UMIAM LAKE

FACING EXTINCTION!

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.

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.

What reveals the grim scenario!

Hydrographic survey Water quality analysis Situation analysis & assessment study of lake

catchments. Sediment flow rate data.

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.

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.

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.

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.

CYCLIC ACTIVATED SLUDGE TECHNOLOGY

RESERVOIRS – Meant for ~

• FLOOD CONTROL• IRRIGATION• DRINKING WATER• HYDROPOWER• INDUSTRIAL

Endangered by Sedimentation

RESERVOIR SEDIMENTATION PROBLEM

• STORAGE CAPACITY LOSS

• DECREASE OF LIFE TIME

SEDIMENTATION FACTORS• RESERVOIR SHAPE• SEDIMENT CHARACTERISTICS• RESERVOIR OPERATION• SEDIMENT/ RESERVOIR VOLUME RATIO

• INFLOW CAPACITY RELATIONSHIP

DEPOSIT AREA

Back Water Area

Delta formation Area

Bottom Deposit Area

Reservoir Level

DAMStreambed

STAGE: II

Flood control space

Conservation Storage

Inactive Storage

Dead StorageOutlet

STAGE: III

Flood control space

Conservation Storage

Inactive Storage

Dead StorageOutlet

STAGE: IV

Flood control space

Conservation Storage

Inactive Storage

Dead Storage Outlet

STAGE: V

Flood control space

Conservation Storage

Inactive Storage

Dead Storage Outlet

BACKWATER DEPOSIT CHARACTERISTICS

• COARSE SAND & GRAVEL• UPSTREAM DEPOSIT ABOVE RESERVOIR

LEVEL• DEPOSIT GROWS UPSTREAM & RESERVOIR • POSSIBLE EROSION DURING HIGH POOL

WATER LEVEL

BOTTOM DEPOSIT CHARACTERISTICS

• SILT & CLAY• TRANSPORTED BEYOND DELTA• SEDIMENTATION CLOSE TO DAM• RESERVOIR TURBIDITY

FLUSHING

Flood control space

Conservation Storage

Inactive StorageDead Storage Outlet

SLUICE OPEN – RAINY SEASON

WATER & SEDIMENT

HYDROSUCTION BYPASSING

Outlet

SEDIMENT DIVERSION

BYPASS PIPELINE

SEGMENTATION & DRY EXCAVATION

AREA CLOSED BY DYKES & DRIED FOR EXCAVATION

DYKE CUM ROAD FOR

MACHINERY

DREDGING

• Material• Process• Dredger types• Disposal

.

Thank You.