Projected Changes in Nile Flows: RCM Results

Mid-Term WorkshopClimate Change Risk Management

Programme Forecasting & IWRM Component

Prepared by: Nile Forecast Center

Outline

1. Modeling Climate Change Impacts

2. Pervious Studies on the Nile

3. Study Methodology

4. Results

5. Conclusions

Modeling Climate Change Impacts Methodology and Uncertainty Cascade

Emissions

Concentrations

Radiative Forcing

Global Climate Models

Regional Details (Downscaling)

Impact Models (e.g. Hydrology) Obs

erva

tions

The Nile Basin

Large area (2.9 x 106 km2) Low specific discharge Spans several climate

regions Variable topography High runoff variability High Sensitivity to Climate

Mongalla

Jinja

Pakwach

Diem

Roseires

Sennar

Khartoum

Malakal

Atbara

KhashmEl-Girba

Aswan

Dongola

Mogren

Hillet Doleib

Masindi

Cairo

LakeNo

TANZAN IABU RU NDI

Gabal Awlia

Paara

-5

0

5

10

15

20

25

30

35

20 25 30 35 40

EGY PT

ETH IOPIA

D.R. CONGO

RWANDA

L IBY A

CENTRALAF RICAN

REP.

U GANDA

SU DAN

ERITRIACHAD

K EN Y A

Lake Nasser Flood & Drought Control Project (2008)

Previous Studies (1)

– 6 Transient scenarios (3 GCMs x 2 Emission Scenarios)

– Statistically downscaled using a spatio-temporal weather generator

– Changes at Dongola from 2010-2100

0

20

40

60

80

100

120

Base 2010s 2020s 2030s 2040s 2050s 2060s 2070s 2080s 2090s

Tota

l Ann

ual F

low

(BC

M)

HadCM3 A2 HadCM3 B2CGCM2 A2 CGCM2 B2ECHAM4 A2 ECHAM4 B2OBS Base

Elshamy, M.E., Sayed, M.A.-A. and Badwy, B., 2009. Impacts of climate change on Nile flows at Dongola using statistically downscaled GCM scenarios. Nile Water Science & Engineering Magazine 2: 1-14

Previous Studies (2)Elshamy et al. (2009)– 17 GCMs x A1B

scenario– Statistically

downscaled using Bias Correction Method

– Blue Nile Flow Changes: -60% to +45%

0

2

4

6

8

10

12

14

16

18

20

22

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Flow

(BCM

)

Ensemble Mean 2081-98

Observed 1961-90

Elshamy, M.E., Seierstad, I.A. and Sorteberg, A., 2009. Impacts of climate change on Blue Nile flows using bias-corrected GCM scenarios. Hydrol. Earth Syst. Sci., 13(5): 551-565.

MethodologyCoarse Scale GCM Boundary Conditions

RCM Downscaling

Fine-Scale Climate(Baseline 1950-2000 & Future 2020-2050)

Calculate Delta Change Factors (DCFs)

Modify Baseline Data (1989-2007) using DCFs

Determine Hydrological Impacts (NFS)

Methodology: Why RCM?RCM GCM

• Higher Resolution: Better Representation of shoreline and terrain

• Physical Model: Consistent Climate Elements

Methodology: Ensemble SelectionEmission Scenario A1B

1

Results: Rainfall Changes - RatiosJan2 3 4 5 6

Black: Ratio cannot be calculated White: Off Scale (>3)

1

Results: Rainfall Changes - RatiosAug2 3 4 5 6

Black: Ratio cannot be calculated White: Off Scale (>3)

1

Results: Temperature Changes - Diffs

Jan2 3 4 5 6

1

Results: Temperature Changes - Diffs

Aug2 3 4 5 6

Results: PET Changes

NFS Selected Scenario

Hydrological Changes: Blue Nile@Diem

1 2 3 4 5 6 7 8 9 10 11 12

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

Rai

nfal

l Cha

nges

1 2 3 4 5 6 7 8 9 10 11 12

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

PET

Cha

nges

1 2 3 4 5 6 7 8 9 10 11 12

-50%

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

50%

Flow

Cha

nges

Hydrological Changes: White Nile@Malakal

1 2 3 4 5 6 7 8 9 10 11 12

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

Rai

nfal

l Cha

nges

1 2 3 4 5 6 7 8 9 10 11 12

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

PET

Cha

nges

1 2 3 4 5 6 7 8 9 10 11 12

-40%

-30%

-20%

-10%

0%

10%

20%

30%

40%

Flow

Cha

nges

Conclusions • Expected ranges for changes in rainfall,

temperature, and PET are smaller than previous studies

• Changes in flows: -19% to +29% for the Blue Nile (Diem)-8% to +10% for the White Nile (Malakal)

• RCM provides a viable downscaling methodology

• RCM results confirm the uncertainty regarding the direction of change for rainfall and flow

• RCM reduced the uncertainty bandwidth but care must be taken that not all sources are included

Way Forward Collaboration within the Nile Basin to exchange data

and experience Nile countries need to Adapt to Flow Changes – In

addition to population growth– Flexibility in Water Management to face uncertainty– No regret step-wise adaptation plans

Translating Climate impacts into hydrological agricultural socio-economic, hydropower, … impacts

Further research: Expansion to other Emission Scenarios, RCMs, etc to better characterize the uncertainty, uncertainty propagation to decision making – adaptation planning