Agreements & MOUs - The Ganga: Water Use in the Indian Subcontinent - page 206

disposal over land at suitable locations was absolutely necessary to keep the chan-
nel silt-free. If 40,000 cusecs of water were released from 1976 continuously, the
reach would have improved and become silt-free. Dredging can be done, even now,
to maintain the depth of the channel.
The river reach from Kashipur to the Hooghly Point in the immediate down-
stream vicinity of Calcutta Port area substantially improved after the induction of
upland discharge from Farakka. The cubic capacity of the reach increased steadily
since 1976, as can be seen from positive percent variations because of increased
tidal influence added with the velocity of upland discharge in this reach. The silt-
load mostly remains mobile, not getting deposited. The Port authority resorted to
continuous dredging to keep the navigation channel silt-free, although its quantum
has been reduced substantially from 1975, as seen in Table 10.13. The percent
reduction of dredging is varying, as per requirement; still the improvement is
substantial.
In some of the years, e.g. 1982-1983, 1986-1987, 1996-1997 and 1998-1999
and some other years, not mentioned in the table, dredging was nominal, or dis-
turbed following break-down of port dredgers. Mean navigable depths over the
bars in the lean season, from January to May, every year and over the crossings
have increased substantially after the induction of upland discharge, as seen in
Table 10.14.
The table shows the increases in mean navigable depths over six bars below
Calcutta Port area in the lean season since 1975; percent increase in depth was
as under:

(i) Panchpara 13-32%

(ii) Sankrail 40-101%

(iii) Lower Munikhali 47-84%

(iv) Pirsareng 5-36%

Table 10.13 Quantum of dredging in the Hooghly river from port area to Hooghly point

Percentage
variation w.r.t.
1975-1976 (+)
or (-)

Percentage
variation w.r.t.
1975-1976 (+)
or (-)

Quantity of
dredging
(10 6 M 3 )

Quantity of
dredging
(10 6 M 3 ) Year Year

1 2 3 4 5 6

1972-1973 1.92 - 1986-1987 0.28 (-)75.0

1973-1974 2.02 - 1987-1988 0.56 (-)50.0

1974-1975 1.12 - 1991-1992 0.75 (-)33.0

1975-1976 1.43 - 1992-1993 0.95 (-)15.20

1976-1977 0.88 (-)21.40 1995-1996 0.32 (-)71.40

1977-1978 0.84 (-)25.0 1996-1997 0.06 (-)94.60

1981-1982 0.46 (-)58.90 1997-1998 0.30 (-)73.20

1982-1983 0.21 (-)81.30 1998-1999 0.09 (-)92.0