Indiscriminate desiltation work can cause “more harm” to a river’s ecology, a high-level panel formed to prepare guidelines for desilting work of 2,525-km Ganga river has said. Countering the popular perception that desiltation improves river’s ecology and its e-flow (environment flow), it has argued that if carried out properly, at best, it could only improve the hydraulic performance of the river.
In its draft report submitted to the Union Water Resources Ministry, the Madhav Chitale-led committee has recommended the Government to make institutional arrangement to appraise any proposal for desiltation works by forming a national-level technical agency.
In the case of Ganga, it has suggested the for entrusting Ganga Flood Control Commission (GFCC), with additional mandate to carry out such studies. GFCC works out plans to control inundation of the river basin.
The four-member committee has advocated such institute to conduct sediment budgeting, morphological and flood routing studies that would substantiate necessity of desilting a river stretch concerned.
The committee also called for avoiding encroachment on the river's flood plain areas, by generally avoid dredging in Ganga and pitched for providing the river with sufficient flood plain areas.
The panel has also insisted on encouraging agricultural practices along flood plains in a way that it does not disturb passage of flood by increasing resistance to flow. The Committee has the opinion that desiltation works can at best improve hydraulic performance of the river and have no direct role in improving ecology and/or environment flow in the river.
Underscoring the need for realising value of sediment and viewing it as an asset, the panel has argued that gravel in a river has a role to play in providing spawning habitat for fish, aerating water with oxygen by increasing local roughness and inducing turbulent flows.
“De-silting/dredging may restrict over bank flow, thereby reducing ground water recharge and flood detention in adjoining low-lying areas, and consequently, reduction in base flow,” the panel has warned.
Insisting the Government to undertake in a comprehensive way river catchment area treatment, it said watershed development and river bank protection works to reduce silt inflow in Ganga.
