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 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) Observations

The Nile Basin  Large area (2.9 x 10 6 km 2 )  Low specific discharge  Spans several climate regions  Variable topography  High runoff variability  High Sensitivity to Climate

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

Methodology Coarse Scale GCM Boundary Conditions RCM Downscaling Fine-Scale Climate (Baseline & Future ) Fine-Scale Climate (Baseline & Future ) Calculate Delta Change Factors (DCFs) Modify Baseline Data ( ) using DCFs Determine Hydrological Impacts (NFS)

Methodology: Why RCM? RCMGCM Higher Resolution: Better Representation of shoreline and terrain Physical Model: Consistent Climate Elements

Methodology: Ensemble Selection Emission Scenario A1B

1 Results: Rainfall Changes - Ratios Jan Black: Ratio cannot be calculated White: Off Scale (>3)

1 Results: Rainfall Changes - Ratios Aug Black: Ratio cannot be calculated White: Off Scale (>3)

1 Results: Temperature Changes - Diffs Jan

1 Results: Temperature Changes - Diffs Aug

Results: PET Changes NFS Selected Scenario

Hydrological Changes: Blue

Hydrological Changes: White

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