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Sedimentation in Ganga River

Ganga river basin is the largest river basin in India in terms of catchment area, constituting 26% of the country's land mass (8,61,404 Sq. km) and supporting about 43% of its population (448.3 million as per 2001 census).

The basin is bounded by the Himalayas on the north, by the Aravalli on the west, by the Vindhyas and Chhotanagpur plateau on the south and by the Brahmaputra Ridge on the east.

The Ganga rises in the Gangotri glacier in the Himalayas at an elevation of about 7,010 m in the Uttarkashi district of Uttarakhand.

The basin covers 11 States, viz., Uttarakhand, Uttar Pradesh, Madhya Pradesh, Rajasthan, Haryana, Himachal Pradesh, Chhattisgarh, Jharkhand, Bihar, West Bengal and Delhi.

The entire stretch of river Ganga (main stem) into three segments, as under:

A. Upper Ganga ≈ 294 km (Gaumukh to Haridwar): The River in the upper segment flows on steep and narrow bed, mostly rocks and boulders, carries cold water, is subjected to much less anthropogenic pollution, has highly sensitive and fragile ecosystem and biodiversity, and most importantly considered to have potential for harnessing hydropower.

B. Middle Ganga ≈ 1082 km (Haridwar to Varanasi): The River in the middle segment enters and flows in plains, meandering mostly on bed of fine sand, has wide river bed and flood plain, and most importantly modified through human interventions in terms of huge quantities of water diversion/abstraction and subjected to high degree of pollutant loads from domestic, industrial and agricultural activities.

C. Lower Ganga ≈ 1134 km (Varanasi to Ganga Sagar): The river in the third segment has experienced considerable changes in the sediment transport and deposition, causes wide spread flooding, undergoes frequent changes in her channel path, and most importantly is subjected to international disputes on flows and interventions made and/or are being carried out/planned.

Sedimentation in Ganga River Basin

Erosion, sediment transport and siltation are very complex phenomena and their estimation has inherent limitations and uncertainties. This is truer in case of large river Ganga, which exhibits large geomorphic diversity as one travels from Haridwar to Farakka.

Sedimentation in rivers has increased due to rapid urbanisation in flood plains, encroachment of river beds, changes due to human activity, and deforestation in catchment area of rivers.

Dams or barrages constructed on rivers also alter the equilibrium of flow of water and sediment in rivers.

Principles for sediment management

Essential principles to be followed for sediment management include:
(i) making sediment management a part of integrated river basin management, and
(ii) evidence based removal of silt, using best practices to minimise damage to the river flow.

Practice question:

1. Which of the following are the effects of Sediment on the Aquatic Environment?
1. Loss of coral reef communities
2. Changes in fish migration
3. Nutrient balance changes which results in turbidity

Codes:

a) 1 and 2

b) 2 and 3

c) 1 and 3

d) All

Ans: d
Exp: The environmental impacts of sedimentation include the following: loss of important or sensitive aquatic habitat, decrease in fishery resources, loss of recreation attributes, loss of coral reef communities, human health concerns, changes in fish migration, increases in erosion, loss of wetlands, nutrient balance changes, circulation changes, increases in turbidity , loss of submerged vegetation, and coastline alteration.

 

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