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Transcript of 3. Monthly water stress The relevance of temporally explicitwater impact assessment in global crop...
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1Monthly water stress: The relevance of temporally explicit water impact assessment in global crop production
Stephan Pfister and Peter Bayer
ETH Zurich, Institute for Environmental Engineering, Ecological Systems Design Group
Email contact: [email protected]
LCA XIII, Orlando, October 1, 2013
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2 So far annual water stress factors with global coverage available Monthly water scarcity factor from WFN (Mekonnen et al. PLOS 2011) has
factors for 405 major watersheds
No data for Italy and many other arid areas
Linear relation with consumption-to-availability
This work is based on annual water stress index (WSI) (Pfister et al. ES&T 2009)
Scaling from 0.01 to 1 (water deprivation factor)
Applied in several LCA studies -> experience of application
Overview water stress assessment (characterization factors)
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3 So far only annual water stress factors with global coverage available (based on water use to availablility) Monthly water scarcity factor from WFN (Mekonnen et al. PLOS 2011) has
factors for 405 major watersheds
No data for Italy and many other arid areas
Linear relation
This work is based on annual water stress index (WSI) (Pfister et al. ES&T 2009)
Scaling function (0.01 to 1) (water deprivation factor)
Applied in several LCA studies -> experience of application
Overview water stress assessment (characterization factors)
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4Deriving monthly WSI
*9.81
0.01
1
1 1monthlymonthly WTA
WSIe
*monthly monthly year
WTA WTA GSD
Withdrawal-to-availability (WTA) based Annual Watergap 2 (Alcamo et al. 2003)
Monthly adjustments based on Vorosmarty et al. (2000)
Include inter-annual precipitation variability:
geometric standard deviation (GSDyear) for 30 years
Adjust annual WSI function (exclude factor for monthly precipitation variability)
was -6.4
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5Annual WSI
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6WSI January
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7WSI February
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8WSI March
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9WSI April
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WSI May
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WSI June
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WSI July
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WSI August
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WSI September
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WSI October
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WSI November
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WSI December
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Monthly WSI of selected rivers
NileWSI
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Average monthly vs. annual WSI
Original WSI
Average monthly WSI
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Use weighted monthly vs. annual WSI
Original WSI
Weighted monthly WSI
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Ratio weighted monthly vs. annual WSI
Monthly resolution reveals higher stress in many watersheds
Weighted monthly
/ annual WSI
< 0.5
0.5-1
1-2
>2.0
Original WSI
Weig
hte
d m
on
thly
WS
I
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Crop water footprint
Water consumption (WC):160 crops on monthly and 5 arc minutes spatial resolution (Pfister et al. ES&T 2011)
Water footprint (WFP):
( )
mon i i
i
year i annual
i
WFP WC WSI
WFP WC WSI
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Water footprint of a region
Marginal vs. average impact
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Water footprint of a region (all crops)
Monthly
Annual
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Conclusions
Temporal resolution is relevant Mainly for foreground process (global picture does merely change)
Crop choice / plantation dates
Annual use-weighte average maps (sector-specific) For background processes (incl. uncertainty)
Storage effects /residence time Dams
Groundwater stocks Water source (ground surface water) -> different impacts!
Include spatial & temporal resolution induced uncertainty (variability induced)
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www.ifu.ethz.ch/ESD
THANKS FOR YOUR ATTENTION!
Paper submitted to J Clean Prod
Characterization maps are published on:http://www.ifu.ethz.ch/ESD/downloads/
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BACKUP SLIDES
LCA Food 2012 , Saint-Malo, October 2, 2012
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EuropeJanuary February
July August
April
November DecemberOctober
March
May June
September
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Avera
ge
ww
(WS
I mon)
WSIyear
Nile Murray Missouri
Nile
Murray
Missouri
Rhone
Rhine
Po
Rhone
Rhine
Po
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UNCERTAINTY WSI (PFISTER & HELLWEG 2011)
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Pfister et al 2009: Water Stress Index (WSI)
Includes:
Withdrawal-to-availability (WTA)
Variability in precipitation (VF) = geometric standard deviation (GSD)
Flow regulation (highly regulated = SRF)
Index following logistic function:
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*
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VF WTA for SRFWTA
VF WTA for non SRF
*6.4 1
0.01
1
1 1WTAWSI
e