Examining the downstream geomorphic impact of a large dam under climate change

•Hydrology and sediment supply in regulated Godavari R., India simulated using SWAT.•Simulations illustrate importance of reservoirs in distributed hydrologic modelling.•Geomorphic stability index computed from pre/post- dam flow and sediment transport.•Observed incision is related to the simulated geomorphic stability index.•Climate change could move rivers below existing dams toward states of net erosion. Long-term geomorphic evolution of rivers depends both on the amount of sediment supply and on the river’s ability to transport that sediment. Climate change is anticipated to change flow frequency distributions and sediment yield and could thus alter the geomorphic trajectory of many regulated rivers. We aim to examine the possible geomorphic response of the upper Godavari River, India, to climate change using two well-accepted metrics: the frequency of the sediment-transporting flows (T*) and the ratio of the sediment flux below and above a dam (S*). Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and sediment yield in the basin. We calibrated and validated the model using SWAT-CUP for pre- (1971–75) and post-dam (1976–81) conditions downstream of Jayakwadi dam. The model performance was good (NS value > 0.6 for discharge and PBIAS < ± 10 for sediment) with low uncertainty (p-factor > 0.6 and r-factor