GUWAHATI, June 18 – Leading hydro-biology expert of the State, Prof SP Biswas is of the opinion that dredging can be undertaken to make the Brahmaputra bed deep enough for the purpose of enhancing its water holding capacity. It will have no adverse impact on the aquatic biodiversity of the Brahmaputra river system, he maintained.
Prof Biswas, who is working with the Dibrugarh University, was contacted by The Assam Tribune for his observations on the proposed bid to excavate the silted bed of the Brahmaputra and construct two expressways on the both banks using the excavated silt.
Prof Biswas said dredging of the river is essential. It is not adverse to aquatic biodiversity; rather, it will create the much-needed cover for the aquatic mega-fauna, he said.
He, however, maintained that construction of embankments or expressways on both sides of the river should be done in such a way that connectivity of the river with other channels and natural wetlands remains undisturbed.
The Brahmaputra is like a highway. It always has the provision for extra space for smooth traffic and the wetlands connected with it also act as reservoirs for holding its excess water, he said.
The professor said he had seen how the dredging of the Kushiyara in Bangladesh was able to restore the river. Now the river is a prominent habitat of the Gangetic dolphin and other large fish species, he added.
Removing silt will not affect the benthic organisms or productivity of the Brahmaputra as its sandy bed is not stable. The Brahmaputra is counted among the highest silt-laden rivers in the world. In fact, coarse sand engulfs the upper stretches of the river and hence, removing this sand layer will have no adverse impact on the rivers biodiversity, Prof Biswas said.
He opined that dredging of the Brahmaputra bed should be carried out as a continuous process as the river is silted up after every flood season because of the high sediment load.
During the rainy months of May to October, the river water remains highly turbid and water velocity often exceeds 40 cm per second. This means primary production in the river is very low during the monsoon months, he said.
It is the adjacent floodplain beels (wetlands) which not only provide food and shelter for most of the riverine species but also breeding grounds for them, he said.
Moreover, beels hold excess floodwater. These water bodies are the natural sinks for flood mitigation, he added.
In the past, a Himalayan blunder was committed by constructing embankments across the Brahmaputra and its tributaries without keeping any provision for lateral passage of river water to these wetlands, he said.
I do not know how much flood is controlled in our State, but one thing is certain the fish production in the affected beels has seen a declining trend over the years, Prof Biswas said referring to consequences of such embankments.
Source : http://assamtribune.com