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MENA Water Outlook 2050 Future Water Availability Peter Droogers, Walter Immerzeel, Wilco Terink The Netherlands.

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Presentation on theme: "MENA Water Outlook 2050 Future Water Availability Peter Droogers, Walter Immerzeel, Wilco Terink The Netherlands."— Presentation transcript:

1 MENA Water Outlook 2050 Future Water Availability Peter Droogers, Walter Immerzeel, Wilco Terink The Netherlands

2 Climate Change


4 Current Problems


6 Shiklomanov, I.A World Water Resources at the Beginning of the 21st Century. Cambridge University Press

7 Food Water Requirements

8 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


10 Study Design Objectives – Detailed water supply and demand analysis – 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

11 Study design

12 Monthly approach MonthRenewable (mm)Irrigation requirement (mm)Water stress (mm) January30100 February20100 March April May June July August September20 0 October30200 November40100 December40100 TOTAL mm shortage?


14 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

15 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 and , averaged over 21 GCMs

16 Selection of General Climate Models GCM Modelr (-)MSE (mm /day)Included BCCR CM CCCMA CGCM 3.1 T CNRM CM CSIRO Mk GFDL CM IPSL CM MPI ECHAM HadCM HadGEM CCCMA CGCM 3.2 T GFDL CM GISS AOM GISS EH GISS ER IAP FGOALS 1.0g INM CM MIROC 3.2 (hires) MIROC 3.2 (medres) MIUB ECHO-G MRI CGCM 2.3.2a NCAR CCSM NCAR PCM 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

17 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



20 Downscaling approach Temperature Reference evapotranspiration Precipitation – Reference period is (NCEP/NCAR and TRMM) – Monthly GCM data from – Monthly absolute anomalies with respect to ( ΔT y,m ) – Select random year – For each day in : – Future ETref using Hargreaves assuming no change in diurnal temperature range (Tmax-Tmin)

21 Climate change in the MENA region

22 Climate change in the MENA region



25 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



28 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)

29 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

30 Key process: vegetation and evaporation E tr EiEi EiEi Interception: I max I Transpiration and soil evaporation: EsEs F(s)F(s) s Evapotranspiration:

31 Model domain


33 Location of GRDC discharge stations Validation of model results using stream flow

34 Validation results


36 Aridity (current)

37 Total and irrigated evapotranspiration

38 Internal water resources and per capita water availability (current)

39 Future water availability

40 Total Renewable Water Resources Total change from 2010 to 2050 in % in total renewable water resources

41 Main Findings Changes MENA ( ): 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


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