The Ganga’s Hydrology - The Ganga: Water Use in the Indian Subcontinent - page 26

Fig. 4.2 Average bed slope of river Ganga along Bhagirathi-Hoogly

Apart from too sudden change in the longitudinal slope which affected the char-
acter and formation of the alluvial plain, the Ganga is also noted for enormous
fluctuations of its flow. It drains a catchment of about 32,300 km 2 at Haridwar with
total yearly run-off of 21,400 million cubic metres. Of this, the total monsoon dis-
charge from June to September is about 16,000 cubic metres, i.e., 75%. The residual
discharge of 5,400 m 3 is spread over other 8 months, from October to May, as shown
in Table 4.3.
The average discharge in the Ganga at Haridwar in monsoon months is about
1,500 m 3 /s; it falls below 200 m 3 in winter. The normal flood discharge goes above
5,860 m 3 /s, almost every year. Further down, at Garh Mukteswar, the normal flood
discharge is about 8,500 m 3 /s owing to additional flows from some small tributaries.
The monsoon discharge goes up, further downstream. At Allahabad, before the
Ganga meets Yamuna, its yearly run-off is about 59,000 million (59 billion) cubic
metres; at this confluence, the Yamuna's run-off is much more than the Ganga's,
about 93,000 million (93 billion) cubic metres. With more discharges from minor
tributaries from both sides, the average annual run-offs at Patna and Farakka are of
the order of 364,000 million (364 billion) and 459,000 million (459 billion) cubic

Table 4.3 Flow of water in the Ganga at hardwar (S. P. Das Gupta, 1975)

Run-off (Million m 3 ) Discharge (m 3 /s)

Period (season) Flow (%)

June-September (monsoon) 15,952 75 1,523

October-December
(Post-monsoon)

2,447 11 308

January-March (Winter) 1,507 7 194

April-May (summer) 1,487 7 282

Total 21,393 100 678