AGRICULTURE WATER DEMAND

Incorporating water in GCAM

Vaibhav Chaturvedi

Background

! Agriculture highest consumer of water globally, more than 70% of global water withdrawals

! Increasing population and food demand expected to put tremendous pressure on global water resources

! Additional water demand for energy crops

! Different challenges for different regions ! Present effort to analyze long term scenarios

related to global agricultural water consumption and withdrawal

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Five Research Issues

1.  How big will future global agricultural water consumption grow?

2.  What is the effect of atmospheric CO2 concentration on agricultural water consumption through increasing plant water use efficiency?

3.  What effect will emissions mitigation policy have on agricultural water consumption?

4.  How big will future global IRRIGATION water consumption grow?

5.  What will be the effect of increasing efficiency of water delivery in irrigation on water withdrawals?

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Biophysical water

Irrigation water

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Background: The Vocabulary of Agricultural Water

Total biophysical

water consumption

Green Water Water from

precipitation, directly used by crops or stored

as soil moisture

Blue Water Water withdrawn for irrigation from rivers,

lakes, aquifers or dams

Blue water demands on

irrigated lands

Green water demands on

rain-fed lands

Green water demands on

irrigated lands

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2000

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6000

8000

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2005 2020 2035 2050 2065 2080 2095

Mt/y

r

Agricultural Production FiberCrop

PalmFruit

OtherGrain

OilCrop

Rice

Wheat

Corn

Root_Tuber

FodderHerb

FodderGrass

MiscCrop

SugarCrop

KEY Terms Calculating Water Consumption

Irrig

ated

R

ainf

ed

AgLU Model

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1. How big will future agricultural water demands grow?

Biophysical Water Consumption by Crops

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Total biophysical water consumption to almost double by 2050, after which the increase will be marginal Energy crops’ water consumption also increases, especially in the later half of the century

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2005 2020 2035 2050 2065 2080 2095

km3/

yr

Biophysical water consumption- CROPS

Biomass

FodderGrass

FodderHerb

PalmFruit

FiberCrop

SugarCrop

Root_Tuber

OtherGrain

Wheat

Rice

OilCrop

MiscCrop

Corn

Biophysical Water Consumption by Regions

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Most of the water demand is in the developing nations of the world

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2005 2020 2035 2050 2065 2080 2095

km3/

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Biophysical water consumption- REGIONS

Korea

Japan

Eastern Europe

Canada

Australia_NZ

Middle East

Western Europe

Former Soviet Union

USA

China

Latin America

India

Southeast Asia

Africa

More than 70% of water for agriculture is consumed by developing regions, which increases to above 75% in 2095 70%

75%

16%

23%

Share of irrigation water

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2. How Will Atmospheric CO2 Concentrations Affect Agricultural Water Demands?

! How will future increases in the atmospheric CO2 concentration from below 400 ppmv to above 750 ppmv affect biophysical water consumption?

! Increasing the atmospheric CO2 concentration ! Increases plant water use efficiency, other things being constant; ! Decreases water requirement for meeting evapo-transpiration

needs during crop growth stage

! We assume that a 1% increase in the atmospheric CO2 concentration decreases plant water consumption by 0.5%. [SOURCE: Leaky et al., 2009]

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Effect of CO2 Concentration on Water Demands by Crops

AgLU Model

Exogenous crop yields; Fixed climate Current experiment only on water component

Effect  of  CO2  Concentra/on  on  Agricultural  Water  Demand  

Global water consumption was reduced by 15% in 2050 and 30% in 2100 due to increasing water use efficiency by plants as a consequence of elevated atmospheric CO2 concentrations

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IMPORTANT CAVEAT: The Impact of climate change on crop yields and water use are NOT included here. Future work.

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2005   2020   2035   2050   2065   2080   2095  

km3/yr  

Water  demand  with    Constant  Atmospheric  CO2  

Biomass  FodderGrass  FodderHerb  PalmFruit  FiberCrop  SugarCrop  Root_Tuber  OtherGrain  Wheat  Rice  OilCrop  MiscCrop  Corn  

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2000  

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6000  

8000  

10000  

12000  

14000  

16000  

2005   2020   2035   2050   2065   2080   2095  km

3/yr  

Water  Demand  with  Increasing  Atmospheric  CO2  (772  ppm)  

Biomass  FodderGrass  FodderHerb  PalmFruit  FiberCrop  SugarCrop  Root_Tuber  OtherGrain  Wheat  Rice  OilCrop  MiscCrop  Corn  

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3. How Will Emissions Mitigation Policies Affect Agricultural Water Demands?

Water Consumption Under Climate Policy

! What could be the effect of a carbon price on land use change emissions on water consumption in agriculture?

! Carbon price can lead to changes in land use patterns

! We will explore the effect of a carbon price that limits radiative forcing to 4.5 W/m2 in the year 2100 on agricultural water consumption ! Note that we are not considering either the effect of climate

change or CO2 concentrations in this analysis

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Effect  of  Emissions  Mi/ga/on  Depends  on  the  Policy—Universal  Carbon  Tax  

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If all carbon is valued equally, then water demands actually decline slightly •  The composition of crops changes—shift away from low carbon animal feed

crops to high carbon animal feed crops to feed livestock •  Land shifts toward high carbon content use, mainly forests

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2005   2020   2035   2050   2065   2080   2095  

km3/yr  

Reference  Scenario  Biomass  FodderGrass  FodderHerb  PalmFruit  FiberCrop  SugarCrop  Root_Tuber  OtherGrain  Wheat  Rice  OilCrop  MiscCrop  Corn  

0  

2000  

4000  

6000  

8000  

10000  

12000  

14000  

16000  

2005   2020   2035   2050   2065   2080   2095  km

3/yr  

Universal  Carbon  Tax  Biomass  

FodderGrass  

FodderHerb  

Palmfruit  

FiberCrop  

SugarCrop  

Root_Tuber  

OtherGrain  

Wheat  

Rice  

OilCrop  

MiscCrop  

Corn  

Effect  of  Emissions  Mi/ga/on  Depends  on  the  Policy—Fossil  Fuel  ONLY  Carbon  Tax  

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If only FOSSIL FUEL carbon is valued, then agricultural water demands increase by more than 1/3 •  Bioenergy demands for water increase dramatically after 2050 •  Bioenergy demands for water alone are more than 40% of all agricultural

water demands by the century end

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10000  

15000  

20000  

25000  

2005   2020   2035   2050   2065   2080   2095  

km3/yr  

Universal  Carbon  Tax  Biomass  

FodderGrass  

FodderHerb  

Palmfruit  

FiberCrop  

SugarCrop  

Root_Tuber  

OtherGrain  

Wheat  

Rice  

OilCrop  

MiscCrop  

Corn   0  

5000  

10000  

15000  

20000  

25000  

2005   2020   2035   2050   2065   2080   2095  km

3  

Fossil  Fuel  Only  Tax  

Biomass  

FodderGrass  

FodderHerb  

Palmfruit  

FiberCrop  

SugarCrop  

Root_Tuber  

OtherGrain  

Wheat  

Rice  

OilCrop  

MiscCrop  

Corn  

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4. How much more irrigation would be required if current climate conditions persist?

Water for Irrigation ! How big will be the irrigation water consumption?

! Irrigation critically important for increasing cropping intensity and productivity

! Agricultural irrigation water consumption depends on the extent of area under irrigation and production from irrigated areas

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200

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2005 2030 2050

Prod

uctio

n in

mill

ion

tons

Increase in irrigated area and production

Production Area

Irrig

ated

are

a in

mill

ion

hect

are

Assumption: FAO projections of

irrigated area and production

Total  Irriga/on  Water  Consump/on  

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0  

500  

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2005   2020   2035   2050   2065   2080   2095  

km3/yr  

Blue  water  consump/on  

Korea  

Japan  

Canada  

Australia_NZ  

Western  Europe  

Eastern  Europe  

Former  Soviet  Union  

USA  

Middle  East  

China  

LaSn  America  

Africa  

Southeast  Asia  

India  

200% increase in irrigation water consumption, which can be expected to increase to more than 3000 km3/yr in 2095 compared to less than 1000 km3/yr in 2005 As a share of global biophysical water consumption, irrigation water increases from 15% in 2005 to 23% in 2095 Highest increase to be observed in India followed by Southeast Asia

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5.  How  large  can  be  the  effect  of  increase  in  irriga/on  water  delivery  efficiency?  

Global  Water  Withdrawal  in  2005  

Consumption 1007 km3

(40%) Efficiency Losses 1506 km3 (60%)

Total 2513 km3

Irrigation Water Delivery Efficiency

! What is the effect of increase in irrigation water delivery efficiency on water withdrawals?

! Difference between water withdrawal for irrigation and blue water consumption due to efficiency losses

! Significant variation in water delivery efficiency across regions

! Increase in efficiency could potentially save substantial water

! Assumption: Constant biophysical water and water for irrigation, but water delivery efficiency increasing at .5%/annum up to maximum of 70%

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0

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2005 2020 2035 2050 2065 2080 2095

km3/

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Increasing Efficiency Korea

Japan

Former Soviet Union

Eastern Europe

Canada

Australia_NZ

Western Europe

USA

China

Middle East

Africa

Latin America

Southeast Asia

India

Irrigation Water Delivery Efficiency

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Global irrigation water withdrawals can be reduced by 20% in 2050 and 32% in 2095 through improving irrigation delivery efficiency

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1000

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7000

8000

9000

2005 2020 2035 2050 2065 2080 2095

km3/

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Constant Efficiency Korea

Japan

Former Soviet Union

Eastern Europe

Canada

Australia_NZ

Western Europe

USA

China

Middle East

Africa

Latin America

Southeast Asia

India

Key Learning

! Total biophysical water consumption to almost double by 2050, after which the increase will be marginal

! CO2 concentration could significantly affect global water consumption by increasing plant water use efficiency

! Emission mitigation policy excluding land use change emissions can result in high water consumption by bio-energy crops

! Future demand for irrigation water can put severe pressure on irrigation water resources

! Irrigation delivery efficiency improvement could yield substantial savings in water withdrawals

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Future Research

! Including water pricing for irrigation water and clearing agricultural water markets

! Introducing end use water consumption technologies in agriculture

! Endogenous water use technology selection on the basis of price and income within AgLU

! Linking water input to crop productivity

! Modeling irrigated and rain-fed land separately within AgLU model

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ENERGY WATER DEMAND Next…

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Backup Slides

Green water demands on

rain-fed lands

Blue water demands on

irrigated lands

Green water demands on

irrigated lands

Ag Production

1 Total

biophysical water

consumption

2 Water consumption on irrigated

areas (G+B)

Ag Area

3 Green Water consumption on irrigated

areas

4 Blue water consumption

5 Water withdrawal

Irrigation Delivery Efficiency

Calculating water consumption in agriculture

Share of irrigated area/

production

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Ag Area

Calculating water for irrigation

Water consumption on irrigated

areas (Green+Blue)

Share/Increase in irrigated production

FAO projection based

assumptions

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Green water consumption on irrigated

areas

Share/Increase in irrigated area

FAO projection based assumptions

Blue water consumption

0

2000

4000

6000

8000

10000

12000

14000

16000

2005 2020 2035 2050 2065 2080 2095

km3/

yr

Biophysical water consumption

Korea

Japan

Eastern Europe

Canada

Australia_NZ

Middle East

Western Europe

Former Soviet Union

USA

China

Latin America

India

Southeast Asia

Africa

Green water fixed/unit irrigated

area

Water  for  Irriga/on  

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Source: www.iwmigmia.org

Some  Key  Terms  and  Rela/onships  

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Biophysical water

Green water Blue water

Green water- to Rainfed

Crops

Green water- to Irrigated

Crops

Green water will be used on both dry land crops and irrigated crops.

What variables are we interested in?

! Biophysical water consumption ! Derived from our virtual water content and crop

production.

! Blue water consumption ! Blue water withdrawal

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