Characterizing Dam Augmented Flow in Downstream of a Hydropower Project to Assist Management Strategies

Abstract

The recent increase in human activities, such as the construction of dams along rivers, has led to significant hydrological changes in downstream regions. A significant effect of dam construction is the disruption of natural flow patterns leading to erratic water levels, seasonal fluctuations, and sporadic sediment transport. This study introduces a modelling framework to analyze the downstream flow impact of hydropower dams. The framework comprises both a reservoir operation model and a hydrodynamic model. A comprehensive investigation was undertaken to assess the hydropower dams' influence across the entire water year. Moreover, a detailed examination was conducted to characterize the outflow hydrographs from Inter Basin Water Transfer (IBWT) and Non Inter Basin Water Transfer (NIBWT) hydropower dams. For NIBWT hydropower, Lower Subansiri Hydropower Project is considered for the analysis. Results showed that with the presence of the dam, the flashy characteristic of the outflow hydrograph increases. Thus, dam-induced flood is a combination of regional flood as well as flash flood. Based on the statement ranking of the dam-induced flood was provided among the global hazards considering the factors suggested by Bryant. To assess the flow contribution by the ungauged tributaries downstream of the dam, a streamflow generation module was developed using the Drainage Area Ratio (DAR) incorporated into the developed model and applied in the operational IBWT hydropower project.