1. UMIAM LAKE FACING EXTINCTION!

2. Umiam Lake - Snippets  Reservoir of Umiam Hydel Project – Stage I.  Commissioned in 1965 – Ist Hydel Project of NE.  Area –10.27 sq km; Area of catchment –220 sq km  Engineering marvel with life span till 2115 faces extinction within 2040 if present ecological impingement continues unabated.  Immense tourism potential besides power generation remains to be harnessed.

3. FACTORS ENDANGERING LIFE OF LAKE.  Colossal flow of the following from catchments:  Sediment & Silt.  Sewage.  Solid Waste.  Multiple pollutants.  Rise of lake bed level due to enormous deposit of above materials reducing volume of water holding capacity.  What causes such inflow into the lake:  Topographical location – valley; surrounded by hilly catchments.  Extensive ecological degradation including loss of forest cover in catchments made soil totally vulnerable to erosion & displacement.  Multiple network of streams originating & flowing through catchments discharge into Wah Umkhrah or Umshyrpi which join with Wah Roro & finally drain into the lake.

4. What reveals the grim scenario!  Hydrographic survey  Water quality analysis  Situation analysis & assessment study of lake catchments.  Sediment flow rate data.

5. Factors responsible for denigration of catchments:  Hilly terrain with deep gorges & ravines.  Extensive loss of forest cover rendering vast stretches into “open” land exposed to severe erosion leading to destabilization of soil profile & structure.  Population growth and human activities like deforestation; diverse land use pattern; faulty cultivation; lack of soil & water conservation; random mining & quarrying; unplanned development of road, buildings et al.

6. Is the situation beyond salvage? Grim! But not yet if we act now.  Implement tangible remedial & preventive measures simultaneously.  Multi pronged approach both short & long term.  Administrative measures & enactment of relevant prohibitive Acts & invoking existing ones with diligence.  People’s participation through mass awareness & sensitization campaign.

7. Interventions ~  Holistic Action Plan for reclamation & rehabilitation of catchments: Massive afforestation programme – all other measures incidental & essential with depletion of this cover.  Extensive soil conservation measures with focus to check run-off & haphazard movement of water to the lake.  Stream management strategy to check silting of such seasonal / perennial drainage channels; reducing flooding & maintaining optimal capacity to canalize storm water.  Essence of rehabilitation need to be based on National River Conservation Plan & National Lake Conservation Plan.  Regulate inflow into Lake.

8.  A viable cyclic technology for treatment of sewage, effluent & other pollutants and regulating sediment, plastic, paper et al in waste water including tertiary treatment before transfer is allowed into the lake.  An alternative route for sewage transfer avoiding the lake.  Dredging & Excavation – most effective mechanism to remove huge silt and other contaminant deposit.  Plug possible seepage points evident in reservoir revealed from down stream discharge study.  Engineering structures as ancillary preventive measures.  Remedial measures primarily desiltation techniques like flushing, density current venting, sluicing et al is imperative.

9. CYCLIC ACTIVATED SLUDGE TECHNOLOGY

10. RESERVOIRS – Meant for ~ FLOOD CONTROL IRRIGATION DRINKING WATER HYDROPOWER INDUSTRIAL Endangered by Sedimentation

11. RESERVOIR SEDIMENTATION PROBLEM STORAGE CAPACITY LOSS DECREASE OF LIFE TIME

12. SEDIMENTATION FACTORS RESERVOIR SHAPE SEDIMENT CHARACTERISTICS RESERVOIR OPERATION SEDIMENT/ RESERVOIR VOLUME RATIO INFLOW CAPACITY RELATIONSHIP

13. DEPOSIT AREA Back Water Area Delta formation Area Bottom Deposit Area Reservoir Level DAM Streambed

14. STAGE: II Flood control space Conservation Storage Inactive Storage Dead Storage Outlet

15. STAGE: III Flood control space Conservation Storage Inactive Storage Dead Storage Outlet

16. STAGE: IV Flood control space Conservation Storage Inactive Storage Dead Storage Outlet

17. STAGE: V Flood control space Conservation Storage Inactive Storage Dead Storage Outlet

18. BACKWATER DEPOSIT CHARACTERISTICS COARSE SAND & GRAVEL UPSTREAM DEPOSIT ABOVE RESERVOIR LEVEL DEPOSIT GROWS UPSTREAM & RESERVOIR POSSIBLE EROSION DURING HIGH POOL WATER LEVEL

19. BOTTOM DEPOSIT CHARACTERISTICS SILT & CLAY TRANSPORTED BEYOND DELTA SEDIMENTATION CLOSE TO DAM RESERVOIR TURBIDITY

20. FLUSHING Flood control space Conservation Storage Inactive Storage Dead Storage Outlet SLUICE OPEN – RAINY SEASON WATER & SEDIMENT

21. HYDROSUCTION BYPASSING Outlet SEDIMENT DIVERSION BYPASS PIPELINE

22. SEGMENTATION & DRY EXCAVATION AREA CLOSED BY DYKES & DRIED FOR EXCAVATION DYKE CUM ROAD FOR MACHINERY

23. DREDGING Material Process Dredger types Disposal

24. . Thank You.