E d i t y o u r s l o g a n h e r e

1 Department of Hydraulic Engineering, Tsinghua University, China2 International Food Policy Research Institute

Global Irrigation Requirement under the scenario of SRA1B

Zhentao Cong1, Jun Liu1, Tingju Zhu2

ICCCFS2011

Background

Irrigation is by far the largest single user of water globally, accounting for approximately 70% of global water withdrawal and 90% of global consumptive water use (FAO, 2011)Irrigated land accounts for no more than 20% of the world's cultivated land, but contributes about 40% of all agricultural production and 60% of cereal production (FAO, 2011). Assessing irrigation water requirement under climate change is essential for understanding potential future water crisis and food security. Given the potential impacts of climate change on irrigation water uses, estimating climate change impacts on irrigation water requirements is a critical step towards evaluating how much water will be needed for irrigation in the future (Döll, 2002).

Framework

Rn, T, RH, u (monthly)

ET0 – Reference Evapotranspiration

Crop water requirement ETc = Kc*ET0

FAO-Penman-Monteith

FAO-KcSAGE

Net Irrigation RequirementIR = ETc－Pe

Pe – Effective Precipitation

IPCC Scenarios + GCMs

IPCC Scenarios and GCMs

Scenarios1PTO2X CO2 concentration increase 1% /year, until DOUBLE; constant thereafter.

1PTO4X  CO2 concentration increase 1%/year, until QUADRUPLE; constant thereafter.

20C3M  Greenhouse gasses increasing as observed through the 20th century.

COMMIT  Atmospheric burdens of long‐lived greenhouse gasses are held fixed at AD2000 levels.

PICTL  Constant pre‐industrial levels of greenhouse gasses.

SRA1BRapid economic growth; Population peaks in mid‐century and declines thereafter; New and more efficient technologies; Balanced energy sources.

SRA2 Heterogeneous world: Continuously increasing population;  Regionally oriented economic growth(more fragmented and slower).

SRB1Convergent world: Same population as SRA1B; Rapid changes in economic structures(towards service and information); Reductions in material intensity; Clean and resource‐efficient technologies.

Baseline: 20C3M scenario, 1961-1990Climate change scenario: SRA1B scenario, 2046-2065

IPCC Scenarios and GCMs

Scenarios

Source: Figure 10.4 in Meehl, et al. (2007)

IPCC Scenarios and GCMs

GCMsBCC‐CM1 ECHAM5/MPI‐OM

BCM2 MRI‐CGCM2.3.2

CGCM3_1‐T47 AOM 4x3

CGCM3_1‐T63 GISS ModelE‐H 

CNRM‐CM3 GISS ModelE‐R

ECHO‐G  CCSM3

CSIRO Mark 3.0 PCM

CM2.0 ‐ AOGCM MIROC3.2‐HI

INMCM3.0 MIROC3.2‐MED

IPSL‐CM4 HadCM3

FGOALS1.0_g HadGEM1

1.125°×1.125°Japan

2.8125°×2.8125°Japan

4°×3°NASA, USA

1.125°×1.125°BCCR

4°×5°INM

Method to calculate ET0

FAO Penman-Monteith equation

Where:– ET0 : reference evapotranspiration [mm day-1]– T : mean daily air temperature [°C]– Rn : net radiation [MJ m-2 day-1]– G : soil heat flux density [MJ m-2 day-1]– es : saturation vapor pressure [kPa]– ea : actual vapor pressure [kPa]– Δ : slope of temperature-pressure curve [kPa °C-1]– γ : psychrometric constant [kPa °C-1]– u: wind speed [m/s]

5 GCMs MIROC3_2-HI

BCM2 INMCM3

AOM MIROC3_2-MED

Change of ET0

R

RH

T

U

The change of ET0 is similar to the air temperature in the future.

What caused the increasing of ET0 ?

SAGEthe Center for Sustainability And the Global EnvironmentUniversity of Wisconsin-MadisonGlobal Land Use Database, 1992, 18 crops, 0.5°× 0.5°

Land use

Wheat

Rice

Maize

Cotton

Kc in FAOKöppen climate classification

Kc in FAO

Crop water requirement

Change of ETc of all crop in 5 GCMs

Change of ETc of rice in 5 GCMs

Change of ETc of maize in 5 GCMs

Change of ETc of wheat in 5 GCMs

Region MIROC3_2‐HI BCM2 INMCM3 AOM MIROC3_2‐MED

China +4.9% +2.6% +7.8% +4.7% +5.4%

USA +12.6% +8.8% +13.6% +4.9% +14.7%

India +4.4% +1.9% +1.2% +1.6% ‐3.2%

Australia +12.4% +6.5% +8.9% +6.8% +5.4%

Europe +10.9% +6.7% +8.8% +3.7% +17.9%

Russia +8.5% +4.6% +9.7% +0.5% +8.7%

Global +8.6% +5.2% +7.7% +4.4% +7.5%

Change of ETc

5 GCMs MIROC3_2-HI

BCM2 INMCM3

AOM MIROC3_2-MED

Change of P

Region MIROC3_2‐HI BCM2 INMCM3 AOM MIROC3_2‐MED

China +12.1% +5.0% +4.3% +1.8% +6.6%

USA ‐2.5% ‐2.2% ‐5.0% +5.8% ‐11.3%

India +3.7% +9.4% +13.0% +11.4% +14.5%

Australia ‐2.0% +4.1% ‐7.1% ‐9.9% +7.6%

Europe +5.8% ‐0.8% ‐0.7% +0.5% +4.4%

Russia +13.0% +4.4% +8.4% +8.1% +10.5%

Global +3.1% +1.6% +1.8% +3.7% +3.0%

Change of P

Effective rainfall (USDA)

Time step: 10 days Random Matching with the ETc

Precipitation vs ETc

5 GCMs MIROC3_2-HI

BCM2 INMCM3

AOM MIROC3_2-MED

Change of Irrigation Requirement (IR)

Region MIROC3_2‐HI BCM2 INMCM3 AOM MIROC3_2‐MED

China +3.7% +0.6% +10.1% +1.4% +5.7%

USA +30.6% +23.4% +27.9% +6.4% +33.6%

India +12.8% ‐1.1% ‐5.7% ‐1.6% ‐10.5%

Australia +15.0% +3.5% +8.3% +7.8% +1.9%

Europe +11.2% +17.1% +22.0% +13.9% +31.3%

Russia +6.2% +12.9% +22.7% +3.8% +5.8%

Global +14.8% +8.5% +11.6% +5.0% +12.1%

Change of Irrigation Requirement (IR)

ETc

P

IR

China:

ETc - increasing

P - inceasing

IR - not obviously

USA, Mediterranean area

ETc - increasing

P - deceasing

IR - increasing obviously

IR‐Irrigation Requirement

Change of Irrigation Requirement (IR)

Doll, 2002, Figure1(C), 2020, ECHAM4

Change of Irrigation Requirement (IR)

Wheat

Rice

Maize

Food production of countries, FAO

It is a big challenge for future world food security.

Change of IR in China

5 GCMs MIROC3_2-HI

BCM2 INMCM3

AOM MIROC3_2-MED

IR‐Irrigation Requirement

Change of IR in SRA1B 2046-2065 with MIROC3.2_HI

Conclusions

Trends of ET0, ETc, P and IR under climate changes depend on different GCMs and different regions.

ET0 and ETc would increase all over the world due to global warming.

IR would significantly increase in the Mediterranean area and in USA due to the increase in ET0 and the decrease in P.

Outlook

More GCMs and RCM;

Coupling the crop growth model and hydrological model to predict the irrigation requirement under climate changes;

To consider the trend of precipitation frequency.

E d i t y o u r s l o g a n h e r e

congzht@tsinghua.edu.cn

ICCCFS2011