Irrigated & Rainfed Crops in GCAM

Transcription

1 Irrigated & Rainfed Crops in GCAM KATE CALVIN Joint GCAM Community Modeling Meeting and GTSP Technical Workshop Joint Global Change Research Institute College Park, Maryland, USA Thursday, October 3, 2013 This work has been done with support from the U.S. Environmental Protection Agency s Climate Change Division, the U.S. Department of Energy s Office of Science, Integrated Assessment Research Program, and the PRIMA project. 1

2 Outline! Developing an irrigation module within the agriculture & land use component of GCAM! Preliminary results:! Reference scenario! Sensitivity analysis with respect to carbon and water prices 2

3 Assumptions: Current Nesting Structure Land Tundra Rock, Ice, Desert Arable Land Urban Gray = Exogenous Green = Non-commercial Red = Commercial Non-Pasture Pasture Grass and Shrubs Crops All Forests Other Pasture Intensively- Grazed Pasture Grass land Shrub land Corn, Corn, wheat, Corn, wheat, bioenergy, Corn, wheat, etc. wheat, etc. etc. etc. Other arable land Commercial Forest Forest 3

4 Assumptions: Adjusted Nesting Structure!"#$%&'()!#"') *+#,&--) 4051")6"&*%1) 7&'().""+/&01()!#"') 2&+'31()!#"').""+/&01() *+#,&--) 2&+'31() *+#,&--) 4

5 Land Allocation! Allocation between irrigated & rainfed is endogenous and depends on economics..""+/&01()!#"')!#"') 2&+'31()!#"')! Profit rate for each will depend on yield, cost of production, and carbon price (if applicable)! Yields are higher for irrigated crops.! Costs are lower for rainfed crops.! Carbon implications are lower for irrigated crops. 5

6 Water Use! We are tracking three types of water within GCAM.! Biophysical water demand: this is the amount of water (green or blue) that is needed to grow a crop.! Both irrigated & rainfed crops have biophysical water demand.! Water consumption: this is use of blue water (irrigation)! Only irrigated crops have water consumption! Water withdrawals: this is demand for blue water (irrigation). The difference between consumption & withdrawals depends on the efficiency of the irrigation technology which is exogenous! Only irrigated crops have water withdrawals! Technically, we can apply a constraint or price to any of these three factors. We have only experimented with pricing water withdrawals thus far. 6

7 Base Year Water Use: Source Data! Water coefficients (green & blue) based on a 2010 report! Report includes gridded & country specific data! Gridded data for 26 crop groups! Country data for all FAO crops! Data is average consumption over a 10 year period, centered around

8 Global Average Water Coefficients! Total biophysical water, per unit of crop produced, vary by crop, region, and AEZ thous m 3 /t Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat 8

9 Global Average Water Coefficients! Total biophysical water, per unit of crop produced, vary by crop, region, and AEZ! Some of the water is met by blue water (irrigation) and some is supplied by green water (rainfall) thous m 3 /t Green Blue Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat 9

10 Results: Global Land Cover Without Irrigation With Irrigation urban 9 urban 8 desert 8 desert tundra forest grass/shrub pasture biomass tundra forest grass/shrub pasture biomass 3 other arable 3 other arable crops crops 10

11 Results: Global Land Cover Without Irrigation With Irrigation urban desert tundra forest grass/shrub pasture biomass other arable urban desert tundra forest grass/shrub pasture biomass other arable irrigated crops crops rainfed crops 11

12 % of land that is irrigated 25% Total Cropland 10 By Crop 9 15% 5% % of Cropland that is Irrigated Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat 12

13 There is a higher % of irrigated production than irrigated land 10 Irrigated Land 10 Irrigated Production 9 9 % of Cropland that is Irrigated Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat % of Production that is Irrigated Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat 13

14 Irrigation varies across regions 10 USA AEZ07 Irrigated Production 10 Latin America AEZ % of Production that is Irrigated Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat % of Production that is Irrigated Corn FiberCrop MiscCrop OilCrop OtherGrain PalmFruit Rice Root_Tuber SugarCrop Wheat 14

15 Global water demand increases significantly over time Biophysical Consumption 2500 Water Withdrawals km Wheat SugarCrop Root_Tuber Rice PalmFruit OtherGrain OilCrop MiscCrop FiberCrop Corn km Wheat SugarCrop Root_Tuber Rice PalmFruit OtherGrain OilCrop MiscCrop FiberCrop Corn

16 Global water demand increases significantly over time Biophysical Consumption 3500 Water Withdrawals km biomass Wheat SugarCrop Root_Tuber Rice PalmFruit OtherGrain OilCrop MiscCrop km biomass Wheat SugarCrop Root_Tuber Rice PalmFruit OtherGrain OilCrop MiscCrop 4000 FiberCrop Corn 1000 FiberCrop Corn Note: only 16 of 86 EJ of biomass are irrigated in

17 Scenarios! Water Price! Reference: Assumes that water is free and unconstrained. A small pumping cost is applied to irrigated crops.! High water cost scenario ($2.50/m 3 ): assumes that desalinated seawater that is transported some distance inland sets the marginal cost for potable water. Cost is phased in over the first few decades of the simulation.! Carbon Price! Reference: Assumes no carbon price is applied! $10/tC: Assumes a carbon price of $10/tC is applied beginning in The price rises at 5% per year and applies to all emissions, including those from land-use change! $25/tC: Assumes a carbon price of $10/tC is applied beginning in The price rises at 5% per year and applies to all emissions, including those from land-use change

18 Carbon & water prices affect irrigation use, which affects average yields. 4 35% 3 % of Cropland that is Irrigated Global Average Sugar Yield Reference $10/tC (5% p.a.) $25/tC (5% p.a.) Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.) % % % Reference $10/tC (5% p.a.) $25/tC (5% p.a.) Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.)

19 This affects cropland extent, which affects land-use change emissions. million km Total Cropland 4 Reference $10/tC (5% p.a.) $25/tC (5% p.a.) 2 Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.) 0 GtCO Cumulative LUC Emissions Reference $10/tC (5% p.a.) $25/tC (5% p.a.) Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.) 19

20 This also affects global water use. 4 35% 3 % of Cropland that is Irrigated Global Water Withdrawals Reference $10/tC (5% p.a.) $25/tC (5% p.a.) Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.) Reference $10/tC (5% p.a.) $25/tC (5% p.a.) Hi Water Price Hi Water Price, $10/tC (5% p.a.) Hi Water Price, $25/tC (5% p.a.) 25% 5000 km % %

21 Summary! We have developed representations of irrigated and rainfed crops within GCAM, where allocations between the two management practices depend on economics.! We are fairly comfortable with the qualitative response of the model to different economic pressures.! Increasing the price of water results in less irrigation, lower average crop yields, more cropland, higher emissions, but lower water use.! Increasing the carbon price results in more irrigation, lower average crop yields, less cropland, lower emissions, but higher water use.! Remaining tasks:! Understanding why our base year blue water use is lower than historical estimates (~750 km 3 vs 900 km 3 )! Understanding the bioenergy water! More thorough testing of the model! Documenting the work in a peer-reviewed journal! Releasing the code/input to the community 21

22 QUESTIONS?