What:
Chitale committee on Desiltation of Ganga has recommended a slew of measures which includeStudy of reach wise sediment transport processes
Establishing annual sediment budgets to guide de-silting activities
Preparation of annual reports (sand registry) describing the previous de-silting/ dredging activity
A technical institute to conduct the sediment budget, morphological and flood routing studies that would examine and confirm the necessity of the de-silting of the reach under consideration.
Background
The committee was constituted in July 2016 by the Ministry of Water Resources River Development and Ganga Rejuvenation
It was to prepare guidelines for desiltation of river Ganga from Bhimgauda (Uttarakhand) to Farakka (West Bengal).
The committee was asked to establish difference between desilting and sand mining and also to establish need for desilting for ecology and e-flow of the river Ganga.
It was to prepare guidelines for desiltation of river Ganga from Bhimgauda (Uttarakhand) to Farakka (West Bengal).
The committee was asked to establish difference between desilting and sand mining and also to establish need for desilting for ecology and e-flow of the river Ganga.
What committee says?
Erosion, sediment transport and siltation are very complex phenomena.
It is impossible to apply a “one-size-fits-all‟ approach to sediment management and control, because the issues involved are frequently very regionally-specific.
Local factors such as topography, river control structures, soil and water conservation measures, tree cover, and riparian land-use or land disturbance (for example agriculture, mining, etc.) can have a large impact on sediment loads in rivers.
River control structures (such as reservoirs), soil conservation measures and sediment control programmes can cause downstream sediment loads to decrease, while factors such as land disturbance (clearing of vegetation, for example) or agricultural practices can cause increased sediment loads.
Indiscriminate de-siltation works may result into more harm to ecology and environment flow.
Thus, there is a need to evolve G. uidelines, better broad principles, while planning and implementing de-silting works.
Ganga
Sediment transport and siltation in large rivers like Ganga are very complex phenomena and their estimation has inherent limitations and uncertainties.
Sedimentation is mainly seen downstream of Bhimgauda barrage and near the confluences of tributary rivers with Ganga.
The discharge congestion, large scale sediment deposition and its negative effects are mainly seen downstream of the confluence of Ghagra and beyond.
The river flood plain drastically widens beyond the confluence of Ghagra and is estimated to be around 12 to 15 kms.
It is impossible to apply a “one-size-fits-all‟ approach to sediment management and control, because the issues involved are frequently very regionally-specific.
Local factors such as topography, river control structures, soil and water conservation measures, tree cover, and riparian land-use or land disturbance (for example agriculture, mining, etc.) can have a large impact on sediment loads in rivers.
River control structures (such as reservoirs), soil conservation measures and sediment control programmes can cause downstream sediment loads to decrease, while factors such as land disturbance (clearing of vegetation, for example) or agricultural practices can cause increased sediment loads.
Indiscriminate de-siltation works may result into more harm to ecology and environment flow.
Thus, there is a need to evolve G. uidelines, better broad principles, while planning and implementing de-silting works.
Ganga
Sediment transport and siltation in large rivers like Ganga are very complex phenomena and their estimation has inherent limitations and uncertainties.
Sedimentation is mainly seen downstream of Bhimgauda barrage and near the confluences of tributary rivers with Ganga.
The discharge congestion, large scale sediment deposition and its negative effects are mainly seen downstream of the confluence of Ghagra and beyond.
The river flood plain drastically widens beyond the confluence of Ghagra and is estimated to be around 12 to 15 kms.
Is it beneficial?
Though de-siltation works can improve hydraulic performance of the river, these have no direct role in improving environment flow in the river.
On the other hand, indiscriminate de-silting or sand mining would cause adverse impacts on river e-flow.
Basic principles of siltation in rivers:
Catchment Area Treatment and Watershed Development works, along with good agricultural practices and river bank protection/anti-erosion works, are necessary to reduce silt inflow into the river system
Erosion, movement and deposition of sediment are natural regulating functions of river and Sediment equilibrium of river should be maintained.
Rivers should be provided with sufficient flood plains (lateral connectivity) without any hindrance to the flow.
Instead of “keeping the silt away”, strategy to “giving the silt way” should be adopted.
Though de-siltation works can improve hydraulic performance of the river, these have no direct role in improving environment flow in the river.
On the other hand, indiscriminate de-silting or sand mining would cause adverse impacts on river e-flow.
Basic principles of siltation in rivers:
Catchment Area Treatment and Watershed Development works, along with good agricultural practices and river bank protection/anti-erosion works, are necessary to reduce silt inflow into the river system
Erosion, movement and deposition of sediment are natural regulating functions of river and Sediment equilibrium of river should be maintained.
Rivers should be provided with sufficient flood plains (lateral connectivity) without any hindrance to the flow.
Instead of “keeping the silt away”, strategy to “giving the silt way” should be adopted.
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