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Calculated Net Evaporation from Reservoirs in the Chi-Mun River Basins, Thailand

Calculated Net Evaporation from Reservoirs in the Chi-Mun River Basins, Thailand. GISWR Term Project 2005 by Nat Marjang. Study Area. Large reservoirs in the Chi-Mun River Basins, in the northeast Thailand The basins cover about 23% of the nation area (120,000 sq.km.). Objective.

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Calculated Net Evaporation from Reservoirs in the Chi-Mun River Basins, Thailand

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  1. Calculated Net Evaporation from Reservoirs in the Chi-Mun River Basins, Thailand GISWR Term Project 2005 by Nat Marjang

  2. Study Area • Large reservoirs in the Chi-Mun River Basins, in the northeast Thailand • The basins cover about 23% of the nation area (120,000 sq.km.)

  3. Objective • To calculate monthly net evaporation over the large reservoirs in the study area (one of the input data for HEC-3)

  4. Methodology • Monthly net evaporations are calculated from: Enet = 0.7Epan – (1 – C)R Enet = Net reservoir evaporation (mm) Epan = Pan evaporation (mm) C = Runoff coefficient R = Rainfall (mm)

  5. Why this formula? Nam Phrom River Basin Pre-Project Condition Present/Future Condition Natural Flow (C*R) CR = CR[out] + CR[reservoir boundary with no water] HEC-3 Reservoir System Analysis for Conservation

  6. Why this formula? Consider the Reservoir Area CW = 1.0 Net Flow = CW*R – 0.7*Epan Depth = R – 0.7Epan + CR[res.] – CR[res.] = {CR[res.]} – {0.7Epan – R + CR[res.]} = {CR[res.]} – {0.7Epan – (1 – C)R} = Natural Flow – Net Evaporation

  7. Data Climate Station with monthly evaporation data • 10 stations inside the area • 13 stations around the area

  8. Data Rainfall stations with monthly rainfall data • 421 stations inside the area • 89 stations around the area

  9. Analysis Evaporation for April by using ArcGIS function (Kriging Method) 198.9 Error 4.5% 172.2 Error 7.1% Units: mm

  10. Evaporation for April by using Surfer program (Kriging Method) 200 m Grid size 208.0 Error 0.1% 161.9 Error 0.2% Units: mm

  11. Evaporation for April

  12. Evaporation for May

  13. Evaporation for June

  14. Evaporation for July

  15. Evaporation for August

  16. Evaporation for Setptember

  17. Evaporation for October

  18. Evaporation for November

  19. Evaporation for December

  20. Evaporation for January

  21. Evaporation for February

  22. Evaporation for March

  23. Annual Evaporation

  24. Rainfall for April

  25. Rainfall for May

  26. Rainfall for June

  27. Rainfall for July

  28. Rainfall for August

  29. Rainfall for September

  30. Rainfall for October

  31. Rainfall for November

  32. Rainfall for December

  33. Rainfall for January

  34. Rainfall for February

  35. Rainfall for March

  36. Annual Rainfall

  37. Result Enet = 0.7Epan – (1 – C)R

  38. Result Enet = 0.7Epan – (1 – C)R

  39. Enet = 0.7Epan – (1 – C)R

  40. Question ?

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