Decline of Bhagirathi-Hooghly Channel - The Ganga: Water Use in the Indian Subcontinent - page 60

Dr. Tomas Oldham said in 1870 that in olden days the main Ganga flowed
through the Bhagirathi-Hooghly channel from the foot of Rajmahal Hills; subse-
quently, it diverted to the Padma, its south-easterly branch. Dr. B. Hamilton wrote
in 1890 that after Kosi river joined it near Mungher in Bihar, the combined flow
started diverting to the Padma as its wider basin could hold the discharge better than
that of the Bhagirathi-Hooghly. Major Hirst, the then Director of the Survey of India
stated in 1870 that the Indo-Gangetic plain, as far as Haridwar, was once under the
sea. The land surface of undivided Bengal was gradually built up by the silt of rivers.
At a point of time, a subsidence occurred, which caused a line from Jalpaiguri to the
sea along the course of the Yamuna. To compensate this subsidence, certain tracts
got elevated, such as the tract north of Dhaka, known as Madhupur jungle. These
earth movements, giving rise to a series of elevations and depressions dominated
the action of rivers in the delta and are still active. To these actions, Major Hirst
attributes crucial changes of rivers, such as the changes in the courses of Teesta
and Brahmaputra in the 18th century. Such changes might have diverted the main
flow of the Ganga towards the Padma. He believed that the main river flowed on
the bed of the present Bhagirathi; thereafter, through the Hooghly after separating
from two tributaries - the Yamuna and the Saraswati near Triveni in West Bengal.
It passed near the present channel of Saptarmukhi (meaning, Hundred Mouths) and
ultimately fell in the Bay of Bengal, near the Saugar Island. According to him, the
main channel of the Ganga diverted gradually to its eastward flowing branch, near
Murshidabad. As a result, the main Ganga flowing from Rajmahal Hills to Saugar
dwindled to the present Bhagirathi-Hooghly down to Kolkata, from where it was
diverted by a cut canal, later on into the unseen channel of the Saraswati, south
of Botanical garden in Howrah. This became the present estuary of the Hooghly,
running from Kolkata to the sea. The eastern channel of the Ganga became the
present river and was subsequently joined, around 1790 AD at Jaffareganj, by the
Brahmaputra which changed its course from east of Dhaka to the west. These
were due to earth movements, depressing one place and elevating another. He also
believed that the death or decline of the tributaries across the Gangetic delta which
previously took the discharges of the Ganga, occurred owing to persistent leaning
of the river to the east, depriving them of their water through this eastward course;
this has been reflected, to a great extent, by the westward shift of the course of the
Brahmaputra.
In 1910 H. H. Haydene and E. H. Pascoe, Director and Superintendent respec-
tively of the Geological Survey of India did not quite believe the elevation and
subsidence theory. They did not think that either of these twin processes need to
be considered to explain the human aspect of the development of Bengal rivers.
They held that conditions prevailing on the Indo-Gangetic plain from early tertiary
time were not dissimilar with those existing at the present and that there was a grad-
ual subsidence, leading to the accumulation of enormously thick alluvial deposits.
Therefore, the change of the Ganga course from the Bhagirathi-Hooghly to the
Padma was not unusual. Supplies on the Ganga were caused by its continuous east-
ward shift, depriving the tributaries of their water through this course. This also was
reflected, to a great extent, by the westward shift of the Brahmaputra.