comment:
This is an IPAT-S script. IPAT-S is an open-source scripting language
for developing sustainability scenarios. It can be run using the free
IPAT-S software, available from:

	http://ipat-s.kb-creative.net/

For more information, please contact the author of IPAT-S,
Eric Kemp-Benedict (eric@kb-creative.net)
:comment

# This script implements an "ImPACT" model where the factors
# differ for different sectors.

baseyear 2000
scenyears 2010 to 2050 by 10

dimension sector 'Agr' 'Mfg' 'Dom'

summvar P I{sector} Itot
ratio A C{sector} T{sector}

P.0 = 283   # million people
# These are water withdrawals in 2000
Itot.0 = 469.00 # cubic km
I.0{sector = 'Agr'} = 46% * Itot.0
I.0{sector = 'Mfg'} = 42% * Itot.0
I.0{sector = 'Dom'} = 12% * Itot.0

# For scenario, assume same rates as for 1970-1995 period from
#  Waggoner and Ausubel. 2002. "A framework for sustainability science: A
#    renovated IPAT identity". PNAS 99(12), pp. 7860-7865.

num p = <1.0%>			# Annual population growth
:: >> growth(p) -> P

num a = <1.5%>			# Income growth rate
A = growth(a) 			# Income growth rate

# Dematerialization
C{sector = 'Agr'} = growth(<-0.7%>)
C{sector = 'Mfg'} = growth(<-0.6%>)
C{sector = 'Dom'} = growth(<0.0%>) # Figure not mentioned in ImPACT paper

# Efficiency
T{sector = 'Agr'} = growth(<-1.7%>)
T{sector = 'Mfg'} = growth(<-5.0%>)
T{sector = 'Dom'} = growth(<-2.0%>) # Figure not mentioned in ImPACT paper

# The ImPACT formula:
#   - Population drives changes in impact
#   - Modified by income, dematerialization and efficiency
:: P >> A * C * T -> I

report 100 * I/I.2000 as "Water use by sector (2000 = 100)"

summarize I as Itot

report 100 * Itot/Itot.2000 as "Total water use (2000 = 100)"