In-reservoir monitoring and modelling concepts to assess the sedimentation dynamics of Enguri reservoir

In this study we combined monitoring and modelling techniques to understand sediment dynamics and improve management strategies in the Enguri reservoir. Methods included topographic differencing, sub-bottom profiling, water sampling, and visual inspection. A Delft3D model simulated sediment transport under various conditions. Topographic differencing indicated a 16% loss in reservoir volume, primarily in the dead storage zone, mainly due to the operation regime. Sub-bottom profiling effectively quantified silt and clay deposition (43% of the total sediment), while showing difficulties in penetrating high density sand and gravel layers. In total 29 modelling scenarios were investigated. Modelling identified reservoir head as a key factor in sedimentation patterns. Partial flushing was found suboptimal, leading to movement of large volumes of sediment within the reservoir. In this case, empty flushing is recommended as the most effective mitigation measure. The combination of monitoring with modelling provided a framework for understanding and managing sediment issues in large reservoirs such as Enguri.