Decline of Bhagirathi-Hooghly Channel - The Ganga: Water Use in the Indian Subcontinent - page 71

river was in spate, the Bhagirathi got a good share of the flood-water, increasing
from a mere one cusec to 3,000 cusecs in August and September. The higher dis-
charge period, however, gradually reduced from the major part of the year to only
about 2 months from the beginning of July to the end of August. For the remaining
10 months, the river at Raghunathpur was a dry bed with a few pools of shallow
water, here and there. The floor of the Bhagirathi, near the offtake point, looked like
a hanging valley, about 15 m higher than the bed of the Ganga.

River Below Offtake

The deterioration of the Bhagirathi-Hooghly began like this from the 16th century;
the upland discharge gradually came down in monsoon months. The mouth was
blocked by silt and the bed too silted following movement of sediment from the
upland discharge and the sea, carried during the flow-tide. The Bhagirathi used to
be nearly moribund in April and May with sand-bars and stagnant pools of water in
between. Navigation became impossible in these months in the upper reach and even
country boats could not ply. People crossed the river on foot and also by improvised
bridges at various points and water for agriculture and drinking became scarce.
Though in the lower reach of the Bhagirathi, some tributaries fell into it and
added some flow in monsoon months, the depth was not enough for navigation in
lean season. The aggradation of the river-bed was caused by reduced flow from the
Ganga at its mouth as also by less time over a number of years. Practically cut off
from the mother-river by a wide sand island at the mouth, the river survived only
by local rainfall, except in monsoon months. The dry weather flow was negligible,
being on an average, 0-2 cusecs for 7 months, from December to June. Table 6.2

Table 6.2 Discharge at offtake point of Bhagirathi near Jangipur

Water level and discharge

Minimum level (m)
Discharge (cumec)

Maximum level (m)
Discharge (cumec)

Time span
(days) Year

1 2 3 4 5 6

1915 15.05 3.10 21.40 2,554 190

1920 16.86 5.80 20.70 1,892 150

1926 14.42 3.60 19.96 1,317 175

1930 14.92 13.30 21.26 2,109 170

1935 14.94 1.60 21.43 2,053 138

1940 14.88 4.60 20.69 2,006 165

1945 15.10 25.00 21.22 1,572 178

1950 15.00 20.10 20.86 1,927 136

1955 14.39 18.20 20.97 1,472 191

1960 14.73 17.10 20.85 1,773 156

1965 13.52 1.10 19.18 1,409 142

1970 14.48 3.70 19.45 1,306 122

1972 14.63 2.90 18.91 952 84