Magnitude-Frequency Analysis for Suspended Sediment Transport in the Ganga River

Sediment load in the Ganga river is among the highest in the world. Effective discharge for suspended sediment transport at 15 stations on the Ganga river has been computed using a mean and rating curve approach in the present study. Discharge and sediment data were procured from Central Water Commission, India. The present study shows that discharges of moderate magnitude and frequency are responsible for maximum sediment transport in the Ganga river. About 90% of the total sediment is transported by discharges with a return period of less than three years on annual maximum series at most of the stations. Bankfull discharge is manifold the effective discharge at most of the stations, except Gandhighat and Hathidah. The ratio of bankfull discharge and effective discharge varied in a wide range of 1.13–3.02. However, effective discharge at these stations had a strong correlation with a discharge of 1.5-year return interval. Application of the rating curve approach led to a systematic underestimation or overestimation of total sediment load, which may result in overestimation of effective discharge. For large rivers, the frequency of data collection, i.e., daily or 10-daily, does not affect the effective discharge and has been found to differ only by 0.5%.