1. In The Name Of GOD SEFIDRUD DAM DESILTATION OPERATION by M.H.Ranjbar Taklimy & E. Tolouie Sefidrud Reservoir desiltation committee, Gilan regional water board, Iran August 8-15,2005, Yichang,Hubei Province, China

2. LOCATION OF SEFIDRUD DAM AND CATCHMENT

3. SEFIDRUD RIVER SYSTEM

4. SEFIDRUD DAM Evacuating system:. 2 morning glory spillways, 3,000 m3/s. 2 auxiliary spillways, 2,000 m3/s. 5 power intakes, 160 m3/s. 5 bottom outlets, 980 m3/s. Total capacity, 6000 m3/s

5. SEFIDRUD DAM

6. Location, 250 km north west of Tehran Type, Buttress-gravity Max height, 106 m Crest length, 425 m Crest elevation, 276.95 masl (metre above sea leavel) Main purpose, Irrigation (Mostly rice field) SEFIDRUD DAM

7. SEFIDRUD RESERVOIR

8. RESERVOIR SEDIMENTATION DATA

9. FEASIBILITY OF FLUSHING OPERATION Changing the rule curve

10. FEASIBILITY OF FLUSHING OPERATION Changing the rule curve

11. FEASIBILITY OF FLUSHING OPERATION Changing the rule curve

12. FEASIBILITY OF FLUSHING OPERATION Changing the rule curve

13. FEASIBILITY OF FLUSHING OPERATION Environmental impacts

14. MITIGATION OF NEGATIVE EFFECTS In order to mitigate negative environmental impacts, comprehensive studies on environmental aspects of sedimentation and desiltaion is carried out since 2003, we hope that the result of the studies will help us to achieve sustainable development in sefidrud river system.

15. RESERVOIR SEDIMENTATION DATA

16. FLUSHING WITH FLOW DIVERSION Diversion scheme Main features

17. FLUSHING WITH FLOW DIVERSION Diversion scheme Layout

18. FLUSHING WITH FLOW DIVERSION Diversion scheme Components (a) diversion dam (b) diversion(pilot)canal

19. FIELD OBSERVATIONS Types of erosion occurred along diversion canal

20. Outflow water vs outflow sediment

21. 1:

22. Rehabilitation of reservoir capacity

23. CONCLUSION: 1- Flushing operation is a suitable tool to conserve and rehabilitate reservoir capacity, provided suitable outlet system is avilable. 2- Flow diversion to the flood plain is an effective and practical method to increase desiltation efficiency in flushing operation. 3- In sefidrud reservoir, flow diversion as a supplementary measure to flushing operation was proved to be very efficient in reducing trap efficiency of the reservoir, as presented below: trap efficiency (inflow sed.- outflow sed.) Inflow sed. during 17 years of normal operation=79%. trap efficiency during 3 years of flushing operation=37% trap efficiency during 7 years of flushing operation + flow diversion = - 96%.

24. PHOTOS

25. SEFID - RUD RESERVOIR DESILTATION Note: Foreset of deposited sediment is above power intake level

26. Different views of deposited sediment U/S of dam

29. Formation of main thalweg with in reservoir area

30. Sampling of suspended sediment

31. Qezel Owzan Diversion Dam during construction

32. View of Diversion Dam after completion

33. Digging pilot canal

34. Initial stage of diversion

35. Retrogressive erosion along pilot canal

36. Massive slide in unconsolidated deposit

37. Constructing fuse Plugg to create Hydraulic shock

39. Extensive erosion of new thalweg due to Hydraulic shock (dam break)

41. The End