Achieving Sustainable Irrigation Water Withdrawals: Global...

1/27

Achieving Sustainable Irrigation WaterWithdrawals: Global Impacts on Land Use

Jing Liu1, Thomas Hertel1, Richard Lammers2, AlexanderPrusevich2, Uris Baldos1, Danielle Grogan2, and Steve Frolking2

1Purdue University, 2University of New Hampshire

12th IWREC meeting, Washington DCSeptember 13, 2016

2/27

Increasing reliance on unsustainable water withdrawal

I Non-renewable groundwater abstraction tripled over theperiod 1960-2000 (Wada et al., 2012)

I Sustainable irrigation: withdrawal less than 20% of available(Alcamo et al., 2000)

I Irrigation vulnerability index:

=Irrigation Withdrawal

Water Available for Irrigation

2/27

Increasing reliance on unsustainable water withdrawal

I Non-renewable groundwater abstraction tripled over theperiod 1960-2000 (Wada et al., 2012)

I Sustainable irrigation: withdrawal less than 20% of available(Alcamo et al., 2000)

I Irrigation vulnerability index:

=Irrigation Withdrawal

Water Available for Irrigation

3/27

Vulnerable irrigation hotspots in 2006

Source: author’s calculation based on 10-yr (2000-2010) average of simulated

irrigation demand and irrigation availability.

4/27

Where to target for sustainable irrigation in the future?

Evolving irrigation vulnerability index, 2050 relative to 2006

Source: author’s calculation.

5/27

Method: Integrated hydro-economic modeling

model structure

6/27

Method: Integrated hydro-economic modeling (cont.)

Global Hydro-model (irrigation supply):

I 30 arc-min, aggregated to 958 sub-basins sub-basin1 sub-basin2

I Water is sourced from surface, reservoir, and soil-stored water

I Water available for irrigation is the residual after subtractingresidential, industrial and livestock uses

Global Econ-model (irrigation demand):

I Partial equilibrium model with sub-national detail on waterand land

I Irrigated and rainfed crop production at the 30 arc-min levelmodel

7/27

Model calibration- Look back in time: calibrate the model to capture the stylizedfacts about historical cropland area change 1961-2006

- Modest overall growth, +12%, but much faster growth ofirrigated area, +112% (FAOSTAT, Siebert et al.,2015)

8/27

Experiments:Reduce sub-basin irrigation vulnerability index to 0.2 in2050

I No adaptationI With adaptation

- inter-basin water transfer- faster TFP growth- integrated market

8/27

Experiments:Reduce sub-basin irrigation vulnerability index to 0.2 in2050

I No adaptationI With adaptation

- inter-basin water transfer- faster TFP growth- integrated market

9/27

Experiments:Reduce sub-basin irrigation vulnerability index to 20% in2050

I No adaptationI With adaptation

- inter-basin water transfer- faster TFP growth- integrated market

land output1 output2

10/27

Result 1: Cropland area change (Mha, no adaptation),2050 relative to 2006

Experiment

RegionSustainable Unsustainable

Irrigated Rainfed Total Irrigated Rainfed Total

S Asia -18 31CHN MNG -20 3

US 9 12S Amer 29 29

SSA 121 120Rest of world 35 45

Total 156 240

- Sustainability constraint suppresses global cropland expansion in2050.

11/27

Result 1: Cropland area change (Mha, no adaptation),2050 relative to 2006

RegionSustainable Unsustainable

Irrigated Rainfed Total Irrigated Rainfed Total

S Asia -40 22 -18 14 17 31CHN MNG -23 3 -20 2 1 3

US -3 12 9 2 10 12S Amer 2 28 29 2 27 29

SSA 3 118 121 3 117 120Rest of world -4 39 35 9 36 45

Total -67 223 156 32 208 240

- Sustainability constraint suppresses global cropland expansion in2050. However, it encourages more expansion into the carbon-richrainfed area.

12/27

- Global cultivated cropland area in 2006: 1486 Mha≈ 1.5 US

- Without sustainability constraint, global cropland area in 2050≈ 1.5 US + Alaska + Texas

- With sustainability constraint, global cropland area in 2050≈ 1.5 US + Alaska

13/27

Result 2: Compare across adaptations

14/27

Result 2: Compare across adaptations

- IBT will keep China from losing 10 Mha cropland.

15/27

Result 2: Compare across adaptations

- Faster TFP growth will reduce global cropland expansion by 1/3,from 156 to 98 Mha.

16/27

Result 2: Compare across adaptations

- Trade has a similar overall effect on suppressing global croplandexpansion, but the spatial distribution is remarkably different.

17/27

Result 3: Grid-level irrigated cropland change (103 ha/grid)

Global sum = -67 Mha

18/27

Summary

I Pursuing sustainable irrigation may undermine otherenvironment and development goals.

I Adaptations affect food supply in a similar manner, but havedifferent implications for land use change.

I The global-local-global approach has the potential to identifysub-national variations and assist decision-making at the locallevel.

19/27

Next step

20/27

SUPPLEMENTARY SLIDES

21/27

Current model features:

I 16 regions, 2 sectors, 4 commodities

I globally 58447 grids (30 arc-min)

I constant elasticity of substitution production function

I split irrigated and rainfed cropland area and crop output,grid-specific irrigation intensity (m3/ha)

I Armington substitution between domestic and importedcommodities

return

22/27

Equilibrium of land (irrigated & rainfed) and water inputs

Demand

qiLandg = qog ,irr − ao − σg ,irr (piLandg − po) (1)

qrLandg = qog ,rfd − ao − σg ,rfd(prLandg − po) (2)

qWaterB =

∑g∈B

γgqiLandg (3)

Supply

qiLandg = ν iLandg (piLandg − λiLandg ) (4)

qrLandg = νrLandg prLandg (5)

return

23/27return

24/27

return

25/27

return

26/27

return

27/27

References

Alcamo, J., T. Henrichs, and T. Rosch (2000). World water in 2025:Global modeling and scenario analysis. World water scenarios analyses.