dependency
(external / total WF) per region

14. Source: Mekonnen & Hoekstra (2015)
The water footprint of humanity: not sustainable
Blue water scarcity = blue WF / maximum sustainable blue WF

15. Blue water footprint reduction targets
Guadiana basin (Spain)
Environmental
flow requirement
The blue WF exceeds the max. sustainable blue WF
from May to November.
Blue WF
reduction
target
Maximum
sustainable
blue WF

16. Water pollution level per river basin
Water pollution level = grey WF / maximum sustainable grey WF
Nitrogen
Source: Liu, Kroeze, Hoekstra and Gerbens-Leenes (2012)

17. Source: Mekonnen & Hoekstra (2014)
The water footprint of humanity: not efficient
Spatial differences in the consumptive water footprint of barley
Worldwide reduction of consumptive water footprints of crops to benchmark levels set by the best 25% of global
production, would result in a global water saving of 40%.

18. Source: Mekonnen & Hoekstra (2014)
The water footprint of humanity: not efficient
Differences in the green-blue water footprint of barley
Worldwide reduction of water footprints of barley to benchmark level set by the best 25%
of global production, would result in a global water saving of 60%.
546
25

19. Global average water footprint
The water footprint of humanity: not fairly distributed
Source: Hoekstra & Mekonnen (2012) The Water Footprint of Humanity, PNAS

20. 40% of the water footprint of European consumers is outside Europe
soybean
coffee
soybean
wheat
cotton
cotton,
industrial
products
wheat, sunflower seed, cotton,
industrial products
soybean,
sunflower seed
cotton
coffee
cocoa
cotton
Source: Hoekstra & Mekonnen (2012) The Water Footprint of Humanity, PNAS
The water footprint of humanity: large inter-regional dependencies

21. soybean
coffee
soybean
wheat
cotton
soybean,
sunflower seed
cocoa
Global blue water footprint of UK consumption
41% of UK's global blue WF is
unsustainable (located in places where
blue WF > max. sustainable blue WF)
51% of the unsustainable part of UK's
blue WF is located in six countries:
1. Spain (15%)
2. USA (11%)
3. Pakistan (8%)
4. India (7%)
5. South Africa (6%)
6. Iran (5%)
dates
apples
grapes
sugarcane
rice
rice, tea
sugarcane
rice, olives,
grapes
rice,grapes
Source: Hoekstra & Mekonnen (2015)

22. The need for contraction and convergence
Source: Hoekstra (2014) Wise freshwater allocation, UNESCO-IHE
0
500
1000
1500
2000
2500
3000
2000 2020 2040 2060 2080 2100
Water footprint per capita (m3/yr/cap)
USA
China
Maximum sustainable water footprint
Time
Business as Usual
Business as Usual

23. Further reading
► Water footprint caps by river basin
► Water footprint benchmarks by product
► Fair water footprint shares by nation
► Water security by region
www.ayhoekstra.nl