mena water outlook 2050 future water availability peter droogers, walter immerzeel, wilco terink the...
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MENA Water Outlook 2050
Future Water Availability
Peter Droogers, Walter Immerzeel, Wilco TerinkThe Netherlands
Climate Change
Current Problems
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1900 1925 1950 1975 2000
Wat
er C
on
sum
pti
on
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3)
Agricultural UseIndustrial UseMunicipal UseReservoirs
Shiklomanov, I.A. 2003. World Water Resources at the Beginning of the 21st Century. Cambridge University Press
Food Water Requirements
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Sub-Saharan
Africa
Asia FormerUSSR
WesternEurope
NorthAmerica
lite
rs /
pe
rso
n /
da
y
• Existing Water-Climate Change studies limitations:– Not only climate change, but global changes
• increased population• increased GDP• increased consumption: domestic, industry
– Conceptual limitations• focus on economics, not on water resources• focus on annual numbers• focus on limited sectors
– Impact and not adaptation
CONCEPTS
Study Design
• Objectives– Detailed water supply and demand analysis 2010-2050– Identification of potential options to overcome water shortage
• Steps– Climate and other change projections– Hydrological impact model– Water resources supply/demand analysis– Cost and benefits adaptation options
• Limitations– Large scale so simplifications, generalizations
Study design
Monthly approach
Month Renewable (mm) Irrigation requirement (mm) Water stress (mm)
January 30 10 0
February 20 10 0
March 10 30 20
April 10 30 20
May 10 40 30
June 10 40 30
July 10 20 10
August 10 20 10
September 20 20 0
October 30 20 0
November 40 10 0
December 40 10 0
TOTAL 240 260 120
20 mm shortage?
DOWNSCALING OF CLIMATE CHANGE SCENARIOS
Projected climate change in the MENA
• IPCC (Intergovernmental Panel on Climate Change) uses four scenario families (A1, A2, B1 and B2)
• Each scenario family explores alternative development pathways
• This study uses the A1B scenario because:– It is widely used and recommended by the IPCC– It is the most likely scenario:
• Assumes a world of rapid economic growth• Global population that peaks in mid-century• Rapid introduction of new and more efficient technologies
Projected climate change in the MENA
• All of MENA is likely to warm during the 21st century• Warming is very likely to be larger than the global, annual mean warming throughout
the continent and in all seasons, with drier subtropical regions warming more than the moister tropics
• Annual rainfall is likely to decrease in much of Mediterranean Africa and northern Sahara
• There is likely to be an increase in annual rainfall in East Africa
Temperature and precipitation changes over Africa. Differences between 1980-1999 and 2080-2099, averaged over 21 GCMs
Selection of General Climate Models
GCM Model r (-) MSE (mm /day) Included
BCCR CM2.0 0.81 1.12 1
CCCMA CGCM 3.1 T47 0.79 1.12 1
CNRM CM3 0.79 1.23 1
CSIRO Mk3.0 0.75 0.97 1
GFDL CM2.0 0.82 1.00 1
IPSL CM4 0.78 0.84 1
MPI ECHAM5 0.88 0.59 1
HadCM3 0.76 0.90 1
HadGEM1 0.81 0.78 1
CCCMA CGCM 3.2 T63 0.84 1.22 0
GFDL CM2.1 0.68 1.03 0
GISS AOM 0.59 1.60 0
GISS EH 0.65 1.19 0
GISS ER 0.71 1.18 0
IAP FGOALS 1.0g 0.60 1.19 0
INM CM3.0 0.58 1.07 0
MIROC 3.2 (hires) 0.83 1.59 0
MIROC 3.2 (medres) 0.76 1.17 0
MIUB ECHO-G 0.61 1.56 0
MRI CGCM 2.3.2a 0.81 1.78 0
NCAR CCSM 3 0.54 1.79 0
NCAR PCM1 0.55 2.11 0
GCM performance in North-East Africa:
• 9 GCMs were selected, because of the large variation in climate projections between the GCMs
• The table shows the mean of monthly correlation and mean squared difference of 20th century GCM experiments with the CRU TS 2.1 analysis
• The first nine GCMs are included in the current study
Why downscaling?
• GCMs generate forcing data (precipitation, temperature) at a coarse spatial resolution (>100 km)
• Hydrological processes occur on a higher spatial resolution
• The statistics of the coarse GCM forcing data do not match the statistics of the observed forcing data
Downscaling approach
• Temperature• Reference evapotranspiration• Precipitation
– Reference period is 2000-2009 (NCEP/NCAR and TRMM)– Monthly GCM data from 2000-2050– Monthly absolute anomalies 2010-2050 with respect to 2000-2009
(ΔTy,m)– Select random year 2000-2009– For each day in 2010-2050:
– Future ETref using Hargreaves assuming no change in diurnal temperature range (Tmax-Tmin)
myii TTRTF ,
Climate change in the MENA region2020-2030 2040-2050
Climate change in the MENA region
Climate change in the MENA region
CHANGES IN POPULATION, DOMESTIC AND INDUSTRIAL WATER DEMAND
Changes
• Irrigation water demand changes– FAO: Agriculutre Towards 2050
• Industrial water demand changes– AquaStat: f(GDP, GDP/cap)
• Domestic water demand changes– AquaStat: f(GDP, GDP/cap)
• Population growth – Environmental Assessment Agency
HYDROLOGICAL MODEL
The MENA hydrological model
• PCRaster - Water Balance• Distributed water balance model• Daily time step• 10 km x 10 km resolution• Model domain includes MENA including upstream
basins (5210 km x 8770 km)
The MENA hydrological model
Model resolution:• Regular grid of 10 km• Daily time step
Each cell describes:• The vertical flow of water through four
compartments– Canopy– Three soil compartments
• Soil and canopy are fed by rainfall and depleted by evapotranspiration
• The transfer of runoff to the drainage network
Sub-grid processes at 1 km:• Short and tall vegetation• Fraction of soil type• Topography• Open water
Key process: vegetation and evaporationEtr Ei
EtrEi
Interception:ImaxI
maxmax
0 ),min(
)1(
iLAIII
IEE
EfPfP
i
igapgapnet
Transpiration and soil evaporation:
Es
wetis
wetcropirtr
fEEE
sFffEEE
)0,min(
)()1()0,min(
0
F(s)
s0 10
1rs
rs
Evapotranspiration:
swettrweti EfEfEET )1(
Model domain
VALIDATION OF MODEL RESULTS
Location of GRDC discharge stations
• Validation of model results using stream flow
Validation results
WATER AVAILABILITY
Aridity (current)
Total and irrigated evapotranspiration
Internal water resources and per capita water availability (current)
Future water availability
Total Renewable Water Resources
Total change from 2010 to 2050 in % in total renewable water resources
Main Findings
• Changes MENA (2010-2050):• Internal renewable water resources: 20% reduction
– (8% less rainfall)– (12% more evapotranspiration)
• Total renewable water resources: 8% reduction• Large variation between countries• Large year-to-year variability• Per capita water availability will drop even further
below critical levels in the future
THANK YOU