We employed a set of seven global hydrological models (GHMs) to quantify the impact of climate change on regional irrigation water demand, and the resulting uncertainties arising from newly available CMIP5 climate projections in the
framework of the Inter-Sectoral Impact Model Intercomparison Project (ISI-MIP; http://www.isi-mip.org/).
GHMs used:
H08, LPJmL, MPI-HM, PCR-GLOBWB, VIC, WaterGAP, WBM (all at a 0.5 degree grid or ≈50km by ≈50km at the equator) The GHMs calculate irrigation water requirement per unit crop area from daily soil water balance under four Representative Concentration Pathways (RCPs) from five Global Climate Models (GCMs) respectively.
RCPs used: RCP2.6, RCP4.5, RCP6.0, RCP8.5 GCMs used:
HadGEM2-ES, IPSL-CM5A-LR, GFDL-ESM2M, MIROC-ESM- CHEM, NorESM1-M
Output used: Potential irrigation water demand
Simulation period: 1971-2099 (Irrigated areas remain constant)
Future irrigation water demand under climate change: regional variability and uncertainties arising from GHMs and CMIP5 climate projections
Jacob Schewe 1 , Yoshihide Wada 2 , and Dominik Wisser 2,3
AGU 2012: H43C-1355: Ecohydrological Systems, Ecosystem Services, and Freshwater Sustainability: Modeling, Uncertainty, and Organizing Principles 1 Potsdam Institute for Climate Impact Research, Germany
2 Department of Physical Geography, Utrecht University, The Netherlands 3 Center for Development Research (ZEF), University of Bonn, Germany jacob.schewe@pik-potsdam.de, y.wada@uu.nl, dwisser@uni-bonn.de
Potential irrigation water demand in million m
3yr
-1AGU Fall Meeting 2012
San Francisco 3-7 December 2012
1. INTRODUCTION
2. METHODS – MODEL and DATA
3. RESULTS
4. CONCLUSIONS The irrigation sector uses by far the largest amount of water and
is responsible for 70% of the global water demand. At a country scale, irrigation water demand often exceeds 90% of the total water demand in many of developing countries such as India, China, Pakistan, where irrigation sustains much of food production and the livelihood of millions of people. The global area of irrigated land is not expected to expand dramatically in the coming decades. Future irrigation water demand is, however, subject to large uncertainties due to anticipated climate change, i.e. warming temperature and changing precipitation variability, in various regions of the world.
Ensemble mean (All) 2090s
2090s 2050s
The relative contribution of each source (GHMs, GCMs, RCPs) of uncertainty (fractional uncertainty; %) in irrigation water demand projections over the period 2005-2100, relative to the period the
1971–2005.
- Global irrigation water demand increased by ~6% by 2050 and ~10% by 2100 respectively primarily due to higher evaporative demand as a result of increased temperature (ensemble mean).
- Regional irrigation water demand decreased over some parts of Europe and Southeast Asia, but increased over South Asia, the U.S., the Middle East and Africa.
- The global and regional projections are highly uncertain over many parts of the world.
- The ensemble projections among the different GHMs, GCMs, and RCPs vary between - 30% and +35% for India, between -25% and +28 for the U.S., between -20% and +28%
for Mexico, between -22% and +26% for Pakistan, and between -22% and +24% for China.
- The model uncertainty among the different GHMs dominates the uncertainty in the irrigation water demand projections by ≈2025. However, afterwards the uncertainty of the climate projections, or specifically in the precipitation projections derived from different RCPs from different GCMs, substantially increases. Thus, the dominant sources of the uncertainty lie both in the GHMs and in the climate projections.
Ensemble coefficient of variation (All)
Coefficient of Variation [ - ] 10.9 0.80.7 0.6 0.50.40.3 0.2 0.1 0
Coefficient of Variation [ - ] 10.9 0.80.7 0.6 0.50.40.3 0.2 0.1 0
Coefficient of Variation [ - ] 10.9 0.8 0.7 0.6 0.5 0.40.3 0.2 0.1 0
Coefficient of Variation [ - ] 10.9 0.8 0.7 0.6 0.5 0.40.30.2 0.1 0
0 - 2 2 - 20 20 - 100 100 - 300 300 - 1000 > 1000
10.90.80.70.60.50.40.30.20.1 0
