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DSD-INT 2018 Simulating sediment transport in irrigation systems using Delft3D - Abd Al-Amear Theol


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Presentation by Shaimaa Abd Al-Amear Theol, IHE Delft Institute for Water Education, The Netherlands, at the Delft3D - User Days (Day 1: Hydrology and hydrodynamics), during Delft Software Days - Edition 2018. Monday, 12 November 2018, Delft.

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DSD-INT 2018 Simulating sediment transport in irrigation systems using Delft3D - Abd Al-Amear Theol

  1. 1. SIMULATING SEDIMENT TRANSPORT IN IRRIGATION SYSTEMS USING DELFT3D Case study: Gizera irrigation scheme, Sudan Shaimaa A. Theol Bert Jagers* Suryadi, Charlotte de Fraiture *Deltares
  3. 3. PROBLEM STATEMENT Sedimentation is a major problem in irrigation systems since it may cause: • Raising canals bed levels • Disruption of water distribution - “ unfair water distribution” • Blockage of outlets • Structure functions elimination • High maintenance costs for sediment removal
  4. 4. JUSTIFICATION • Typically 1D models are used to study irrigation canals as they are computationally most efficient; • The use of 2D model has been chosen to study sediment patterns near offtakes and structures in more details. Other studies and models Delft3D model Cohesive and non- cohesive Multi-dimensions (2D, 3D) models Networks (DD) tool Operations practice (RTC) tool Non-cohesive sediment mostly 1D models
  5. 5. STUDY AREA Zanada, width = 6m, length=17 Km, S=0.00002, SS=1:1, there are weirs and two contractions. Toman, width=2 m, length=6 Km, S=0.00001, SS=1:1 with gate
  6. 6. METHODOLOGY AND CHALLENGES • Getting the details of case study from Google Earth, data was in spherical coordinates. • Constructing the grid with coarse resolution where the selected canals have a small width. • Validate Delft3D with other 1D-model which is used in irrigation canals. • Adapting wall roughness for the canals. • Using DD tool close to the area of interest to avoid the long simulations periods. • Applying different scenarios.
  7. 7. SCENARIOS • Reference case (gate full open, weir1=weir2=0.3 m) • Upstream weir (raising and lowering the weir height) • Downstream weir (raising and lowering the weir height) • Fixed gate openings (0.2, 0.4, 0.6, 0.8) m. • Operation (Plan 1 and Plan 2)
  8. 8. RESULTS
  9. 9. Cont. Results (-): The reduction in sediments deposition, (+): The increase in sediments deposition. 1 = strongly not satisfied, 2= poor, 3= satisfied, 4= quite satisfied, 5= strongly satisfied Scenarios Description Main Branch Meeting Cohesive Non-cohesive Cohesive Non-cohesive CWR Scenario 2 Weir effects Upstream weir w1=0 -0.50% -0.50% No change No change 5 w1=0.6 1% 1% 2% 2% 4 Downstream weir w2=0 No change No change 3% 3% 4 w2=0.6 No change No change -12% -12% 5 Scenario 3 Gate effect Fixed gate height g=0.2 4% 4% -99% -99% 1 g=0.4 4% 4% -96% -96% 2 g=0.6 3% 3% -71% -71% 3 g=0.8 1% 1% -19% -19% 4 Operation Plan1 -0.10% -0.10% No change No change 5 Plan2 3% 3% -54% -55% 4
  10. 10. G=0.2 m G=0.8 m Plan 1 Plan 2
  11. 11. Conclusions • Delft3D 4 has been helpful in the analysis, however, I had to use a rather coarse model to keep run times acceptable. • The position of the controlled weirs has a significant influence on their effectiveness. • By adjusting the gate of the branch canal depending on the upstream discharge I was able to meet (CWR) in a satisfactory manner while significantly reducing the overall sedimentation. • For variable sediment concentrations, OP2 is vital to be used. The gate can be closed when high concentrations enter the canals and opened with less concentrations.
  12. 12. Recommendations • Delft3D 4 can be efficiently used in simulations of sediment transport in irrigation systems. • For future studies I propose to use the Delft3D FM Suite as it will allow to keep run times short by using 1D mode for the long straight canals while simulating the areas of interest at higher resolution in 2D or 3D.