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IUKWC Workshop Nov16: Developing Hydro-climatic Services for Water Security – Session 3 – Item 5 P_Mani

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IUKWC Workshop November 2016: Developing Hydro-climatic Services for Water Security
Session 3.5 Pankaj Mani

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IUKWC Workshop Nov16: Developing Hydro-climatic Services for Water Security – Session 3 – Item 5 P_Mani

  1. 1. Incorporating Climate Change Impacts in Estimating Design Basis Flood Level at a Project Site Pankaj Mani (mailofpmani@yahoo.com) National Institute of Hydrology, Patna
  2. 2. Climate Change impacts on Water Resources Projects • Design flood hydrograph is a key input for Water Resources Projects particularly flood protection/ management works. • The design flood is computed by convoluting design storm with unit hydrograph. • The general prediction from climate change research indicates comparatively more vigorous hydrological cycle resulting into – increased precipitation (intense storm with altered temporal distribution) – Increased evaporation rates • This in turn affect the design storm and further the design flood and then the maximum flood level
  3. 3. % increase in peak of flood hydrograph with % increase in peak of UH
  4. 4. % decrease in peak of flood hydrograph with loss rate
  5. 5. Design storm distribution patterns
  6. 6. Sc-1 98 yrs data (base run) Sc-2 Highest 20% increased by 5% Sc-3 Highest 20% increased by 5% Lowest 20% decrease by 5% Sc-4 Highest 20% increased by 20% Sc-5 Highest 20% increased by 20% Lowest 20% decrease by 20%
  7. 7. Return Periods 25 50 100 1000 Scenario 1 8978 10418 12042 19208 Scenario 2 9403 11049 12945 21676 Scenario 3 9408 11025 12868 21186 Scenario 4 10603 12896 15657 29802 Scenario 5 10685 12842 15358 27317 Return Periods 25 50 100 1000 Scenario 2 4.73 6.05 7.50 12.85 Scenario 3 4.78 5.83 6.86 10.30 Scenario 4 18.0 23.8 30.0 55.2 Scenario 5 19.0 23.3 27.5 42.2
  8. 8. PMF 6842 m3/s 1.05 PMP 1.10 PMP 1.15 PMP 1.20 PMP Peak of PMF 7064 7401 7737 8073 % Deviation in PMF 3 8 13 18
  9. 9. 9 • Breach in FBC • Breach in BML • Catchment flooding • Local site rainfall Effect of climate change on maximum flood level at a plant site Case Study: NPCIL, Harayana
  10. 10. ~14.7% ~14.85
  11. 11. 11 Rainfall estimate is increased by 15% to account for the future climate change The maximum flood level is computed as RL 218.25 m which was otherwise RL 218.15 m. An increase of 0.1 m is computed due to increase in rainfall estimate by 15% Effect of climate change on maximum flood level at a plant site
  12. 12. 12 DBE
  13. 13. 13178 ha additional area is flooded DBE +CC
  14. 14. Effect of climate change on maximum flood level at a plant site Various sources of flooding: Upstream catchments floods Back water effect of Bargi dam Failure of upstream dams Local site rainfall
  15. 15. 15 The impact of climate change has been considered by increasing the rainfall by 15% and thus the corresponding river flow is computed and its effect on flooding has been estimated as 2.02 m. Effect of climate change on maximum flood level at a plant site

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