projected changes in nile flows: rcm results
DESCRIPTION
Projected Changes in Nile Flows: RCM Results. Mid-Term Workshop Climate 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. - PowerPoint PPT PresentationTRANSCRIPT
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