Decline of Bhagirathi-Hooghly Channel - The Ganga: Water Use in the Indian Subcontinent - page 64

catastrophe, diminishing the flow in the Bhagirathi-Hooghly channel. Similar tec-
tonic change or catastrophe might have changed the Brahmaputra course too from
east of Madhupur to its present course, west of this area. While many experts believe
that the change in the Brahmaputra's course occurred between 1720 and 1830, that
of the Ganga came much earlier, probably in the 14th or 15th century. As the Bengal
delta was formed by the alluvial deposits of the Ganga, the Brahmaputra and the
Meghna, not so long ago, the entire basin was susceptible to high tectonic and mor-
phological changes. Added to this was human interference through agriculture and
other activities which might have more often caused such changes.
Causes and Extent of Deterioration
Though more and more flow of the Ganga diverted to the Padma, no danger to the
Bhagirathi-Hooghly river was seen until about 200 years ago. Rivers of Nadia -
Bhairab, Jalangi and Mathabhanga-Churni were also carrying sufficient discharge
from the Padma, round the year, which kept the Bhagirathi-Hooghly channel deep
and wide. The tributaries from the right were also adding sufficient but ephemeral
flow during monsoon months. This collective upland flow kept the entire river sys-
tem clear and did not let it deteriorate through siltation. Gradual south-easterly
diversion of the main flow from 18th century generated in the Ganga a tendency
to flow through the Padma, making it gradually the main river. Even Nadia rivers
carried less and less flow and became moribund.
In 1930, G. C. Chatterjee listed the causes of deterioration of the Ganga's dis-
tributaries. He compared a river to a headless estuary and observed that an estuary,
the flow of whose feeder river had diminished, would die in no time. He imag-
ined the Gangetic delta as a triangular island with its apex at the confluence of
the Bhagirathi with the Ganga at Geria; its western boundary was the Bhagirathi-
Hooghly and the eastern was a curvilinear line, formed by the bed of the Ganga
from the apex of the mouth of the Gorai-Madhumati and the bed of the latter river.
Its base-line was formed by the sea, between the outlets of the Hooghly and the
Madhumati in the Bay of Bengal. The apex was not a point but a line prolonged
like the beak of a bird whose two parts are the channel from Geria to near the
foot of Rajmahal Hills. The upper part is formed by the bed of the Ganga and the
lower by the Farakka channel - a dry branch of the Bhagirathi between Suti and the
Bhagirathi offtake. It existed in those days but was covered with swamps, marshy
land and agricultural fields. The mouth of the dry channel was not static; it was
near Kissengunj but shifted gradually to Nurpur and is now at Geria. The upper part
of the delta is traversed by Jalangi, a tributary of the Ganga and the lower part by
Mathabhanga-Churni; both join the Hooghly at Nabadweep and Ranaghat.
Besides, the fluvial force, created by the current formed in rivers, flowing from
mountainous regions, joins the tidal force and during ebb tide, scours the bed; it
does the contrary during flow-tide. This way, it cleans the silt deposits in the lower
reaches. It is obvious, therefore, that more water a river brings from its mountain