Necessity of Regional Co-operation - The Ganga: Water Use in the Indian Subcontinent - page 266

The minimum discharge of the Ganga normally falls to about 1,275 cumecs,
or 45,000 cusecs, in mid-April. In the Brahmaputra, it goes down to about 3,170
cumecs, or 112,000 cusecs, and in the Meghna to about 370 cumecs, or 13,000
cusecs, in mid-February. The discharge in the Ganga rises appreciably from mid-
June and falls appreciably from mid-October, every year but in the Brahmaputra
and the Meghna, the flow rises appreciably from mid-April and falls from mid-
September. For a comparative study of the average monthly discharge in the three
rivers, the location of discharge observation sites within Bangladesh, as reported by
James M Coleman in 1968 were considered. These are the Hardinge Bridge site for
the Ganga, Bahadurabad for the Brahmaputra and Bhairab Bazar for the Meghna as
shown in Table 14.3.
The Table 14.3 shows that whereas the Ganga starts rising from May, the
Brahmaputra and the Meghna do so fromMarch. Thus, there is a minimum time-lag
of two months for flood in the Ganga and the other two rivers, the former follows the
latter. Also, there is a time-lag of one month for the high flood, which comes in the
Ganga in September and in the Brahmaputra in August. The minimum discharge in
the Ganga, about 1,275 cumecs, occurs in April and that in the Brahmaputra, about
3,170 cumecs, about two months ahead, in February. Thus, the minimum discharge
in the Ganga is over 2 1 / 2 times less than that of the Brahmaputra, leaving plenty
of water in the latter, even in lean season. From the schematic diagram shown in
Fig. 14.3, it is seen that over 138,700 cumecs, or 4.9 million cusecs of water flow
into the Bay of Bengal during floods through a single outlet of the three combined
rivers, namely the Ganga, the Brahmaputra and the Meghna in Bangladesh. This is
the largest in the world for a single outlet to the sea and exceeds even the Amazon
by about 1 1 / 2 times.

CHINA (TIBET)

BRAHMAPUTRA
BASIN

NEPAL

BHUTAN

GANGES
BASIN

BURMA

MEGHNA
BASIN

INDIA

BAY OF BENGAL

Fig. 14.3 The Ganges, Brahmaputra and Meghna basins (See also Plate 11 on page 373 in the
Colour Plate Section)