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Projected Changes in Nile Flows: RCM Results

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.

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Projected Changes in Nile Flows: RCM Results

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  1. Projected Changes in Nile Flows: RCM Results Mid-Term Workshop Climate Change Risk Management Programme Forecasting & IWRM Component Prepared by: Nile Forecast Center

  2. Outline 1. Modeling Climate Change Impacts 2. Pervious Studies on the Nile 3. Study Methodology 4. Results 5. Conclusions

  3. Modeling Climate Change Impacts Methodology and Uncertainty Cascade Emissions Concentrations Radiative Forcing Global Climate Models Regional Details (Downscaling) Observations Impact Models (e.g. Hydrology)

  4. 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

  5. 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 Lake Nasser Flood & Drought Control Project (2008) 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

  6. 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., 2009. Impacts of climate change on Blue Nile flows using bias-corrected GCM scenarios. Hydrol. Earth Syst. Sci., 13(5): 551-565.

  7. Methodology Coarse 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)

  8. Methodology: Why RCM? RCM GCM • Higher Resolution: Better Representation of shoreline and terrain • Physical Model: Consistent Climate Elements

  9. Methodology: Ensemble SelectionEmission Scenario A1B

  10. Results: Rainfall Changes - Ratios Jan 1 2 3 4 5 6 White: Off Scale (>3) Black: Ratio cannot be calculated

  11. Results: Rainfall Changes - Ratios Aug 1 2 3 4 5 6 White: Off Scale (>3) Black: Ratio cannot be calculated

  12. Results: Temperature Changes - Diffs Jan 1 2 3 4 5 6

  13. Results: Temperature Changes - Diffs Aug 6 1 2 3 4 5

  14. Results: PET Changes NFS Selected Scenario

  15. Hydrological Changes: Blue Nile@Diem

  16. Hydrological Changes: White Nile@Malakal

  17. 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

  18. 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

  19. THANK YOU

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