Only a Barrage Can Save! - The Ganga: Water Use in the Indian Subcontinent - page 88

moorings and adopted special navigational procedures to take fullest advantage of
tides but free flow of traffic was hindered by draft limitations. The bars and crossings
which had to be negotiated in the course from Kolkata to Diamond Harbour were
(their distance in kilometres from Calcutta port in brackets) Panchpara (8), Sankrail
(10.5), Munikhali (14.5), Pirsareng (17), Poojali (21), Moyapur (35), Royapur (41),
Ninan (58), Eastern Ghat (63) and Kukrahati (72).
The first five crossings between Garden Reach and Uluberia were being nego-
tiated by ships of moderate to low draft, which could negotiate them in ebb tides.
Ships of deep draft crossed these bars during night tide and anchor at Uluberia
before ebb tide began. Dredgers constantly worked to maintain sufficient depth
over these bars to let ships of moderate draft to leave on the ebb, as the number
of ships that could leave on the night flow tide was restricted by lack of space and
berths at Uluberia and Royapur anchorages. Deterioration of these bars was more in
December when the upland supply stopped; their condition was worst at the end
of the dry season in May. The cumulative result of these seasonal changes was
long-term deterioration of the river, making it extremely difficult for even low to
medium-draft ships to cross low-water bars during ebb tides. In spite of intensive
dredging, the maximum depth over the bars and crossings went down between 1920
and 1954, as given in Table 7.1 below.
Study of the bars and crossings in freshet seasons led to the findings below:

• Separate channels were created by flood currents in dry season and freshet

discharges during monsoon;

• During the monsoon, flood channels were affected by sands brought with freshet

discharges;

•

Depths over the bars and crossings increased following prolonged upland
discharges but critical discharges varied for each bar and crossing;

• Most of the bars deteriorated when upland discharges decreased; this continued

throughout the entire dry season;

• Depths over bars and crossings reduced, affecting the navigability of the channel

from the sea, making dredging a temporary and partial palliative.

Table 7.1 Diminution in maximum low water depth over bars and crossings (between Kidderpore
Docks and Hooghly Point, 34 n. miles)

Diminution

Location of bars
and crossings

Depths in
1920(m)

Depths in
1950(m) Actual Percentage

1. Panchpara
2. Sankrail
3. Munikhali
4. Pir Sarang
5. Poojali
6. Moyapur
7. Roypur
8. Ninan
9. Eastern Gut

8.54
7.11
8.31
7.47
8.23
5.03
5.23
6.66
4.83

6.33
5.06
4.88
5.34
6.40
4.63
4.45
3.73
3.96

2.21
2.05
3.43
2.13
1.83
0.40
0.78
2.93
0.87

26
29
42
29
22
4
15
44
18