The Ganga’s Hydrology - The Ganga: Water Use in the Indian Subcontinent - page 24

Rajasthan. The Himalayas are spread on the entire northern border of India with
Pakistan, Afghanistan, Tibet, China, Nepal and Bhutan and all northern tributaries
to the Ganga are fed by snow-melting water and rainfall from the southern side of
the range. Here also, rains on the eastern Himalayas is more than those on western
ranges, varying from 500 to 280 cm. Rainfall is also higher in the lower foothills
and decreases in the upper ranges.
Over the whole of the Ganga basin, stretching from Dehradun in UP near which
the Bhagirathi joins Alakananda in Uttarkashi district of Uttarakhand (carved out
from UP) to south 24-Parganas district in West Bengal the annual rainfall aver-
ages about 90 cm but on Dehradun and nearby Haridwar, it is 210 and 150 cm,
respectively. Its intensity wanes to about 100 cm in Aligarh in UP Bihar's Purnea
district receives the highest rainfall of the State, about 170 cm while Mungher in
the same State receives the lowest, about 95 cm. The annual rainfall on Farakka in
West Bengal, is about 130 cm while on Kolkata and Howrah, it is about 150 cm. On
Kakdweep in south 24-Parganas, about 160 cm rains fall in a year. The rainfall data
on the Ganga basin follows in Table 4.2.

Table 4.2 Annual rainfall in Ganga basin

Annual
rainfall (cm) Sl. No. Place District State

1 2 3 4 5

1 Bhagirathi-Alakananda junction Uttarkashi Uttarakhand 90.0

2 Dehradun Dehradun -Do- 210.0

3 Hardwar Aligarh -Do- 100.0

4 Purnia Purnia Bihar 170.0

5 Munghyr Munghyr -Do- 95.0

6 Ganga Murshidabad West Bengal 130.0

7 Calcutta Calcutta -Do- 150.0

8 Kakdwip South 24-Paraganas -Do- 160.0

Seasonal Distribution

Except in Kashmir, Tamilnadu and some other regions, winter rainfall is very mea-
gre and much less than in other seasons over the rest of India (January-February).
From March to May, rainfall is good over Kerala, Assam and Jammu & Kashmir.
Between June and September, the south-west wind blows over most parts of the
country, including the Ganga basin and brings good rains. Over two-thirds of annual
rainfall occurs in this period except in a few places, as stated. Its sub-basin has
distinct wet and dry seasons; the wet season receives about 75% of total annual
downpour in monsoon months, from June to September, followed by a dry summer
spell fromMarch to May and a short winter from December to February. Water-flow
in streams fluctuates considerably in both the seasons.