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DSD-INT 2019 Hydrodynamic modelling of Inner Niger Delta (DIN) - Barbet

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Presentation by Olivier Barbet, ISL Ingénierie, France, and Eelco Verschelling, Deltares, The Netherlands, at the Delft3D - User Days (Day 1: Hydrology and hydrodynamics), during Delft Software Days - Edition 2019. Monday, 11 November 2019, Delft.

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DSD-INT 2019 Hydrodynamic modelling of Inner Niger Delta (DIN) - Barbet

  1. 1. Cliquez et modifiez le titre Hydrodynamic modelling of Inner Niger Delta (DIN) Olivier Barbet (ISL) Eelco Verschelling (Deltares) Niger Basin Authority (ABN)
  2. 2. •Specify and quantify the wetland ecosystem and socio-agro- economic services provided by the annual flooding of the Inner Niger Delta (DIN) in Mali •Provide ABN (Niger Basin Authority) and the governments of Mali and Guinea with all the indicators that will enable them to decide on development choices to implement in the Niger Basin •Provide NBA with a modeling tool able to simulate different development scenarios 2 Project objectives
  3. 3. Today, a not recommended area ➔ Dependency on open data and very old local data One of the first consultancy projects with the new lateral 1D2D coupling in Delft3D FM Suite 3 Interesting and Challenging project
  4. 4. Inner Niger Delta (DIN area) 4 Niger Basin ~ 4 200 km (5 countries) ~ 2,2 Mkm² (9 countries)
  5. 5. Faguibine Lac Takara Lac Kamango Lac Gouber Lac Télé Lac Fati Lac Horo Lac Aougoundou Lac Niangaye Lac Do Lac Garou Lac Haribonga Lac Korarou Lacs Debo et Walado Lac Korientzé Yearly Inundation area: 36 000 km² Around 400km in length Total area : 250 000 km² Lac Takadji Lac Tanda Lac Kabara 5 Inner Niger Delta
  6. 6. Fomi dam (planned) Large irrigation area (Office du Niger) Selingue dam 6 Impact of upstream projects on DIN stakeholders?
  7. 7. MIKE-BASIN model of Upper Niger basin Delft3D FM 1D2D MODEL OF DIN area IMPACT ASSESSMENT MODELS / ECOSYSTEM SERVICES MODELS Modelling tools 7
  8. 8. MIKE-BASIN model of Upper Niger basin Delft3D FM 1D2D MODEL OF DIN area IMPACT ASSESSMENT MODELS / ECOSYSTEM SERVICES MODELS Modelling tools – this presentation 8
  9. 9. 9 Field information Structure of hydrodynamic model Modelisation area Representation in the model => Rivers in 1D => Inundation area in 2D
  10. 10. 10 Construction – basic data • 1D stream network : open access EO images (Landsat – 8) • river geometry : (very old ~1980) surveyed cross sections in paper format • 2D surface levels: open access DEM/DTMs (SRTM/MERIT) • limited information on secondary networks and hydraulic structures Structure of hydrodynamic model
  11. 11. 11 Construction – basic data illustration - 1D streams - method: GIS Structure of hydrodynamic model Digitalization of network from Landsat 8 images ➔ 99 polylines on the study area ➔ Good correspondance with MERIT DEM
  12. 12. 12 Construction – flexible mesh Structure of hydrodynamic model Cut river from 2d grid to prevent double counting Lateral 1d2d links Finer gridcells closer to the river Mopti : confluence Niger / Bani
  13. 13. 13 Forcing Structure of hydrodynamic model Rating curve at Taoussa Direct Precipitation & PET on the grid (source: Earth2Observe / open access ) Inflows (MIKE-BASIN & OBSERVED)
  14. 14. 14 Calibration data used - Levels and rating curves at a limited number of gauging stations - Inundation patterns derived from Satellite Images (MODIS) using appropriate water indices (MNDWI / NDMI1) Model calibration 1 (Modified) Normalised Difference Water Index
  15. 15. 15 - Model ready - Currently running climate scenarios and strategies - Providing the results (inundation areas, durations, heights,…) for the socio- agro-economic services model - Preparation for the training of NBA’s experts Current status
  16. 16. Some lessons learned • 1D2D link works well • Much easier to combine different resolutions compared to SOBEK 1D2D (nested grids…) • Lot of work needed to align MERIT DEM with local data • Calibration results were surprisingly well, given state of data • Year-round wetland modelling using Delft3D FM 1D2D could benefit from inclusion of simple groundwater model to model infiltration & exfiltration Interesting aspects & Challenges: • One of first consultancy projects with 1D2D coupling in Delft3D FM • Dependency on open data and old local data
  17. 17. Thank you! Questions?

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