MENA Water Outlook 2050

Future Water Availability

Peter Droogers, Walter Immerzeel, Wilco TerinkThe Netherlands

Climate Change

Current Problems

0

500

1000

1500

2000

1900 1925 1950 1975 2000

Wat

er C

on

sum

pti

on

(km

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

0

1000

2000

3000

4000

5000

6000

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