Decline of Bhagirathi-Hooghly Channel - The Ganga: Water Use in the Indian Subcontinent - page 66

In the light of the above, the fact remains that following gradual reduction of
water volume of the Bhagirathi-Hooghly since the 16th century, the Bhagirathi basin
was continuously silted. Its load started depositing at the mouth and the bed owing
to the reduction in velocity and gradually raised the bed. The passage of water was
blocked continuously, causing further reduction in flow. Reaks gave an account of
such reduction in 1919. The Bhagirathi on which large boats plied throughout the
dry season of 1840-1841 gradually worsened from next year. Boats of only 2 6
draft could pass and in 1842-1843 it was more obstructed than in previous 5 years,
giving rise to many complaints. With great difficulty, a depth of about 3 feet was
maintained in the next dry season and by 1845-1886 a passage was secured for
boats of 2 draft. In the next season, the entrance was so unfavourable that it closed
in February, 1846 and by May, the depth fell to one foot . The entrance in 2008

tended south-east from the Bhagirathi about 5 km (3 miles) from the mouth and
inclined downstream of the main current. The bed of the Bhagirathi at the entrance,
which at the end of April 1913 was 54 9 above Kidderpur (Khidirpur) Old Dock
Sill (K.O.D.S.) and about 20 feet higher than the bed of the Farakka channel,
appears to have risen higher since, being 55 6 at the end of October 1914, 57 6 at
the end of October 1915, and in the last dry season of 1918, it was 62 9 above
datum. The Ganga level at the mouth falls lowest to about 50 feet above datum. The
relationship of K.O.D.S. level with the G.T.S. level is shown in Fig. 6.2.
While the entrance is closed by sand, blocking any influx from the Ganga, the
Bhagirathi, lower down, carries a stream which apparently increases progressively.
This supply can only be due to percolation of subsoil water through the bed and the
banks. Its source is usually attributed to the Ganga but this view cannot be easily
accepted, because at a low stage, in the dry season with a sand bar blocking the
mouth, the level of water in the Bhagirathi is much higher than in the Ganga, to
the extent of 4 -5 and even more. This water percolates through the sand at the
entrance, draining the Bhagirathi into the Farakka channel. The Hooghly, Reaks
added, 'is tidal throughout the dry season'. During ordinary spring tides in the dry
season, a flood current is noticed as far up as about 13 km (7 miles) south of Nadia
district and during the highest spring tides, a slight upward current is sometimes
seen in Nadia

...

...

. Considering this normal natural phenomenon, the section of the
Bhagirathi from Kalna to Dumurdaha is the tidal head of the river during the freshet
season. The down-flowing current, surcharged with silt, meets the tide here; the
velocity is checked and deposition occurs.
In 1774 and 1776 respectively, H. Wedderbourne and J. Richie who also studied
the Hooghly conditions in those days, held that the river had deteriorated gradu-
ally, because of shoaling and contraction of its deep channels from accumulation
of silt and that under such conditions, deterioration will continue. In a report to
the Lieutenant Governor of Bengal, they said, every means has to be taken to avert
a catastrophe, with the aid of highest engineering skill. They also recommended
minute and periodical survey of the whole length and breadth of the river from
Kolkata to the sea.
In 1853-1854, Piddington, a member of the Hooghly Commission, reviewed the
deterioration from a more scientific angle. He said, 'I am of the opinion that it is