How is Indira Sagar Dam Altering the Suspended Sediment Transport in Central Indian Region?

The hydraulic structures, such as dams and reservoirs, are built for flood mitigation, drinking & irrigation water supply, and hydropower generation. Despite their positive roles, large dams and reservoirs are well known to trap a significant portion of the incoming sediment fluxes. In turn, sedimentation reduces the reservoir's water storage capacity. The Indra Sagar dam, located in the Narmada River Basin, is the largest reservoir in India (total capacity ~ 12.2 Bm³). Therefore, in this study, our objective is to set up a data-driven, i.e., Generalized Additive Model Location Scale and Shape (GAMLSS) to simulate the impact of the Indira Sagar dam on the downstream sediment transport. The daily sediment and water discharge data are used from 1987 to 2019, from June to November, at upstream and downstream gauge stations. Preliminary analysis reveals a significant alteration in downstream sediment discharge after constructing the Indira Sagar dam. However, the pre-dam period doesn't significantly alter sediment transport behavior. In addition, pre-and post-dam water discharge behaviors do not exhibit considerable alteration. The difference between 5-yearly sediment duration curves reveals around 60% to 95% reduction in high and moderate magnitudes sediment load. Further observation suggests an increase in low sediment magnitude flows downstream after the dam construction from the base period 1989-1993. The significance of the study is that it will help water managers in understanding the dam's water storage capacity, which may be affected due to sediment deposition. It is also crucial to understand the geomorphological changes and implications of less sediment supply in the downstream region. The results obtained from this study will further provide additional insights into evolving flood and drought processes and their forecasting around the dam-affected region. This work is in progress, and further results will be presented at the conference.